Abstract
The end-Permian mass extinction (EPME) led to reorganization of marine predatory communities, through introduction of air-breathing top predators, such as marine reptiles. We report two new specimens of one such marine reptile, Eretmorhipis carrolldongi, from the Lower Triassic of Hubei, China, revealing superficial convergence with the modern duckbilled platypus (Ornithorhynchus anatinus), a monotreme mammal. Apparent similarities include exceptionally small eyes relative to the body, snout ending with crura with a large internasal space, housing a bone reminiscent of os paradoxum, a mysterious bone of platypus, and external grooves along the crura. The specimens also have a rigid body with triangular bony blades protruding from the back. The small eyes likely played reduced roles during foraging in this animal, as with extant amniotes (group containing mammals and reptiles) with similarly small eyes. Mechanoreceptors on the bill of the animal were probably used for prey detection instead. The specimens represent the oldest record of amniotes with extremely reduced visual capacity, utilizing non-visual cues for prey detection. The discovery reveals that the ecological diversity of marine predators was already high in the late Early Triassic, and challenges the traditional view that the ecological diversification of marine reptiles was delayed following the EPME.
Highlights
The modern marine ecosystem would be incomplete without air-breathing, tetrapod predators, such as cetaceans and pinnipeds[1], which dominate the list of the heaviest marine predators
Hupehsuchia has been known since 195911 but remained poorly understood until the recent rush of discoveries made by the Wuhan Centre of China Geological Survey (WGSC)[5,12,13,14,15]
The purpose of the paper is to assess the anatomical features of E. carrolldongi that are indicative of its ecology, including the superficial resemblance to O. anatius, in order to provide further information on the ecological diversification of early marine reptiles after end-Permian mass extinction (EPME)
Summary
The modern marine ecosystem would be incomplete without air-breathing, tetrapod predators, such as cetaceans and pinnipeds[1], which dominate the list of the heaviest marine predators. Most of the earliest marine reptiles were Ichthyosauromorpha[4], a clade that eventually gave rise to fish-shaped ichthyosaurs by the latest Middle Triassic[9]. WGSC collected two new hupehsuchian specimens that reveal surprising cranial morphology from the dorsal and ventral aspects, respectively. They are referred to Eretmorhipis carrolldongi, for which only headless specimens have been known[15]. The purpose of the paper is to assess the anatomical features of E. carrolldongi that are indicative of its ecology, including the superficial resemblance to O. anatius, in order to provide further information on the ecological diversification of early marine reptiles after EPME
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