Riabininohadros

Riabininohadros; Temporal range: Late Cretaceous, 72–66 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	†Ornithischia
Clade:	†Neornithischia
Clade:	†Ornithopoda
Clade:	†Ankylopollexia
Genus:	†Riabininohadros; Lopatin & Averianov, 2020
Species:	†R. weberae
Binomial name
	†Riabininohadros weberae; (Riabinin, 1945) Lopatin & Averianov, 2020
Synonyms
	Orthomerus weberi ; Riabinin, 1945; Orthomerus weberae ; (Riabinin, 1945) Nessov, 1995;

Riabininohadros (meaning "Riabinin's hadrosaur") is an extinct genus of ankylopollexian dinosaur from the Maastrichtian of Crimea. Its type species is Riabininohadros weberi, emended to Riabininohadros weberae.^[1]^[4] It was originally classified as a species of Orthomerus, until 2015.^[4]

Discovery and history

It was originally named Orthomerus weberi when first described by Anatoly Nikolaevich Riabinin in 1945 for hindlimb elements from an unnamed Maastrichtian-age formation in Crimea of what is now Ukraine.^[2] These were in 1934 near Bakhchysarai found by Gertruda Weber who is honoured in the specific name. The find was in 1937 reported in the scientific literature.^[5] As Weber was female, Lev Nesov in 1995 emended the name to Orthomerus weberae so the ending of the species name was also feminine.^[3] Although tossed as a nomen dubium in recent reviews of Hadrosauridae,^[6]^[7] it was informally given its own genus "Riabininohadros" by Russian amateur paleontologist Roman Ulansky.^[4] As this publication did not meet the requirements of the International Code of Zoological Nomenclature, "Riabininohadros" was not a valid name for the taxon until the name was formally published as new by Lopatin and Averianov in 2020.^[1]

The holotype, specimen ZGTM 5751, was found alongside the remains of an unnamed member of Styracosterna in an unnamed Late Cretaceous (Maastrichtian)-aged marine deposit at Mt. Besh-Kosh in Crimea in a Belemnella casimirovensis ammonoid zone.^[8] It largely consists of a left hindlimb, including the thighbone, the shinbone, the calf bone, the astragalus, the calcaneus, the second and third metatarsal and the first phalanx of the second toe. In 2018, it transpired that Riabinin had misidentified several elements. Also a part of the right calf bone proved to be present. A postcranial juvenile skeleton in 1965 excavated at Aleshino, was considered to represent a different species, a hadrosaurid.^[9]

Classification

As Orthomerus has typically been classified within or very close to Hadrosauridae, Riabininohadros weberae was placed similarly by reviews of the family.^[6]^[7]^[4] However, as discussed by Lopatin and Averianov in 2020, the femur of Riabininohadros is very distinctive, and has no morphological equivalents within Iguanodontia, the clade that includes hadrosaurs and their relatives. Instead, Lopatin and Averianov, in view of its basal astragalus, classified Riabininohadros as a primitive member of the Ankylopollexia, more specially the Styracosterna, well outside Hadrosauroidea, with uncertain relationships to other taxa in the clade.^[1]

References

^ ^a ^b ^c ^d ^e Lopatin, A.V.; Averianov, A.O. (2020). "Riabininohadros, a New Genus for the Ornithischian Dinosaur Orthomerus weberae (Ornithopoda, Iguanodontia) from the Late Cretaceous of Crimea". Paleontological Journal. 54 (3): 320–322. Bibcode:2020PalJ...54..320L. doi:10.1134/S0031030120030089. S2CID 219958457.
^ ^a ^b Riabinin, A.N. (1945). "Dinosaurian remains from the Upper Cretaceous of Crimea". Vsesoy. Nauch.-Issledov. Geol. Inst. Matl. Paleontol. Strat. (in Russian). 4: 4–10.
^ ^a ^b Nessov, L.A. (1995). "Dinozavri severnoi Yevrazii: Novye dannye o sostave kompleksov, ekologii i paleobiogeografii". Institute for Scientific Research on the Earth's Crust, St. Petersburg State University (in Russian): 1–156.
^ ^a ^b ^c ^d Ulansky, Roman E. (2015). "Riabininohadros, a new genus for hadrosaur from Maastrichtian of Crimea, Russia. Dinologia" (PDF). dinoweb.narod.ru (in Russian). p. 10.
^ Weber, G.F., (1937), "From Yalta via the village of Kokkoz to Bakhchysarai", in: Mezhdunarodnyi Geological Congress, XVII sessiya. Yuzhnaya ekskursiya, Krymskaya ASSR, Moiseev, A.A., Ed., Moscow–Leningrad: Glavn. Red. Geol. Razved. Liter., 1937: 48–58
^ ^a ^b Weishampel, David B.; Horner, Jack R. (1990). "Hadrosauridae". In Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.). The Dinosauria (1st ed.). Berkeley: University of California Press. pp. 534–561. ISBN 0-520-06727-4.
^ ^a ^b Horner, John R.; Weishampel, David B.; Forster, Catherine A (2004). "Hadrosauridae". In Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.). The Dinosauria (2nd ed.). Berkeley: University of California Press. pp. 438–463. ISBN 0-520-24209-2.
^ A. N. Riabinin. (1946). Novyye nakhodki iskopayemykh reptiliy v krymu [New finds of fossil reptiles in Crimea]. Priroda 1946(11):65-66
^ Lopatin, A.V., Averianov, A.O., & Alifanov, V.R., (2018), "New Data on Dinosaurs of the Crimean Peninsula", Dokl. Biol. Sci., 482: 206–209