''Marmorerpeton'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of prehistoric

stem group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...

salamander Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All ten ...

s that lived in Britain during the

Bathonian In the geologic timescale the Bathonian is an age and stage of the Middle Jurassic. It lasted from approximately 168.3 Ma to around 166.1 Ma (million years ago). The Bathonian Age succeeds the Bajocian Age and precedes the Callovian Age. Strat ...

stage of the

Middle Jurassic The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from about 174.1 to 163.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relatively rare, but geological formations co ...

. They are among the oldest known salamanders. Two species were named when the genus was first described by

Susan E. Evans Susan E. Evans is British palaeontologist and herpetologist. She is the author or co-author of over 100 peer-reviewed papers and book chapters. She received a BSc in Zoology at Bedford College in 1974, and in 1977 a PhD in vertebrate palaeon ...

et al. in 1988, ''M''. ''freemani'', and ''M''. ''kermacki'', from fragmentary remains found via screenwashing in the

Forest Marble Formation The Forest Marble is a geological formation in England. Part of the Great Oolite Group, it dates to the late Bathonian stage of the Middle Jurassic.Weishampel, David B; et al. (2004). "Dinosaur distribution (Middle Jurassic, Europe)." In: Weisham ...

of England. Due to the size of their osteocytic lacunae suggesting a large genome size and some morphological characters, like the presence of calcified cartilage in the medulla of its

humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...

, it was assumed that ''Marmorerpeton'' was

neotenic Neoteny (), also called juvenilization,Montagu, A. (1989). Growing Young. Bergin & Garvey: CT. is the delaying or slowing of the physiological, or somatic, development of an organism, typically an animal. Neoteny is found in modern humans compared ...

. New more complete remains of a new species ''M. wakei'' were described in 2022 from the

Kilmaluag Formation The Kilmaluag Formation is a Middle Jurassic geologic formation in Scotland. It was formerly known as the Ostracod Limestone for the abundance of fossil freshwater ostracods within it. The Kilmaluag Formation is very fossiliferous, with ostracods ...

of the Isle of Skye, Scotland. These conclusively demonstrated that ''Marmorerpeton'' was neotenic, and was a member of the family

Karauridae The Karauridae are a family of stem-group salamanders (Caudata) that are known from the Middle Jurassic to Late Jurassic in Central Asia (Kazakhstan and Kyrgyzstan) and Western Europe (United Kingdom). The family includes three members: ''Karauru ...

, with the other two members of the family, ''

Karaurus ''Karaurus'' (meaning ''head-tail'') is an extinct genus of stem-group salamander (Caudata) from the Middle to Late Jurassic (Callovian–Kimmeridgian) Karabastau Formation of Kazakhstan. It is one of the oldest salamanders known. ''Karaurus'' w ...

'' and ''

Kokartus ''Kokartus'' is an extinct genus of prehistoric stem-group salamander (Caudata) from the Middle Jurassic Balabansai Formation of Kyrgyzstan. The absence of clear lines of arrested growth and annuli in long bones suggests that the animals lived i ...

'' being known from the Middle-Late Jurassic of Central Asia. The teeth appear to have been weakly

pedicellate In botany, a pedicel is a stem that attaches a single flower to the inflorescence. Such inflorescences are described as ''pedicellate''. Description Pedicel refers to a structure connecting a single flower to its inflorescence. In the absenc ...

References

Jurassic amphibians of Europe Fossil taxa described in 1988 Prehistoric amphibian genera {{Jurassic-animal-stub