Cymbospondylus

Cymbospondylus Temporal range: Olenekian-Anisian ~251–242 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Partial holotype skeleton of C. buchseri (PIMUZ T 4351), on display at the Paleontological Museum of the University of Zurich, Switzerland.
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	†Ichthyosauria
Family:	†Cymbospondylidae
Genus:	†Cymbospondylus Leidy, 1868
Type species
†Cymbospondylus piscosus nomen dubium Leidy, 1868
Other species
List †C. petrinus Leidy, 1868 †C. buchseri Sander, 1989 †C. nichollsi Fröbisch et al., 2006 †C. duelferi Klein et al., 2020 †C. youngorum Sander et al., 2021
Synonyms
List of synonyms Synonyms of genus Chonespondylus Leidy, 1868 Synonyms of C. petrinus Chonespondylus grandis Leidy, 1868 Cymbospondylus (?) grandis (Leidy, 1868) Merriam, 1902

Cymbospondylus (meaning "cupped vertebrae") is an extinct genus of large ichthyosaurs, of which it is among the oldest representatives, that lived from the Lower to Middle Triassic in what are now North America and Europe. The first known fossils of this taxon are a set of more or less complete vertebrae which were discovered in the 19th century in the Fossil Hill member outcropping in various mountain ranges of Nevada, in the United States, before being named and described by Joseph Leidy in 1868. It is in the beginning of the 20th century that more complete fossils were discovered through several expeditions launched by the University of California, and described in more detail by John Campbell Merriam in 1908, thus visualizing the overall anatomy of the animal. While many species have been assigned to the genus, only five are recognized as valid, the others being considered synonymous, doubtful or belonging to other genera. Cymbospondylus was formerly classified as a representative of the Shastasauridae, but more recent studies consider it to be more basal, view as the type genus of the Cymbospondylidae.

As an ichthyosaur, Cymbospondylus had flippers for limbs and a fin on the tail. Like other non-parvipelvian ichthyosaurs, Cymbospondylus has a very slender profile, unlike later ichthyosaurs which have a morphology similar to those of dolphins. The different species of Cymbospondylus vary greatly in size, with the smallest reaching around 4 to 5 metres (13 to 16 ft) in length. The largest known species, C. youngorum, is estimated over 17 metres (56 ft) long, making Cymbospondylus one of the largest ichthyosaurs identified to date, but also one of the largest animals known of its time. The animal has a skull with a long, thin snout, proportionally small eye sockets, an elongated trunk, and a less pronounced tail than in later ichthyosaurs. The teeth are conical and pointed, having longitudinal ridges, indicating a diet of fishes and cephalopods, and possibly other marine reptiles for larger species.

Unlike cetaceans, Triassic ichthyosaurs like Cymbospondylus show that they reached large sizes very quickly after their appearance, probably because of the adaptive radiation of their prey, conodonts and ammonites, after the Permian–Triassic extinction. The size of ichthyosaurs began to decrease later, notably due to the increase in the size of their eyes, which were very useful for spotting prey. All established species of Cymbospondylus are known from the fossil records of Nevada and Switzerland, with referred specimens without specific affiliations having nevertheless been discovered in Idaho, the rest of the Alps and Spitsbergen, an island in Norway. The formations where the recognized species were discovered show that Cymbospondylus lived in marine ecosystems alongside molluscs like bivalves and ammonites, bony fishes like Saurichthys and coelacanths, cartilaginous fishes like hybodonts, and marine reptiles like sauropterygians and other ichthyosaurs. The different ichthyosaurs from these localities would have used different feeding strategies to avoid competition.