{{Short description|Extinct genus of reptiles}} {{Automatic taxobox | taxon = Uatchitodon | fossil_range = [[Late Triassic]] {{fossilrange|Carnian|Norian|refs=<ref>{{Cite journal|last1=Burch |first1=H. E. |last2=Eddins |first2=H.-M. S. |last3=Stocker |first3=M. R. |last4=Kligman |first4=B. T. |last5=Marsh |first5=A. D. |last6=Parker |first6=W. G. |last7=Nesbitt |first7=S. J. |year=2024 |title=A small venomous reptile from the Late Triassic (Norian) of the southwestern United States |journal=PeerJ |volume=12 |at=e18279 |doi=10.7717/peerj.18279 |doi-access=free |pmc=11485104 }}</ref>}} | image = Uatchitodon kroehleri Sues, 1991.jpg | authority = [[Hans-Dieter Sues|Sues]], [[1991 in paleontology|1991]] | subdivision_ranks = [[Species]] | subdivision = * {{extinct}}''U. kroehleri'' <small>Sues, 1991 ([[Type species|type]])</small> * {{extinct}}''U. schneideri'' <small>Mitchell ''et al.'', 2010</small> }}
'''''Uatchitodon''''' is an extinct [[genus]] of [[Late Triassic]] [[reptile]] known only from isolated teeth. Based on the structure of the teeth, ''Uatchitodon'' was probably a carnivorous [[Archosauromorpha|archosauromorph]]. Folded grooves on the teeth indicate that the animal was likely venomous, with the grooves being channels for [[saliva]]ry [[venom]]. The teeth are similar to those of living venomous [[squamate]]s such as ''[[Heloderma]]'' and venomous [[snake]]s.<ref name=SHD91>{{cite journal |last=Sues |first=H.-D. |year=1991 |title=Venom-conducting teeth in a Triassic reptile |journal=Nature |volume=351 |pages=141–143 |doi=10.1038/351141a0 |issue=6322|bibcode=1991Natur.351..141S }}</ref> ''Uatchitodon'' and ''[[Microzemiotes]]'' are the earliest known potentially venomous reptiles.<ref name=SHD96>{{cite journal |doi=10.1080/02724634.1996.10011340 |last=Sues |first=H.-D. |year=1996 |title=A reptilian tooth with apparent venom canals from the Chinle Group (Upper Triassic) of Arizona |journal=Journal of Vertebrate Paleontology |volume=16 |issue=3 |pages=571–572}}</ref><ref>{{Cite journal |last1=Burch |first1=H. E. |last2=Eddins |first2=H.-M. S. |last3=Stocker |first3=M. R. |last4=Kligman |first4=B. T. |last5=Marsh |first5=A. D. |last6=Parker |first6=W. G. |last7=Nesbitt |first7=S. J. |date=14 October 2024 |title=A small venomous reptile from the Late Triassic (Norian) of the southwestern United States |journal=[[PeerJ]] |language=en |volume=12 |article-number=e18279 |doi=10.7717/peerj.18279 |issn=2167-8359 |pmc=11485104 |pmid=39421413 |doi-access=free}}</ref>
==Description and species== The genus was first named with the description of the type species ''U. kroehleri'' by [[Hans-Dieter Sues]] in the journal ''[[Nature (journal)|Nature]]'' in 1991.<ref name=SHD91/> ''U. kroehleri'' is known from several teeth found from the early middle [[Carnian]] [[Turkey Branch Formation]] of the [[Newark Supergroup]] in [[Virginia]], uncovered from the Tomahawk locality. The teeth average around 10 mm in length. The [[tooth crown]] is strongly [[Anatomical terms of location#Teeth|labiolingually]] compressed, recurved, and serrated along both the anterior and posterior edges. The serrations are formed from individual denticles, each of which is further denticulated.<ref name=KP94a>{{cite book |last=Sues |first=H.-D. |author2=Olsen, P.E. |author3=Kroehler, P.A. |year=1994 |chapter=Small tetrapods from the Upper Triassic of the Richmond basin (Newark Supergroup), Virginia |chapter-url=http://www.ldeo.columbia.edu/users/polsen/newark_gechron/sues_et_al_94.pdf |title=In the Shadow of the Dinosaurs: Early Mesozoic Tetrapods |editor1=Fraser, N.C. |editor2=Sues, H.-D. |publisher=Cambridge University Press |location=Cambridge and New York |pages=161–170 |archive-date=2016-03-03 |access-date=2010-04-23 |archive-url=https://web.archive.org/web/20160303230425/http://www.ldeo.columbia.edu/users/polsen/newark_gechron/sues_et_al_94.pdf }}</ref> On both the [[Anatomical terms of location#Teeth|labial]] (outer) and [[Anatomical terms of location#Teeth|lingual]] (inner) surfaces of the tooth, there is a deep central groove running longitudinally. The grooves form deep [[invagination]]s that constrict the inner [[Pulp (tooth)|pulp cavity]] of the tooth. The grooves do not reach the tip of the tooth.<ref name=SHD96/>
A single tooth from the [[Petrified Forest National Park|Petrified Forest Formation]] of the [[Late Triassic]] [[Chinle Group]], found at the [[Placerias Quarry]] at [[St. Johns, Arizona]], has been identified as one of ''Uatchitodon''.<ref name=SHD96/><ref name=IRB05>{{cite book |last=Irmis |first=R.B. |year=2005 |chapter=The vertebrate fauna of the Upper Triassic Chinle Formation in Northern Arizona |chapter-url=http://socrates.berkeley.edu/~irmisr/chinlerev.pdf |title=Guidebook to the Triassic Formations of the Colorado Plateau in northern Arizona: Geology, Paleontology, and History |series=Mesa Southwestern Museum Bulletin |volume=9 |editor1=Nesbitt, S.J. |editor2=Parker, W.G. |editor3=Irmis, R.B. |pages=63–88}}</ref> It is slightly younger than the teeth of ''U. kroehleri'' found in Virginia.<ref name=KP94b>{{cite book |last=Kaye |first=F.T. |author2=Padian, K. |year=1994 |chapter=Microvertebrates from the ''Placerias'' Quarry: a window on Late Triassic vertebrate diversity in the American Southwest |title=In the Shadow of the Dinosaurs: Early Mesozoic Tetrapods |editor1=Fraser, N.C. |editor2=Sues, H.-D. |publisher= Cambridge University Press |location=Cambridge and New York |pages=171–196}}</ref> Venom-conducting teeth were first noted from the ''Placerias'' Quarry in the 1980s, but they were not interpreted as belonging to ''Uatchitodon'' until 1992.<ref name=JM80>{{cite book |last=Jacobs |first=L.L. |author2=Murry, P.A. |year=1980 |chapter=The vertebrate community of the Triassic Chinle Formation near St. Johns, Arizona |title=Aspects of Vertebrate History |editor1=Jacobs, L.L. |publisher=Museum of Northern Arizona Press |location=Flagstaff |pages=55–70}}</ref><ref name=KP92>{{cite journal |last=Kaye |first=F.T. |author2=Padian, K. |year=1992 |title=Microvertebrates from the ''Placerias'' Quarry (Chinle Formation, Carnian, Arizona): A window on Late Triassic diversity |journal=Journal of Vertebrate Paleontology |volume=12 |issue=Suppl. 3 |pages=36A| doi = 10.1080/02724634.1992.10011483}}</ref> The tooth, known as [[Museum of Northern Arizona|MNA]] V3680, differs from those of ''U. kroehleri'' in that the grooves are fully enclosed and form tubes within the teeth. There are faint furrows at the sutures that enclose these tubes. The tubes, which are presumably venom canals, end at discharge orifices near the tip of the crown. MNA V3680 is the earliest example of a [[tetrapod]] with completely enclosed tooth canals for the delivery of oral toxins, which are seen today in [[elapid]] snakes.
MNA V3680, along with several other teeth from the [[Cumnock Formation]] near [[Raleigh, North Carolina]], represent a second species of ''Uatchitodon'', ''U. schneideri''. This species, although recognized since 1996, remained unnamed until 2010.<ref name=SHD96/><ref name=MHS10>{{cite journal |last=Mitchell |first=J.S. |author2=Heckert, A.B. |author3= Sues, H.-D. |year=2010 |title=Grooves to tubes: evolution of the venom delivery system in a Late Triassic "reptile" |journal=Naturwissenschaften |volume=97 |issue=12 |pages=1117–1121 |doi=10.1007/s00114-010-0729-0 |pmid=21060984|bibcode=2010NW.....97.1117M }}</ref> ''U. schneideri'' was named in honor of Vince Schneider of the [[North Carolina Museum of Natural Sciences]]. The holotype tooth, known as [[North Carolina Museum of Natural Sciences|NCSM]] 24753, was found from a locality referred to as NCPALEO 1906, along with many other teeth and uncatalogued fragments. NCPALEO 1906, better known as the Moncure microvertebrate locality, was discovered and excavated by Schneider.<ref name=MHS10/>
The teeth from the Moncure locality are similar to MNA V3680 in that they all have enclosed venom canals that open at the ends of the teeth. The teeth of ''U. schneideri'' can be distinguished from those of ''U. kroehleri'' by enclosure of the canals as well as a lesser degree of labiolingual compression.<ref name=MHS10/>
==Paleobiology== The tubular venom canals of ''U. schneideri'' are similar to those found in the teeth of venomous snakes, while the grooved teeth of ''U. kroehleri'' are similar to those of living [[gila monster]]s. The teeth of ''U. kroehleri'' in the Tomahawk locality are older than those of ''U. schneideri'' in the Moncure locality and ''Placerias'' quarry, suggesting that the grooved teeth of ''U. kroehleri'' developed into the tubular fangs of ''U. schneideri''. A similar transition is thought to have occurred in snakes. The earliest venomous snakes appeared in the [[Miocene]] epoch with fully formed tubular fangs, but there is no fossil evidence of earlier snakes with grooved teeth. In the development of living venomous snakes, however, the fangs have open grooves before erupting. One they emerge from the gum line, the fangs have enclosed canals.<ref name=NN10>{{cite journal |title=When snake fangs moved out of the groove |last=Kaplan |first=Matt |date=17 November 2010 |url=http://www.nature.com/news/2010/101117/full/news.2010.617.html |access-date=23 November 2010 |doi=10.1038/news.2010.617 |journal=Nature|url-access=subscription }}</ref>
The grooves of ''U. kroehleri'' may indicate that it had a lifestyle similar to the living gila monster, chewing prey to pass venom into it. With enclosed canals, ''U. schneideri'' may have been able to inject venom in a similar way to venomous snakes. Like venomous snakes, it may have been able to pump venom into its prey through venom glands and compressor muscles. However, as the jaws of ''U. schneideri'' are not known, there is no evidence for such glands or muscles.<ref name=NN10/>
==References== {{Reflist}}
==External links== *[https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=57686 ''Uatchitodon''] in the [[Paleobiology Database]]
{{Archosauromorpha|B.}} {{Taxonbar|from=Q7876363}}
[[Category:Archosauriformes]] [[Category:Prehistoric reptile genera]] [[Category:Late Triassic reptiles of North America]] [[Category:Triassic Arizona]] [[Category:Paleontology in Arizona]] [[Category:Triassic geology of North Carolina]] [[Category:Fossils of North Carolina]] [[Category:Triassic geology of Virginia]] [[Category:Paleontology in Virginia]] [[Category:Fossil taxa described in 1991]] [[Category:Taxa named by Hans-Dieter Sues]] [[Category:Tooth taxa]]