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Re: [dinosaur] DECODING COPE'S TEXAS TAXA: Eryops and Dimetrodon natalis



I've been lurking for 2 1/2 years because I got into an important discussion 
both on- and offlist, then suddenly broke off because I was traveling, and 
haven't had time to go back to it since as one thing chased the other. I think 
I should weigh in on a few things in this thread, though.

First of all, thanks for the etymology of *Eryops* and *Eryosuchus*! I was 
wondering about them again recently. "Euryops", 'broad/wide face', would have 
made sense, but that's not what the name is... The position of the jaw joints 
well behind the occiput, so rare in amniotes and extant amphibians, is very 
noticeable if you aren't used to Paleozoic tetrapods, and nobody was used to 
them when *Eryops* was named.

=============

> *Clepsydrops* "hourglass-look (vertebrae)" (Greek *klepsydra* "hourglass" 
> (funnels connected by a small opening)

Incidentally, those were originally filled with water, not sand; hence the name 
kleps-hydr-a, which refers to stealing water (one drop at a time).

=============

> *Empedocles* "firm-set (vertebrae) glory" (from Greek *empedos* "firm-set, 
> fixed in place, steadfast" + Greek *klees* "glory, fame") [Reptiliomorpha]
>
> For interlocking processes on the vertebrae that help strengthen and hold the 
> spine more rigid. The name is a pun on the name of a famous ancient Greek 
> philosopher Empedocles (c. 492—432 BCE) (5th century BCE); name preoccupied 
> and replaced with the name *Empedias* Cope, with a similar etymology

Alas, now considered a junior synonym of *Diadectes*.

=============

> (Cope used Pario- (from *pareia* "cheek") in a number of generic names to 
> refer to the post-orbital region and not just the zygomatic arch (cheekbone) 
> as such.)

Hence also the "microsaur" *Hapsidopareion*, "arch cheek" (from (h)apsis), 
after its large temporal embayment. It looks a bit like in a snake, where the 
bars between and ventral to the large temporal fenestrae have disappeared, 
though in this "microsaur" and a few others the jugal and (unless lost) the 
quadratojugal are bent upwards; there never was a fenestra.

_Pareia_ is a plural/collective; the expected singular _pareion_ occurs in 
Homer. (I recently looked this up for a paper; it's mentioned in one of the 
dictionaries on the Perseus site.)

=============

> "The external border of the epiotic next the auditory notch is acute,"

The epiotic, BTW, is now called postparietal. I don't know if that's a question 
of priority or if the reason is that the pro- and opisthotic are endochondral 
bones of the otic capsule (which houses the inner ear) while the postparietal 
is a dermal bone and has nothing to do with the otic capsule except for more or 
less lying on top of it.

=============

> *Trimerorhachis* "three-part spine" (Greek *trimeres* "three-part" + Greek 
> *rhakhis* "spine") [Temnospondyli]
>
> "The centrum is represented by three cortical ossifications of the 
> chorda-sheath, a median inferior, and two lateral."

These are the intercentrum and the two pleurocentra. Intercentra start out 
paired, too, but fuse early in ontogeny.

=============

> *Clepsydrops natalis* (now *Dimetrodon natalis*)
>
> [...]
>
> Cope (1878) noted in particular the unusual construction of the ischia:
>
> "The ischium is a remarkable bone. It is greatly produced anteriorly and 
> posteriorly to the acetabulum, in forming with that of the opposite side, a 
> keeled boat-shaped body..."
>
> Based mainly on this specimen (along with the new *Dimetrodon incisivus*), 
> Cope erected the group Pelycosauria "pelvis lizards" (Greek *pelyx* (genitive 
> *pelykos*) "basin, pelvis"), proposed as a division of the Rhynchocephalia 
> ("beak heads"), and thus the earliest known group of reptiles.  
>
> "Of the general affinities of this genus [*Clepsydrops*] it is only necessary 
> now to state that my reference of it to the Rhynchocephalia is confirmed. It 
> differs from the recent species of the order in the absence of quadrato-jugal 
> arch, and the remarkably developed ischia. On this account I refer to 
> *Clepsydrops* and its allies as a distinct suborder under the name of 
> Pelycosauria."
>
> Unfortunately, Cope's choice of the specific name *natalis* was not explained 
> and his reason for the name is not immediately obvious based on the 
> description of the specimen itself.

I think it's fairly clear, though:

> *natalis* "having large buttocks"
>
> [...]
>
> Although "having big buttocks" on a fish doesn't make much sense, a possible 
> reference to buttocks cannot be completely ruled out for Cope's *Clepsydrops 
> natalis*, in as much as Cope thought the construction of the pelvis, and in 
> particular the ischia, was important and distinctive. However, there are good 
> reasons to doubt such a meaning:
>
> 1) The term *nates* "buttocks, rump" properly refers to fleshy tissues rather 
> than to bones.

Do you really think Cope was above making butt jokes? :-) This is the man who 
named *Anisonchus cophater* and then wrote (quoting from memory): "Osborn, it's 
no use looking up the Greek derivation of cophater. I named it for the 
Cope-haters who surround me"...

> 2) Greek had a word *ischiadikos* to refer to the ischia or the hips, so Cope 
> could have used the more appropriate existing term *ischiadicus* (or maybe 
> the Latin-derived equivalent *coxalis* (from Latin *coxa* "hip bone") to 
> refer to the ischia or hips rather than *natalis* obscurely derived from 
> *nates* "buttocks" instead of from *natus* "birth."

Maybe he wanted the derivation to be an inside joke like *A. cophater*. 
"ischiadicus" would have been too obvious and not funny enough.

> 3) Cope's name Pelycosauria "pelvis lizards" already highlighted the 
> distinctive construction of the pelvis in *Clepsydrops* and *Dimetrodon*.

Why would that stop him from mentioning it again? There are even genus and 
species names (coined by other people) that repeat exactly the same meaning, 
like *Diceros bicornis* (the black rhino – Greek "two-horn" + Latin "with two 
horns") and *Tetracerus quadricornis* (the four-horned antilope – Latinized 
Greek "four-horn" + Latin "with two horns").

=============

> This species (*cruciger*) would only be recognized much later as belonging to 
> Cope's genus *Edaphosaurus* Cope, 1883 "pavement (tooth) lizard" (Greek 
> *edaphos* "ground, foundation, pavement"), first described and named based on 
> an isolated skull and lower jaw, notable for densely packed, small teeth that 
> formed a "dental pavement" (Cope's phrase) on each side in the back of the 
> upper and lower jaws.

The upper pavement is mostly on the ectopterygoid in the palate; the lower one, 
remarkably, is on the prearticular like in a lungfish.

> Confusingly, Cope's various early versions of the Pelycosauria and 
> Theromorpha included, in addition to synapsids such as *Dimetrodon* and 
> *Ophiacodon* [*Theropleura*], other species that are now classified as 
> lepospondyls (*Diplocaulus*), microsaurs (*Pariotichus*), reptiliomorphs 
> (*Diadectes*, *Empedias*, *Lysorophus*), and parareptiles 
> (*Bolosaurus*)--thus some of the perceived mammal-like qualities and features 
> of the Pelycosauria originally were not strictly based on synapsids.

"Microsaurs" are lepospondyls. Or at least most of them are. After the dust 
settles on the upcoming phylogenetic upheavals (nothing is properly published 
yet, but SVP meeting abstracts have been out there since 2011), they may even 
be the only lepospondyls left, in a way. We'll all be very confused next year.

*Lysorophus* is a nomen dubium based on 2 1/2 incomplete vertebrae as usual. 
Most of the referred material has been moved to *Brachydectes* ("short-biter", 
after the length of the toothrow; also by Cope), which is a (or the?) 
lysorophian lepospondyl, differing from the brachystelechid "microsaurs" mostly 
in its reduced limbs and drastically elongated trunk.

The name Reptiliomorpha is sometimes used for the amniote total group. (It was 
coined for a clade in 1934 by Gunnar Säve-Söderbergh, who believed that the 
amniotes were a polyphyletic assemblage; the age of phylopessimism had begun.) 
*Diadectes* including *Empedias* certainly belongs there; I can't even exclude 
that it's actually an amniote (Amniota having a crown-group definition). 
Whether *Brachydectes* and the other lepospondyls (whichever those will turn 
out to be) belong there depends on where the extant amphibians belong: if (some 
or) all of them are lepospondyls, which is what I keep finding in my analyses – 
though with less than overwhelming support –, *Brachydectes* is an amphibian 
rather than a reptiliomorph. If they're temnospondyls instead, the amniote 
total group is much larger and includes Lepospondyli – and possibly even 
Anthracosauria, which is an old and widespread idea that's slowly and steadily 
been looking less and less likely for the last twenty years.