''Serpentisuchops'' (meaning "snaky crocodile-face") is a genus of

polycotylid Polycotylidae is a family of plesiosaurs from the Cretaceous, a sister group to Leptocleididae. They are known as false pliosaurs. Polycotylids first appeared during the Albian stage of the Early Cretaceous, before becoming abundant and widesprea ...

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 late

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 ...

Pierre Shale The Pierre Shale is a geologic formation or series in the Upper Cretaceous which occurs east of the Rocky Mountains in the Great Plains, from Pembina Valley in Canada to New Mexico. The Pierre Shale was described by Fielding Bradford Meek, Meek a ...

Wyoming Wyoming ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States, Western United States. It borders Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho t ...

, United States. The genus contains a single species, ''S. pfisterae'', known from a partial skeleton.

Discovery and naming

The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

specimen, GPM5001, was found at the Old Woman Anticline in the upper

in 1995 and brought to the collection of the Paleon Museum in Glenrock. This locality is dated to the lower

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 ...

age of the upper

period, around 69.59 to 70.00 million years old. It consists of a partial

skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...

lower jaw In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...

, and

vertebral column The spinal column, also known as the vertebral column, spine or backbone, is the core part of the axial skeleton in vertebrates. The vertebral column is the defining and eponymous characteristic of the vertebrate. The spinal column is a segmente ...

, in addition to the left ilium and pubis. In 2022, ''Serpentisuchops pfisterae'' was described as a new genus and species of polycotylid plesiosaur by Walter S. Persons, Hallie P. Street, and Amanda Kelley based on these remains. The generic name, "''Serpentisuchops''", is derived from the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

words "serpens", meaning "snake", and "suchus" meaning "crocodile", and the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

word "ops", meaning "face". 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 ...

, "''pfisterae''", honors Anna Pfister, on whose land the holotype was discovered.

Description

''Serpentisuchops'' is a medium-sized plesiosaur, reaching over in total body length. It is unusual among derived plesiosaurs, as it has both a long snout and long neck. In contrast,

elasmosaurids Elasmosauridae, often called elasmosaurs or elasmosaurids, is an extinct family (biology), family of plesiosaurs that lived from the Hauterivian Stage (stratigraphy), stage of the Early Cretaceous to the Maastrichtian stage of the Late Cretaceou ...

and microcleidids had short snouts and elongated necks, and many

pliosaurids Pliosauridae is a family (biology), family of plesiosaurian marine reptiles from the Late Triassic, Latest Triassic to the early Late Cretaceous (Rhaetian to Turonian stages). The family is more inclusive than the archetypal short-necked large he ...

and other

polycotylids Polycotylidae is a family of plesiosaurs from the Cretaceous, a sister group to Leptocleididae. They are known as false pliosaurs. Polycotylids first appeared during the Albian stage of the Early Cretaceous, before becoming abundant and widesprea ...

had long snouts and short necks. This unusual feature may have evolved because of ecological

niche partitioning In ecology, a niche is the match of a species to a specific environmental condition. Three variants of ecological niche are described by It describes how an organism or population responds to the distribution of resources and competitors (for e ...

. Its long, flexible neck may have allowed it to more effectively catch prey by striking from the side.

Classification

In their

phylogenetic analyses In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as Computational phylogenetics, phylogenetic inference. It infers the relationship among organ ...

, Persons, Street & Kelley (2022) recovered ''Serpentisuchops'' as a member of the

Polycotylinae Polycotylidae is a family of plesiosaurs from the Cretaceous, a sister group to Leptocleididae. They are known as false pliosaurs. Polycotylids first appeared during the Albian stage of the Early Cretaceous, before becoming abundant and widesprea ...

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

within

Polycotylidae Polycotylidae is a family of plesiosaurs from the Cretaceous, a sister group to Leptocleididae. They are known as false pliosaurs. Polycotylids first appeared during the Albian stage of the Early Cretaceous, before becoming abundant and widesprea ...

, as the

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

to ''

Trinacromerum ''Trinacromerum'' is an extinct genus of sauropterygian reptile, a member of the polycotylid plesiosaurs. It contains two species, ''T. bentonianum'' and ''T. kirki''. Specimens have been discovered in the Late Cretaceous fossil deposits of what ...

'', '' Georgiasaurus'', and ''

Dolichorhynchops ''Dolichorhynchops'' is an extinct genus of polycotylid plesiosaur from the Late Cretaceous of North America, containing the species ''D. osborni'' and ''D. herschelensis'', with two previous species having been assigned to new genera. Definitiv ...

'' spp. The long snout of ''Serpentisuchops'' was likely an ancestral trait, while the long neck was secondarily derived and convergent with ancestral

plesiosaurs 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 ...

, contemporary

, and some more basal members of the Polycotylidae. The

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

below displays the results of their phylogenetic analyses.

References

{{Taxonbar, from=Q114355683 Late Cretaceous plesiosaurs of North America Fossil taxa described in 2022 Polycotylidae Sauropterygian genera