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The mystery of Mystriosaurus: Redescribing the poorly known Early Jurassic teleosauroid thalattosuchians Mystriosaurus laurillardi and Steneosaurus brevior

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Sachs S., Johnson M. M., Young M. T., Abel P.

Acta Palaeontologica Polonica

2019

tom 64

nr 3

The genus Mystriosaurus, established by Kaup in 1834, was one of the first thalattosuchian genera to be named. The holotype, an incomplete skull from the lower Toarcian Posidonienschiefer Formation of Altdorf (Bavaria, southern Germany), is poorly known with a convoluted taxonomic history. For the past 60 years, Mystriosaurus has been considered a subjective junior synonym of Steneosaurus. However, our reassessment of the Mystriosaurus laurillardi holotype demonstrates that it is a distinct and valid taxon. Moreover, we find the holotype of “Steneosaurus” brevior, an almost complete skull from the lower Toarcian Whitby Mudstone Formation of Whitby (Yorkshire, UK), to be a subjective junior synonym of M. laurillardi. Mystriosaurus is diagnosed in having: a heavily and extensively ornamented skull; large and numerous neurovascular foramina on the premaxillae, maxillae and dentaries; anteriorly oriented external nares; and four teeth per premaxilla. Our phylogenetic analyses reveal M. laurillardi to be distantly related to Steneosaurus bollensis, supporting our contention that they are different taxa. Interestingly, our analyses hint that Mystriosaurus may be more closely related to the Chinese teleosauroid (previously known as Peipehsuchus) than any European form.

A new species of the metriorhynchid crocodylomorph Cricosaurus from the Upper Jurassic of southern Germany

100%

Sachs S., Young M. T., Abel P., Mallison H.

Acta Palaeontologica Polonica

2019

tom 64

nr 2

Here we describe a new species of the metriorhynchid thalattosuchian Cricosaurus, C. bambergensis sp. nov., from the Upper Jurassic Torleite Formation of Wattendorf near Bamberg, Bavaria (southern Germany). The holotype and only known specimen is a nearly complete skeleton that shows a number of diagnostic traits including a bicarinate dentition formed by labiolingually compressed tooth crowns that lack a conspicuous enamel ornamentation and the presence of a distinct midline ridge with paired depressions on the palatines. Our phylogenetic analysis recovers a grouping of Cricosaurus bambergensis sp. nov. with C. elegans and C. suevicus. The implications of the new Cricosaurus species to the species complex from the late Kimmeridgian–early Tithonian of southern Germany is discussed. Our description of C. bambergensis demonstrates that the specific, and morphological, diversity of Cricosaurus in southern Germany was higher than previously thought. This coincides with the recent trend of re-evaluating the species-complexes of extant taxa, and the identification of new “cryptic species”. As such, the crocodylomorph fossil record will need to be re- examined to ensure there is not an underestimation of their biodiversity.

Ograniczanie wyników

2 Acta Palaeontologica Polonica

2 Abel P.

2 Sachs S.

2 Young M. T.

1 Johnson M. M.

1 Mallison H.

2 2019

Wyniki wyszukiwania

The mystery of Mystriosaurus: Redescribing the poorly known Early Jurassic teleosauroid thalattosuchians Mystriosaurus laurillardi and Steneosaurus brevior

A new species of the metriorhynchid crocodylomorph Cricosaurus from the Upper Jurassic of southern Germany