A new species of the plesiosaur genus Polycotylus from the Upper Cretaceous of the southern Urals

Fossil marine vertebrates (Chondrichthyes, Actinopterygii, Reptilia) from the Upper Cretaceous of Akkermanovka (Orenburg Oblast, Southern Urals, Russia)

“…Mesozoic vertebrate records, especially reptiles, have been known from Upper Cretaceous marine deposits in the Orenburg Oblast since the early 20th century ( Bogolyubov, 1910 , 1911 , 1912a , b ). These horizons have been dated to the early Campanian based on chondrichthyan remains ( Efimov et al, 2016 ; Averianov et al, 2021b ).…”

“…Polycotylid remains are well known from the Orenburg Oblast and were assigned to the genus Polycotylus ( Efimov et al, 2016 ). Based on fragmentary skeletal material, Bogolyubov (1912b) described two polycotylid taxa from the Orenburg Oblast, P. orientalis Bogolyubov, 1911 and P .…”

“…balticus Bogolyubov, 1911 , but both species are now regarded as nomina dubia ( Adams, 1997 ; Storrs et al, 2000 ). Another polycotylid, P. sopozkoi Efimov, Meleshin and Nikiforov, 2016 , was described from an lower Campanian deposit near the village of Izhberda in the Gaiskii District (Orenburg Oblast), but was recently discussed to be a junior synonym of P. latipinnis ( Zverkov et al, 2023b ). Teeth are not regarded to be diagnostic beyond family level in this group ( Storrs et al, 2000 ) and in the absence of more complete skeletal material, we conservatively leave this taxon in open nomenclature as Polycotylidae indet.…”

“…Due to the fragmentary nature of the material, considerable doubt exists about the validity of these species, and many are now considered to be nomina dubia and are left in open nomenclature ( Storrs et al, 2000 ). Recently, new vertebrate-rich deposits were discovered in the Izhberda quarry (close to the city Orsk), yielding the most complete Late Cretaceous plesiosaur skeleton from the Southern Urals to date ( Efimov et al, 2016 ); it was assigned to the new species Polycotylus sopozkoi Efimov, Meleshin and Nikiforov, 2016 . Also in these vast coastal marine deposits, rare finds of terrestrial vertebrates, i.e., remains of dinosaurs (Dinosauria indet., Iguanodontia indet.)…”

“…Russian Upper Cretaceous marine deposits are widespread in the Southern Urals and numerous reports of marine vertebrates, especially marine reptiles ( Bogolyubov, 1910 , 1911 , 1912a , b ; Efimov et al, 2016 ) and cartilaginous fishes ( Glickman and Zhelezko, 1979 , 1990) exist from this region. However, these reports usually lack detailed taxonomic descriptions and illustrations are often of poor quality, if present at all.…”