ABSTRACT
The seas of the Mesozoic (266–66 Myr ago) were remarkable for predatory marine reptiles, but their modes of locomotion have been debated. One problem has been the absence of tracks, although there is no reason to expect that swimmers would produce tracks. We report here seabed tracks made by Mesozoic marine reptiles, produced by the paddles of nothosaurs (Reptilia, Sauropterygia) in the Middle Triassic of the Luoping localities in Yunnan, southwestern China. These show that the track-making nothosaurs used their forelimbs for propulsion, they generally rowed (both forelimbs operating in unison rather than alternately), and the forelimb entered medially, dug in as the paddle tip gained purchase, and withdrew cleanly. These inferences may provide evidence for swimming modes, or it could be argued that the locomotory modes indicated by the tracks were restricted to such contact propulsion. Such punting behaviour may have been used to flush prey from the bottom muds.
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| The nothosaur, Lariosaurus, prowls along the seafloor, searching for lobsters and fishes hiding in the soupy bottom mud. She uses her front paddles to punt along, keeping at the right height for feeding, and leaving the Dikoposichnus track behind. The reconstruction scene is based on the tracks, and our identification of the most likely track maker, as well as an interpretation of a likely function. |
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| A small nothosaur (Lariosaurus cf. hongguoenis) forages on a shallow seabed in search of lobsters and small fishes. It propels itself along with rowing motions of it's paddle-like forelimbs, leaving behind distinctive prints on the sediment (ichnotaxon Dikoposichnus luopingensis)
Lariosaurus goes for a stroll by Gogosardina on @deviantART
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| Relationship of the print impressions (lower slab) and the mould. Photograph taken within minutes of uncovering a new trackway, showing the imprint moulds on the overlying bed bottom and the imprints on the top of bed 107. The animal was moving from left to right.
photo: Chengdu Center of China Geological Survey.
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Zhang Qiyue, Wen Wen, Hu Shixue, Michael J Benton, Zhou Changyong, Xie Tao, Lu Tao, Huang Jinyuan, Brian Choo, Chen Zhong-Qiang, Liu Jun, Zhang Qican. 2014. Nothosaur Foraging Tracks from the Middle Triassic of southwestern China. Nature Communications. 5(3973): 1-12. DOI: dx.doi.org/10.1038/ncomms4973
Newly discovered paddle prints show how ancient sea reptiles swam
Trackways formed on an ancient seabed have shed new light on how nothosaurs, ancient marine reptiles that lived during the age of the dinosaurs, propelled themselves through water. The evidence is described by a team from Bristol and China in Nature Communications today.
NH Notes: Discovery of a Marine Reptile Fossil Trackway