Scalamagnus is an extinct genus of polycotylid plesiosaur from the Late Cretaceous Tropic Shale Formation of the United States. The genus contains a single species S. tropicensis, known from a skull and two partial skeletons. Scalamagnus was historically considered to represent a species of the genus Dolichorhynchops before it was moved to its own genus.
Scalamagnus is an extinct genus of polycotylid plesiosaur from the Late Cretaceous Tropic Shale Formation of the United States. The genus contains a single species S. tropicensis, known from a skull and two partial skeletons. Scalamagnus was historically considered to represent a species of the genus Dolichorhynchops before it was moved to its own genus.
==History== The taxon was first named as a species of Dolichorhynchops by Rebecca Schmeisser McKean in 2012. The specific name is derived from the name of the Tropic Shale, in which the two specimens were found. It is known from the holotype MNA V10046, an almost complete, well-preserved long skeleton including most of the skull and from the referred specimen MNA V9431, fragmentary postcranial elements. It was collected between 2003 and 2005 by the Museum of Northern Arizona from a single locality within the Tropic Shale of Utah, dating to the early Turonian stage of the early Late Cretaceous, about 93.5-91 million years ago. D. tropicensis extended the known stratigraphic range for Dolichorhynchops back by approximately 7 million years. Previously three additional polycotylid taxa, Eopolycotylus, Palmulasaurus and Trinacromerum, have been named from the same formation, two of which are currently endemic to the Tropic Shale. A 2023 study assigns D. tropicensis to a new genus, Scalamagnus. The generic name is a combination of the Latin scala, "staircase", and magnus, "large", referring to the Grand Staircase-Escalante National Monument.
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).