''Rarosaurus'' is an extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

marine reptile Marine reptiles are reptiles which have become secondarily adapted for an aquatic or semiaquatic life in a marine environment. Only about 100 of the 12,000 extant reptile species and subspecies are classed as marine reptiles, including mari ...

that lived during the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

. It contains one valid species, ''R. singularis'', and it was found in the

Muwaqqar Chalk Marl Formation The Muwaqqar Chalk-Marl Formation or Muwaqqar Formation is a Late Cretaceous (Maastrichtian) and early Paleogene-aged geological formation in Jordan, cropping out across the Jordanian Highlands from north to south. It is the geological formation c ...

Jordan Jordan, officially the Hashemite Kingdom of Jordan, is a country in the Southern Levant region of West Asia. Jordan is bordered by Syria to the north, Iraq to the east, Saudi Arabia to the south, and Israel and the occupied Palestinian ter ...

Discovery and naming

The holotype, a partial

rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit ** podium * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ...

with teeth, was discovered in the latest

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 ...

-aged

. Hani Faig Kaddumi first mentioned this specimen in 2006, and then named and described it in 2009. The generic name ''Rarosaurus'', meaning "rare lizard", is attributed to the paucity of plesiosaur fossils where it was found, while the specific name ''singularis'' refers to the type specimen of ''Rarosaurus'' being possibly the only plesiosaur specimen found from the area.

Description

''Rarosaurus'' is known from the rostral portion of a fossil skull, which is well preserved and bears teeth. The fossil is about twenty centimetres long and very elongate. The surface of the bone is rugose, marked by small holes and grooves. The teeth are relatively short and conical; the first tooth in the jaw protrudes far forward. If the taxon is indeed a

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 ...

, it is notable for being the latest-surviving

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 ...

and is currently the only one from the late Maastrichtian. However, Alhalabi and colleagues questioned its identity as a plesiosaur in 2024, since the known traits of ''Rarosaurus'' are actually typical of

crocodylomorph Crocodylomorpha is a group of pseudosuchian archosaurs that includes the crocodilians and their extinct relatives. They were the only members of Pseudosuchia to survive the end-Triassic extinction. Extinct crocodylomorphs were considerably mor ...

s based on its "external bone ornamentation, tooth arrangement and implantation". Text was copied from this source, which is available under
Creative Commons Attribution 4.0 International License

References

{{Taxonbar, from1=Q21368834, from2=Q3930357 Prehistoric marine reptiles Maastrichtian genera Fossil taxa described in 2009