Venom delivery systems occur in a wide range of extant and fossil vertebrates and are primarily based on oral adaptations. Teeth range from unmodified (Komodo dragons) to highly specialized fangs similar to hypodermic needles (protero- and solenoglyphous snakes). Developmental biologists have documented evidence for an infolding pathway of fang evolution, where the groove folds over to create the more derived condition. However, the oldest known members of venomous clades retain the same condition as their extant relatives, resulting in no fossil evidence for the transition. Based on a comparison of previously known specimens with newly discovered teeth from North Carolina, we describe a new species of the Late Triassic archosauriform Uatchitodon and provide detailed analyses that provide evidence for both venom conduction and document a complete structural series from shallow grooves to fully enclosed tubular canals. While known only from teeth, Uatchitodon is highly diagnostic in possessing compound serrations and for having two venom canals on each tooth in the dentition. Further, although not a snake, Uatchitodon sheds light on the evolutionary trajectory of venom delivery systems in amniotes and provide solid evidence for venom conduction in archosaur-line diapsids.
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We would like to acknowledge two anonymous reviewers for their helpful critiques and comments, as well as the North Carolina Museum of Natural Sciences field crew for excavating the Moncure locality, Liz Sues, Pete Kroehler, and Ken Pitt for assistance in the excavation of the Tomahawk locality and the Appalachian State University Department of Geology and Office of Student Research for travel and research grants.
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Graphs showing the Uatchitodon lateral compression data (a, b) and size-related data (c, d). Lateral compression of a U. schneideri and b U. kroehleri. c Plot of the ln of the distance from the tip as a function of the ln of tooth width (least-squares regression yields an R 2-ad = 0.97, p < 0.001) and d canal shape as a function of the fore-aft length and distance from the tip. (PDF 3 kb)
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Mitchell, J.S., Heckert, A.B. & Sues, H. Grooves to tubes: evolution of the venom delivery system in a Late Triassic “reptile”. Naturwissenschaften 97, 1117–1121 (2010). https://doi.org/10.1007/s00114-010-0729-0
- Uatchitodon schneideri
- Evolutionary trajectory