Thursday 17 October 2019

Eromangateuthis soniae: A large fossil Squid from the Early Cretaceous of Queensland, Australia.

The Family Plesioteuthididae are a group of elongate, flattened Cephalopod Molluscs known from Cretaceous deposits. Their exact taxonomic placement is unclear, with some palaeontologists regarding them as True Squid, Decapodiformes, while others believe them to be Vampire Squid, Vampyromorphida, a group more closely related to Octopus. While whole body fossils of Plesioteuthidids are known from exceptional deposits such as the Solnhoffen Limestone of Germany, most are known only from their gladius (a rigid internal structure that supports the squid's body).

In 1993 palaeontologist Mary Wade of the Queensland Museum described a series of exceptionally large  Plesioteuthidid gladii from the late Early Cretaceous Allaru Formation of southern Queensland, the largest of which was 1.2 m in length, suggesting a living animal twice the size of the living Giant Pacific Octopus, Enteroctopus dofleini. She considered these fossils to belong to the genus Boreopeltis, a group otherwise restricted to the Northern Hemsiphere, and described them as a new species, Boreopeltis soniae.

In a paper published in the journal Paleontological Contributions on 8 October 2019, Dirk Fuchs of the Bayerische Staatssammlung für Paläontologie und Geologie, re-examines the material from which Wade describes the material from which Wade described Boreopeltis soniae, as well as other specimens from the collection of the Kronosaurus Corner, a public museum in Richmond, Queensland.

Fuchs could not find any grounds for including the Allaru Formation materian within the genus  Boreopeltis, noting that the specimens 'have little in common' with Boreopeltis, and that 'neither the anterior nor the posterior gladius part show a vague resemblance'. The Allaru Formation specimens have a pronounced median (middle) keel, which is absent in Boreopeltis, whereas Boreopeltis has two reinforcing lateral (side) keels, which are strongly pronounced in the midpart of the fossil and project forwards at the front, but which are completely absent in the Allaru Formation material. The Allaru Formation specimens also have a pronounced waist, absent in Boreopeltis, and the conus (lateral portion of the gladius) of the Allaru Formation specimens is flattened, while that of Boreopeltis is slightly conical.

Based upon this analysis Fuchs concludes that the specimens should not be placed within the genus  Boreopeltis, and erects a new genus to describe them, Eromangateuthis, from the Eromanga Basin, where the fossils were discovered, plus '-teuthis', meaning Squid. Thus the species name for the specimens bcomes Eromangateuthis soniae.

Comparative gladius morphology of the Boreopeltis species complex and Eromangateuthis soniae. (A) Boreopeltis helgolandiae (Aptian, Germany); (B) Boreopeltis sagittata (Tithonian, Lebanon); (B1) gladius reconstruction in dorsal view; (B2) photograph of specimen BSPG 2011 XLI 332-08; (B3) gladius reconstruction in ventrolateral view; (C) Boreopeltis smithi (Cenomanian, Lebanon); (C1) gladius reconstruction in dorsal view; (C2) gladius reconstruction in ventrolateral view; (D) Eromangateuthis soniae (Albian, Queensland); (D1) gladius reconstruction in dorsal view; (D2) gladius reconstruction in ventrolateral view; (D3) photograph of a gladius in the exhibition of the Kronosaurus Korner Museum, Richmund, Queensland, Australia, dorsal view; black dots show position of conus apex; scale bars are 10 cm. Fuchs (2019).

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