This is the first time the four tiny scattered fingers
of Trypanognathus were collected and added to a reconstruction (Fig 1). They were too hard to find earlier. This taxon is the most primitive tetrapod in the large reptile tree (LRT, 2168 taxa) despite its late appearance (Latest Carboniferous, 300 mya) in the fossil record. An earlier origin of fingers is documented in the Middle Devonian (390 mya) based on ichnite (footprint) data.
The Bauplan of the Trypanognathus manus
falls neatly into a phylogenetic slot provided by precursor and descendant taxa (Fig 1). Trypanognathus has been ignored and omitted by tetrapod workers perhaps due to its late appearance in the fossil record. Workers have favored the eight-finger hypothesis based on discoveries and the fascinating, but invalid stories told by including unrelated taxa and omitting pertinent taxa. Simply adding taxa will let the cladogram tell you which is which.
That omission problem
also happens in origin hypotheses for turtles, pterosaurs, whales, Vancleavea, dinosaurs, birds (e.g. omitting all but one specimen attributed to Archaeopteryx), reptiles, diapsids, mesosaurs, sharks, bony fish, sturgeons, etc. etc. as longtime readers of this blogpost have seen.
(Schoch and Voigt 2019; latest Carboniferous) This is a late-surviving specimen of the first taxon in the LRT with fingers, toes and dorsal nares. It nests in a more basal position than originally thought, between Panderichthys and Laidleria. Derived states are the penetration of vomerine tusks through the splenial and symphyseal tusks through the premaxilla. The body is elongate with well-ossified, but small limbs, the presacral count is ca. 28, The pleurocentra are large and reached ventrally almost as far as the intercentrum.
First appearing several years ago, this still appears to be a novel hypothesis
of interrelationships not taught in vertebrate paleontology textbooks. If not, please provide a citation so I can promote it here.
Schoch RR and Voigt S 2019. A dvinosaurian temnospondyl from the Carboniferous-Permian boundary of Germany sheds light on dvinosaurian phylogeny and distribution. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2019.1577874.