SVP abstracts 2017: The enigmatic New Haven Reptile

Pritchard et al. 2017
introduce the concepts of a ‘pan-archosaur’ and a ‘pan-lepidosaur’ as they describe the small, enigmatic “New Haven Reptile” (Latest Triassic; 2.5cm skull length).

From the Pritchard et al. abstract:
“The fossil record of early-diverging pan-archosaurs and pan-lepidosaurs in the Triassic is biased towards large-bodied animals (1+ meters). The Triassic Newark Supergroup of eastern North America has produced tantalizing specimens of small reptiles, hinting at high diversity on the continent. Among these is a remarkable diapsid skull (~2.5 cm length) lacking teeth and a mandible, from the Upper Triassic New Haven Arkose of Connecticut that has been referred to as one of the oldest sphenodontians from North America (referred to herein as the New Haven Reptile). 

“Following further preparation, we re-assessed the affinities of the New Haven Reptile using three-dimensional reconstruction of microCT data. The ontogenetic state of the New Haven Reptile is uncertain; despite the extensive reinforcement of the skull, the skull roof exhibits a large fontanelle between frontals and parietals. The feeding apparatus of this species is distinct from most small-bodied Triassic diapsids, with a strongly reinforced rostrum, a narrow sagittal crest on the parietals, and transverse expansion of postorbitals and jugals. The latter two conditions suggest transverse expansions of deep and superficial adductor musculature in a manner very similar to derived Rhynchosauria. This may suggest a specialized herbivorous diet similar to rhynchosaurs, although the New Haven Reptile is smaller than most modern herbivorous diapsids. 

“A phylogenetic analysis suggests that the New Haven Reptile is not a sphenodontian but an early pan-archosaur, representing a distinctive and previously unrecognized lineage. Regardless of its affinities, the New Haven Reptile differs from other small-bodied Triassic Sauria in its hypertrophied jaw musculature suggesting a greater dietary specialization in these taxa than previously understood. It underscores the importance of geographically undersampled regions in understanding the true ecomorphological diversity in the fossil record.”

So, what is the New Haven reptile?
Without seeing the fossil or the presentation, we start with what was offered:

1. a small taxon (skull = 2.5cm)
2. like a sphenodontian, diapsid temporal openings
3. lacking teeth
4. extensive reinforcement of the skull
5. large fontanelle between frontals and parietals (pineal?)
6. strongly reinforced rostrum
7. a narrow sagittal crest on the parietals
8. transverse expansion of postorbitals and jugals, like rhynchosaurs
9. hypertrophied jaw musculature

Figure 1. Priosphenodon model. Is this what the New Haven Reptile looked like? Note the dorsal fontanelle, the pineal opening that largely disappears in rhynchosaurs. 

This sounds like
Priosphenodon avelasi, (Figs. 1, 2) which is a transitional taxon more derived than sphenodontians and more primitive than rhynchosaurs. The only skull known to me is about 8cm in length, or 3x larger than the New Haven Reptile. Priosphenodon was a late-surviving Cenomian, Cretaceous taxon, more derived  than the even later-surviving extant taxon, Sphenodon.

Figure 2. Priosphenodon nests closer to rhynchosaurs than Mesosuchus does, yet it was not included in the Ezcurra et al. 2016 study.

If my guess is valid,
its no wonder that Pritchard et al. are confused. To them rhynchosaurs are not related to sphendontians. These fellow workers need to include more taxa in their analysis and a suggested list is found at the large reptile tree (LRT, 1069 taxa). 

If it is something different
please send an image or publication and I will add it to the LRT.

References
Pritchard AC, Bhullar B-A S and Gauthier JA 2017. A tiny, early pan-archosaur from the Early Triassic of Connecticut and the diversity of the early saurian feeding apparatus. SVP abstracts 2017.