Polysphenodon

{{Taxobox

| name = Polysphenodon

| fossil_range = Late Triassic, {{fossil_range|235|205}}

| image = Polysphenodon skull.svg

| image_caption = Reconstructed skull

| regnum = Animalia

| phylum = Chordata

| classis = Reptilia

| ordo = Sphenodontia

| familia =

| subfamilia =

| genus = {{extinct}}Polysphenodon

| genus_authority = Jaeckel, 1911

| type_species = {{extinct}}Polysphenodon mulleri

| type_species_authority = Jaeckel, 1911

}}

Polysphenodon is an extinct genus of sphenodontian reptile with a single species Polysphenodon mulleri from the Late Triassic Keuper Group of Germany.N. C. Fraser and M. J. Benton. (1989) The Triassic reptiles Brachyrhinodon and Polysphenodon and the relationships of the sphenodontids. Zoological Journal of the Linnean Society 96:413-445

History of discovery

The genus and only known species Polysphenodon mulleri was described by Otto Jaekel in 1911.Jaekel, O (1911) Die Wierbeltiere. Eine Übersicht über diefossilen und lebenden Formen. Borntraeger, Berlin, 252p Polysphenodon mulleri is known from a single partial skeleton recovered from a borehole sample at {{convert|775|m|ft}} depth, which includes parts of the skull, limbs and tail vertebrae. This specimen has been lost since the 1930s, but is known from several casts.

Description

The skull was around {{Convert|2.5|cm|in}} long in life. The snout is relatively short, even when accounting for post-mortem distortion. The limbs of Polysphenodon, particularly the tibia, are long relative to the size of the skull and are similar in proportions to some species of Homoeosaurus. This resemblance is considered to be indicative of similar locomotory requirements rather than close evolutionary relationships.

Taxonomy

Recent studies have placed Polysphenodon as a member of Eusphenodontia.{{Cite journal |last1=Romo de Vivar |first1=Paulo R. |last2=Martinelli |first2=Agustín G. |last3=Schmaltz Hsiou |first3=Annie |last4=Soares |first4=Marina Bento |date=2020-07-02 |title=A New Rhynchocephalian from the Late Triassic of Southern Brazil Enhances Eusphenodontian Diversity |url=https://www.tandfonline.com/doi/full/10.1080/14772019.2020.1732488 |journal=Journal of Systematic Palaeontology |language=en |volume=18 |issue=13 |pages=1103–1126 |doi=10.1080/14772019.2020.1732488 |bibcode=2020JSPal..18.1103R |issn=1477-2019|url-access=subscription }} Some authors have placed Polysphenodon as part of the family Clevosauridae alongside Clevosaurus and Brachyrhinodon,{{Cite journal |last1=Hsiou |first1=Annie Schmaltz |last2=De França |first2=Marco Aurélio Gallo |last3=Ferigolo |first3=Jorge |date=2015-09-10 |editor-last=Beatty |editor-first=Brian Lee |title=New Data on the Clevosaurus (Sphenodontia: Clevosauridae) from the Upper Triassic of Southern Brazil |journal=PLOS ONE |language=en |volume=10 |issue=9 |pages=e0137523 |doi=10.1371/journal.pone.0137523 |doi-access=free |issn=1932-6203 |pmc=4565693 |pmid=26355294|bibcode=2015PLoSO..1037523H }} though other studies have recovered Polysphenodon as unrelated to these taxa.

Cladogram following Sues and Schoch, 2023:{{Cite journal |last1=Sues |first1=Hans-Dieter |last2=Schoch |first2=Rainer R. |date=2023-11-07 |title=The oldest known rhynchocephalian reptile from the Middle Triassic (Ladinian) of Germany and its phylogenetic position among Lepidosauromorpha |url=https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.25339 |journal=The Anatomical Record |volume=307 |issue=4 |pages=776–790 |language=en |doi=10.1002/ar.25339 |issn=1932-8486 |pmid=37937325 |s2cid=265050255|url-access=subscription }}{{clade|{{clade

|label1=Rhynchocephalia

|1={{clade

|1=Wirtembergia hauboldae

|2={{clade

|1=Gephyrosaurus bridensis

|label2=Sphenodontia

|2={{clade

|1=Diphydontosaurus avonis

|label2=Acrosphenodontia

|2={{clade

|1=Planocephalosaurus robinsonae

|2={{clade