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RE: [dinosaur] Puzzles and Perils of the Prefix Eu "Good": from Eubontes to Euarchontaglires

Hi Ben,


Youâre right. It recalls a âbattleâ of wills some of us had with physiologists about the taxon Eutheria. There is no doubt that the original intent was a term to encompass both marsupials and placentals and taxa nearer to these groups than any other subclassâi.e., âmodernâ mammals as opposed to monotremes. Within Eutheria, subgroups Marsupialia and Placentalia made perfect sense. When we incorporated the term in its original context in our 1982 classification (Aplin & Archer 1982 , Recent advances in marsupial systematics with a new syncretic classification. Pp. xv-lxxii in Archer, M. (ed.) âPossums and Opossums: Studies in Evolutionâ. Surrey Beatty & Sons Pty Ltd and the Royal Zoological Society of New South Wales: Sydney), some Australian physiologists protested because in days post-Owen, placentas were known to be present in marsupials. They argued, therefore, that a new physiologically-OK term should replace Marsupialia and pounced on Metatheria, and that a new term was required for Placentalia and hijacked Eutheria with no concern about the original meaning of the term. Efforts to explain broad principles of systematics to the physiologists, and that taxonomic names do not have to be changed to reflect changed understanding about the anatomy or relationships of included taxa, were a waste of time. We pointed out that although phascolarctids are not pouched bears, thylacomyids are not pouched mice and thylacinids are not pouched dogs, these higher-level names were perfectly acceptable to everyone, including the physiologists. Eventually we gave up and Eutheria began its inappropriate new life as a clade that incorporated crown group Placentalia and all groups closer to that clade than to marsupialsâutterly different than the original concept of Eutheria and the purpose for which it was established. Part of the problem, of course, is the fact that the ICZN doesnât provide rules of usage for taxonomic ranks about the family category coordinate level.





From: vrtpaleo-l-request@usc.edu [mailto:vrtpaleo-l-request@usc.edu] On Behalf Of Ben Creisler
Sent: Monday, January 01, 2018 12:41 PM
To: dinosaur-l@usc.edu; Vrtpaleo-l
Subject: Puzzles and Perils of the Prefix Eu "Good": from Eubontes to Euarchontaglires



Ben Creisler



Puzzles and Perils of the Prefix Eu "Good":  from Eubontes to Euarchontaglires


Happy New Year to the lists!

In many ways, it's hard to see 2017 as a "good" year (kilonova breakthrough and scientific descriptions of some major fossils aside)...

So it may be fitting in the new year, as a counterpoint, to look at how the idea of "good" has been expressed in names used in vertebrate paleontology--more precisely, how the Ancient Greek prefix *eu*- (meaning, in basic terms, "good, well ") has been put to service in composing names for taxa.


When the notion of "good" is extended to taxonomy, zoological nomenclature has often interpreted the prefix *eu*- with a derived Neo-Latin meaning "true, genuine, typical"--but not in every case. As it turns out, *eu*- has a complicated range of intended meanings when names are looked at in their historical contexts and matched with their authors' original intentions. Examples include names such as *Eubrontes*, *Euclastes*, *Eucoelophysis*, *Euparkeria*, Eutheria, Euarchonta, etc.

This post was originally inspired by an offlist query some time back about the etymology of the clade name Euarchontaglires, which includes primates and rodents, and was first proposed by molecular biologists. A potential source of confusion is whether the name was formed as the common Neo-Latin prefix *eu*- as "good, true" + the older higher category name Archonta (proposed by Gregory) + Glires (dating back to Linnaeus) or as a combination of the newer clade name Euarchonta (proposed by molecular biologists) + Glires.

A recent discussion on the vertpaleo list about the use of the name Cetartiodactyla highlights issues of redefining older names (most often from traditional morphology-based taxonomy, such as Archonta and Artiodactyla) versus using new names after adding or removing member groups to create "new" updated clades, such as Cetartiodactyla and Euarchonta anproposed by molecular biologists. [More on these issues later...]


One particular point I have tried to unravel is the complicated and puzzling history surrounding the name Eutheria (attributed to either Theodore Gill or to Thomas Huxley), and to suggest a more accurate citation form. For reasons explained later, the following citation would seem to be fit better with the history of the name and its current usage:

Eutheria Huxley, 1881, sensu Flower, 1883 (non Gill, 1872)


This post is mainly an historical review and is intended as a helpful resource.  (It turned out a bit long and the display may be clipped in Gmail and some other email programs. The full post should be viewable by clicking on the "view entire message" version.)  I have tried to provide links to freely available material on the internet wherever I can. Any errors (missed typos mainly, I hope) or mistranslations are mine and regretted. Corrections are welcome!



Ancient Greek Meanings of *eu*

For the record, here is how different forms of *eu* were used and understood in Ancient Greek:

*eus* masculine/feminine adjective; *eu* neuter adjective: "good, noble, brave" [more on the meaning "noble" later on...]

 *eu* as a neuter noun [*to eu*]: "the good, perfection, the ideal, the right cause" (derived from neuter form of adjective *eus* above)

 *eu*! as an exclamation, equivalent to Bravo! or Well done!

 *eu* as an adverb: "well"

 *eu*- combined as a prefix with nouns and adjectives: "well" or "good"-- but very often expressing or intensifying a positive quality such as strength, skill, beauty, greatness, abundance, or easiness of doing something, depending on the combination. The accurate translation in English depends on the context.

Examples include:

*euagros* "lucky at hunting" from *agras* "hunting"; *euarkhia* "good government" from *arkhia* "government"; *euarithmetos* "easy to count" from *arithmos* "number, sum"; *eudromias* "fast swimmer" (name of a type of fish) from  *dromao* "run"; *eudynamos* "mighty" from *dynamis* "strength, power*; *eumorphia* "beauty of form" from  *morphe* "form, shape"; *Eupator* "having a noble or an illustrious father" (a title given to various ancient rulers), *eustomos* "with a large mouth" from *stoma* "mouth", etc.




Prefix *eu*-: Ancient Greek vs. Modern Neo-Latin Meanings

Beginning mainly in the 17th Century, scholars, naturalists, inventors, physicians, and others in Europe began coining new terminology and new names based on Greek and Latin, often to fit new inventions, new scientific concepts, or to provide formal Latin names and descriptions for animals and plants, etc. Much of the scientific correspondence and formal writing at the time was done in Latin, a practice which only waned in the early 19th century.

A point worth emphasizing again is how modern scientific, zoological, botanical, microbiological, medical, and technical Neo-Latin word and name formation often have modified the meanings, and sometimes the grammar, of the original ancient Greek and Latin sources. In the case of the prefix *eu*-, the most notable distinction between Ancient Greek and modern Neo-Latin usage is a meaning "true" for *eu*- in zoological nomenclature, which was not found as such in ancient texts.

The Neo-Latin meaning "true" for *eu*- developed from the idea of "good" in the context of taxonomy during the 19th century, often in the sense of "typical" (representing or matching a "type"), but also in a more generalized sense as "genuine" or "true" (that is, clearly falling within a particular identifiable taxonomic or morphological category). Of particular note is how, after Darwin's Origin, *eu*- came to indicate the most advanced or most important higher taxonomic group in terms of evolution (Eusuchia, Eutheria, Eucynodontia, etc.). This usage can largely be credited to Thomas Huxley, based on the early examples of his Eusuchia and Eutheria. (See discussions below.)



Prefix *eu*- in Generic Names in Vertebrate Paleontology

Two very different ways of using the prefix *eu*- stand out for generic names in zoological nomenclature: *eu*- to modify only certain elements of a new taxonomic name or *eu*- to modify an entire and already existing generic name to create a new name.




A. Using Ancient Greek Combinations:


As noted above, Ancient Greek had hundreds of words (mainly compound adjectives but also some compound nouns) formed with a prefix *eu*- to express some positive quality. Such compounds have been used to form generic names as noted below (but sometimes with a different meaning).

*Eurhinodelphis* Du Bus, 1867 "well snouted dolphin" (Ancient Greek *eurhis* (*eurhinos*)" "having a keen sense of smell" (from *rhis* (*rhinos*) "snout, nose") + Greek *delphis* "dolphin")-- here for a dolphin with an "excessively elongated and thin snout":



A resemblance to *Eurhinodelphis* in turn inspired the name *Eurhinosaurus* for an ichthyosaur with a similar elongated snout and short lower jaw (previously *Ichthyosaurus longirostris*).

*Eurhinosaurus* Abel, 1909 "well snouted reptile"




*Eunotosaurus* Seeley, 1892 "strong-backed lizard" --(from Ancient Greek *eunotos* "having a strong back" (from Greek *notos* "back" (with a long first 'o' [omega])) for a reptile whose "ribs are remarkably massive."


[NOT *eu* "true" + Greek *notos* "south" (with a short first 'o' [omicron]) + sauros "lizard" for "true south lizard" as suggested in some sources (i.e., Colbert's Dinosaur Book ).]


*Euoplocephalus* Lambe, 1910 "well armed head" (Greek *euoplos* "well armed" [from *hoplon* "shield"] + kephale "head" + -os) for an armored ankylosaur




B. Using Modern Invented Combinations (ones not found in ancient texts)

*Eucrotaphus* Leidy, 1850 "large [good] temples" (from *eu*- "good" + Greek *krotaphos* "temple of the skull")

"Both fragments belong to new genera of mammalia. The smaller of these I have named *Eucrotaphus*, on account of the comparatively very large size of the temporal bones. " pg. 90



*Euclastes* Cope, 1867 "strong [good] breaker" (from *eu*- "good" + Greek *klastes* "breaker, one who breaks" [from Greek *klao* "break"]) for a turtle with powerful beak and jaws specialized for crushing mollusks:

"The broad, regular alveolar surfaces have no doubt supported a massive corneous table ..... with little or no external cutting margin. This arrangement, as well as the compactness of structure, is appropriate to a nutrition dependent on crushing more or less hard bodies, as molluscs."



*Euskelesaurus* Huxley, 1867 "good-legged reptile" (*eu*- + Greek *-skeles* "-legged" from *skelos* "leg*)

"An animal the thigh-bone of which approaches three feet in length, may be fitly said to have 'good legs,' whence I propose the generic name of *Euskelesaurus* for this new African reptile..."




C. To indicate a "typical" kind of animal:

 *eu*- + general animal name (sometimes also a generic name): to indicate a genus (or subgenus) that is clearly identifiable as a particular type of animal. This is mainly a 19th century usage for *eu*- in paleontology and zoology.

*Eucastor* Leidy, 1858 "typical beaver" from Greek *eu* "good [= typical]" + Latin *castor* "beaver"

"The jaw and incisor teeth have the same form as the corresponding part of the recent Beaver." 


In a similar way, *Euchoerus* Leidy , 1853 "typical hog" and *Eumys* Leidy, 1856 "typical mouse, *Eusyodon* "typical hog tooth" *Eubradys* "typical sloth"

However, in Leidy's names *Eumylodus* "good grinding tooth" (Gr. *mylo-* "grind" + Gr. *odous* "tooth") for a fish and *Eupachemys* (Gr. *pakhys* "thick, stout" + Gr. *emys* "turtle") "very stout turtle" for a large tortoise, *eu*- is used as in *Eucrotaphus* to intensify some quality, feature, or ability.



A very different use of the prefix *eu*- in zoological nomenclature adds *eu*- to an already existing generic name to create a new name that may express a number of ideas--or may simply replace or prevent a preoccupied name, often with minimal extra meaning.

1. *eu*- "true" (or "good") + existing generic name

A. To create a similarly spelled name to replace a preoccupied name. In such cases, *eu*- is usually intended to add minimal extra meaning:

*Euconcordia* Reisz, Haridy & MÃller, 2016

"An alteration of the previous name *Concordia*, by adding the prefix Eu, meaning true."

Robert Reisz, Yara Haridy & Johannes MÃller (2016) *Euconcordia* nom. nov., a replacement name for the captorhinid eureptile *Concordia* MÃller and Reisz, 2005 (non Kingsley, 1880), with new data on its dentition. Vertebrate Anatomy Morphology Palaeontology 3:1-6 



*Concordia* MÃller and Reisz, 2005

MÃller, J., and R.R. Reisz. 2005. An early captorhinid reptile (Amniota, Eureptilia) from the Upper Carboniferous of Hamilton, Kansas. Journal of Vertebrate Paleontology 25:561â568.


"The generic name is based on the Latin word 'concordia,' meaning 'unity, agreement, harmony' referring to the fact that the taxon finally corroborates the long held assumption that captorthinids must also have existed in the Late Carboniferous."


B. To prevent a possible preoccupied name:

Scottish-born South African paleontologist Robert Broom (1866 - 1951) created a number of names in honor of notable people by adding the prefix *eu*- to a Latinized form of their surnames formed with a standard Latin -ia feminine singular ending: *Euparkeria* Broom, 1914; *Eumatthevia* Broom, 1930; *Euchambersia* Broom, 1931; *Eumantellia* Broom, 1935. The prefix *eu*- in these cases simply served to prevent possible homonymy with any existing generic names and would appear to have no real added meaning (although I've seen interpretations such as "Parker's good animal" for *Euparkeria*).

*Euparkeria* Broom, 1913, for William Kitchen Parker (1823 â 1890), British zoologist:

"...in honour of Prof. W. Kitchen Parker, whose works formed my chief recreation in early student days, and have been the inspiration of much of my research."


Broom, R. 1913. Note on *Mesosuchus browni* Watson and on a new South African Triassic pseudosuchian (*Euparkeria capensis*). Records of the Albany Museum 2: 394â396

The name *Parkeria* already existed in zoology as *Parkeria* Carpenter, 1869 and *Parkeria* Gabb, 1881.


*Euchambersia* Broom, 1931, for Robert Chambers (1802-1871), Scottish geologist and anonymous author of Vestiges of the Natural History of Creation:

"I am naming this remarkable genus after the very famous Scots evolutionist Robert Chambers, whose pre-Darwinian 'Vestiges' though sneered at by many is a very remarkable work."

Broom, R., 1931. Notices of some new genera and species of Karroo fossil reptiles. Records of the Albany Museum 4 (1): 161-166.

*Chambersia* already existed as *Chambersia* Riley, 1891.



C. Erect a new genus (or subgenus) for an existing species or for fossil material that previously has been classified under or referred to by an older generic name, now modified with *eu*-:

*Eubaena* Hay, 1908 (pg. 82), new genus for the existing fossil turtle species *Baena cephalica* Hay, 1904.

Here the prefix *eu*- possibly may allude to the "fine skull" holotype as mentioned by Hay ("fine baenid"?), highlighted also by the specific name *cephalica* [*kephalikos* "cephalic, of the head"). Leidy's original generic name *Baena* remains valid, with a different type species, *arenosa* "sandy, gritty" (probably for the "finely fretted appearance" of the carapace and sternum).


Hay, O. P. 1908. Descriptions of five species of North American fossil turtles, four of which are new. Proceedings of the U. S. National Museum. XXXV 161-169, pls. xxvi-xxvii, 3 text-figs.


*Baena* Leidy, 1870-- from an Arapaho word for a turtle


Hayden, F. V. 1862. Contributions to the ethnography and philology of the Indian tribes of the Missouri Valley. Philadelphia: C. Sherman & Son, Printers, 1862. [Leidy's source as well for the generic names *Sinopa* (Blackfoot for "small kit fox") (pg. 265) and *Saniwa* (Arapaho for "rock lizard") (pg. 333)]


page 338: "turtle, ba-en'-a"


Leidy 1870

"For the genus I have adopted a name which, according to Prof. Hayden, is used by one of the Indian tribes of the Upper Missouri as that of a turtle."


Leidy, Joseph. 1870. [Descriptions of Emys jeanesi, E. haydeni, BaÃna arenosa, and Saniwa ensidens.]. Proc. Acad. Nat. Sci. Phila. 1870 pp. 123-124.


*Eustreptospondylus* Walker, 1964, new generic name for the Oxford "Streptospondylus"--but explained by Walker as meaning, literally, "well-curved vertebra" (pg. 124).


Walker, A. D.. 1964. Triassic reptiles from the Elgin area: *Ornithosuchus* and the origin of carnosaurs. Philosophical Transactions of the Royal Society of London, Series B, Biological Sciences 248:53-134

But note that *Streptospondylus* von Meyer, 1832 was meant as "reversed vertebrae" (from Greek *streptos* "reversed, turned"), so named by Hermann von Meyer for its convexo-concave centra (convex in front, concave in back), the reverse of vertebrae in modern crocodilians: <<mithin gerade umgekehrt, als in den Crocodilen>> (Palaeologica (1832): 226).


 D. Create a name for a new genus with *eu*- to show relatedness or some historical connection to another existing genus used as part of the new name. A potential peril of such names is if the connection to another genus turns out to be inaccurate or inappropriate.

*Eudimorphodon* Zambelli, 1973 "truly *Dimorphodon*": to indicate a Triassic pterosaur that lived even earlier than the Early Jurassic *Dimorphodon*, the previously oldest known pterosaur.

"Da *eu* (*eu* = veramente) *Dimorphodon* (genere del pià antico pterosauro precedemente noto)."

[From *eu* (*eu* = truly) *Dimorphodon* (genus of the most ancient pterosaur previously known)]

R. Zambelli. 1973. *Eudimorphodon ranzii* gen. nov., sp. nov., uno pterosauro Triassico. Rendiconti Scienze di Instituto Lombardo, B 107:27-32


*Dimorphodon* Owen, 1859

"Professor Owen proposed the name *Dimorphodon* for this new subgenus, in reference to the two kinds of teeth, or two features of dentition, one of them borrowed, as it were, from the fish or batrachian, by this early form of flying dragon. "

Owen, R. (1859). On a new genus (*Dimorphodon*) of pterodactyle, with remarks on the geological distribution of flying reptiles. Report to the British Association for the Advancement of science 28 (1858): 97â103.



*Eucoelophysis* Sullivan & Lucas, 1999 "true *Coelophysis*"

'Derived from the name of the ceratosaurian theropod *Coelophysis* (to which it is closely related) and the Greek *eu*, " good" or "true;" *coelo* "hollow;" and *physi* " nature."' (pg . 82)

Sullivan, R.M. and Lucas, S.G. (1999). *Eucoelophysis baldwini*, a new theropod dinosaur from the Upper Triassic of New Mexico, and the status of the original types of *Coelophysis*. Journal of Vertebrate Paleontology 19(1): 81-90.


'Etymology-The specific name [*baldwini*] honors the 19th century fossil collector David Baldwin, who collected the original type material of *Coelophysis* , one element of which can now be referred to this new taxon.

Referred Material-AMNH 2706, nearly complete right pubis (previously referred to *Coelophysis longicollis*).'


*Eucoelophysis* "true Coelophysis" was used for a supposed Triassic theropod that, as originally described, also included referred elements of Cope's original type material for *Coelophysis longicollis*. The name was proposed after the ICZN had rejected the name *Rioarribasaurus* for the Ghost Ranch theropod material and designated a neotype specimen for *Coelophysis* Cope (AMNH 7224) to preserve historical nomenclatural usage for the Ghost Ranch theropod as established by Edwin Colbert based on specimens in the American Museum of Natural History.

ICZN OPINION 1842 *Coelurus bauri* Cope, 1887 (currently *Coelophysis bauri*; Reptilia, Saurischia): lectotype replaced by a neotype. Bulletin of Zoological Nomenclature 53(2): 142-144 (June 1996)



*Eucoelophysis baldwini* was based on a pubis and a femur holotype (NMMNM P-22298) from the Upper Triassic Petrified Forest Formation of the Chinle Group in north-central New Mexico. However, the holotype pubis and femur for *Eucoelophysis* were later identified as belonging to a dinosauromorph silesaurid (Nesbitt, Irmis, Parker (2007): 211-214)--and not to a theropod, or even to a dinosaur (although the plant-eating silesaurids have been included in the Dinosauria by some authors). Thus the taxon *Eucoelophysis* as now defined has no real connection with the theropod *Coelophysis.*

Nesbitt, S. J., R. B. Irmis, and W. G. Parker. (2007). A critical re-evaluation of the Late Triassic dinosaur taxa of North America. Journal of Systematic Palaeontology 5:209-243.




2. The *Eubrontes* Puzzle: "great (thunder?) giant"

The ichnotaxon genus name *Eubrontes* Hitchcock (for large *Dilophosaurus*-like Jurassic theropod tracks) presents a number of puzzles. Edward Hitchcock (1793 â 1864) only used the name once in a report of a talk that he delivered to the Association of American Geologists and Naturalists in April 1845, applied to the earlier *Ornithoichnites giganteus* and other species of large fossil "bird tracks." The etymology was given in Greek spelling as *eu* + *Brontes*.

"Pres. H. said, hitherto names have been given to the footmarks and not to the animals. But since all geologists now admit that these impressions are real tracks, this paper attempts to name the animals that made them, and to classify and describe them, so far as it can be done from the data hitherto obtained...

I. Struthionidae

*Eubrontes* (*eu* and *Brontes*)

(pg. 23)




Hitchcock, E. (1845) An attempt to name, classify, and describe, the animals that made the fossil footmarks of New England. Proceedings of the 6th Annual Meeting of the Association of American Geologists and Naturalists, New Haven, CT: 23â25.

 In all his later publications, Hitchcock used the name *Brontozoum* for the proposed animal that made the tracks, explained as Greek *Brontes*, a giant , and Greek *zoon*, an animal, thus "giant animal" (pg. 50). Hitchcock's use of *zoon* in his new names and his revised names was meant to show that he was naming the animal, not simply the track marks.



Hitchcock, Edward. 1847. Description of two new species of fossil footmarks found in Massachusetts and Connecticut, or of the animals that made them. American Journal of Science 2, pp. 46-57, with 3 text.


In 1902 Oliver Hay (p. 543) revived the then obscure name *Eubrontes* in place of *Brontozoum* for the tracks based on historical priority and made *giganteus* the type species. *Eubrontes* is now treated as the valid ichnogenus name.

The often given meaning "true thunder" for the name *Eubrontes* is likely not the meaning that Hitchcock originally intended. Weems (2003) suggested "truly huge giant" as the meaning of *Eubrontes*.

Robert E. Weems (2003). *Plateosaurus* foot structure suggests a single trackmaker for Eubrontes and Gigandipus footprints. In P. M. LeTourneau & P. E. Olsen (eds.). The Great Rift Valleys of Pangea in Eastern North America, Volume 2: Sedimentology, Stratigraphy, and Paleontology. New York: Columbia University Press, pp. 294â295.



In Greek mythology, Brontes "Thunderer" (personified form of Greek *bronte* "thunder") was the name of a giant cyclops who forged thunderbolts for Zeus (Jupiter) inside Mount Etna on the island of Sicily, along with two other giant cyclopes, traditionally named Steropes ("Lightning Bolt") and Arges ("Bright Flash"). Their forging work explained the volcano's flames, smoke, and thunderous noise.





Hitchcock (1845) used the names *Steropoides* and *Argoides* for other tridactyl tracks, both explained as formed with the name of a cyclops (page 24 under Tridactylidae).


(Hitchcock later changed the names to *Steropezoum* and *Argozoum*.)

Given the grouping of Brontes, Steropes, and Arges as giants in mythology, why Hitchcock used *Eubrontes* instead of "Brontoides" in the same pattern is a bit of a puzzle. The generic name *Brontes* had already been used at least three times before in zoology, including for a trilobite (as well as for a living insect (the earliest and therefore valid *Brontes*) and a small living fish), so perhaps Hitchcock wanted to avoid a name that could imply a misleading resemblance (-oides) to an existing genus *Brontes* (none of which was gigantic (although the trilobite *Brontes* (later changed to *Bronteus*) was large compared to other trilobites)). In addition, some *Eubrontes* tracks were much larger than *Steropoides* and *Argoides* tracks.

The prefix *eu*- in *Eubrontes* was likely meant to amplify the idea of a giant animal, so "great giant" may come closer to his intention, as made clearer with the later replacement name *Brontozoum*, explained as "giant animal." In both names, it appears that a strict and literal reference to the mythical proper name Brontes is not intended but "Brontes" was used instead to mean a giant in a generic sense (as with Hitchcock's name *Otozoum* for the giant Otos, etc.).

Suggestions that Hitchcock might have named the animal *Eubrontes* because it supposedly made a sound like thunder when it walked or personified North American Indian legends of a "Thunderbird" would seem a stretch (but maybe not impossible) based on his own words and his other names for animals that made tracks.





The use of the prefix *eu*- added to higher category names began after publication of Darwin's Origin and in many cases has come to indicate some special evolutionary status for the named group. As explained later in more detail, this evolutionary usage was largely established by Thomas Huxley with the names Eusuchia and Eutheria.

Just as a reminder...

The ICNZ does not provide rules for the formation or usage of higher category names in zoology above the level of a superfamily. Nevertheless, some basic principles are usually followed.

All higher category names more inclusive than a "genus" must be in plural form, with Greek or Latin plural endings for nouns or for adjectives used as substantives. Note that the endings -a and -ia in such names are neuter plural forms, NOT feminine singulars. They also should take a plural verb such as "are" rather than "is," a common point of confusion: "the Dinosauria are..."; "the Archonta are..."; "the Mammalia are...'; "the Sauropsida are...", etc. (BUT singular "the clade Dinosauria is..." or the "the group Dinosauria is...," etc.)

Higher category names that do not end in the designated family-rank suffixes -oidea, -idae, -inae, -ini (which require a type genus) are not governed by ICZN rules. (Note that researchers who used unranked phylogenetic categeories in classifications typically ignore this set of formal ICZN rules and use -idae and -oidea arbitrarily without a type genus or a relative rank. Also, since the masculine plural suffix -*idae* (Greek -*idai*) meant "descendants of" or "father and descendants," it still needs to suffix a proper name (genus) to be grammatical.) Thus the use of higher category names that end in -a, -ia, -ida, -i, -ae, etc., (apart from the family endings already noted) is more a matter of choice and usage consensus.

Citation of authors and dates for zoological names is optional, and more a matter of historical record. It can matter in the case of generic and specific names when the earliest valid name for a taxon is required to be used by the ICZN (with some exceptions or change by petition). Historical publication precedence and original spelling for non-family higher category names is not required, but is often observed in the literature.


A basic rule for generic and specific names under the ICZN is that they must be in Latin form to be valid. Historically, the situation with higher category names is a bit murkier. Authorship is sometimes assigned either to the first author to describe a group without a Latin name, or to give a group a colloquial name (without a formal Latin grammatical ending)--OR to the first author to put the name in proper Latin form. The scope and complications of these nomenclatural issues might be a topic for a future post.


[As an example, Owen used the term "placental mammals" in print early in 1837 but NOT the Latin form Placentalia, which first appeared in print in 1838 in a shortened version in Latin of a classification of vertebrates presented in public by the French biologist Charles Lucien Bonaparte later in 1837. The 1838 summary version referred to Owen's work in a footnote, using the Latin form Placentalia. The full version of Bonaparte's 1837 classification (with the same footnote naming Placentalia) was not formally published until 1840. The name has been cited variously as Placentalia Owen, 1837, Placentalia Bonaparte, 1837, Placentalia Bonaparte, 1838, or even Placentalia Bonaparte, 1840.

See note at the end of this post for detailed corrections on the original source of the name Placentalia! ]


And additional problem is the date of publication. Higher category names are sometimes cited with the date a name or a taxonomic concept was first presented in a public lecture rather than in published form, or cited with the sequential year-volume date for a journal where it first appeared in print (although the paper in fact may have been published in the following year or later).





Higher category names formed with *eu*- fall into three broad categories. These lists are based on how the names were originally proposed and does not necessarily reflect their current phylogenetic status or other taxonomic usage.

1. To create a core taxonomic subgroup for the most advanced, important, typical, or characteristic members within a larger group whose name has been modified with *eu*- to name the subgroup:

Olson divided the class Reptilia into the subclasses Eureptilia Olson, 1947 + Parareptilia Olson, 1947

Eureptilia Olson, 1947 "main reptiles" or "typical reptiles"

"Eureptilia... These are typical reptiles characterized by lack of an otic notch or by a strong tendency toward its loss. They constituted the main radiation of the reptiles..." (pg. 44)

Named to show a contrast, the Parareptilia ("alongside reptiles") differ mainly in the configuration and evolution of the dermal bones in the skull: "This pattern of changes of dermal bones is very different from that witnessed in the Eureptilia."


table (pg. 45):


Olson, E. C. (1947). The family Diadectidae and its bearing on the classification of reptiles. Fieldiana Geology 11: 1â53.

Although the taxonomic categories Eureptilia and Parareptilia have been retained by many authors (with different definitions in modern phylogenetics depending whether they are treated as stem-based or node-based), both have been revised a number of times to exclude a number of groups originally included by Olson and to add other groups described by later authors.

The Eureptilia have been redefined in modern usage to include mainly captorhinids and diapsids (including former Euryapsida and Parapsida), along with a few related forms and groups, but excluding the Synapsida (which Olson had included in Eureptilia). In turn, there is a usual division of amniotes into Synapsida and Sauropsida (made up of Eureptilia and Parareptilia). However, some authors use Reptilia for Sauropsida, while others retain Sauropsida but use Reptilia in place of Eureptilia. Other taxonomic arrangements have also been proposed that retain Sauropsida, Reptilia, and Eureptilia as distinctly defined clades.

The Parareptilia now exclude the Seymouriamorpha and the Diadectomorpha, as well as the Chelonia [Testudines], recently revised as diapsids (thus in the Eureptilia), and include a number of additional groups not mentioned by or known to Olson in 1947.


Tsuji, L. A., and J. MÃller. 2009. Assembling the history of the Parareptilia: phylogeny, diversification, and a new definition of the clade. Fossil Record 12:71â81.




Similar examples of *eu*- to indicate an evolutionarily important subgroup include (as originally proposed):

Eucynodontia Kemp, 1982

Cynodontia Owen, 1861 = Eucynodontia Kemp, 1982 + Procynosuchia Brink, 1963 Kemp, 1982

Eupelycosauria Kemp, 1982

Pelycosauria Cope, 1878 = Eupelycosauria Kemp, 1982 + Caseasauria Williston, 1912

Kemp, T.S. 1982. Mammal-like Reptiles and the Origin of Mammals. Academic Press, London, UK.



Eupantotheria Kermack and Musset, 1958

Pantotheria Marsh, 1880 = Eupantotheria Kermack and Musset, 1958 + Symmetrodonta Simpson, 1925

Kermack, K.A. and Mussett, F. 1958. The jaw articulation of the Docodonta and the classification of Mesozoic mammals. Proceedings of the Royal Society, London 149: 204â215. DOI: 10.1098/rspb.1958.0063 http://rspb.royalsocietypublishing.org/content/149/935/204



Eumaniraptora Padian, Hutchinson & Holtz 1999

K. Padian, J. R. Hutchinson, and T. R. Holtz, Jr. 1999. Phylogenetic definitions and nomenclature of the major taxonomic categories of the carnivorous Dinosauria (Theropoda). Journal of Vertebrate Paleontology 19(1): 69-80

Maniraptora Gauthier (stem-based) including Eumaniraptora 1999 (node-based)[including = stem-based Deinonychosauria + Aves]



The Euornithes Muddle


(See also: Theropoda Database:




Euornithes Stejneger, 1885 "typical birds"

"With the above name I have designated the rest of the existing birds. This superorder, therefore, embraces all living birds except the Dromaeognathae [ratites] and the penguins." (pg. 64)



Stejneger, 1885. Birds. Standard Natural History, IV. Boston : S.E. Cassino and Company,1884-85

Cope (1889) used Stejneger's taxon Euornithes in a similar way (excluding palaeognaths and penguins) but with a different arrangement of subdivisions , referring to the Euornithes as "typical birds," within the Eurhipidurae Cope, 1889 "typical fan tails" (eu "good" + rhipis (rhipidos) "fan" + oura "tail) for all recent birds, excluding the Saururae "lizard tails" (Archaeopteryx) and the toothed Odontolcae "toothed forrows" (*Hesperornis*) and Odontormae "toothed sockets" (*Ichthyornis*) .



Cope, E. D. 1889 Synopsis of the Families of Vertebrata. American Naturalist 23: 849-877



Note that Euornithes Cope, 1889 is now often wrongly cited as the original authorship of Euornithes rather than Euornithes Stejneger, 1885.


Confusingly, the name Euornithes has been reused, or, more accurately, reintroduced with different definitions by a number of later authors who were apparently unaware of earlier citations.


Euornithes Dementjev, 1940

Dementjev, G. P. 1940. Handbook on Zoology. Volume 6, Vertebrates. Birds. Academy of Sciences, Moscow-Leningrad, 856 pp. [Russian]. (Not seen)


I can't confirm exactly how Dementjev used Euornithes without seeing the original text, apparently not available online at the moment.


Euornithes Sanz & Buscalioni, 1992

J. L. Sanz and A. D. Buscalioni (1992). A new bird from the Early Cretaceous of Las Hoyas, Spain, and the early radiation of birds. Palaeontology 35(4): 829-845

free pdf:


SUBCLASS: Archaeornithes = Archaeopteryx

SUBCLASS: Euornithes Sanz & Buscalioni 1992 = Iberomesornis + (Concornis + (Ambiortus + (Enantiomithes + Ornithurae))))

"clade Euornithes, diagnosed by a strut-like coracoid, a derived avian furcula and a pygostyle"


Euornithes Sereno, 1998

Euornithes Sereno, 1998 "true birds" as the sister taxon to the Enantiornithes "opposite birds" in a stem-based dichtomy within the Ornithothoraces: "all ornithothoracines closer to Neornithes than to *Sinornis*."

Ornithothoraces = Enantiornithes + Euornithes

Sereno, Paul (1998). A rationale for phylogenetic definitions, with application to the higher-level taxonomy of Dinosauria. Neues Jahrbuch fur Geologie und Palaontologie 210:41-83






2. To indicate a larger and more inclusive group: (may include a member group with the unmodified original name)

Euornithopoda Sereno 1986 = Ornithopoda Marsh, 1881 + Heterodontosauria Cooper, 1985


3. To create a new name based on the existing name of a recognized taxonomic group after excluding previous members and/or by adding additional groups. The original name without *eu*- is then considered invalid. This practice is controversial in some quarters. Two examples from molecular biology include:

Euarchtona Waddell, et al. , 1999, to supersede Archonta Gregory, 1910, to include only Dermoptera + Scandentia + Primates (and excluding bats))

Eulipotyphla Waddel, et al., 1999, to supersede Lipotylpha Haeckel, 1866, to include only hedgehogs, moles, shrews, and solenodons (and excluding golden moles and tenrecs, both placed in Afrotheria)

Pdf link:


P. J. Waddell, N. Okada, and M. Hasegawa. 1999. Towards resolving the interordinal relationships of placental mammals. Systematic Biology 48(1): 1-5



A bit of history here...

American geologist James Dwight Dana (1813 â1895) proposed the Archontia as a separate subclass of mammals that only contained humans:

Archontia Dana, 1863, pg. 70, in

Art. X. â On the higher subdivisions of the Classification of Mammals ; by James D. Dana.

The American Journal of Science 1863 Series 2: 35(1): 65-71


Dana initially rejected Darwin's ideas and evolution, but eventually came to accept at least some basic aspects (Neo-Lamarckian rather than Darwinian), reflected in the later editions of his famous Manual of Geology.



The name Archontia was essentially ignored, since the idea (also championed by Owen with his Archencephala) that humans were inherently separate from other Primates (monkeys, apes) because of their special brain construction was effectively demolished by Thomas Huxley.

William King Gregory (1876 â 1970) was either unaware of Dana's Archontia or evidently assumed that there would be no confusion between the presumably forgotten Archontia and his own similarly spelled Archonta in 1910.

Archonta Gregory, 1910 "chiefs" [chief (ones)] (from Greek *arkhon* (genitive *arkhontos*) "chief, ruler" + -a (neuter plural ending); alluding to the Latin-derived name Primates for the taxon as originally defined by Linnaeus (see below)). For Gregory, Archonta included Chiroptera (bats)+ Dermoptera (colugos) + Menotyphla (at the time, tree shrews + elephant shrews (later excluded from Archonta)) + Primates:

"...Archonta1 in allusion to the fact the Linnaeus included in the Primates the genera *Homo*, *Simia*, *Lemur* (including the Lemuroids and the 'Flying Lemur'), *Vespertilio*.

1 *Arkhon* chief, cf. German Herrenthiere. "



Gregory, W. K. (1910) The orders of mammals. Bulletin of the AMNH ; v. 27


NOTE: The group name Primates Linnaeus, 1758 is the plural form of the masculine Latin noun *primas* (genitive *primatis*) "first one, principal, chief"-- and thus similar in meaning to the Greek noun *arkhon* "chief, ruler" as Gregory indicates. Linnaeus' original Primates consisted of humans, apes, monkeys, and lemurs (comprised of *Lemur catta*, the colugo as *Lemur volans* ("flying lemur") [now *Cynocephalus volans*], and the loris as *Lemur tradigradus* [now *Loris tardigradus* ]), and bats [as *Vespertilio*].

Latin *primas*(genitive *primatis*):


Linnaeus, C. 1758. Systema Naturae (10th Edition)

Genera of Primates, pg. 18

I. Primates


Species of Primates, pgs. 20-32

Humans , *Simia* (apes and monkeys), lemurs, colugos, and bats were grouped together because they have four upper front teeth, arranged in parallel, and two nipples on the chest. The inclusion of humans undoubtedly inspired the choice of a name meaning "first ones" in rank.

"Dentes Primores superiores IV, parallelli, Mammae Pectorales II."

[Upper front teeth 4, parallel, pectoral teats 2]






Based on early results from molecular analyses, Waddell et al., (1999) proposed the new name Euarchonta: "A suggested true Archonta, or Euarchonta, (of Primates, Dermoptera, Scandentia) (pg. 4) ..." by excluding bats.

Pdf link:


P. J. Waddell, N. Okada, and M. Hasegawa. 1999. Towards resolving the interordinal relationships of placental mammals. Systematic Biology 48(1): 1-5

See also:

Silcox, M. T., J. I. Bloch, D. M. Boyer, and E. J. Sargis. 2005. "Euarchonta (Dermoptera, Scandentia, Primates)," in Rise of Placental Mammals. Edited by K. D. Rose and J. D. Archibald, pp. 127-144. Baltimore: Johns Hopkins University Press

Free pdf of chapter:



Eulipotyphla Waddel, et al., 1999 for Lipotylpha Haeckel, 1866

In addition to the Euarchonta, Waddell, et al., (1999) proposed the new name Eulipotyphla in place of Lipotyphla, excluding golden moles and tenrecs (both transferred to the new Afrotheria).

As originally proposed by Haeckel (1866 (vol. 2): CLX), the Insectivora were divided into:

Menotyphla Haeckel, 1866 "retaining cecum"

(Greek *meno* "retain, remain" + *thyphlon* "intestinal cecum" ("blind gut" from Greek *typhlos* "blind"))


Lipotyphla Haeckel, 1866 "lacking cecum"

(Greek *leipo* "leave out, be missing" + *thyphlon* "intestinal cecum")



III. Ordo: lnsectivora. Insectenfresser.

I. Subordo: Menotyphla , H. Insectenfresser mit Blinddarm. [insectivores with cecum]

1. Familia: Cladobatida s. Scandentia (Cladobates, Tupaja) [tree shrews]

2. Familia: Macroscelidia s. Salientia (Macroscelides , Rhynchocyon). [elephant shrews]

II. Subordo: Lipotyphla, H. Insectenfresser ohne Blinddarm. [insectivores without cecum]

1. Familia: Soricida (Sorex, Crossopus, Crocidura) [shrews]

2. Familia: Talpida (Talpa, Condylura, Chrysochloris) [moles + golden moles]

3. Familia: Erinaceidea (Erinaceus , Gymnura) [hedgehogs]

4. Familia : Centotida (Centetes , Solenodon). [tenrecs + solenodons]


In: Haeckel, E. (1866) Generelle Morphologie der Organismen : allgemeine Grundzuge der organischen Formen-Wissenschaft, mechanisch begrundet durch die von Charles Darwin reformirte Descendenz-Theorie. Zweiter Band: Allgemeine EntwickelÃngsgeschichte der Organismen. (Vol. 2) Georg Reimer, Berlin, 462 pp.



Also, in English:



Objections have been raised to the practice of replacing an existing higher category names such as Archonta and Lipotyphla with new names (Euarchonta, Eulipotyphla) after removing some previously included taxonomic groups (or adding new groups)--rather than retaining the existing name with a revised taxonomic definition, such as has happened with redefined Eureptilia and Parareptilia, or even Linnaeus's original version of Primates.

See this open access article for a discussion:

Robert J. Asher and Kristofer M. Helgen (2010) Nomenclature and placental mammal phylogeny. BMC Evolutionary Biology 10:102 doi:10.1186/1471-2148-10-102



As a result, the current literature includes Archonta and Lipotyphla, or Euarchonta and Eulipotyphla, depending on the preferences of the authors. The definitions of the taxa are the same, however. Full citations might be:

Archonta Gregory, 1910 (sensu Euarchonta Waddell, et al., 1999, non Archontia Dana, 1863)

Lioptyphla Haeckel, 1866 (sensu Eulipotyphla Waddell, et al., 1999)


As noted in Asher and Helgen (2010) above, the clade name Euarchontaglires Murphy, et al., 2001 was derived from Euarchonta + Glires, and thus is unaffected by continued use of Archonta.

'Within Euarchontoglires, our molecular results are the first to render robust support for the monophyly and internal structure of Euarchonta (3). Euarchonta is similar to the morphology-based Archonta hypothesis, but bats are excluded." pg. 2348

[A point of grammar here: Archonta and Euarchonta are neuter plural substantives in Latin (not feminine singulars), so "is" should be "are"...]

Euarchontoglires Murphy, et al., 2001

Murphy, William J.; Eizirik, Eduardo; O'Brien, Stephen J.; Madsen, Ole; Scally, Mark; Douady, Christophe J.; Teeling, Emma; Ryder, Oliver A.; Stanhope, Michael J.; de Jong, Wilfried W.; Springer, Mark S. (2001). Resolution of the Early Placental Mammal Radiation Using Bayesian Phylogenetics. Science 294 (5550): 2348â2351. doi:10.1126/science.1067179. PMID 11743200.


Supplementary material (free pdf)


Free pdf:


Also, Murphy, et al., 2007:


[= Gliriformes Wyss and Meng 1996]




Darwin's Challenge to Taxonomists

In Chapter 13 of The Origin of Species (1859 edition), Charles Darwin challenged the common approaches to taxonomic classification in his day:

"Naturalists try to arrange the species, genera, and families in each class, on what is called the Natural System. But what is meant by this system? Some authors look at it merely as a scheme for arranging together those living objects which are most alike, and for separating those which are most unlike; or as an artificial means for enunciating, as briefly as possible, general propositions, that is, by one sentence to give the characters common, for instance, to all mammals... I believe that something more is included; and that propinquity of descent, the only known cause of the similarity of organic beings, is the bond, hidden as it is by various degrees of modification, which is partially revealed to us by our classifications." (1859: 413)


Forms of "typological" classification, often based on groupings by general morphological features, were standard in the 19th century. Such classifications were later often reinterpreted (post Darwin) to also reflect evolutionary histories.


Darwin's hope for taxonomies based on the true phylogenetic histories of groups of plants and animals remains an ongoing challenge--and one not addressed directly until the adoption of cladistics beginning in the 1970s. The advent of taxonomies based on molecular evidence (DNA, proteins, etc.) beginning in the 1990s has added new ways to address Darwin's challenge, although contradictory results and other complexities remain--not to mention the limited application of such molecular analyses to fossil remains.




Thomas Huxley's Eusuchia and Eutheria

The English biologist Thomas Huxley (1825-1895) looms large in 19th century science, most famously as "Darwin's Bulldog" for his public defense of Darwin's theories on evolution--above all (and in Huxley's day, most controversially) for the evolutionary relationship between apes and humans. Moreover, Huxley's ideas and positions on a range of different scientific and social issues enjoyed great recognition and respect among his contemporaries, both in the general public and in the scientific community.

With the Dinosaur Renaissance in the late 1960 and early 1970s, Huxley's ideas about the close evolutionary connections between birds and dinosaurs saw a revival, with general confirmation of his insights.

For a good discussion, see:

Switek, Brian (2010) Thomas Henry Huxley and the reptile to bird transition. Dinosaurs and Other Extinct Saurians: A Historical Perspective; Geological Society, London, Special Publications 343:251-263, doi:10.1144/SP343.15





His historical importance notwithstanding, Huxley had views on evolution that sometimes were at odds with those of Darwin--and with modern thinking. His ideas also changed over time and he never truly developed a complete or consistent theory of his own.

My main source for Huxley's approach to evolution has been this book:

Lyons, Sherrie L. (1999) Thomas Henry Huxley: the Evolution of a Scientist. Prometheus Books, New York pp. 347.




Based on the Lyons book and a number of additional sources, some of the key phases of Huxley's thinking over time might be summarized very roughly in this form.

Pre-Darwin Period

Influence of Estonian embryologist Karl Ernst von Baer (1792-1876) (wrote in German)

Influence of geologist Charles Lyell (1797-1875 ) (pre-Darwinian phase)

Persistent types (general rejection of idea that the history of life is progressive, similar to early Lyell)

Influence of Darwin

Friendship and correspondence with Charles Darwin, who wanted to recruit Huxley to the evolutionary cause (1850s)


Huxley adopts Darwin's ideas about evolution after publication of the Origin in 1859, but with reservations about progress (vs. "persistent types"), about gradual rates of incremental change and the lack of fossil evidence for gradually changing intermediate forms (vs. "saltation" or sudden or rapid changes in species), and about natural selection (problems of "hybrid sterility," etc.).


1876 and after

Visit to America and meeting with O.C. Marsh at Yale, who gave Huxley a guided presentation of the extensive North American horse fossil collection--which prompted Huxley to drastically revise his views on the process of evolution. He saw Marsh's horse sequence as "proof" of progressive evolution. Huxley then proposed that progress is inherent in evolution in an orthogenetic pattern, with natural selection acting more as a trigger that stimulates or modifies progressive changes already inherent or predetermined in a particular evolutionary lineage, evoking parallels to embryonic development of an organism toward a fully mature individual of a species that represents a distinct, morphological "type" (with continuing influence of von Baer).



In nearly all of his work on taxonomy, Huxley made a clear distinction between classifications based purely on morphology and more speculative classifications based on evolution. This split approach was clearly followed in both his 1875 classification of "Crocodilia" (with Eusuchia) and his 1880 (published 1881) classification of mammals (with Eutheria).



At least three examples of adding the prefix *eu*- to a higher category name predate Huxley's combination Eusuchia in 1875.

Euganoidei LÃtken, 1868 [1869] "typical ganoids"

Danish zoologist Christian Frederik LÃtken (1827-1901) published discussions of Darwin in Danish, but remained critical of the theory.



LÃtken used the name Euganoidei [as Euganoiderne with Danish ending] (pg. 40) in a paper published in Danish in January, 1869 as a supplement to the 1868 volumes of Videnskabelige Meddelelser fra Dansk naturhistorisk Forening i KjÃbenhavn.


LÃtken, Christian. 1868 [1869]. Om Ganoidernes Begraendsning og Inddeling. of Videnskabelige Meddelelser fra Dansk naturhistorisk Forening i KjÃbenhavn 1868 1-82, 14 text-figs.

LÃtken provided a summary version in French 1871, which was then translated into English and appeared the same year in The Annals and Magazine of Natural History Vol. 7 (329-339), using the fully Latin name form Euganoidei.



The full paper appeared in a German translation in Palaeontographica in 1876.



Euichthyes Claus, 1872 "true fishes"

German zoologist Carl Friedrich Wilhelm Claus (1835-1899) reportedly appreciated Darwin's theory, but found it left some unanswered questions and thought that the "great riddle of evolution" still remained to be solved.

He used the name Euichthyes in 1872 in the second edition of his textbook on zoology:

Euichthyes Claus, 1872 "Echte Fische" ("true fishes") [pgs. xi and 834]

Claus, Carl. 1872. GrundzÃge der Zoologie. Volume 1 (2nd edition)



Eutheria Gill, 1872 "full mammals"

The American ichthyologist Theodore Gill (1837-1914), who worked at the Smithsonian for nearly 50 years , is now a rather overlooked figure.





He supported evolution and Darwin in general , but, as a Neo-Lamarckian, maintained doubts about the adequacy of "unaided" natural selection to explain the results of evolution, :


Gill, Theodore (1881) The Doctrine of Darwin. Proceedings of the Biological Society of Washington 1 (1880-1881): 47-55


Reservations about natural selection expressed in:


Address by Theodore Gill, the retiring president. EDWARD DRINKER COPE, NATURALIST â A CHAPTER IN THE HISTORY OF SCIENCE. American Association for the Advancement of Science s.n., 1898


Gill's Classification of Mammals

Gill used the name Eutheria in 1872 in the table of contents at the front of a pamphlet on the classification of mammals. Eutheria (in context, "full mammals") were a subgroup ("infraclass") within the class Mammalia that encompassed the two subclasses Placentalia (or Monodelphia) and Didelphia (Marsupialia)--making Eutheria Gill equivalent to Theria in modern usage--and contrasting with the Prototheria ("primitive mammals"), subclass Ornithodelphia (monotremes):

Sub-Class (Eutheria) Placentalia s. Monodelphia

Sub-Class (Eutheria) Didelphia

Sub-Class (Prototheria) Ornithodelphia

Gill, T. 1872. Arrangement of the families of mammals. With analytical tables. Prepared for the Smithsonian Institution. Smithsonian Miscellaneous Collections 11(1): 98 pp.





A few years later Gill became the main contributor of articles on zoology for the American encyclopedia Johnson's New Universal Cyclopaedia. (O.C. Marsh and E.D. Cope also contributed articles on paleontology and other topics.)

Gill's articles "Mammalogy" (the history of mammal classification and studies) and "Mammals" appeared in Johnson's New Universal Cyclopaedia vol. 3. (1877 edition). On page 252, he provided additional explanations for his distinctions between Eutheria and Prototheria based on anatomical grounds, and provided a branching diagram of proposed mammal evolution and relationships:



Gill apparently expected this encyclopedia article to be treated as a valid and original scientific publication, putting forth his own theories (which he evidently did not discuss in any detail in more conventional scientific print venues).

Of special note was Gill's grouping of marsupials and placentals together (as sister groups in modern terms) under the Eutheria, based on a suite of shared anatomical features, in contrast to the usual grouping at the time of monotremes and marsupials together (as proposed by Owen). Gill followed Bonaparte's 1837 classification in dividing placentals based on brain features into Educabilia (two or three brain lobes) and Ineducabilia (single brain lobe). However, Bonaparte had classified marsupials and monotremes together in a separate subclass he called the Ovovivipara based on Owen (implying that they produced internal eggs at some stage of reproduction, a physiological detail still largely deduced from anatomy and not yet confirmed or disproved by direct scientific evidence).

Gill (1877) contrasted the more "reptile-like" Prototheria ("primitive mammals," again, without knowing that they laid reptile-like eggs) with the Eutheria ("full mammals" with teats, etc., for marsupials and placentals), noting that marsupials represented a less developed stage of evolution than placentals.

A still unanswered historical question is whether Huxley saw or read Gill's 1872 or 1877 classifications of mammals with the names Eutheria and Prototheria, which Huxley used in his 1880 classification of mammals discussed below.




Eusuchia Huxley, 1875 "complete crocodilians"

In April 1875, Huxley gave a talk on the classification and evolution of the Crocodilia to the Geological Society of London, published a few months later in the Quarterly Journal:

Huxley, Thomas H. 1875. On *Stagonolepis* robertsoni, and on the evolution of the Crocodilia. Quarterly Journal of the Geological Society of London. 31: 423-438, with pl. x.


Huxley divided the Crocodilia into three suborders based on morphology, but also noted that these taxa formed a sequence of anatomical changes that could also reflect the evolution of crocodilians from the Triassic to present:

Parasuchia Huxley, 1875 "near crocodilians"--transitional between Huxley's generalized Lacertilia and typical crocodiles, combining "lacertian" and crocodilian features in their anatomy.

Mesosuchia Huxley, 1875 "intermediate crocodilians" --transitional between the Parasuchia and the Eusuchia

Eusuchia Huxley, 1875 "complete crocodilians"-- "the most Crocodilian of Crocodiles" (1875: 429); "those Crocodilia which depart most widely from the Lacertilian type and are the most completely specialised Crocodiles." (1877: 41)

"The kind of change which would convert a Parasuchian Crocodile into a Mesosuchian, would, if continued, convert a Mesosuchian into a Eusuchian. Hence, if there is any valid historical foundation for the doctrine of evolution, the Eusuchia ought to have been developed from the Mesosuchia, and these from the Parasuchia; and if this process of evolution has taken place under such conditions that the skeletons of the Crocodilia which have been subject thereto have been preserved, geological evidence should show that the Parasuchia have preceded the Mesosuchia, and the Mesosuchia the Eusuchia, in order of time. " (1875: 429)


Huxley later provided a more detailed description of *Stagonolepis* and a slightly revised discussion of the classification of crocodiles. He also added Haeckel's hypothetical Prosuchia (pg. 43) to the series as intermediate between the Lacertilia (sensu Huxley) and the Parasuchia.


Huxley, Thomas Henry. 1877. The crocodilian remains found in the Elgin sandstones, with remarks on the ichnites of Cummingstone. Memoirs of the Geological Survey of the United Kingdom (Brit. organ. Rem.), Monograph III 1-58, pls. I-XVI.


A "transitional, intermediate" meaning for para- is indicated in what Huxley said about *Stagonolepis*, *Parasuchus*, and Parasuchia, citing a mix of "lizard-like" and crocodile-like features:

In *Stagonolepis* : "The humerus is more Lacertian than that of existing Crocodiles in the expansion of its ends, and the presence of a ridge and groove on the radial side of its distal end. The ilium differs from that of existing Crocodiles and is more Lacertian..." (1875: 425)


"Prof. Huxley, in reply, stated that the Indian Crocodile (*Parasuchus*) was very like *Belodon* in the jaw and teeth, the scapula and coracoid, the vertebras, the ilium and the tibia. The tibia had the proximal end like that of a Lizard, the distal like that of a Crocodile." (1875: 437)


"In fact I know of no other reptile in which the skull and pectoral arch so nearly approach the structure found in *Belodon* and *Stagonolepis* [members of the Parasuchia] as they do in *Hatteria* [*Sphenodon*, a member of Huxley's Lacertilia]. On the other hand, the Eusuchia are those Crocodilia which depart most widely from the Ornithoscelida [Dinosauria] and Lacertilia, and are the most Crocodilian of Crocodiles." (1875: 429)


Huxley's roughly linear classification of "Crocodilia" in successive morphological and evolutionary stages stands in contrast to his proposed "extremely polyphyletic" (Gregory 1910) evolutionary classification of mammals presented a few years later in 1880. A possible explanation may be that for Huxley the modern crocodilians all fall within a particular "morphological type"--unlike the disparate and highly specialized "morphological types" found in the wide range of modern placental mammals.



Eutheria Huxley, 1880 and the 1876 Visit to America

A major turning point in Huxley's approach to evolution came during his visit to America in 1876, where he had been invited on a lecture tour. For the historical background, see:

Jensen, J. V. (1988) Thomas Henry Huxley's Lecture Tour of the United States, 1876. Notes and Records of the Royal Society of London 42(2): 181-195



O.C. Marsh provided a rather self-flattering account of Huxley's revelatory visit to Yale in his 1895 obituary for Huxley:

"One of Huxley's lectures in New York was to be on the genealogy of the horse, a subject which he had already written about, based entirely upon European specimens. My own explorations had led me to conclusions quite different from his, and my specimens seemed to me to prove conclusively that the horse originated in the New World and not in the Old, and that its genealogy must be worked out here. With some hesitation, I laid the whole matter frankly before Huxley, and he spent nearly two days going over my specimens with me, and testing each point I made. He then informed me that all this was new to him, and that my facts demonstrated the evolution of the horse beyond question, and for the first time indicated the direct line of descent of an existing animal. With the generosity of true greatness, he gave up his own opinions in the face of new truth, and took my conclusions as the basis of his famous New York lecture on the horse. He urged me to prepare without delay a volume on the genealogy of the horse, based upon the specimens I had shown him. This I promised, but other work and new duties have thus far prevented."



Huxley's biography and published letters by his son Leonard (1860 â 1933) added an oft quoted detail, but the original source is not stated (a letter, a family anecdote? ):

By Leonard Huxley Leonard Huxley

Huxley, L. Life and Letters of Thomas Henry Huxley.

Vol. 1


Vol. 2.



"At each inquiry, whether he had a specimen to illustrate such and such a point or exemplify a transition from earlier and less specialised forms to later and more specialised ones, Professor Marsh would simply turn to his assistant and bid him fetch box number so and so, until Huxley turned upon him and said, 'I believe you are a magician; whatever I want, you just conjure it up.'" (vol. 1, pg. 495)



Huxley famously revised his third lecture on evolution ("The Demonstrative Evidence of Evolution") to incorporate Marsh's horse fossils, including Marsh's illustration of the successive anatomical changes in the teeth and limbs of horses over time. He noted that the Yale fossil collection showed that the origin of the horse occurred in America, not in Europe, and that the details of the horse's ancestry were far better preserved in the fossil record of America than in Europe--both details no doubt sources of pride and pleasure for his American audiences.

Huxley, T. H. (1877) American Addresses: With a Lecture on the Study of Biology.



The broader impact of Huxley's visit to Yale and his rethinking of the process of evolution can be seen in his article on Evolution in 1878 for the 9th edition of the Encyclopaedia Britannica:



Huxley, T.H. (1878). Evolution in Biology. Encyclopaedia Britannica. 9th ed., 8: 744â775

"How far 'natural selection' suffices for the production of species remains to be seen. Few can doubt that, if not the whole cause, it is a very important factor in that operation; and that it must play a great part in the sorting out of varieties into those which are transitory and those which are permanent.

But the causes and conditions of variation have yet to be thoroughly explored; and the importance of natural selection will not be impaired, even if further inquiries should prove that variabilitv is definite, and is determined in certain directions rather than in others, by conditions inherent in that which varies. It is quite conceivable that every species tends to produce varieties of a limited number and kind, and that the effect of natural selection is to favour the development of some of these, while it opposes the development of others along their predetermined lines of modification."


Huxley's phrase " predetermined lines of modification" is open to different interpretations. Some of his contemporaries took it to mean that Huxley supported the idea of "design" in evolution. However, in correspondence from 1888 (pgs. 56-57), Huxley firmly rejected the misinterpretation.


Thomas Henry Huxley Life and Letters of Thomas Henry Huxley, Volume 3,(pgs . 56-57),


In the conclusion of the Britannica Evolution article, Huxley cited the evolution of horses as "fully worked out," and referred to his own work on "the gradations between birds and reptiles" and on "the modifications undergone by the Crocodilia, from the Triassic epoch to the present day" as providing additional support for evolution.


"Those who desire to inform themselves of the nature and extent of the evidence bearing on these questions may consult the works of RÃtimeyer, Gaudry, Kowalewsky, Marsh, and the writer of the present article. It must suffice, in this place, to say that the successive forms of the Equine type have been fully worked out; while those of nearly all the other existing types of Ungulate mammals and of the Carnivora have been almost as closely followed through the Tertiary deposits; the gradations between birds and reptiles have been traced; and the modifications undergone by the Crocodilia, from the Triassic epoch to the present day, have been demonstrated. On the evidence of palaeontology, the evolution of many existing forms of animal life from their predecessors is no longer an hypothesis, but an historical fact; it is only the nature of the physiological factors to which that evolution is due which is still open to discussion."


Eutheria and Huxley's Odd Phylogeny of Mammals

In November 1880 (published 1881), Huxley presented an evolutionary classification of mammals to the Zoological Society, identifying as well a set of "laws" for evolution.



Huxley, T. H. (1880) [1881] On the Application of the Laws of Evolution to the Arrangement of the Vertebrata, and more particularly of the Mammalia. Proceedings of the Zoological Society of London 43(4): 649-661

(1880 date on title page but November 1880 meeting content was published April 1881 according to a note at the end of the last 1880 issue. See:

https://www.biodiversitylibrary.org/item/90456#page/918/mode/1up )


His stages or grades of mammalian evolution were given as the following (indicated meanings are based on Huxley's own terms and phrases):

Hypotheria "sub-mammals" [NOT "hypothetical mammals" as sometimes misread] -- A hypothetical stage between amphibians and true mammals, not then known in the fossil record. Huxley rejected a reptilian stage for mammal ancestry as proposed by Owen and Cope. Huxley cited the glandular skin in both amphibians and mammals among the evidence for a non-reptilian descent.

Prototheria "primal mammals" -- represented by monotremes among living mammals. Huxley did not know in 1880 that monotremes laid eggs the way reptiles do (see above).

Metatheria "intermediate mammals" -- represented by marsupials among living mammals, a stage between the Prototheria and the more advanced Eutheria.

Eutheria "higher mammals"-- for placentals, divided into forms with deciduate placentas (placenta shed at birth) and non-deciduate placentas (placenta reabsorbed). This distinction led Huxley to separate the non-deciduate Lemuroidea from the deciduate Primates (humans, apes, monkeys) as completely separate lines of evolution.

Huxley saw the Eutheria as the "main line" of evolution in vertebrate animals. The egg-laying Sauropsida (Reptiles and Birds) were still at a post-amphibian stage equivalent to the Hypotheria and "lie off the main line of evolutionâto represent, as it were, side tracks starting from certain points of that line." Similarly, the living monotremes and marsupials, although more specialized than the ancient Prototheria and the Metatheria stages, had stalled in some sense on the path of evolution. The existing orders of the Monodelphia (placentals) had each independently passed through a prototherian and metatherian stage during the Mesozoic.


Huxley evidently did not intend the Hypotheria, Prototheria, Metatheria, and Eutheria to be seen as true taxa but rather as names for hypothetical progressive stages or grades of evolution. The traditional morphologically based Monodelphia, Marsupialia, and Monotremata existed as taxonomic groups distinct from, but roughly coinciding with, his evolutionary stages.

Huxley's classification chart arranged the different suborders or groups in a series similar to Cuvier's classifications, grouping edentates and monotremes together, for example. The X indicates forms that are missing from the fossil record.



Huxley's 1881 paper poses a number of important puzzles, most notably his knowledge of Gill's 1872 and 1877 classifications of mammals.

The normally well read Huxley may have reused Gill's 1872 terms Prototheria and Eutheria without giving credit--or, a bit less likely but also possible, he may have been unaware of Gill's work and reinvented the terms by pure coincidence. I have not found any reference to Gill in the Huxley material available online or any direct evidence that Huxley had seen Gill's 1872 work.

During his 1876 visit to America, Huxley was given a four-hour sight-seeing tour of Washington, D.C., before he gave a talk at nearby Johns-Hopkins University, but apparently he did not visit the Smithsonian collections nor meet with Theodore Gill.

Gill later (1888) defended his categories Eutheria and Prototheria as valid terms, and dismissed Huxley's Eutheria and Prototheria as "unnecessary" and simply synonyms of the older Monodelphia and Ornithodelphia.


Gill, T. 1888. Eutheria aud Prototheria. American Naturalist, 22 (March, 1888): 258,259


Huxley assumed a vast number of hypothetical forms not yet known from fossils to fill in gaps in his proposed system, including prototherian and metatherian stages during the Mesozoic for carnivorans, horses, etc. Haeckel similary had created numerous hypothetical evolutionary higher taxa to fill out his phylogenies (Promammalia, Prodinosauria, etc.), as well as hypothetical geologic time periods where crucial evolutionary events occurred and fossils were lacking. (Huxley did not accept Haeckel's hypothetical geologic periods, however).



Huxley also appeared to have found a partial clue to the "nature of the physiological factors" in evolution mentioned in his 1878 Britannica article on evolution cited above:

"It is of profound interest to remark that this law, or generalized statement of the nature of the ancestral evolution of the Horses, is precisely the same as that which formulates the process of individual development in animals generally... This coincidence of the laws of ancestral and individual development creates a strong confidence in the general validity of the former and a belief that we may safely employ it in reasoning deductively from the known to the unknown."

Huxley also put aside his earlier resistance to "progress" as a basic pattern of evolution over time (which Darwin had accepted as a general (but not a necessary) result of natural selection) and now endorsed a progressive path of lower to higher forms as a fundamental process in evolution:

"For though no one will pretend to defend Bonnet's 'Ãchelle' at the present day, the existence of a 'scala animantium' [ladder of living things] is a necessary consequence of the doctrine of evolution; and its establishment constitutes, I believe, the foundation of scientific taxonomy."


His earlier phrase "predetermined lines of modification" apparently had taken on a more precise meaning--that is, the potential stages and results of evolution were in a sense established from the very origin of an evolutionary lineage that then proceeded from a generalized to a specialized form, roughly analogous to how the embryo of an animal developed from an early generalized form to a fully developed member of a distinct species by preset internal processes established at conception.

Most strikingly, Huxley extended a polyphyletic origin for the different suborders of Eutheria or placental mammals to an extreme. One of the most puzzling aspects of Huxley's classification of the mammals is his insistence that each group of placental mammals had no "genetic connection" to any other, and instead each represented an independent line of evolution tracing back to the hypothetical Hypotheria--requiring that such basic features as hair, warm-bloodedness, advanced heart and circulation, only two sets of teeth, etc., in addition to a placental form of reproduction and long embryonic development, evolve in parallel repeatedly and not as shared inheritance by descent from a common ancestor.

"In discussing the relations of the various existing groups of the higher Mammalia with one another, it would be a mistake to attempt to trace any direct genetic connection between them. Each, as the case of the Equidae suggests, has probably had a peculiar line of ancestry; and, in these lines, Eutherian forms with deciduate placentation constitute the latest term..." 

Huxley applied this approach to the evolution of all placental mammals, not just horses, in a way that put him at odds with Haeckel (1866), who had depicted placental mammals as branching as a group from marsupials after the end of the Cretaceous (during a hypothetical Anteocene, missing from the geological record), with marsupials and placentals on a separate branch from monotremes that dated back to a hypothetical pre-Triassic period (Ante-Trias), and the living marsupials on a separate branch from the marsupials ancestral to placentals.


Eutheria after Huxley

The name Eutheria has had a complicated history, with different usage in America (where Eutheria Gill, 1872 was used into the early 20th century to group together marsupials and placentals) and in Britain (where Eutheria Huxley was repurposed by Flower in 1883 as a preferred taxonomic synonym for Monodelphia Blaineville, 1834 or Placentalia Bonaparte, 1838).


Eutheria Gill in America

American paleontologist Jacob Wortman explained Eutheria in 1886 as proposed by Gill, noting Huxley's usage "without credit" of Gill's names Prototheria and Eutheria (footnote, pg. 394).


Wortman, Jacob Lawson. 1886. The comparative anatomy of the teeth of the Vertebrata. American System of Dentistry (Philadelphia) 351-504, figs. 187-269, pls. I-VI.

In addition, Cope, Osborn, and Hay used Eutheria as Gill had and credited him with authorship.



Eutheria Huxley in Britain

The name Eutheria Gill, 1872 initially appeared to be unknown to most British researchers--or possibly was ignored, given Huxley's prestige at the time. However, Huxley's 1881 paper was reinterpreted in a number of important ways.

In 1883 the British zoologist William Henry Flower (1831--1899) used Huxley's Eutheria, Metatheria, and Prototheria as the preferred synonyms for the then still widely used Monodelphia, Didelphia (Marsupialia), and Ornithodelphia (Monotremata)--thus converting Huxley's hypothetical evolutionary stages into conventional taxa, the status accepted by other British authors. (So far, I have not been able to find an earlier formal usage of Huxley's names Eutheria and Metatheria for true taxa.)

Flower's revised usage first appeared in 1883 in volume 15 of the 9th edition of the Encyclopaedia Britannica (pg. 371). Shortly after, Flower presented an abstracted version of the article to the Zoological Society of London:

"These three groups are often called by the names originally proposed for them by Blainvilleâ(1) Ornithodelphia, (2) Didelphia, (3) Monodelphiaâ the first being equivalent to the order Monotremata, the second to the Marsupialia, and the third including all the remaining members of the class. Although actual palaeontological proof is wanting, there is much reason to believe that each of these, as now existing, are survivors of distinct branches to which the earliest forms of Mammals have successively given rise, and for which hypothetical branches Professor Huxley has proposed the names of Prototheria, Metatheria, and Eutheria, names which, being far less open to objection than those of Blainville, are here used as equivalents of the latter."

Mammalia in Encyclopaedia Britannica 19th Edition, 1883, vol. 15, pg. 371:



Proceedings of the Scientific Meetings of the Zoological Society of London. 1883, pg. 180:


Flower, W. H. 1883 On the Arrangement of the Orders and Families of existing Mammalia. The Proceedings of the Scientific Meetings of the Zoological Society of London. 1883: 178â186.

Full article:




Flower's explicit redesignation of Huxley's Eutheria, Metatheria, and Prototheria as names for conventional taxa in place of Blainville's names became common British usage that eventually prevailed in most scientific literature, including in America. However, Simpson (1945) apparently overlooked Flower's role and attributed this later usage more to "confusion":

Simpson 1945

"Despite Huxley's decidedly different usage, his terms were confused with Gill's, and the names Eutheria, Metatheria, and Prototheria are now almost invariably used for taxonomic, phyletic divisions to include the Placentalia (not also Marsupialia as in Gill's original usage), Marsupialia, and Monotremata, respectively. Although these terms have poor authority in the light of original definitions, they are so widely accepted and so generally understood in these senses that it would be puristic to reject them or to attempt to maintain their forgotten original significations. They are used in the present classification in the way usual in other recent work." (pg. 164)

Simpson, George Gaylord (1945) The principles of classification and a classification of mammals. Bulletin of the American Museum of Natural History 85: 350 pp.




Although Huxley's proposed three progressive stages of mammal evolution (Prototheria > Metatheria > Eutheria) were accepted in some form, his extremely polyphyletic derivation of each distinct order of mammals from a separate origin out of the Hypotheria was usually rejected--although not a possible origin of mammals from amphibians rather than from reptiles. (Note that the idea that placental carnivores may have evolved from marsupial carnivores turned up from time to time in some later authors, with either creodonts or Insectivora interpreted as intermediate between marsupials and true Carnivora.) Also, the two-way division of the Eutheria into forms with deciduous and nondeciduous placentas (a split already set out by other authors before 1880) was later recognized as over-simplified and that there was a complex variety of placental structures among even related types of mammals (lemurs and monkeys within primates, for example).

A good early example of how Huxley's ideas and terminology were adopted and modified early on in an academic context can be found in this 1885 British textbook:

Herdman, W. A. (1885) A Phylogenetic Classification of Animals: (for the Use of Students). Macmillan and Company, London.



For a classification of mammals using Huxley's terms as conventional taxa as in Flower 1883 (pages 67-68):


Note that the evolution of mammals was depicted as a branching pattern from a single ancestral stock, more consistent with Darwin's approach and not based on Huxley's extremely polyphyletic scheme.

See table following text:



Parker's "Noble Beasts" for Eutheria

The earliest attempt that I can find to present Huxley's terms Prototheria, Metatheria, and Eutheria to a more general audience came in 1884 in a series of lectures by British zoologist William Kitchen Parker (later honored by Broom with the name *Euparkeria*, as mentioned above!), published a few months later in book form with added footnotes.

Parker, William Kitchen (1885) On Mammalian Descent: The Hunterian Lectures for 1884. Charles Griffin & Company, London





As noted near the beginning of this post, the Ancient Greek adjective *eus* could also mean "noble." Parker played on this ancient meaning (Greek then being taught in schools) as a possible interpretation of the name Eutheria throughout his mammal lectures, with a certain Victorian imperialist (if not to say, bloodthirsty!) gusto:

"...Marsupials are intermediate between the Monotremes and the placental or nobler forms of mammals (Eutheria). (pg. 59)


...if Nature had not dispossessed the Metatheria, and placed nobler beasts in their room, we ourselvesâthe Eutheria of the Eutheria, the noblest of the nobleâshould have had no existence... (pg. 66)


The noble races show no mercy to the ignoble; when Nature elected that the Eutheria should increase, and multiply, and fill the land, then she practically culled out, and appointed for slaughter, these poor silly pouch-bearers, the Metatheria." (pg. 81-82)


While a meaning "noble beasts" or "noble mammals" was not adopted beyond Parker's work, the name Eutheria was interpreted in a variety of ways by different authors (mainly British) in textbooks and other technical or reference sources: "good mammals," "high beasts," "high mammals,""highest mammals," "perfect mammals," "complete mammals," "typical mammals," "proper mammals," "full mammals," "true mammals," etc., usually to emphasize the presumed superiority of placentals over marsupials and, more obviously, monotremes.

As suggested above, Gill's probable intended meaning for Eutheria would have been something like "full mammals" (to contrast marsupials and placentals with the more primitive (and teatless) Prototheria), while Huxley used the phrase "higher mammals" in association with his Eutheria to indicate that they were more advanced than the Metatheria and Prototheria evolutionary stages.


Theria Parker and Haswell, 1897

As noted earlier, from a modern perspective, Gill's Eutheria as a group to unite placentals and marsupials was an important evolutionary insight, contrasting with Owen's grouping of monotremes and marsupials together as Implacentalia or Ovovivipara. However, the later name Theria Parker and Haswell, 1897 has been adopted in place of Eutheria in Gill's original sense, based mainly on Gregory 1910 and Simpson 1945.

Theria (pg. 448)


Parker, T. J. & Haswell, W.A. (1897) A text-book of zoology. (vol. 2). Macmillan and Company, London




Eutheria in the 1990s and beyond

Both Placentalia and Eutheria remained in use after Simpson 1945.

McKenna and Bell (1997) noted this inconsistent usage and chose Placentalia over Eutheria:

M. C. McKenna, and S. K. Bell (1997) Classification of Mammals Above the Species Level. Columbia University Press, New York. 631 pp.

page 80, explained in footnote:

'Huxley's EUTHERIA may not have been taken from Gill, 1872. EUTHERIA Gill, (1872) covered both marsupials and placentals and until recently lay fallow. EUTHERIA Huxley, 1880 covered "placentals" and putative "placentals," but not members of the MARSUPIALIA as well. Huxley's term was accepted for nearly a hundred years by most students (but not by Osborn, 1910: 515). Moreover, re-elevation of Gill's original EUTHERIA to become a senior synonym of THERIA creates new confusion... In an attempt to avoid argument about the "true meaning" of EUTHERIA, we return here to Owen's PLACENTALIA, endorsed by Gill himself in preference to MONODELPHIA = "les monodelphes" de Blainville, 1816: 109.'




However, in the late 1990s, a group Eutheria that was not a total synonym of Placentalia took on a new role as the clade containing extinct groups more closely related to placentals than to marsupials, with Placentalia as the crown group, along with various extinct stem groups. Similarly, Metatheria contained the crown group Marsupialia, along with extinct stem groups more closely related to Marsupialia than to Eutheria.



Rougier, G.W., Wible, J.R. and Novacek, M.J. (1998) Implications of Deltatheridiun specimens for early marsupial history. Nature 396: 459â463.


Archibald, J. D. (2001). Eutheria; pp. 1â4 in Encyclopedia of Life Sciences.Macmillan Publishers, Nature Publishing Group, London.



Eutheria is usually given a stem-based (maximum-clade) definition:

"Eutheria Gill 1872 --The most inclusive clade containing Mus musculus Linnaeus, 1758 but not Didelphis marsupialis Linnaeus 1758."

Sereno, P. (2006). Part 3: 10. Shoulder Girdle and Forelimb Multituberculates: Evolution of Parasagittal Forelimb Posture in Mammals. In Amniote paleobiology: perspectives on the evolution of mammals, birds, and reptiles (eds Carrano M. T., Gaudin T. J., Blob R. W., Wible J. R.), pp. 315â366. Chicago, IL: University of Chicago




But a node-based (minimum-clade) definition is found as well:

"Huxley (1880) modified the scope of Eutheria, limiting it to Placentalia only. We follow Huxley's [1880] modification of Eutheria node-based definition of the group, that is, the most recent common ancestor of all living placentals, plus all of its descendants."

Kielan-Jaworowska Z., Cifelli R. L. & Luo Z.-X. 2004. Mammals from the Age of Dinosaurs. Origins, Evolution and Structure. New York: Columbia University Press. 630 pp

Some objections have been raised. Kemp (2005), for example, argued that a clade Eutheria in this sense was likely paraphyletic and used Placentalia as in McKenna and Bell (1997).

"Others, particularly Kielan-Jaworowska et al. (2004) discriminate between the two, using Placentalia for the living groups and their fossil relatives, and Eutheria for the more inclusive group consisting of these plus their stem-group. The problem is that the relationships of the various early fossil members to living placentals is far from safely established, and therefore Placentalia in Kielan-Jaworowska et al's sense may be a paraphyletic group. McKenna and Bell's terminology is therefore adopted in the present work." (pg. 169)

T. S. Kemp (2005) Origin and Evolution of Mammals. OUP Oxford, 331 pp.

entire book is available here:




Currently, Eutheria remains the common choice for early extinct forms related to or potentially directly ancestral to placentals:

"Eutherian mammals (Placentalia and all mammals phylogenetically closer to placentals than to marsupials)..."

Steven C. Sweetman, Grant Smith, and David M. Martill (2017)

Highly derived eutherian mammals from the earliest Cretaceous of southern Britain.

Acta Palaeontologica Polonica 62 (4), 2017: 657-665 doi:https://doi.org/10.4202/app.00408.2017




In current literature, the name Eutheria is cited in multiple ways for author and date, most often as either Eutheria Gill, 1872 or as Eutheria Huxley, 1880.

A possibly more accurate way to cite Eutheria based on its historical and modern usage would be:

Eutheria Huxley, 1881, sensu Flower, 1883 (non Gill 1872)

This form would emphasize that the modern usage (excluding marsupials, included by Gill) derives from Huxley's restriction of the term Eutheria to placental mammals, but as applied by Flower as a standard taxonomic name for placentals (not merely as Huxley's intended name for a hypothetical evolutionary stage) . The 1881 date is the true date of publication for Huxley's paper (although the journal issue was dated "1880" on the cover). There is also apparently no direct evidence that Huxley or Flower acknowledged or perhaps even knew of Gill's earlier classification.

Similarly, Metatheria could be cited as: Metatheria Huxley, 1881, sensu Flower, 1883.

In more recent phylogenetic work, Huxley's original use of Eutheria and Metatheria for evolutionary stages has been recast as anticipating clades with a broader definition beyond the living (crown) groups of Placentalia and Marsupialia, and thus including related extinct groups. This new perspective on Huxley's work strengthens the case for citing him as the author of Eutheria, despite his (fairly absurd in modern terms) polyphyletic ancestry scheme for different mammal groups.




As a final note on the prefix *eu*-, it may be good to remember a version of what might be called the "Humpty Dumpty Rule" in nomenclature (which I would credit to the late Don Baird):

from Lewis Carrol in Through the Looking Glass:

"When I use a word," Humpty Dumpty said, in rather a scornful tone, "it means just what I choose it to meanâneither more nor less." "The question is," said Alice, "whether you can make words mean so many different things." "The question is," said Humpty Dumpty, "which is to be masterâthat's all."

As noted in examples above, the prefix *eu*- had multiple meanings in Greek and has been used in multiple ways in zoological nomenclature.

In 1998, Jennifer Clack described an early tetrapod from East Kirkland in Scotland and gave it the name *Eucritta melanolimnetes*:

Jennifer A. Clack (1998)

A new Early Carboniferous tetrapod with a mÃlange of crown-group characters.

Nature 394: 66â69



The name was discussed in news stories at the time and explained as a reference to a well known 1954 3-D science fiction movie "The Creature from the Black Lagoon."

A reminder about the movie...

"A team of scientists hire a barge and a captain to sail up the Amazon river to find the fossil of a presumed fish-man, an evolutionary 'missing link' between sea and land creatures. To their astonishment they donât find a fossil, but a living, breathing gill-man â a humanoid unchanged since the Devonian age, in a remote lagoon."


Notable quotes include these  evolutionary insights:

"This lungfish - the bridge between fish and the land animal. How many thousands of ways nature tried to get life out of the sea and onto the land. This one failed."

"Except that the Kamongo fish, which has lungs, exists today here in the Amazon. It hasn't changed in millions of years. That doesn't prove the possibility of a gill-man. If the evolution of that species reached a dead end back then and still survived, why couldn't another?"



News stories:

The creature from the black lagoon

"Clack has given a fitting name to her subject: *Eucritta melanolimnetes*, the Creature from the Black Lagoon."




Creature from black lagoon found - in fossil form, that is

"Clack, a senior assistant curator at Cambridge University's zoology museum, said she first added the ancient Greek word 'eu' to American slang to indicate 'true critter.' That sounded rather nice, she said, and she added the 'black lagoon' part from the Greek because the creature lived by a hot-spring lake ...'




Jennifer A. Clack (2002) Gaining Ground: The Origin and Evolution of Tetrapods. Indiana University Press. 225 pp.

"*Eucritta*, based on the American vernacular word 'critter,' meaning 'creature,' and the specific name *melanolimnetes* meaning 'from the black lagoon,' a reference to the nature of the East Kirkton locality (Clack 1998a)."

However, an alternate explanation for the prefix *eu*- in the name was revealed in 2014:

"In 1998, the palaeontologist Jennifer Clack described a fossil to which she gave the name *Eucritta melanolimnetes* ('true creature from the black lagoon'). I have a suspicion that the prefix is merely an attempt to provide a classical gloss on the decidedly unclassical 'critta', however. I wrote to Professor Clack, and she kindly told me that the prefix merely expressed her view the creature was beautiful."

John Wright (2014) The Naming of the Shrew: A Curious History of Latin Names. Bloomsbury Publishing 265 pp.

For a video of a talk by the author:

The Naming of the Shrew | John Wright

Linnean Society



Understanding *Eucritta* as the "beautiful creature from the Black Lagoon" seems like a positive note to end on in 2017 when facing 2018. There were a number of "beautiful" fossils (exceptionally well preserved and complete, or providing important evolutionary evidence) described in 2017, and more are on the way for 2018--something to look forward to despite what perverted politics, mangling of monuments, rejection of science, fake content cable television documentaries, and natural disasters may be in store for the new year. In a few ways at least, 2018 may be a "good" year after all.





A New Year's Resolution of Sorts...

The following citation, still widely given as the supposed source for "Placentalia Owen, 1837," is an error that dates from Simpson 1945 and has been repeated in many later works (including McKenna and Bell 1997). This source should NOT be cited with the date given nor used as the source of Placentalia!

Simpson 1945 (pg. 47):

"Infraclass EUTHERIA Gill, 1872, p. 13 (= Monodelphia De Blainville, 1816, p. 109; Placentaria Fleming, 1822, p. 169; Placentalia Owen, 1837, p. 903)."

The 1837 citation for Owen was given as:


1837. Teeth. In Todd, Robert B., The cyclopaedia of anatomy and physiology. London, Sherwood, Gilbert, and Piper, vol. 4, pt. 2, pp. 864-935."

Volume 4 in fact has a 1849-1852 publication date. The passage cited by Simpson on page 903 makes a single mention of the name Placentalia (which was already in use as early as 1838):

Pg. 903:



The 1837 date for the article "Teeth" is wrong. The correct date would appear to be 1852, as indicated in the Bibliography section in volume 2 of Owen's biography by his grandson, which lists the articles Owen contributed to the Cyclopaedia of Anatomy and Physiology with the actual publication dates:

Articles in Todd's ' Cyclopedia of Anatomy.' [Acrita, 1836 ; Articulata, 1836 ; Aves, 1836 ; Cephalopoda, 1836 ; Entozoa, 1839 ; Mammalia, 1847 ; Marsupialia, 1847 ; Mollusca, 1847 ; Monotremata, 1847 ; Teeth, 1852.] (pg. 338)


Owen, R. (1894) The Life of Richard Owen. Vol. II. London, Murray


A correct citation for Owen's "Teeth" article (but NOT for Placentalia!) would be:

Owen, R. (1852) Teeth. In Todd R.B. (Ed.) The Cyclopaedia of Anatomy and Physiology Vol. 4 Part 2, pp. 864-935. London: Longman, Brown, Green, Longmans and Roberts, 1849-1852.




The actual history of the name Placentalia appears to be the following:

"placental Mammalia" in:

Owen, R. 1837. On the Structure of the Brain in Marsupial Animals. Philosophical Transactions of the Royal Society of London 127: 87-96


(Simpson may have had this paper in mind as the "Owen 1837" reference for Placentalia, but was misled about the true source.)

In his earlier works, Owen had used the combinations "true Mammalia," "normal Mammalia," and "ordinary Mammalia" for placentals (along with terms such as "placental generation") , with marsupials and monotremes seen as "aberrant" mammals (with monotremes as "edentate" marsupials). By 1837 Owen had recognized monotremes, marsupials, and placentals as distinct groups (a three-way division dating back to Blainville), but with monotremes and marsupials being "ovoviviparous" mammals (later renamed "implacental Mammalia" or Implacentalia).


On November 7, 1837, French biologist Charles Lucien Bonaparte (1803-1857) (a nephew of the emperor Napolean Bonaparte) presented his new classification of vertebrates to the Zoological Society of London, presumably in English. The exact order and dates for the published versions of Bonaparte's classification get a little complicated. However, the following summary version in Latin from 1838 included a footnote giving the Latin name Placentalia.

Bonaparte, C.L., 1838. Synopsis vertebratorum systematis. Nuovi Annali delle Scienze Naturali 2: 105-133 [in Latin] (Placentalia pg. 107, with footnote attributing Placentalia to Owen)




NOTE: This is the source given for Placentalia Bonaparte, 1838 cited recently in:

Jackson, S. & Groves, C. 2015. Taxonomy of Australian Mammals. Clayton South (Australia) : CSIRO Publishing , 536 pp.


Footnote in Latin (pg. 107):

"Divisionem vero in Placentalia atque Ovovivipara, etsi ab aliis adumbratam, certis limitibus hodie conclusam cl. Oweno, Anglo. debemus."

In close to literal translation:

"The division, however, into Placentalia and Ovovivipara, although outlined by others, now circumscribed with proper boundaries, we owe to the celebrated Englishman Owen."

The Latin names Placentalia and Ovovivipara to Owen were derived presumably from Owen's English forms "placental Mammalia" as published earlier in 1837 and "ovoviviparous Mammalia" from 1834. I have not found any evidence of special correspondence between Owen and Bonaparte on the topic.

["ovoviviparous or marsupial Mammalia" in:

Owen, R. 1834. On the Generation of the Marsupial Animals, with a Description of the Impregnated Uterus of the Kangaroo. Philosophical Transactions of the Royal Society of London 124: 333-364

https://www.jstor.org/stable/108068?seq=1#page_scan_tab_contents ]


Bonaparte's full work did not appear in print until the June 1840, number 3 issue of the Transactions of the Linnean Society of London. This version is still often cited as dating from 1837, the date the research was presented in public, not the date it was published in full.

Bonaparte, C. L. 1840. A new systematic arrangement of vertebrated animals. [Read November 7th, 1837] Transactions of the Linnean Society of London 18(3): 247â304 (June 1840) [in Latin]


(The entire bound volume 18 of the journal (including the later issue 4) did not appear in print until 1841.)


The full work (retaining the original page numbers) was republished in book pamphlet form with a Latin title, dated 1840:

Bonaparte, Charles Lucian. 1840. Systema vertebratorum. London, R. and J.E. Taylor .





Owen later took personal credit for the name Placentalia, as stated in his 1847 Cyclopaedia of Anatomy and Physiology article Mammalia:

"These primary groups or sub-classes I have named Placentalia and Implacentalia, indicative of the adherence of the ovum to the uterus in the one, and its non-adherence, as in the ovo-viviparous reptiles, in the other group." (pg. 244)


Owen, R. 1847. Mammalia. The Cyclopaedia of Anatomy and Physiology. vol. 3: 864â935.

The earliest use by Owen (anonymously) of the Latin form Placentalia appears to be in 1840 (published 1841). Owen used the Latin forms Sub-Class Placentalia (pg. 253) and Sub-Class Implacentalia (pg. 259) in the Zoological Index to Volume 5 to the Hunterian Museum Catalogue.

Owen, R. 1840 [1841] (Anonymous) Descriptive and Illustrated Catalogue of the Physiological Series of Comparative Anatomy Contained in the Museum of the Royal College of Surgeons in London: Products of generation, Volume 5. R. Taylor, London.






Based strictly on first publication in proper Latin form, this appears to be a better citation for Placentalia:

Placentalia Bonaparte, 1838 (ex "placental Mammalia" in Owen, 1837)


At the very least, Owen's name should be cited in parentheses to indicate his original 1837 form was different:

Placentalia (Owen, 1837) or Placentalia (Owen, 1837 as "placental Mammalia")






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