# Uatchitodon

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Extinct genus of reptiles

Uatchitodon Temporal range: Late Triassic Carnian–Norian[1] PreꞒ Ꞓ O S D C P T J K Pg N Scientific classification Kingdom: Animalia Phylum: Chordata Class: Reptilia Clade: Archosauriformes Genus: †Uatchitodon Sues, 1991 Species †U. kroehleri Sues, 1991 (type) †U. schneideri Mitchell et al., 2010

***Uatchitodon*** is an extinct [genus](/source/Genus) of [Late Triassic](/source/Late_Triassic) [reptile](/source/Reptile) known only from isolated teeth. Based on the structure of the teeth, *Uatchitodon* was probably a carnivorous [archosauromorph](/source/Archosauromorpha). Folded grooves on the teeth indicate that the animal was likely venomous, with the grooves being channels for [salivary](/source/Saliva) [venom](/source/Venom). The teeth are similar to those of living venomous [squamates](/source/Squamate) such as *[Heloderma](/source/Heloderma)* and venomous [snakes](/source/Snake).[2] *Uatchitodon* and *[Microzemiotes](/source/Microzemiotes)* are the earliest known potentially venomous reptiles.[3][4]

## Description and species

The genus was first named with the description of the type species *U. kroehleri* by [Hans-Dieter Sues](/source/Hans-Dieter_Sues) in the journal *[Nature](/source/Nature_(journal))* in 1991.[2] *U. kroehleri* is known from several teeth found from the early middle [Carnian](/source/Carnian) [Turkey Branch Formation](/source/Turkey_Branch_Formation) of the [Newark Supergroup](/source/Newark_Supergroup) in [Virginia](/source/Virginia), uncovered from the Tomahawk locality. The teeth average around 10 mm in length. The [tooth crown](/source/Tooth_crown) is strongly [labiolingually](/source/Anatomical_terms_of_location#Teeth) compressed, recurved, and serrated along both the anterior and posterior edges. The serrations are formed from individual denticles, each of which is further denticulated.[5] On both the [labial](/source/Anatomical_terms_of_location#Teeth) (outer) and [lingual](/source/Anatomical_terms_of_location#Teeth) (inner) surfaces of the tooth, there is a deep central groove running longitudinally. The grooves form deep [invaginations](/source/Invagination) that constrict the inner [pulp cavity](/source/Pulp_(tooth)) of the tooth. The grooves do not reach the tip of the tooth.[3]

A single tooth from the [Petrified Forest Formation](/source/Petrified_Forest_National_Park) of the [Late Triassic](/source/Late_Triassic) [Chinle Group](/source/Chinle_Group), found at the [Placerias Quarry](https://en.wikipedia.org/w/index.php?title=Placerias_Quarry&action=edit&redlink=1) at [St. Johns, Arizona](/source/St._Johns%2C_Arizona), has been identified as one of *Uatchitodon*.[3][6] It is slightly younger than the teeth of *U. kroehleri* found in Virginia.[7] Venom-conducting teeth were first noted from the *Placerias* Quarry in the 1980s, but they were not interpreted as belonging to *Uatchitodon* until 1992.[8][9] The tooth, known as [MNA](/source/Museum_of_Northern_Arizona) 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](/source/Tetrapod) with completely enclosed tooth canals for the delivery of oral toxins, which are seen today in [elapid](/source/Elapid) snakes.

MNA V3680, along with several other teeth from the [Cumnock Formation](/source/Cumnock_Formation) near [Raleigh, North Carolina](/source/Raleigh%2C_North_Carolina), represent a second species of *Uatchitodon*, *U. schneideri*. This species, although recognized since 1996, remained unnamed until 2010.[3][10] *U. schneideri* was named in honor of Vince Schneider of the [North Carolina Museum of Natural Sciences](/source/North_Carolina_Museum_of_Natural_Sciences). The holotype tooth, known as [NCSM](/source/North_Carolina_Museum_of_Natural_Sciences) 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.[10]

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.[10]

## 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 monsters](/source/Gila_monster). 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](/source/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.[11]

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.[11]

## References

1. **[^](#cite_ref-1)** Burch, H. E.; Eddins, H.-M. S.; Stocker, M. R.; Kligman, B. T.; Marsh, A. D.; Parker, W. G.; Nesbitt, S. J. (2024). ["A small venomous reptile from the Late Triassic (Norian) of the southwestern United States"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11485104). *PeerJ*. **12**. e18279. [doi](/source/Doi_(identifier)):[10.7717/peerj.18279](https://doi.org/10.7717%2Fpeerj.18279). [PMC](/source/PMC_(identifier)) [11485104](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11485104).

1. ^ [***a***](#cite_ref-SHD91_2-0) [***b***](#cite_ref-SHD91_2-1) Sues, H.-D. (1991). "Venom-conducting teeth in a Triassic reptile". *Nature*. **351** (6322): 141–143. [Bibcode](/source/Bibcode_(identifier)):[1991Natur.351..141S](https://ui.adsabs.harvard.edu/abs/1991Natur.351..141S). [doi](/source/Doi_(identifier)):[10.1038/351141a0](https://doi.org/10.1038%2F351141a0).

1. ^ [***a***](#cite_ref-SHD96_3-0) [***b***](#cite_ref-SHD96_3-1) [***c***](#cite_ref-SHD96_3-2) [***d***](#cite_ref-SHD96_3-3) Sues, H.-D. (1996). "A reptilian tooth with apparent venom canals from the Chinle Group (Upper Triassic) of Arizona". *Journal of Vertebrate Paleontology*. **16** (3): 571–572. [doi](/source/Doi_(identifier)):[10.1080/02724634.1996.10011340](https://doi.org/10.1080%2F02724634.1996.10011340).

1. **[^](#cite_ref-4)** Burch, H. E.; Eddins, H.-M. S.; Stocker, M. R.; Kligman, B. T.; Marsh, A. D.; Parker, W. G.; Nesbitt, S. J. (14 October 2024). ["A small venomous reptile from the Late Triassic (Norian) of the southwestern United States"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11485104). *[PeerJ](/source/PeerJ)*. **12** e18279. [doi](/source/Doi_(identifier)):[10.7717/peerj.18279](https://doi.org/10.7717%2Fpeerj.18279). [ISSN](/source/ISSN_(identifier)) [2167-8359](https://search.worldcat.org/issn/2167-8359). [PMC](/source/PMC_(identifier)) [11485104](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11485104). [PMID](/source/PMID_(identifier)) [39421413](https://pubmed.ncbi.nlm.nih.gov/39421413).

1. **[^](#cite_ref-KP94a_5-0)** Sues, H.-D.; Olsen, P.E.; Kroehler, P.A. (1994). ["Small tetrapods from the Upper Triassic of the Richmond basin (Newark Supergroup), Virginia"](https://web.archive.org/web/20160303230425/http://www.ldeo.columbia.edu/users/polsen/newark_gechron/sues_et_al_94.pdf) (PDF). In Fraser, N.C.; Sues, H.-D. (eds.). *In the Shadow of the Dinosaurs: Early Mesozoic Tetrapods*. Cambridge and New York: Cambridge University Press. pp. 161–170. Archived from [the original](http://www.ldeo.columbia.edu/users/polsen/newark_gechron/sues_et_al_94.pdf) (PDF) on 2016-03-03. Retrieved 2010-04-23.

1. **[^](#cite_ref-IRB05_6-0)** Irmis, R.B. (2005). ["The vertebrate fauna of the Upper Triassic Chinle Formation in Northern Arizona"](http://socrates.berkeley.edu/~irmisr/chinlerev.pdf) (PDF). In Nesbitt, S.J.; Parker, W.G.; Irmis, R.B. (eds.). *Guidebook to the Triassic Formations of the Colorado Plateau in northern Arizona: Geology, Paleontology, and History*. Mesa Southwestern Museum Bulletin. Vol. 9. pp. 63–88.

1. **[^](#cite_ref-KP94b_7-0)** Kaye, F.T.; Padian, K. (1994). "Microvertebrates from the *Placerias* Quarry: a window on Late Triassic vertebrate diversity in the American Southwest". In Fraser, N.C.; Sues, H.-D. (eds.). *In the Shadow of the Dinosaurs: Early Mesozoic Tetrapods*. Cambridge and New York: Cambridge University Press. pp. 171–196.

1. **[^](#cite_ref-JM80_8-0)** Jacobs, L.L.; Murry, P.A. (1980). "The vertebrate community of the Triassic Chinle Formation near St. Johns, Arizona". In Jacobs, L.L. (ed.). *Aspects of Vertebrate History*. Flagstaff: Museum of Northern Arizona Press. pp. 55–70.

1. **[^](#cite_ref-KP92_9-0)** Kaye, F.T.; Padian, K. (1992). "Microvertebrates from the *Placerias* Quarry (Chinle Formation, Carnian, Arizona): A window on Late Triassic diversity". *Journal of Vertebrate Paleontology*. **12** (Suppl. 3): 36A. [doi](/source/Doi_(identifier)):[10.1080/02724634.1992.10011483](https://doi.org/10.1080%2F02724634.1992.10011483).

1. ^ [***a***](#cite_ref-MHS10_10-0) [***b***](#cite_ref-MHS10_10-1) [***c***](#cite_ref-MHS10_10-2) Mitchell, J.S.; Heckert, A.B.; Sues, H.-D. (2010). "Grooves to tubes: evolution of the venom delivery system in a Late Triassic "reptile"". *Naturwissenschaften*. **97** (12): 1117–1121. [Bibcode](/source/Bibcode_(identifier)):[2010NW.....97.1117M](https://ui.adsabs.harvard.edu/abs/2010NW.....97.1117M). [doi](/source/Doi_(identifier)):[10.1007/s00114-010-0729-0](https://doi.org/10.1007%2Fs00114-010-0729-0). [PMID](/source/PMID_(identifier)) [21060984](https://pubmed.ncbi.nlm.nih.gov/21060984).

1. ^ [***a***](#cite_ref-NN10_11-0) [***b***](#cite_ref-NN10_11-1) Kaplan, Matt (17 November 2010). ["When snake fangs moved out of the groove"](http://www.nature.com/news/2010/101117/full/news.2010.617.html). *Nature*. [doi](/source/Doi_(identifier)):[10.1038/news.2010.617](https://doi.org/10.1038%2Fnews.2010.617). Retrieved 23 November 2010.

## External links

- [*Uatchitodon*](https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=57686) in the [Paleobiology Database](/source/Paleobiology_Database)

v t e Archosauromorpha Kingdom: Animalia Phylum: Chordata Class: Sauropsida Clade: Diapsida Clade: Sauria Clade: Archelosauria Sauropsida see Sauropsida Archosauromorpha see below↓ Archosauromorpha Archosauromorpha †Aenigmastropheus †Czatkowiella †Elachistosuchus? †Elessaurus †Malutinisuchus †Manistropheus †Mecistotrachelos †Prolacertoides †Protorosaurus †Rhombopholis †Vritramimosaurus †Tanysauria Jesairosaurus? Trachelosauridae Austronaga Dinocephalosaurus Fuyuansaurus? Gracilicollum? Protanystropheus Pectodens Sclerostropheus? Trachelosaurus Sharovipterygidae? Ozimek Sharovipteryx Tanystropheidae Akidostropheus Amotosaurus Augustaburiania Cosesaurus Fuyuansaurus? Gracilicollum? Gwyneddosaurus Langobardisaurus Luxisaurus Macrocnemus Raibliania Sclerostropheus? Tanystropheus Tanytrachelos Sharovipterygidae? Crocopoda †Boreopricea †Cryptovaranoides? †Tasmaniosaurus †Teyujagua †Allokotosauria see Allokotosauria †Rhynchosauria see Rhynchosauria †Prolacertidae? Kadimakara Prolacerta Archosauriformes see below↓ Archosauriformes Archosauriformes †Antarctanax †Cuyosuchus †Eorasaurus? †Kalisuchus †Koilamasuchus †Sarmatosuchus †Syntomiprosopus †Proterosuchidae Archosaurus Chasmatosuchus? Gamosaurus Jaikosuchus Proterosuchus Samsarasuchus Tsylmosuchus? Vonhuenia? †Protopyknosia Kranosaura Triopticus †Erythrosuchidae Bharitalasuchus Chalishevia Erythrosuchus Fugusuchus? Garjainia Guchengosuchus Shansisuchus Uralosaurus Eucrocopoda †Asperoris †Dorosuchus †Heteropelta †Litorosuchus †Marcianosuchus †Polymorphodon †Silescelida †Vancleavea †Euparkeriidae Euparkeria Halazhaisuchus Osmolskina †Proterochampsia see Proterochampsia Crurotarsi †Phytosauria see Phytosauria Archosauria Incertae sedis †Sikannisuchus? †Smok Avemetatarsalia see Avemetatarsalia includes birds Pseudosuchia see Pseudosuchia includes crocodilians Related topics Tooth taxa †Crosbysaurus †Lucianosaurus †Tecovasaurus †Palaeosaurus †Protecovasaurus †Uatchitodon †Zanclodon Nomina dubia †Albisaurus †Ankistrodon †Avipes †Blomosuchus †Collilongus †Exilisuchus †Fenhosuchus †Megacnemus †Microcnemus †Vjushkovisaurus †Wangisuchus Paraphyletic groups Proterosuchia Protorosauria Thecodontia Possible members Choristodera Drepanosauromorpha Kuehneosauridae Ichthyosauromorpha Sauropterygia Thalattosauria Category

Taxon identifiers Uatchitodon Wikidata: Q7876363 GBIF: 4821697 IRMNG: 1039300 Open Tree of Life: 4127220 Paleobiology Database: 57686

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Adapted from the Wikipedia article [Uatchitodon](https://en.wikipedia.org/wiki/Uatchitodon) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Uatchitodon?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.