Herbivory is a common ecological function among extant lepidosaurs, but little is known about the origin of this feeding strategy within Lepidosauria. Here we describe a sphenodontian (Lepidosauria) from the Late Triassic of western North America, Trullidens purgatorii n. gen. n. sp., that reveals new aspects of the earliest radiation of herbivorous lepidosaurs. This taxon is represented by an isolated lower jaw with robust structure bearing transversely widened dentition and extensive wear facets, suggesting a masticatory apparatus specialized for herbivory. An unusual ‘incisor-like’ tooth is present at the anterior end of the jaw; a unique feature among lepidosaurs, this tooth is convergent with the incisors of extant rodents and lagomorphs. Phylogenetic analyses support the placement of this taxon within opisthodontian sphenodontians, a group sharing derived cranio-dental morphologies specialized for herbivory. The new taxon was recovered in a recently discovered and unnamed series of Upper Triassic strata in southeastern Colorado, USA, exposed in Canyons incised by the Purgatoire River and its tributaries. These strata comprise a dominantly red-bed sequence of conglomerates, sandstones, and siltstones deposited in a fluvio-lacustrine setting, preserving a Late Triassic biota of invertebrate and vertebrate ichnofossils, plant macrofossils, bony fish, temnospondyl amphibians, and reptiles. We use aetosaur osteoderms as biostratigraphic links to the nearby Chinle Formation of Arizona, USA, establishing a middle Norian age for these strata. The presence of an opisthodontian from western equatorial Pangaea in the Norian Stage reveals a near-global radiation of this clade across the Pangaean supercontinent during the Late Triassic.UUID: http://zoobank.org/A737c03f-863a-488e-a860-5cc914548774.

中文翻译：

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来自北美西部三叠纪晚期古生物群的新蝶龙目（爬行动物：鳞龙类）揭示了草食性鳞龙类的最早辐射

食草是现存鳞龙类中常见​​的生态功能，但对于鳞龙类中这种摄食策略的起源知之甚少。在这里，我们描述了北美西部晚三叠世的蝶齿龙目（鳞龙目），炼金术士n. 将军 n. sp.，它揭示了草食性鳞龙类最早辐射的新方面。该分类群由一个孤立的下颌代表，具有坚固的结构，具有横向加宽的牙列和广泛的磨损面，表明专门用于食草的咀嚼装置。下颌前端有一颗不寻常的“门牙状”牙齿；鳞龙类中的一个独特特征，这颗牙齿与现存啮齿动物和兔形动物的门牙会聚。系统发育分析支持将这一分类群置于蛇齿兽类蝶齿类动物中，该类群共享专门用于食草动物的衍生颅齿形态。在美国科罗拉多州东南部最近发现且未命名的上三叠统地层系列中发现了新的分类单元，这些地层暴露在被炼狱河及其支流切割的峡谷中。这些地层包括沉积在河湖相环境中的主要红层砾岩、砂岩和粉砂岩序列，保留了无脊椎动物和脊椎动物石化石、植物大型化石、硬骨鱼、两栖动物和爬行动物的晚三叠世生物群。我们使用 aetosaur 骨皮作为与美国亚利桑那州附近 Chinle 组的生物地层联系，为这些地层建立了中诺里纪时代。在诺里安阶段，来自西赤道盘古大陆的角齿兽人的存在揭示了该进化枝在晚三叠世期间横跨泛大陆超大陆的近乎全球辐射。UUID：植物大型化石、硬骨鱼、temnospondyl 两栖动物和爬行动物。我们使用 aetosaur 骨皮作为与美国亚利桑那州附近 Chinle 组的生物地层联系，为这些地层建立了中诺里纪时代。在诺里安阶段，来自西赤道盘古大陆的角齿兽人的存在揭示了该进化枝在晚三叠世期间横跨泛大陆超大陆的近乎全球辐射。UUID：植物大型化石、硬骨鱼、temnospondyl 两栖动物和爬行动物。我们使用 aetosaur 骨皮作为与美国亚利桑那州附近 Chinle 组的生物地层联系，为这些地层建立了中诺里纪时代。在诺里安阶段，来自西赤道盘古大陆的角齿兽人的存在揭示了该进化枝在晚三叠世期间横跨泛大陆超大陆的近乎全球辐射。UUID：http://zoobank.org/A737c03f-863a-488e-a860-5cc914548774.