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| Pliosaurid-like plesiosaur mandible section (PIMUZ A/III0521) recovered from the Passwang Formation near Arisdorf (Switzerland).
in Sachs, Klug & Kear, 2019.
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Abstract
Here, we describe part of a large-bodied macrophagous plesiosaur jaw from the lower Bajocian (Middle Jurassic) Passwang Formation near Arisdorf in the Basel-Land canton of Switzerland. The specimen preserves the posterior glenoid extremity of the right mandibular ramus comprising the surangular, angular, articular, and probably the prearticular. Notable character states include a transversely expanded surangular that incorporates a prominent medial ridge adjacent to the glenoid and a shallow dorsal fossa, together with a conspicuous trough extending across the lateral surfaces of both the surangular and angular; there is also a basally broad and medially deflected retroarticular process. Collectively, these features suggest affinities with Middle–Late Jurassic pliosaurids, as well as some coeval rhomaleosaurids. Based on such comparisons, we estimate that the Passwang Formation mandible was approximately 1.5 m long when complete, and thus approaches the size range of the largest-known pliosaurids. This discovery supplements the sparse record of diagnostic pliosaurid-like remains from Switzerland and contributes to the currently incomplete knowledge of pre-Callovian Middle Jurassic plesiosaurs globally.
Keywords: Plesiosauria, Pliosauromorph, Pliosauridae, Rhomaleosauridae, Bajocian, Apex predator
Systematic palaeontology
Sauropterygia Owen 1860
Plesiosauria de Blainville 1835
?Pliosauridae indet.
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| Pliosaurid-like plesiosaur mandible section (PIMUZ A/III0521) recovered from the Passwang Formation near Arisdorf (Switzerland). |
Material: PIMUZ A/III0521, the glenoid extremity of a right mandibular ramus.
Stratigraphic and geographic provenance: Emileia sauzei Zone (early Bajocian) of the upper Passwang Formation exposed on the north-western slope of the Eileten, southeast of Arisdorf, Canton of Basel-Land, north-western Switzerland.
Conclusions:
Our documentation of the incomplete plesiosaur mandible, PIMUZ A/III0521, from the lower Bajocian upper Passwang Formation near Arisdorf in Basel-Land is significant because it provides a new addition to the hitherto sparse record of plesiosaur fossils from Switzerland (e.g. Geister 1998; Peyer 1940; von Meyer 1856; Wild 1968). It is also one of only a handful of pre-Callovian Middle Jurassic plesiosaur occurrences currently reported from Europe, and indeed, worldwide (e.g. Buchy 2004; Gasparini 1997; Gasparini and Fernández 2006; Godefroit 1994; Kear 2012; Sachs and Hornung 2016; Vincent et al. 2007, Vincent et al. 2013b). PIMUZ A/III0521 displays key traits that suggest affinity with Pliosauridae (Benson and Druckenmiller 2014), as well as morphological compatibility with coeval taxa, especially Simolestes keileni (Godefroit 1994), and the rhomaleosaurids Maresaurus coccai (Gasparini 1997) and Borealonectes russelli (Sato and Wu 2008). However, PIMUZ A/III0521 is proportionately larger, with an estimated complete mandible length of around 1.5 m; this not only hints at possible taxonomic distinction, but also implies that pliosaurid-like plesiosaurs had achieved giant body sizes and radiated ecologically as dominant marine apex predators by at least the early Middle Jurassic.
Sven Sachs, Christian Klug and Benjamin P. Kear. 2019. Rare Evidence of A Giant Pliosaurid-like Plesiosaur from the Middle Jurassic (lower Bajocian) of Switzerland. Swiss Journal of Palaeontology. DOI: 10.1007/s13358-019-00200-9
Rare evidence of a giant Jurassic pliosaur from Switzerland uu.se/en/news-media/news/article/?id=13528
