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gorgonopsian wip… teeth

so… questions to Rubidgeinae teeth: Christian, if you could clarify?
Here are quick paint-overs… do these guys have palatal teeth? Your paper shows them, would just like to make sure before modeling them in. Also… what do we know about the teeth on the jaw? I only have other illustrations to go on for them, they are absent in the papers I’ve seen. And if there are no molar-type teeth for crushing towards the back of the mouth where forces would make that feasible, does this mean they tore off and swallowed flesh? No processing of bones, etc? Were those massive skulls muscled only for attack / demobilization with primarily front portion of snout? (Would perhaps explain that somewhat unique ‘chin’.)

wip_b

Also made a quick sketch of what the open mouth would look like:

wip_b

There are 8 Comments to this article

albertonykus says:
03/09/2016

What is the ear position based on? I’m aware there’s some controversy over this and that the squamosal sulcus is homologous with the mammalian ear canal, but I know of at least two recent papers that argue for the placement of the actual eardrum on the side of the jaw in non-mammalian therapsids. (C in Fig. 5 of the second paper linked is a good schematic of this concept.) This suggestion makes a good amount of sense from my non-specialist perspective, given that the ear position corresponds to the same bones that support the eardrum in mammals.

dmaas says:
03/09/2016

@Albertonykus… thanks for writing!
What are those papers? I don’t see any links… and are they accessible?
I assume “on the side of the jaw” would here mean lower just beneath the skull. Is that correct? I’m completely guessing just now. :-\

albertonykus says:
03/09/2016

The words “recent papers” was meant to each link to a paper in my comment. The second works for me, but the first one doesn’t. Here they are again; both are open access:
http://app.pan.pl/article/item/app001402014.html
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0131174

albertonykus says:
03/09/2016

(And side of the jaw literally means side of the jaw – more precisely, the reflected lamina of the angular. The figure I referenced should make things clearer.)

Christian Kammerer says:
03/10/2016

Hi, sorry for the delay in feedback, I’ve been out in the wilds doing fieldwork. First, I agree with albertonykus’ concerns about ear position, and I strongly recommend finding the following book chapter about it (not sure if there is a PDF out there, but worth tracking down):
Allin EF, Hopson JA (1992) Evolution of the auditory system in Synapsida (“mammal-like reptiles” and primitive mammals) as seen in the fossil record. In: Webster DB, Fay RR, Popper AN, editors. The evolutionary biology of hearing. New York: Springer-Verlag. pp. 587–614.

Regarding teeth, yes, for Lycaenops (which appears to be what you are modeling here) and the basal rubidgeines (like Aelurognathus) there is extensive palatal dentition. For the lower teeth, there are four incisors, a big canine (almost but not quite as large as the upper) and typically fewer postcanines than the uppers but directly opposite them (so not as far back on the jaw as you’ve circled). For a taxon with 6 upper postcanines, I know at least some specimens with 4 lowers. Gorgonopsians tend to reduce their postcanine counts. In some taxa the postcanines are pretty extensive and would still have been used in prey processing (e.g. Arctognathus with 6-7 postcanines or Aelurosaurus with 6) but most are in the 3-5 range and in some the postcanines are basically either reduced to uselessness (Smilesaurus, Inostrancevia, Rubidgea) or totally lost (Clelandina). These taxa also have reduced palatal teeth, with no teeth on the transverse process or pterygoid boss and only a few small teeth on the palatine boss. As far as what this means for their feeding, yes, they would not be doing much “chewing”–like some carnivorous reptiles they would have been highly reliant on just tearing off large pieces of prey with the anterior dentition and swallowing it whole.

dmaas says:
03/10/2016

Thanks albertonkus! Christian!
Wow… lots to chew. Update forthcoming – expect a quick paintover to get things laid out before modeling them in.
I’ve gone through Laass’ cochlea and Gaetano/Abdala’s Stapes papers. Also the first page of Hobson’s chapter, though I need the graphics 🙂 Shall continue the hunt.

Christian Kammerer says:
03/12/2016

Also, a fairly minor point: but these things are called either gorgonopsians or gorgonopids, not “gorgonopsids.” The larger clade is Gorgonopsia and the family in question is Gorgonopidae.

dmaas says:
03/12/2016

Thanks Christian. Edited.
I should have some time this weekend again… will start on the uvs and first sculpt

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