Open Paleo

Orthomerus

Seeley, 1883 or-THOM-er-us Nomen dubium

From Greek 'orthos' (straight) and 'meros' (thigh); meaning 'straight femur', in reference to the remarkably straight femur shaft of the type material. The specific epithet 'dolloi' honors Belgian paleontologist Louis Dollo, who identified the bones in 1882 during a visit to London.

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

Orthomerus is a dubious genus of hadrosauroid dinosaur from the latest Cretaceous of the southern Netherlands or adjacent Belgium. It is today an obscure genus, but in the past was conflated with the much better known Telmatosaurus.

Species

Orthomerus dolloi Seeley, 1883 Nomen dubium

Type species

Honors Belgian paleontologist Louis Dollo, who identified the bones in August 1882 during a visit to London.

Lectotype
NHMUK PV R 42955 , Natural History Museum
Material
Right femur (~500 mm proximodistal length).
Horizon
Maastricht Formation, Maastrichtian, Late Cretaceous , 72.2–66.0 million years ago
Locality
Limburg, Netherlands The syntypes came from the 18th-century workings under the Sint-Pietersberg with nothing documenting where; Madzia, Jagt and Mulder (2019) state that "the precise stratigraphical setting of the material is unknown" and that it can only be placed at "some level(s) within the Maastricht Formation". They give the type locality as an unspecified site in southern Limburg or contiguous Belgian territory, so the country is not certain.

Synonyms

  • Telmatosaurus dolloi reassigned

    The combination used by Mulder (1984), who treated Orthomerus and Telmatosaurus as one genus but used the junior name. Earlier authors who merged the two, starting with Nopcsa (1915), sank Telmatosaurus into Orthomerus instead. Brett-Surman (1989) separated them because O. dolloi is a nomen dubium based on a juvenile femur, and Madzia, Jagt and Mulder (2019) also treat O. dolloi as a nomen dubium, with no features that set its femur apart.

Synonyms of the genus

Name Type Reason
Protrachodon nomen nudum Informal name attributed to Nopcsa, evidently back-formed from Nopcsa's family-level usage. Olshevsky (1991) lists Protrachodontidae (Nopcsa, 1915) and Protrachodontinae (Abel, 1919) as family-rank synonyms of Hadrosauridae but gives no genus-level Protrachodon entry. Olshevsky (1999, personal communication) treated Protrachodon as a synonym of Orthomerus.

References

  1. Seeley, H. G. (1883). On the Dinosaurs from the Maastricht Beds. Quarterly Journal of the Geological Society of London 39(1-4): 246-253. Geological Society of London. doi:10.1144/gsl.jgs.1883.039.01-04.19

    Original description of Orthomerus dolloi on hindlimb material from the van Breda collection; placed by Seeley in Iguanodontia close to Iguanodon and Hadrosaurus.

    seeley1883a
  2. Olshevsky, G. (1991). A revision of the parainfraclass Archosauria Cope, 1869, excluding the advanced Crocodylia. Mesozoic Meanderings 2: 1-196.

    Designates Orthomerus Seeley, 1883 as nomen dubium; lists Telmatosaurus dolloi as historical reassignment and ?O. weberi (later split into Riabininohadros) as second species.

    olshevsky1991a
  3. 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.

    Splits Orthomerus weberi Riabinin, 1945 into the new genus Riabininohadros.

    ulansky2015a
  4. 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

    Designates the lectotype and treats the taxon as a nomen dubium in Hadrosauroidea; its majority-rule trees place it just outside Hadrosauridae, a subset of second-run trees inside.

    madzia2019a
  5. Abel, O. (1919). Die Stämme der Wirbeltiere [The lineages of the vertebrates]. Walter de Gruyter.

    Named Protrachodontinae, later listed as a family-rank synonym of Hadrosauridae.

    abel1919a
  6. Nopcsa, B. F. (1915). Die Dinosaurier der siebenbürgischen Landesteile Ungarns [The Dinosaurs of the Transylvanian Territories of Hungary]. Mitteilungen aus dem Jahrbuche der Königlich Ungarischen Geologischen Reichsanstalt 23: 1-26.

    Coined Protrachodontidae, later a family-rank synonym of Hadrosauridae. Sinks Limnosaurus, Telmatosaurus and Hecatasaurus into Orthomerus and compares the femoral condyles of the two species.

    nopcsa1915a
  7. Mulder, E. W. A. (1984). Resten van Telmatosaurus (Ornithischia, Hadrosauridae) uit het Boven-Krijt van Zuid-Limburg [Remains of Telmatosaurus (Ornithischia, Hadrosauridae) from the Upper Cretaceous of South Limburg]. Grondboor en Hamer 38(3/4): 108-115.

    Describes a left femur, tibia and fibula fragment from the Meerssen Member at Curfs quarry, Geulhem, as Telmatosaurus dolloi, treating Orthomerus and Telmatosaurus as one genus.

    mulder1984a
  8. Brett-Surman, M. K. (1989). A revision of the Hadrosauridae (Reptilia: Ornithischia) and their evolution during the Campanian and Maastrichtian. 1-272. Doctoral thesis, The George Washington University.

    Treats Orthomerus as a nomen dubium based on a juvenile femur and separates Telmatosaurus from it, reporting that "Steel (1969)" had made Telmatosaurus a junior synonym of Orthomerus.

    brett-surman1989a
  9. Steel, R. (1969). Ornithischia. Handbuch der Paläoherpetologie (Kuhn, O., ed.) 15: 81 pp. Gustav Fischer Verlag, Stuttgart.

    Cited by Brett-Surman (1989) as the work that made Telmatosaurus a junior synonym of Orthomerus.

    steel1969a