Cynosphenodon

{{Short description|Extinct genus of reptiles}}

{{italic title}}

{{automatic taxobox

| fossil_range = {{fossil_range|170|160|Middle Jurassic}}

| image = Cynosphenodon.svg

| image_caption = Diagram of preserved skull elements

| taxon = Cynosphenodon

| authority = Reynoso, 1996

| type_species = {{extinct}}Cynosphenodon huizachalensis

| type_species_authority = Reynoso, 1996

}}

Cynosphenodon ({{IPAc-en|ˌ|s|aɪ|n|ə|ˈ|s|f|ɛ|n|ə|d|ɒ|n}} {{respell|SY|nə|SFEN|ə|don}}; "Dog Sphenodontian") is an extinct genus of rhynchocephalian in the family Sphenodontidae from the Middle Jurassic La Boca Formation of Tamaulipas, Mexico. It is known from a largely complete lower jaw and fragments of the upper jaw. It is suggested to be among the closest known relatives of the tuatara, with both being placed in the Sphenodontinae,{{Cite journal|last=Reynoso|first=Victor-Hugo|date=1996|title=A Middle Jurassic Sphenodon-like sphenodontian (Diapsida: Lepidosauria) from Huizachal Canyon, Tamaulipas, Mexico|url=https://www.researchgate.net/publication/254313647|journal=Journal of Vertebrate Paleontology|language=en|volume=16|issue=2|pages=210–221|doi=10.1080/02724634.1996.10011309|bibcode=1996JVPal..16..210R |issn=0272-4634}} which is supported by among other characters, the growth pattern of the teeth.Reynoso, V. H. (2003). Growth patterns and ontogenetic variation of the teeth and jaws of the Middle Jurassic sphenodontian Cynosphenodon huizachalensis (Reptilia: Rhynchocephalia). Canadian Journal of Earth Sciences 40(4), 609–619

Cladogram after Simoes et al. 2022.{{Cite journal |last1=Simões |first1=Tiago R. |last2=Kinney-Broderick |first2=Grace |last3=Pierce |first3=Stephanie E. |date=2022-03-03 |title=An exceptionally preserved Sphenodon-like sphenodontian reveals deep time conservation of the tuatara skeleton and ontogeny |journal=Communications Biology |language=en |volume=5 |issue=1 |page=195 |doi=10.1038/s42003-022-03144-y |issn=2399-3642 |pmid=35241764 |doi-access=free|pmc=8894340 }}{{clade|{{clade

|1=†Diphydontosaurus

|label2=Eusphenodontia

|2={{clade

|1=†Planocephalosaurus

|2=†Clevosaurus

|label3=Neosphenodontia

|3={{clade

|1= {{clade

|1={{clade

|1=†Homoeosaurus

|2= †Pleurosauridae

|3={{clade

|1=†Leptosaurus +†Kallimodon

|2=†Sapheosauridae

}}

}}

|label2=Sphenodontidae

|2={{clade

|label2=Sphenodontinae

|1=†Eilenodontinae

|2={{clade

|1=†Navajosphenodon

|2=†Cynosphenodon

|3={{clade

|1=†Sphenofontis

|2={{clade

|1=†Kawasphenodon

|2=Sphenodon (tuatara)

}}}}}}}}}}}}}}}}|label1=Sphenodontia}}{{portal|Paleontology}}