Giant ichthyosaurs of the Late Triassic: current challenges at excavating a new specimen from France

Among marine reptiles of the Mesozoic, ichthyosaurs exemplify a typical case of morphological adaptation toward a pelagic lifestyle. Beside their extensive stratigraphic range, spanning the early Triassic to mid-Cretaceous interval, they are noteworthy for having achieved gigantic (up to 21 m total length) body sizes during the first third of their evolutionary history. Such sizes were never paralleled in subsequent ichthyosaur lineages. The presence of such giants, belonging to Shastasauridae and Cymbospondylidae, is now well attested from the North American fossil record, especially prior to the Norian (e.g. Nicholls and Manabe, 2004; Scheyer et al., 2014; Sander et al., 2021). Although already recorded from Asia by limited material such as Himalayasaurus (Motani et al., 1999), the European record also begins to unveil giant forms of younger stratigraphic age (Fischer et al., 2014; Martin et al. 2015; Lomax et al., 2018; Sander et al., 2022). Yet, despite their giant size, the European record is limited to a handful of partial skeletal elements. Here, we report new postcranial material belonging to a giant shastasaurid from the Rhaetian of Var, southern France. We recount the logistical attempts at retrieving skeletal elements of a single individual cropping out from the middle of a cliff since 2015. The elements recovered so far are referred to Shonisaurus sp. on the basis of vertebral morphology. Although challenging in its extraction, such specimen holds promises for questioning the ecological role of giant ichthyosaurs and the reason of their extinction at the end of the Triassic.
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