Daemonosaurus cervicals and the recurring problem of taxon exclusion

Updated March 9, 2015 with the note that Sues et al. did not use suprageneric data,as reported earlier.. The supplemental data shows that several ornithischians were employed. I spent the day yesterday making the SuppData computer friendly and am today reviewing the scorings. I see several typos and reinterpretations. A later post will present both nexus files. 

Earlier we looked at the palate and occiput of Daemonosaurus Today we’ll reexamine the cervicals and update some notes.

Little noticed and poorly preserved,
the cervicals of the basal phytodinosaur, Daemonosaurus (Sues et al. 2011, CM 76821, Carnegie Museum of Natural History, Late Triassic) appear curiously small and elongated relatively to the tall, narrow skull (Fig. 1).

Figure 1. Daemonosaurus cervicals traced from in situ fossils and compared to sister taxa, Eoraptor, Leyesaurus, Heterodontosaurus and Pisanosaurus. Among these taxa, Daemonosaurus has the largest skull and most gracile cervicals. Click to enlarge.

Figure 1. Daemonosaurus cervicals traced from in situ fossils and compared to sister taxa, Eoraptor, Leyesaurus, Heterodontosaurus and Pisanosaurus. Among these taxa, Daemonosaurus has the largest skull and most gracile cervicals. Daemonosaurus likely had four more cervicals than preserved.

If the cervicals have been correctly traced
then, compared to sister taxa, Daemonosaurus has the largest skull relative to the most gracile cervicals. And there were likely four and a half more cervicals that were not preserved.

The cervicals are long, like those of basal sauropodomorphs, but the skull is tall, short and narrow, like those of basal ornithischians, like Heterodontosaurus. Overall the imagined body of Daemonosaurus was larger than all sister taxa except Leyesaurus, which had a longer neck. Note the similarities of Daemonosaurus to Pisanosaurus, which had much shorter cervicals, but was more closely related to other ornithischians, and to Dryosaurus, which also had shorter cervicals and no premaxillary teeth, but otherwise rather similar in morphology.

Here’s where Sues et al. 2011 differ from the large reptile tree
Sues et al. 2011 found Ornithischia and Sauropodomorpha branched off prior to Herrerasaurus. In  the large reptile tree they both branched off close to Eoraptor (which confirms sauropodomorph affinities according to Sereno et al. 2013) and Daemonosaurus is a basal ornithischian. Using the Sues et al. taxa (Fig. 2 and deleting all sauropodomorphs and ornithischians) the large reptile tree recovers the same tree topology. Different than I thought when this blogpost was first published, Sues et al. 2014 used genus-based taxa. A review of their work is in progress, but since they used Nesbitt 2011 for their database, I found several problems and strange-bedfellows earlier.

Figure 4. Daemonosaurus tree from Sues et al. 2014. Their one mistake was assuming sauropods and ornithischians branched off prior to Herrerasaurus. The large reptile tree has these clades branching off after Eoraptor. Delete those suprageneric clades and the tree recovered here matches the large reptile tree with similar deletions.

Figure 2. Daemonosaurus tree from Sues et al. 2014. Their one mistake was assuming sauropods and ornithischians branched off prior to Herrerasaurus. The large reptile tree has these clades branching off after Eoraptor. Delete those suprageneric clades and the tree recovered here matches the large reptile tree with similar deletions.

Daemonosaurus diagnosis (with my additions in color).
“Distinguished by the following unique combination of characters: skull proportionately deep and narrow (like Jeholosaurus, Heterodontosaurus = J, H), with short antorbital region (like J, H); premaxillary and anterior maxillary teeth much enlarged relative to more posterior maxillary teeth (like J, H)prefrontal large and occupies about 50 per cent of the dorsal margin of the orbit (like J, H); ventral process of lacrimal with slender posterior projection extending along anterodorsal margin of jugal (cannot confirm, this may be part of the jugal); dorsoventrally deep jugal with prominent lateral ridge (like H); postorbital with anterolateral overhang over orbit (like J, H); first two dentary teeth large and procumbent (like J, H); alveolar margin of dentary downturned at symphysis (like J, H); and third cervical vertebra with deep, rimmed, ovoid pleurocoel on the anterolateral surfaces of both centrum and neural arch (hard to see). Possible autapomorphies of Daemonosaurus include long posterior process of premaxilla that almost contacts anterior process of lacrimal (like J, H); and antorbital fenestra nearly the same size as external naris (like J, H);.”

It’s too bad
these authors missed this big, I mean really big discovery (the basalmost ornithischian!) due to their use of supragreneric taxa, false assumptions and taxon exclusion. It is also puzzling that no one since 2011 has raised their hand about these issues, except yours truly. Come on people, now that we know the problem, let’s fix this!

So, these questions pop up:
did the Ornithischia inherit short cervicals directly from a sister to Eoraptor? Or did basal phytodinosaurs enjoy a brief fling with elongate cervicals, as in the intervening sauropodomorphs — AND as demonstrated by Daemonosaurus? Or did Daemonosaurus independently elongate its cervicals?

That’s the frustration, joy and mystery of incomplete fossils.

PS Good news! Just heard Hans Sues and Sterling Nesbitt are working on a detailed description of Daemonosaurus.

References

Nesbitt SJ 2011. The early evolution of archosaurs: relationships and the origin of major clades. Bulletin of the American Museum of Natural History 352: 292 pp.
Sereno PC, Martínez RN and Alcober OA 2013. Osteology of Eoraptor lunensis (Dinosauria, Sauropodomorpha). Journal of Vertebrate Paleontology Memoir 12:83-179.
Sues H-D, Nesbitt SJ, Berman DS and Henrici AC 2011. 
A late-surviving basal theropod dinosaur from the latest Triassic of North America. Proceedings of the Royal Society Bpublished online

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4 thoughts on “Daemonosaurus cervicals and the recurring problem of taxon exclusion

  1. “Had Sues et al. 2014 avoided suprageneric taxa and instead used generic taxa for Ornithischia and Sauropodomorpha, it is likely they would have arrived at a tree similar to that of the large reptile tree. Yet another case of taxon exclusion here.”

    They DID use generic taxa, the figure you posted (your fig. 2, their fig. 3) just simplified the phylogram by not listing each sauropodomorph or ornithischian genus. I already compared your matrix to Sues et al.’s in my 4-19-2013 blog post and determined “Comparison indicates massive miscoding by you, a lack of included taxa and characters, and in this particular case using a largely fictional skull for Daemonosaurus.” Sure you’ve added more dinosaurs since then and may have updated some codings, but you haven’t added any characters and still use a skull reconstruction that neither I nor Sues et al. agree with. We’ll see if your heterodontosaur-like skull is correct once the osteology is published. In the meantime, those elongate cervicals (with pleurocoels, a character you don’t use) are a ‘red flag’ as you say, being like Tawa and coelophysoids.

  2. Would it be possible to, in case a correction/suggestion has been provided to you by an external source in your comment section (say Mickey Mortimer, see above), to list the name of the commenter who made the original correction/suggestion? I think it will go a long way in underlining that you seek to improve the quality of your published results based on active discussions/conversations held in your ‘comments’ section. To be specific, it gives your ‘comments’ section a clear purpose that goes beyond simply offering a platform for interested parties to say that they either like or dislike your findings.

    • I thanked MM privately earlier. Not sure what you mean by “list” as the comment by the commenter is already ‘listed’ with an attribution.

      To MMs comment about ‘massive miscodings’ two years ago, the data matrix keeps getting renewed as data comes in. So that comment reflects several generations of changes ago. Perhaps the same can be said of the Sues et al matrix, now 4 years old. Over the weekend I was able to make the Sues et al. matrix into a usable .nex file. Unfortunately typos, missed codings and miscodings are also to be found there. It happens, especially when you have an animal like Daemonosaurus that looks like a super predator. Early returns indicate that Daemonosaurus, sharing so many traits with Heterodontosaurus (listed above), is going to end up nesting very close to it using the 100 or so skull traits among the 319 traits overall.

      About the pleurocel on the long neck issue… let’s see how that pans out first. The correspondence may be convergent as both long necks and pleurocels have more than one origin in the Dinosauria and Daemonosaurus nests very close to the origin of the Sauropodomorpha. It’s one of those ‘more answers beget more questions’ scenarios.

      Thanks for your note, Rutger.

  3. You are welcome David. I guess what I was ‘shooting for’ was an attribution to the comment in the yellow piece of text currently headlining your post. For example, “Updated March 9, 2015 with the note that Sues et al. did not use suprageneric data,as reported earlier.” could be “Following a comment made by Mickey Mortimer, I have updated my post from March 9, 2015 …”. What do you think?

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