Grooves to tubes: evolution of the venom delivery system in a Late Triassic “reptile”
- 531 Downloads
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.
KeywordsVenom Uatchitodon Uatchitodon schneideri Evolutionary trajectory Triassic
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.
- Bogert CM (1943) Dentitional phenomena in cobras and other elapids with notes on adaptive modifications of fangs. Bull Am Mus Nat Hist 81:285–360Google Scholar
- Fry BG, Wroe S, Teeuwisse W, van Osch MJP, Moreno K, Ingle J, McHenry C, Ferrara T, Clausen P, Scheib H, Winter KL, Greisman L, Roelants K, van der Weerd L, Clemente CJ, Giannakis E, Hodgson WC, Luz S, Martelli P, Krishnasamy K, Kochva E, Kwok HF, Scanlon D, Karas J, Citron DM, Goldstein EJC, Mcnaughtan JE, Norman JA (2009) A central role for venom in predation by Varanus komodoensis (Komodo dragon) and the extinct giant Varanus (Megalania) prisca. Proc Nat Acad Sci USA 106:8969–8974CrossRefPubMedGoogle Scholar
- Gianechini F, Agnolín F, Ezcurra M (2010) A reassessment of the purported venom delivery system of the bird-like raptor Sinornithosaurus. Paläont Z (Early view) doi: 10.1007/s12542-010-0074-9
- Godefroit P, Cuny G (1997) Archosauriform teeth from the Upper Triassic of Saint-Nicolas-de-Port (northeastern France). Palaeovertebrata 26:1–34Google Scholar
- Heckert AB (2004) Late Triassic microvertebrates from the lower Chinle Group (Otischalkian–Adamanian: Carnian), Southwestern U.S.A. Bull New Mex Mus Nat Hist Sci 27:1–170Google Scholar
- Kaye FT, Padian K (1994) Microvertebrates from the Placerias Quarry: a window on Late Triassic vertebrate diversity in the American Southwest. In: Fraser NC, Sues H-D (eds) In the shadow of the dinosaurs: early Mesozoic tetrapods. Cambridge University Press, Cambridge, pp 171–196Google Scholar
- Lucas SG, Heckert AB, Hunt AP (1997) Lithostratigraphy and biostratigraphic significance of the Placerias quarry, east-central Arizona. Neues Jb Geol Paläontol Abh 203:23–46Google Scholar
- Sander PM (1999) The microstructure of reptilian tooth enamel: terminology, function, and phylogeny. Münchener Geowissenschafliche Abhandlungen Reihe A 38:1–102Google Scholar
- Sues H-D, Olsen PE, Kroehler PA (1994) Small tetrapods from the Upper Triassic of the Richmond basin (Newark Supergroup), Virginia. In: Fraser NC, Sues H-D (eds) In the shadow of the dinosaurs: early Mesozoic tetrapods. Cambridge University Press, Cambridge, pp 161–170Google Scholar