Another, more complete Colobomycter adds data to this enigma

Revised June 10, 2016 with a new reconstruction and nesting with Eothyris. 

A new paper
by MacDougall et al. 2016 introduces Colobomycter vaughni (BRMP 2008.3.1, Fig. 1) a new toothy specimen that adds much needed data to the former enigma taxon, Colobomycter pholeter. They report on the synapomorphies, “enlarged premaxillary tooth and paired enlarged maxillary teeth, unique dentition that grants it an appearance quite distinct from other parareptiles at Richards Spur. This new material differs from that of C. pholeter in that it possesses at least three more teeth on its maxilla, the enlarged premaxillary and maxillary teeth are more gracile than those in C. pholeter, and the lacrimal is restricted externally to the orbital margin and does not exhibit an extra lateral exposure.” 

Figure 1. The new Colobomycter compared to the original pasted on a ghost of the new material. We're learning more about this genus!

Figure 1. The new Colobomycter compared to the original pasted on a ghost of the new material. We’re learning more about this genus!

Unfortunately, 
MacDougall et al. considered Colobomycter a member of the Lanthanosuchoidea. According to MacDougall et al. taxa in that clade include Feeserpeton, Lanthanosuchus, Acleistorhinus and Delorhynchus.

In the large reptile tree 
(Fig. 2) Lanthanosuchus
 nests with Bashkyroleter, Macroleter and Emeroleter.

On the other hand (and this is revised from the original posting)
Colobomycter pholeter
(Vaughn 1958, Modesto and Reisz 2008, UWBM 95405), Lower Permian ~278 mya, was originally considered a caseid pelycosaur, like Eothyris. (But note that Eothyris is not considered a pelycosaur in the large reptile tree (subset Fig. 2). Later, Modesto and Reisz (2008) considered Colobomycter a “parareptile” close to Acleistorhinus. After further consideration, it turns out that Colobomycter is indeed quite similar to Eothyris, as Vaughn 1958 indicated with much less data and fewer optional candidate taxa to consider. Hats off to Vaughn!

Figure 2. Revised cladogram of Colobomycter nesting this genus with Eothyris in an unnamed clade that includes caseasauria.

Figure 2. Revised cladogram of Colobomycter nesting this genus with Eothyris in an unnamed clade that includes caseasauria.

Sharp-eyed observers will note
that earlier I nested the rostrum of Colobomycter with procolophonids based on a smaller portion of rostrum. Clearly. I’m not as sharp as Vaughn was.

At this point
Colobomycter likely had a lateral temporal fenestra.

Herbivore or carnivore?
There are herbivores, carnivores and omnivores related to Colobomycter. It looks like the anterior dentary teeth could scrape off or collect whatever the premaxillary tusks had stabbed into. Eothyris had similar large maxillary teeth.

Figure 3. Eothyris skull in three views. This taxon is the closest known relative to Colobomycter.

Figure 3. Eothyris skull in three views. This taxon is the closest known relative to Colobomycter.

This is only one of tens of thousands of errors I have made
I’m only embarrassed by the ones that have yet to surface. Science and scientists don’t always have all the answers, but if the formula (or in this case cladogram) recovers a sticking point, as it did earlier, it will reward you to go back in and figure out where the errors were made. In this case several little errors among several taxa added up, but are corrected here, resulting once again in a completely resolved tree, hopefully more closely echoing Nature.

References
MacDougall MJ, Modesto SP and Reisz RR 2016. A new reptile from the Richards Spur Locality, Oklahoma, USA, and patterns of Early Permian parareptile diversification, Journal of Vertebrate Paleontology (advance online publication). www.tandfonline.com/doi/

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6 thoughts on “Another, more complete Colobomycter adds data to this enigma

    • Wait, I’m confused. All of your trees (those for Tridentinosaurus, and for Stenopelix, etc.) have those majority rule percentages, but that means that you don’t have a single tree after all. For instance, in your figure 2 above, Colobomycter only groups with Eothyris in 69% of the most parsimonious trees that PAUP found. Can you send me your most recent Reptile matrix in NEXUS/PAUP format?

      • Sorry, just saw a part of this query earlier. The single tree is a product of a heuristic search. The bootstrap scores arise from overlapping subsets of the entire tree. Of course, this avoids unrelated convergent taxa and is necessary due to computer memory restrictions. .nex file coming to your email shortly.

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