A Middle Jurassic mammaliaform with aquatic adaptations and preserved integument. The fossil supplies a minimum occurrence for a fur-bearing covering, not the exact origin date of endothermy. [ref]
A swimming mammaliaform from the Middle Jurassic and ecomorphological diversification of early mammals by Qiang Ji and others. Science 311, pp. 1123–1127; Castorocauda skeleton and preserved integument
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