Open Paleo

Riabininohadros

Lopatin & Averianov, 2020 ree-ah-BEE-ni-no-HAD-ros

Named for Russian paleontologist Anatoly Nikolaevich Riabinin, who first described the type material, combined with 'hadros' as in Hadrosauridae; meaning 'Riabinin's hadrosaur.'

72.2–66.0 million years ago Maastrichtian, Late Cretaceous
Late Cretaceous stages

Riabininohadros is an extinct genus of ankylopollexian dinosaur from the Maastrichtian of Crimea. Its type and only species, Riabininohadros weberae, was originally described as a species of Orthomerus before being placed in its own genus.

Diagnosis

  1. Extensor groove between the distal femoral condyles completely open laterally, with the anterior ends of the medial and lateral condyles at different levels
  2. Bridge between the distal femoral condyles positioned near the anterior margin of the bone rather than centrally, associated with reduction of the lateral condyle
  3. Lateral malleolus of the tibia noticeably longer than the medial condyle and directed distally
  4. Deep notch along the posteromedial edge of the proximal surface of the third metatarsal, extending distally onto the proximal third of the bone
  5. Large depression on the distal lateral femoral condyle for the anterior cruciate ligament

Species

Riabininohadros weberae (Riabinin, 1945)

Type species

First named as Orthomerus weberi

Named for Gertruda F. Weber, who discovered the holotype hind-limb material on Mt. Besh-Kosh near Bakhchysarai, Crimea, in 1934. Riabinin's original epithet weberi was emended to the feminine form weberae, in Weber's honor, by Nessov in 1995.

Holotype
CCMGE 5751 , F.N. Chernyshev Central Museum of Geological Exploration
Material
Fragmentary left hind limb comprising the distal femur, tibia, astragalus, calcaneus, second and third metatarsals, and proximal phalanx of the second digit, plus the proximal end of a right fibula
Horizon
Maastrichtian, Late Cretaceous , 72.2–66.0 million years ago
Locality
summit of Besh-Kosh Mountain, east of Bakhchisaray, Autonomous Republic of Crimea, Ukraine

Synonyms

  • Orthomerus weberi reassigned

    Originally described as Orthomerus weberi by Riabinin (1945); epithet emended to weberae by Nessov (1995) and reassigned to the new genus Riabininohadros by Lopatin and Averianov (2020).

References

  1. Riabinin, A. N. (1945). Dinosaur remains in the Upper Cretaceous of Crimea. Paleontologiya i Stratigrafiya (4): 4-10.

    Posthumous original description of the type material as Orthomerus weberi, a hadrosaurid.

    riabinin1945a
  2. Nessov, L. A. (1995). Dinozavri severnoi Yevrazii: Novye dannye o sostave kompleksov, ekologii i paleobiogeografii [Dinosaurs of northern Eurasia: new data about assemblages, ecology, and paleobiogeography]. Institute for Scientific Research on the Earth's Crust, St. Petersburg State University, St. Petersburg 1-156.

    Emended the specific epithet from weberi to weberae.

    nessov1995a
  3. Lopatin, A. V.; Averianov, A. O.; Alifanov, V. R. (2018). New Data on Dinosaurs of the Crimean Peninsula. Doklady Biological Sciences 482(1): 206-209. doi:10.1134/s0012496618050150

    Restudied the holotype and identified it as a non-hadrosauroid styracosternan, closest in its metatarsals to Hypselospinus.

    lopatin2018a
  4. Averianov, A. O.; Lopatin, A. V. (2019). Dinosaur Fossils from the Upper Cretaceous of Crimea. Paleontological Journal 53(4): 398-410. doi:10.1134/S0031030119040026

    Redescription of the holotype as a non-hadrosauroid styracosternan, correcting several of Riabinin's original element identifications.

    averianov2019a
  5. Ulansky, R. E. (2015). Riabininohadros, novyy rod dlya gadrozavra iz maastrikhta Kryma Rossiya [Riabininohadros, a new genus for hadrosaur from Maastrichtian of Crimea, Russia]. Dinologia 1-10.

    Informally coined the name Riabininohadros for a hadrosaurid, but the electronic publication lacked an ISSN or ISBN, so the name was unavailable under ICZN Article 8.5.3.2.

    ulansky2015a
  6. 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. doi:10.1134/S0031030120030089

    Formally erected the genus Riabininohadros to make the name available and valid.

    lopatin2020a
  7. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Source of the body length estimate.

    jones2026a
  8. Madzia, D.; Jagt, J. W. M.; Mulder, E. W. A. (2019). Osteology, phylogenetic affinities and taxonomic status of the enigmatic late Maastrichtian ornithopod taxon Orthomerus dolloi (Dinosauria, Ornithischia). Cretaceous Research 108: 104334. Elsevier BV. doi:10.1016/j.cretres.2019.104334

    Treats Riabininohadros as a non-euhadrosaur styracosternan.

    madzia2019a
  9. Magyar, J.; Ősi, A.; Csiki-Sava, Z.; Budai, S.; Botfalvai, G. (2026). New early Maastrichtian 'duck-billed' dinosaur from Hațeg Basin (Densuș-Ciula Formation, Romania) documents an endemic clade of non-hadrosaurid hadrosauroids in the south-eastern Late Cretaceous European Archipelago. Journal of Systematic Palaeontology 24(1): 2607800. Informa UK Limited. doi:10.1080/14772019.2025.2607800

    Treats Riabininohadros as falling outside Hadrosauroidea.

    magyar2026a