The type species, S. megistorhynchus, was originally named as a species Steneosaurus in 1866.[3] The genus Steneosaurus was used as a longtime wastebasket taxon for various teleosauroid specimens and had more than a dozen species. The type species, Steneosaurus rostromajor is undiagnostic, making the genus and species dubious and invalid.[1] Additionally, many species of so-called "Steneosaurus" were found to be quite different and unrelated to one another, thus needing new generic names.[1]
In 2020, Michela Johnson and colleagues reassigned "Steneosaurus" megistorhynchus to the new genus Seldsienean, resulting in the new combination Seldsienean megistorhynchus.[1] The generic name is derived from Old English and translates to “seldom seen one” in reference to its fossils being rarer compared to other Bathonian teleosauroids.[1]
Classification
Seldsienean was initially recovered as a basal member of Machimosauridae, a family of large-bodied, marine-adapted reptiles. Members of this group are characterized by robust skulls, powerful jaws, and heavily built bodies, adaptations that positioned them among the apex predators within their respective marine ecosystems. The cladogram below is from the 2020 analysis by Johnson and colleagues.[1]
A later study in 2024 by Mark Young and colleagues found Seldsienean to be part of a different teleosauroid group called Teleosauridae. It was found to be most closely related to the subgroup Aeolodontini.[4]
Young et al., 2024 also submitted a proposal to the International Commission on Zoological Nomenclature to designate Seldsienean megistorhynchus as the new type species for Steneosaurus and to adopt this revised type species as the basis for defining the family Steneosauridae.[4] However, as of 2025 this issue is not fully resolved and Seldsienean remains valid.
Ecology
Based on its jaw morphology, Seldsienean is thought to have been a longirostrine generalist. It possessed long thin jaws that had a fast but relatively weak bite. These adaptations point to a lifestyle of catching and eating fish and other smaller marine animals.[2]
↑ Eudes-Deslongchamps, J. A. "Sur la découverte d’une mâchoire inférieure entière de Steneosaurus megistorhynchus (GEOFF.) trouvée à Allemagne et comparaison de cette espèce avec le Teleosaurus larteti (DESL.)." Bulletin de la Société linnéenne de Normandie 10 (1866): 80-85.
This page is based on this Wikipedia article Text is available under the CC BY-SA 4.0 license; additional terms may apply. Images, videos and audio are available under their respective licenses.
