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Ben Creisler


The seasons of autumn in the Northern Hemisphere and spring in the
Southern Hemisphere bring to mind leaves on trees...so it may be as
good a moment as any to squelch a couple of etymological "myths" about
oak leaves.  The two "biggies" in vertpaleo are that  1) the Jurassic
dinosaur Dryosaurus Marsh, 1894 was named for teeth that resembled oak
leaves and that 2) the Miocene ape Dryopithecus Lartet, 1856 was named
after oak leaves found in the same deposits as the original fossil
bones. Based on primary sources, Dryosaurus means "tree lizard" (NOT
"oak lizard") and Dryopithecus means "tree ape" (NOT "oak ape")--and
neither name has anything to do with oak leaves.


Meanings of "Dryo-"

The Ancient Greek noun *drys* could mean a "tree" in general or an
"oak tree" in particular:


In Neo-Latin terminology and zoological nomenclature, compounds with
*drys* (*dry-*) commonly mean "tree" -- such as various generic names
proposed for tropical tree snakes (Dryophis "tree snake," Dryomedusa
"tree ruler," Dryonastes "tree dweller," Dryophylax "tree guardian"),
the mammal Dryoryx "tree pickax" (a synonym for Tamandua, a tropical
arboreal edentate with large claws), tropical island birds such as
Dryococcyx "tree cuckoo," Dryolimnas "tree rail" -- all animals with
no  association with oak trees. The more specific meaning "oak" for
names in dryo- is found with some generic names for insects that live
or prey on oak trees such as  Dryobius "oak living" and Dryophilocoris
"oak-loving bug."


Marsh's Official Etymologies

American paleontologist O. C. Marsh (1831-1899) published official
lists of his genera  with etymologies:

Marsh, O. C. 1880.  List of genera established by Prof. O. C. Marsh,
1862-1879.   Pp. 1-12. Privately published.

Marsh, O. C. 1889.  Additional genera established by Prof. O. C.
Marsh, 1880-1889.   Pp. 13-17. Privately published.

The two lists (1862-1879; 1880-1889) published during his lifetime
currently can be viewed and downloaded online at:


The Additional Genera 1880-1889 list is also included a second time in
the same bound volume, but without hand-written notes, at this link:


Marsh undoubtedly would have published a third list of genera with
etymologies in 1900 to cover his new generic names from 1890 through
1899 (including Dryosaurus), but his death in 1899 left the list

In lieu of an official third list, the online copy of Volume 4 of
Marsh's bound collected papers includes an inserted supplemental
type-written list for  generic names  that Marsh published between
1890 and 1896, with hand-written corrections,  additions, synonyms,
and Greek words . The compiler is not indicated for this supplemental
list. The indication of synonyms such as Triceratops flabellatus for
Sterrholophus would suggest that  the list was compiled after Marsh's
death. Nonetheless, the etymologies would appear to be accurate and
are consistent with Marsh's earlier etymologies. The only missing
generic name would be Telmatocyon Marsh, 1899.


[Scanning quality is very poor for some pages, however. The entire set
of six volumes of Marsh's collected works is found at this link:


Much better quality reproductions of some of the material can be found
on the Biodiversity Heritage Library website:

http://www.biodiversitylibrary.org/creator/12437#/titles   ]


Marsh's published lists put to rest a number of major and minor
misunderstandings about the meanings of his generic names.

Notably, Cimolestes means "Cretaceous robber"  as a contraction from
Greek *kimolia* "white earth" [= chalk (Cretaceous)] -- NOT "bug
thief" as if from Latin *cimex* after Bug Creek or a supposed insect
diet (per various online sources).


Some well known dinosaurs also have names with intended meanings
slightly different from those commonly given: Allosaurus  "strange
lizard"; Stegosaurus  "covered lizard";  Camptosaurus "flexible (back)

There are clear patterns to Marsh's nomenclature based on his
published descriptions and comments, with certain terms reused in
multiple names with similar intended meanings.

He used Greek *allos* (which he defined  as "strange") for forms with
"aberrant" or "peculiar" features compared to other related animals.
Thus for Marsh,  Allosaurus "strange lizard" had vertebrae that were
"PECULIARLY modified to ensure lightness"  for a dinosaur because the
centra had the weight reduced by excavation of the sides rather than
by internal pneumatic structures like those in the vertebrae of his
recently discovered and described dinosaurs Atlantosaurus and


The mammal group Allotheria "strange beasts"  were " highly
specialized ABERRANT forms, which apparently have left no descendants"
- -unlike the Pantotheria "all beasts," which Marsh thought gave rise
to living marsupials and insectivores.



Marsh used Greek *apatao* "deceive"  to indicate animals with some
feature that resembled that found in an unrelated form: Apatosaurus
"deceptive lizard" had tail chevrons resembling those of certain
mosasaurs; Apatornis "deceptive bird" had biconcave vertebrae like
those of fish; Apatemys "deceptive mouse" was an insectivore with
rodent-like incisors.


He also formed multiple names with Greek *limne* "morass, lake," Greek
*telma* (*telmatos*) "swamp"  and Greek *this* (*thinos*) "shore" for
animals found around ancient Eocene lakes in Wyoming:  Limnocyon,
Limnofelis, Limnohyops, Limnohyus, Limnophis, Limnosaurus,
Limnotherium, Telmalestes, Telmatherium, Telmatocyon, Telmatornis,
Thinocyon, Thinohyus, Thinolestes, Thinosaurus, Thinotherium.


Dryosaurus  Marsh, 1894 "tree lizard" (NOT "oak lizard," "oak tree
lizard," or "oak forest lizard")

Before he named Dryosaurus, Marsh gave the etymology for the Jurassic
mammal Dryolestes Marsh, 1878 as "tree robber" (*drys*, a tree, and
*lestes*, a robber):


The original description suggested Dryolestes was related to opossums
and was the size of a weasel, but offered no reason for Marsh's choice
of the name:



Given his patterns in forming names, it seems reasonable that Marsh
had a similar etymology and intended meaning for "dryo-" in the name
Dryosaurus for a dinosaur from the same Jurassic-age Atlantosaurus
beds as Dryolestes. (A meaning "oak robber" would make little sense
for Jurassic Dryolestes in any case!) Again, Marsh did not explain his
choice of the name Dyrosaurus -- nor was he able to publish an
official etymology, which he likely would have done in 1900 to match
his other lists of genera.

Although difficult to read, the typed supplemental list of genera  for
1890-1896 inserted in the collected papers gives the etymology for
Dryosaurus as "tree lizard" -- but Marsh himself presumably did not
provide the typed etymology.



The name Dryosaurus is now widely explained as meaning "oak lizard" or
"oak tree lizard" for the supposed resemblance of its teeth to oak
leaves.  See for example:





A supposed meaning such as  "oak(-leaf-toothed) lizard" for Dryosaurus
has NO basis in anything Marsh himself said anywhere. His descriptions
say nothing about the teeth of Dryosaurus (or of any other dinosaur)
resembling "oak leaves" -- and it is difficult to see any particular
resemblance to the typical rounded lobate pattern of oak leaves in
Marsh's single figured tooth for what became Dryosaurus:

As Laosaurus altus:


figures (including tooth)


As Dryosaurus




The best clue to Marsh's intended meaning of the name Dryosaurus
remains the earlier name Dryolestes from same Jurassic fossil beds.
Although the mammal  name Dryolestes "tree robber" might suggest an
opossum-like arboreal animal, it seems unlikely that Marsh thought of
the plant-eating dinosaur Dryosaurus "tree lizard" as normally
arboreal, given its estimated size (12 feet long according to Marsh)
and long legs. (Abel's  theory that Hypsilophodon was arboreal was not
proposed until 1912.)

Instead, the two names Dryolestes "tree robber" and Dryosaurus "tree
lizard" most likely alluded to an ancient forest habitat that Marsh
mentioned in a number of places. Trees would  have been a food source
for the leaf-eating Dryosaurus and a shelter from predators. [The
modern vision of Dryosaurus as a gazelle-like cursorial dinosaur fits
life in a more open environment.]

As early as 1877 Marsh stated that Atlantosaurus [as Titanosaurus]
"fed upon the foliage of mountain forests, portions of which are
preserved with its remains." [pg. 348]


Marsh, O. C. 1877.  Introduction and succession of vertebrate life in
America. Vice-president's address before Amer. Assoc. Adv. Science,
1877.  Amer. Jour. Sci. 3 pp. 337-378.

Geologist and fossil collector Arthur Lakes (1844--1917) provided a
more detailed vision of the world of the Atlantosaurus beds according
to Marsh during the Jurassic:

"Such were some of the monsters which enjoyed themselves in olden
times around the Rocky Mountains, then islets just peeping above an
inland sea in the marshes and bayous of these islets the Atlantosaurus
and other Dinosaurs enjoyed life, sometimes plunging in for a bath, at
other times walking boldly on the land and cropping the LEAVES FROM


Lakes, A. 1879. The Dinosaurs of the Rocky Mountains. The Kansas City
Review of Science and Industry 2 (12): 731-735

NOTE:  The article includes numerous typos for dinosaur names, but
provides an amusing anecdote about Marsh parodying a Tennyson poem
while removing the fossils of Stegosaurus (unnamed and still
interpreted as an armored aquatic reptile) from the hard matrix at
Yale. [pg.  734-735]


Marsh himself described the "Atlantosaurus beds" [Morrison] as a lush
forest environment surrounding great fresh-water lakes where animals
became fossilized, noting in 1897 that the "gigantic herbivorous
dinosaurs of the Jurassic were denizens of a tropical climate, in
which rank vegetation supplied them with food and served to protect
them from carnivorous enemies." [pg. 525]


Marsh, O. C. (1897) Paleontology. Section II. Vertebrate Fossils. in
Emmons S. F., Cross, W. and Eldridge, G. H. (1897). Geology of the
Denver Basin in Colorado. Monographs of the United States Geological
Survey, v. 27: 473--527.


Since neither the fossils for Dryolestes priscus nor the fossils for
Dryosaurus altus came from the "Three Trees" Quarry 7 at Como Bluff in
Wyoming, some trivial association with that quarry location in a name
alluding to trees seems excluded.

For quarry info see:

Ostrom, J. H., and J. S. Mcintosh. 1966.  Marsh's dinosaurs. The
collections from Como Bluff.   New Haven and London: Yale Univ. Press.
xiv + 388 pp., 13 figs., 155 pls.


As an additional side note, the Neo-Latin element  *hylaeo-* (from
Greek *hylaios* "belonging to a forest") was already established in
paleontology with the meaning "Wealden'' (from the forested Weald
region of southern England containing Early Cretaceous deposits) as in
Hylaeosaurus Mantell, 1833 "Wealden lizard" and Hylaeochampsa Owen,
1874  "Wealden crocodile"(found in Early Cretaceous rocks on the Isle
of Wight)-- so it would not have been appropriate. Nor would the very
similar spelling "Hylosaurus" (Greek *hyle* "forest") seem fitting
since it was close to Hylaeosaurus in meaning.

[A different take on the name Dryosaurus is found with the just
described Eousdyrosaurus, published with an etymology that interpreted
the name as "oak forest lizard":

"The generic name is derived from the Latin 'Eous,' eastern, and from
Dryosaurus, referring to an oak-forest lizard dweller to the east of
the proto-North Atlantic."

Fernando Escaso, Francisco Ortega, Pedro Dantas, Elisabete Malafaia,
Bruno Silva, José M. Gasulla, Pedro Mocho, Iván Narváez & José L. Sanz
(2014) A new dryosaurid ornithopod (Dinosauria, Ornithischia) from the
Late Jurassic of Portugal. Journal of Vertebrate Paleontology 34(5):
1102-1112 DOI:10.1080/02724634.2014.849715


Dryopithecus Lartet, 1856 "tree ape" (NOT "oak ape")

Unlike Marsh with Dryosaurus, French paleontologist Édouard  Lartet
(1801–1871) clearly stated how he wanted the name Dryopithecus to be

"La réduction des incisives s'alliant à un grand développement des
molaires indique un régime essentiellement frugivore. Le peu que l'on
connaît d'ailleurs de l'ossature des membres, dénote plus d'agilité
que d'énergie musculaire. On serait donc ainsi conduit à supposer que
ce Singe, de très-grande taille, vivait habituellement sur les arbres,
comme le font les Gibbons de l'époque actuelle; aussi proposerai-je de
le désigner par le nom générique de Dryopithecus (de drus (1), arbre,
chêne, et pithekos, singe)...


"(1) On croit avoir reconnu des troncs de chêne, de châtaignier et de
pin, dans des dépôts de lignites existants sur les premiers
contre-forts pyrénéens. Ces lignites sont probablement du même âge que
les gisements fossilifères de Saint-Gaudens et de Sansan, car j'y ai
recueilli des restes de mammifères appartenant à  la même faune." [pg.

Lartet, Édouard. 1856.  Note sur un grand singe fossile qui se
rattache au groupe des singes supérieurs.  C. R. Acad. Sci. Paris
XLIII 219-223, pl.



My rough translation:

"The reduction of the incisors combined with an enlarged development
of the molars indicates an essentially frugivore diet. In addition,
the little that is known of the bone structure of the limbs denotes
more agility than muscular strength. One would thus be led to suppose
that this ape, of very large size, habitually lived in the trees, as
do the gibbons of the present day;  therefore, I propose to give it
the generic name Dryopithecus (from drus (1), tree, oak, and pithekos,

"(1) What are believed to be the trunks of oaks, chestnuts and pines
have been identified in the lignite deposits in the foothills of the
Pyrenees. These lignites are probably of the same age as the fossil
beds of Saint-Gaudens and Sansan, for I have collected the remains of
mammals there belonging to the same fauna."


Lartet makes no mention of any oak leaves found in association with
the fossils. The fossil trunks of oaks and other trees were found
relatively near the area where the ape's fossils were unearthed,
indicating that a forest environment may have existed over much of the
region at the time. There is no stated direct association, however,
between Dryopithecus and oak trees  (it ate mainly fruit after all).

The shift in meaning from "tree ape" to "oak ape" or "oak forest ape"
apparently started with Scottish geologist Charles Lyell (1797

Lyell followed Lartet's explanation of the name Dryopithecus more or
less accurately in an 1857 supplement (the second edition) appended to
the 1855 edition of his popular Manual of Elementary Geology.

"The Dryopithecus is supposed to have been frugivorous and to have
climbed trees, whence its generic name, the trunks of oaks being
common in the lignite of Saint-Gaudens, at the foot of the Pyrenees,
where this fossil was obtained." [(2nd ed.) Supplement to the  1855
Fifth Edition, pg. 15]


Lyell, C. 1857. Lyell's Elementary Geology. Supplement to the Fifth
Edition. London. pp. 40. in Lyell, C.  1855. A manual of elementary
geology. John Murray, London. pp. 655.


In later editions of Lyell's works, an explanation of the name
Dryopithecus was incorporated into the main text, but simplified and
somewhat misleadingly reworded:

"As the trunks of oaks are common in the lignite beds in which it lay,
it has received the generic name of Dryopithecus."



What it is harder to pin down is where the idea that Dryopithecus was
named after oak LEAVES (instead of oak trunks) started. Romer gives
this explanation of the name in the book Man and the Vertebrates, but
it evidently predates Romer. Later sources have usually cited Romer in
explaining the name Dryopithecus as "oak ape" for an association with
oak leaves.

"Dryopithecus, the 'oak ape,' so called because of the presence of oak
leaves in the deposits from which the first remains of this form were
obtained." [pages 228-229]


Romer, A.S. 1937. Man and the Vertebrates. University of Chicago
Press, Chicago. (2nd ed.).

[Side note: The scientists posing with an obviously freshly shot
mountain gorilla might not be the ideal photo in a modern book....]

Some recent papers, textbooks, and other educational materials in
biology and anthropology still give the unfounded "oak leaves"
explanation for the name Dryopithecus.

For example:




For the record  then, the name Dryosaurus Marsh, 1894 should be
understood as "tree lizard"--most likely alluding to the Jurassic
tropical forest environment (with no oak trees!) that Marsh thought
the plant-eating dinosaur inhabited along with the similarly named
mammal Dryolestes "tree robber" (Marsh's published etymology). The
widely cited meaning "oak lizard" (also as "oak tree lizard," "oak
forest lizard") for Dryosaurus is a modern misunderstanding  that has
no basis in Marsh's published descriptions and ignores the alternative
meaning "tree" for Greek *drys* (dryo-) commonly used in zoological

Dryopithecus Lartet, 1856 should be understood as "tree ape" according
to the author's published etymology--for gibbon-like arboreal habits
in a presumed forest environment that included oaks along with other
types of trees (chestnuts, pines).

Neither the name Dryosaurus nor the name Dryopithecus is a reference
to "oak leaves."