Arjan Mann, Thomas W. Dudgeon, Amy C. Henrici, Dave S. Berman and Stephanie E. Pierce (2021)
Digit and ungual morphology suggest adaptations for scansoriality in the late Carboniferous eureptile Anthracodromeus longipes.
Frontiers in Earth Science Â9:675337.
doi:
https://doi.org/10.3389/feart.2021.675337https://www.frontiersin.org/articles/10.3389/feart.2021.675337/full A new skeleton of the exceedingly rare, late Carboniferous eureptile Anthracodromeus longipes (Carroll and Baird, 1972), reveals the presence of a reduced phalangeal count in the manus and pedes and uniquely recurved unguals. With these data, we quantitatively evaluate the locomotor ecology of Anthracodromeus using morphometric analyses of the phalangeal proportions, ungual curvature, and ungual shape. Our findings indicate that the anatomy of Anthracodromeus likely facilitated scansorial clinging to some degree via distally recurved unguals and increased surface area of the large manus and pes. This suggests that Anthracodromeus was among the earliest amniotes to show climbing abilities, pushing back the origins of scansoriality by at least 17 million years. It further suggests that scansoriality arose soon after the origin of amniotes, allowing them to exploit a wide range of novel terrestrial niches.
Andrew B. Heckert, Tabitha C. Viner, and Matthew T. Carrano (2021)
A large, pathological skeleton of Smilosuchus gregorii (Archosauriformes: Phytosauria) from the Upper Triassic of Arizona, U.S.A., with discussion of the paleobiological implications of paleopathology in fossil archosauromorphs.
Palaeontologia Electronica 24(2): a21.
doi:
https://doi.org/10.26879/1123https://palaeo-electronica.org/content/2021/3385-pathological-phytosaurPhytosaurs were a widespread clade of Triassic predatory archosauriforms whose skull anatomy is well known, but whose paleobiology is underexplored. Here we report on a well-preserved specimen from Adamanian (early-mid-Norian) strata in Arizona that includes not only the skull and lower jaws but much of the postcranial skeleton, which exhibits extensive evidence of pathologies. This specimen has a complex taxonomic history, and we verify its referral to Smilosuchus gregorii based on multiple cranial characters.
The shafts of eight limb bones preserve extensive exostoses--more paleopathological elements than in any other Triassic archosauromorph. These exostoses are often centered on cavitations reminiscent of draining tracts. Extensive, irregular, proliferative lesions have completely engulfed the left deltopectoral crest and thoroughly altered the architecture of both femora. The animalâs presumed low metabolic rate would have allowed several months of lesion progression before it died of either nutritional deficiency or systemic infection. This is the fourth, and by far the most extensive, report of pathology in a phytosaur, and only the eighth in a non-dinosaurian Triassic archosauromorph.
The character and location of the lesions evokes aspects of both osteomyelitis and hypertrophic osteopathy--though neither is fully consistent with the changes present, nor are these conditions well-explored in extant reptiles. The most likely cause of the pathologies exhibited here is osteomyelitis; indeed, this specimen bears more osteomyelitis-like paleopathological elements than any other fossil archosaur.