''Hydrotherosaurus'' (meaning "fisherman lizard") is an extinct genus of

elasmosaurid Elasmosauridae, often called elasmosaurs or elasmosaurids, is an extinct family of plesiosaurs that lived from the Hauterivian stage of the Early Cretaceous to the Maastrichtian stage of the Late Cretaceous period (c. 130 to 66 mya). The taxo ...

plesiosaur The Plesiosauria or plesiosaurs are an Order (biology), order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia. Plesiosaurs first appeared in the latest Triassic Period (geology), Period, possibly in the Rhaetian st ...

from the Upper

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

(

Maastrichtian The Maastrichtian ( ) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (geology), age (uppermost stage (stratigraphy), stage) of the Late Cretaceous epoch (geology), Epoch or Upper Cretaceous series (s ...

stage)

Moreno Formation The Moreno Formation is a Mesozoic geologic Formation (geology), formation located in San Joaquin Valley (California).Dinosaur remains diagnostic to the genus level are among the fossils that have been recovered from the formation.Weishampel, et ...

of Fresno County,

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

, USA. The only known species, ''H. alexandrae'', was named for

Annie Montague Alexander Annie Montague Alexander (29 December 1867 – 10 September 1950) was an Exploration, explorer, Natural history, naturalist, Paleontology, paleontological collector, and Philanthropy, philanthropist. She founded the University of California Museu ...

in 1943 by

Samuel Paul Welles Samuel Paul Welles (November 9, 1909 – August 6, 1997) was an American palaeontologist. Welles was a research associate at the Museum of Palaeontology, University of California, Berkeley. He took part in excavations at the Placerias Quarry in ...

Discovery and naming

The first remains of ''Hydrotherosaurus'' to be found were several

vertebra Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spina ...

e discovered by Frank C. Paiva on his own property in the

Panoche Hills The Panoche Hills are a low mountain range in the Southern Inner California Coast Ranges System, in western Fresno County, California, Fresno County, California. They are east of the Diablo Range, on the west side of the San Joaquin Valley. They ...

Fresno County, California Fresno County (), officially the County of Fresno, is a county located in the central portion of the U.S. state of California. As of the 2020 United States census, the population was 1,008,654. The county seat is Fresno, the fifth-most popu ...

, which were taken to

Berkeley Berkeley most often refers to: *Berkeley, California, a city in the United States **University of California, Berkeley, a public university in Berkeley, California *George Berkeley (1685–1753), Anglo-Irish philosopher Berkeley may also refer to ...

in the spring of 1937 by W. M. Tucker, who was the Chairman of the Department of Geology of

Fresno State College California State University, Fresno (Fresno State) is a public university in Fresno, California, United States. It is part of the California State University system. The university had a fall 2020 enrollment of 25,341 students. It offers 60 ba ...

. Afterwards, Fresno State College and the

University of California Museum of Paleontology The University of California Museum of Paleontology (UCMP) is a paleontology museum located on the campus of the University of California, Berkeley. The museum is within the Valley Life Sciences Building (VLSB), designed by George W. Kelham ...

organized a joint expedition which would uncover a nearly complete fossilized skeleton of the animal, with only parts of the skull,

shoulder girdle The shoulder girdle or pectoral girdle is the set of bones in the appendicular skeleton which connects to the arm on each side. In humans, it consists of the clavicle and scapula; in those species with three bones in the shoulder, it consists o ...

, flippers and certain vertebral elements missing. This specimen, designated UCMP 33912, was collected in a ravine on the property of the Sun Ray Gypsum Mine, about 22 miles west of

Mendota, California Mendota is a city in Fresno County, California, United States. The population was 12,595 at the 2020 U.S. Census. State Routes 180 and 33 run through the agricultural city. Mendota is located south-southeast of Firebaugh. Geography Accordi ...

, and the deposits from which it originates are part of the

. In 1943, American paleontologist

found that the specimen was notably different from other known

s and declared it as the type specimen of a new genus and species which he named ''Hydrotherosaurus alexandrae''. The generic name means "fisherman lizard", while the

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

honors

, who has done plenty of research on the vertebrates of the western United States.

Description

''Hydrotherosaurus'' was a medium-sized plesiosaur, measuring approximately long.Supplementary Information
/ref> It has one of the longest necks relative to total length among elasmosaurids, with 60 vertebrae in total. It had a small head that measured about long, a streamlined body, and four large flippers that were specially designed to help the huge animal balance, move, and accelerate itself.

References

Late Cretaceous plesiosaurs of North America Fossil taxa described in 1943 Elasmosauridae Taxa named by Samuel Paul Welles Sauropterygian genera {{plesiosaur-stub

Discovery and naming

Description

See also

References