Mitchell Jonathan S, Heckert Andrew B, Sues Hans-Dieter
Committee on Evolutionary Biology, The University of Chicago, 1025 57th Culver 402, Chicago, IL 60637, USA.
Naturwissenschaften. 2010 Dec;97(12):1117-21. doi: 10.1007/s00114-010-0729-0.
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.
毒液输送系统存在于广泛的现存和化石脊椎动物中，主要基于口腔适应性。牙齿从未经过改造的（科莫多龙）到类似于皮下注射针头的高度特化毒牙（前沟牙和管牙类蛇）不等。发育生物学家已经记录了毒牙进化的内陷途径的证据，即凹槽折叠形成更进化的状态。然而，已知最古老的有毒类群成员与它们现存的亲属保持相同的状态，因此没有过渡的化石证据。基于对先前已知标本与来自北卡罗来纳州新发现牙齿的比较，我们描述了一种晚三叠世主龙形类的新物种——乌阿奇托龙，并提供了详细分析，为毒液传导提供了证据，并记录了从浅沟到完全封闭的管状管道的完整结构系列。虽然仅从牙齿为人所知，但乌阿奇托龙具有复合锯齿且每颗牙齿上有两条毒液管道，具有高度的诊断性。此外，尽管乌阿奇托龙不是蛇，但它揭示了羊膜动物毒液输送系统的进化轨迹，并为主龙类双孔亚纲动物的毒液传导提供了确凿证据。
