Temporal range: Cretaceous
An artist's illustration of Acamptonectes densus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: †Ichthyosauria
Family: †Ophthalmosauridae
Subfamily: †Ophthalmosaurinae
Genus: Acamptonectes
Fischer et al., 2012
Species: A. densus
Binomial name
Acamptonectes densus
Fischer et al., 2012

Acamptonectes(meaning "rigid swimmer") is an extinct genus of ichthyosaur . It is an extinct genus of ophthalmosaurid ichthyosaur that lived between 134 and 132 million years ago during the Early Cretaceous. Known from fossil deposits in England and Germany, the genus currently contains the single species A. densus, which was first described in 2012. Its discovery was important in the research of ichthyosaurs, as being one of the first known ophthalmosaurines from the Early Cretaceous, it provided evidence that no mass extinction of ichthyosaurs occurred during the Jurasic-Cretaceous boundary as previously understood. Nevertheless, Acamptonectes remains one of only eight genera of ichthyosaurs known during the Cretaceous. In life, Acamptonectes was probably a generalist predator. Its teeth were slender and textured with longitudinal ridges, which were best adapted for impaling prey; as a result, Acamptonectes likely fed on soft, fleshier prey such as fish and squid. The ichthyosaur's body was rigid and compact, which was suited for swimming at high speeds in tuna-like locomotion. Its remains have been discovered in the United Kingdom and Germany.

History of discovery

Over a series of weekends in 1958, four students and a technician from the geology department of Hull University collected an ichthyosaur (or "fish lizard", a Mesozoic group of marine reptiles) specimen from the Speeton Clay Formation of Speeton in northern England. It was transferred to the Hunterian Museum of the University of Glasgow in 1991, when the geology department of Hull University was closed, where it was catalogued as specimen GLAHM 132855 (it was also known as the "Speeton Clay ichthyosaur"). It consists of a partial skeleton of an adult, including a fragmentary skull roof, a mandible, the axial skeleton, and the scapular girdle. Palaeontologist Robert M. Appleby described the specimen and assigned it to the genus Platypterygius as the species "P. speetoni" (which he considered primitive within that genus), in a monograph that remained unpublished at the time of his death in 2003. A second specimen of this ichthyosaur was found in 1985, also in the Speeton Clay, and is catalogued as NHMUK R11185 at the Natural History Museum, London. It consists of a partial rostrum and mandible, fragmentary ribs, and a complete right humerus





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