Carbonodraco lundi (Mann et al. 2019; Middle Pennsylvanian, Moscovian) was originally considered a type of Cephalerpeton, then a sister to Acleistorhinus. Here Carbonodraco nests with Kudnu (see below) at the base of the Stephanospondylus (see below) + Pareiasauria + turtles. The freehand sketch is distinctly different than the bones indicate. Several bones were left unidentified.

Wirtembergia hauboldae (Schoch and Sues 2023, Middle Triassic) was originally considered the basalmost rhynchocephalian. Adding taxa moved it to Carbonodraco and Kudnu, two taxa basal to Stephanospondylus + pareiasaurs (including turtles), a sister clade to the diadectids (including procolophonids). Note the extra large lateral naris and the bulbous premaxillary teeth together with a downturned dentary tip.

Kudnu mackinlay (Bartholomai 1979; Early Triassic, ~1cm long skull) was originally considered a paliguanid. Evans and Jones 2010 thought it might be a procolophonid. Here it nests basal to Stephanospondylus, a late survivor from deep in the lineage of pareiasaurs + turtles, not far from bolosaurids + diadectids + procolophonids. It seems to be phylogenetically miniaturized.

Stephanospondylus pugnax (Geinitz and Deichmuller 1882) Early Permian ~290 mya was originally considered a rarely studied diadectid, and therefore a pre-amniote, not part of the reptile clade. Here it nests between bolosaurs, like Bolosaurus, and pareiasaurs like Anthodon.

Larger and distinct from Belebey, the skull of Stephanospondylus had long sharp teeth. The nares were oriented anteriorly. No lateral fenestra pierced the cheek.

The neural spines were inflated. The dorsal ribs had expanded costal plates, as in Odontochelys and Diadectes. The scapula had an acromion process, as in turtles. The pelvis had a tall ilium and a separated pubis and ischium. The pubis included a distal attachment to a presumed ventral plastron.

The limbs were robust and short. The femur had a distintly angled neck, as in turtles.

Williston (1917) classified reptiles based on their temporal fenestra or openings and so placed turtles with primitive reptiles without temporal openings.

Broom (1924) reported, "Those who regard the structure of the temporal region of the skull as the safest guide to affinity will naturally place the chelonianans either with the primitive mammal-like reptiles or the cotylosaurs (primitive reptiles without temporal fenestration); those who hold that more reliance can be placed on the structure of the girdles and limbs will be more impressed with the affinities to the primitive diapsids such as Sphenodon."

Rieppel and DeBraga (1996) considered turtles to be diapsids close to Placodus in which the temporal fenestra had resealed. Unfortunately they also considered the squamosal to be the quadratojugal and the supratemporal to be the squamosal in the turtle Proganochelys. Further confusing the issue, they nested Placodus within the Lepidosauriformes following Younginiforms.

Gregory (1946) compared living and fossil turtles with placodonts, "cotylosaurs" (captorhinids, pareiasaurs, procolophonoids, and diadectomorphs, all considered amniotes at the time), and with seyrnouriamorphs. He concluded that Testudines were derived from Paleozoic "cotylosaurs," and that among those, pareiasaurs approached Triassic turtles more closely than the geologically older diadectids. Although placodonts. especially Henodus, had evolved an amazingly turtle-like appearance, Gregory concluded
that they were not related to turtles and that convergent evolution, especially related
to dermal armor, causes a serious problem in recognizing testudine relationships.

Commenting on the Li et al. (2008) paper on Odontochelys, Reisz and Head reported, "Its osteology contradicts the view that turtles have pareiasaurian affinities, and, along with molecular data, supports evolutionary hypotheses that they are closely related to another group, the diapsid reptiles.”

In the present, more inclusive study, turtles do have their origins with pareiasaurs AND turtles are somewhat close to the purported diapsids Reisz and Head were referring to: the lepidosaurs via owenettids. Turtles are NOT related to placodonts as Rieppel and DeBraga (1996) suggest.

New micro RNA studies by Lyson et al. (2011) support a lizard/turtle relationship.

Bartholomai A 1979. New lizard-like reptiles from the Early Triassic of Queensland. Alcheringa,3:225–234.

Broom R 1924. On the classification of the reptiles. Bulletin of the American Museum of Natural History 51:39-45.

Evans SE and Jones MEH 2010. Chapter 2 The Origin, Early History and Diversification of Lepidosauromorph Reptiles

Geinitz HB and Deichmüller JV 1882. Die Saurier der unteren Dyas von Sachsen. Paleontographica, N. F. 9:1-46.

Gregory WK 1946. Pareiasaurs versus placodonts as near ancestors to turtles. Bulletin of the American Museum of Natural History 86:275-326

Kissel R 2010. Morphology, Phylogeny, and Evolution of Diadectidae (Cotylosauria: Diadectomorpha). Toronto: University of Toronto Press. pp. 185. online pdf

Li C, Wu X-C, Rieppel O, Wang L-T, Zhao L-J 2008. An ancestral turtle from the Late Triassic of southwestern China. Nature 456: 497-501.

Lyson TR, Sperling EA, Heimberg AM, GauthierJA, King BL, and Peterson KJ 2011. MicroRNAs support a turtle + lizard clade. Biol Lett 2011 : rsbl.2011.0477v1-rsbl20110477. abstract - online news story

Reisz RR and Head JJ 2008. Turtle origins out to sea. Nature 456, 450–451.

Rieppel O and deBraga M 1996. Turtles as diapsid reptiles. Nature 384:453-454.

Rieppel O and Reisz RR 1999. The Origin and Early Evolution of Turtles. Annual Review of Ecology and Systematics 30: 1-22.

Romer AS 1925. Permian amphibian and reptilian remains described as Stephanospondylus. Journal of Geololgy 33: 447-463.

Sues H-D and Schoch RR 2023. The oldest known rhynchocephalian reptile from the Middle Triassic (Ladinian) of Germany and its phylogenetic position among Lepidosauromorpha. The Anatomical Record. https://doi.org/10.1002/ar.25339

Stappenbeck R 1905. Uber Stephanospondylus n. g. und Phanerosaurus H. v. Meyer: Zeitschrift der Deutschen Geologischen Gesellschaft, v. 57, p. 380-437.

Williston SW 1917. The phylogeny and classification of Reptilies. Journal of Geology 28: 41-421.

wiki/Stephanospondylus
wiki/Wirtembergia - not yet posted
wiki/Kudnu - not yet posted
wiki/Carbonodraco