Amphibamus, CM 81532 and Platyrhinops

Amphibamus lyelli (Cope 1865) Late Carboniferous, ~310 mya, ~15 cm in length, was derived from a sister to Utegenia and phylogenetically precededDendrerpeton and Cacops.

Distinct from Utegenia, the intertemporal fused to the postfrontal. The vomers were broad with lateral palatine processes. The pterygoids were narrower and more widely separated.

Only 18 presacral vertebrae were present, all with short straight ribs.

The scapulocoracoid was narrower. The forelimb was gracile. The hand was longer than the ulna. Only four fingers (1-4) were present.

The pelvis extended anteriorly as a plate separate from the ischium. The hindlimb was larger than the forelimb, but equally gracile. Metatarsals 3 and 4 were longer than the others.

An eardrum filled the posterior skull. Together these traits indicate adaptations to locomotion over land. Even so, aquatic tadpoles are known.

Platyrhinops lyelli ( Steen 1931, originally Raniceps lyelli, Wyman 1858,) Westphalian, Late Carboniferous ~305 mya, ~15 cm in length, was derived from a sister to Amphibamus and and together phylogenetically preceded Dendrerpeton and Cacops.

Distinct from Amphibamus the skull was wider. the torso was longer with more vertebrae. The limbs were longer with longer digits.

This confusing specimen has been referred to several other genera in the past, including Eryops, Tuditanus and Amphibamus among others.

CM 81532 (Mann et al. 2021; Late Carboniferous) was originally considered a reptile and an Anthracodromeus, but here nests with Platyrhinops and other basal Reptilomorpha. Only four fingers are present. Long fingers and toes indicate an arboreal niche.

Cope ED 1865. On Amphibamus grandiceps, a new Batrachian from the Coal Measures: Proceedings of the National Academy of Science, 1865, p. 134-137.

Mann et al. 2021. Digit and Ungual Morphology Suggest Adaptations for Scansoriality in the Late Carboniferous Eureptile Anthracodromeus longipes. Front. Earth Sci. 9:675337.
doi: 10.3389/feart.2021.675337

Moodie RL 1916. Journal of The coal measures Amphibia of North America. Carnegie Institution of Washington #238. 222 pp.

Wyman J 1857. On a batrachian reptile from the coal formation. Proceedings of the American Association for the Advancement of Science, 10th Meeting, 172-173.

wiki/Amphibamus
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Reptilomorpha

Amphibamus

Seymouriamorpha

Protoreptilia