Loncosaurus

Loncosaurus (meaning uncertain; either Araucanian "chief" or Greek "lance" "lizard"[1]) was a highly dubious genus of ornithopod dinosaur from the Upper Cretaceous of Provincia de Santa Cruz, Argentina. The type (and only known) species is Loncosaurus argentinus, described by the famous Argentinian paleontologist Florentino Ameghino, but is considered a dubious name. Details on this animal are often contradictory, befitting a genus that was long confused for a theropod.

Loncosaurus
Temporal range: Late Cretaceous, 75–66 Ma
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Sauropsida
Superorder:
Dinosauria
Order:
†Ornithischia
Suborder:
†Ornithopoda
Genus:
†Loncosaurus

Ameghino, 1899
Binomial name
†Loncosaurus argentinus
Ameghino, 1899
Synonyms

Teeth attributed to cf. Carnosaurus may have actually belonged to Loncosaurus.[2]

History

The holotype femur and tooth were discovered by Carlos Ameghino, Florentino's brother, between 1887 and 1898.

Ameghino named this dinosaur in 1899[3][4][5][6][7][8][9][10][11] from a proximal femur (MACN-1629) and tooth found near Rio Sehuen, Santa Cruz, in either the Cardiel Formation (most sources) or the Matasiete Formation[10] (both being Upper Cretaceous).

Either way, he thought the remains belonged to a "megalosaurid" dinosaur, a carnivore, which Friedrich von Huene agreed with.[12] Upon further review, von Zittel assigned it to the Coeluridae,[13] recognized today as a "wastebasket taxon" for small carnivorous dinosaurs. The carnivore tooth helped this misidentification take hold.

It was ignored for decades until Ralph Molnar reassessed it.[14] He found that the tooth did not belong to the same animal as the femur and removed it from the type, and suggested that the femur belonged to a hypsilophodont or turtle. Professional opinion has not changed much since then, although based on size, it appears more likely to be an iguanodont than a hypsilophodont.[10] Reviews either put it at Ornithopoda incertae sedis[10] or Iguanodontia.[4][5] Oddly, a semipopular reference reassigned it to Genyodectes without comment,[15] a view which has not been followed since.

Paleobiology

Coria estimates the size of the Loncosaurus type individual at about 5 m (16.4 feet) long.[10] As a small to medium-sized ornithopod, it would have been an agile bipedal herbivore.[5]

References
  1. Dinosaur Translation Guide L Archived 2006-03-15 at the Wayback Machine
  2. Olshevsky, DML 1999. http://dml.cmnh.org/1999Nov/msg00507.html
  3. Ameghino, F. 1898. Sinopsis geológico-paleontológica. Segundo censo de la República Argentina. Folia:Buenos Aires, 1:112-255. [Spanish]
  4. Norman, D.B., and Weishampel, D.B. 1990. Iguanodontidae and related ornithopods. In: Weishampel, D.B., Dodson, P., and Osmólska, H. (eds.). The Dinosauria. University of California Press:Berkeley, 510-533. ISBN 0-520-06727-4
  5. Norman, D.B. 2004. Basal Iguanodontia. In: Weishampel, D.B., Dodson, P., and Osmólska, H. (eds.). The Dinosauria (second edition). University of California Press:Berkeley, 413-437. ISBN 0-520-24209-2
  6. George Olshevsky's Dinosaur Genera List
  7. Ameghino, F. 1899. Nota preliminar sobre el Loncosaurus argentinus, un representante de la familia Megalosauridae de la República Argentina. Anales de la Sociedad Cientifica Argentina 49:61-62. [Spanish]
  8. Coria, R.A., and Salgado, L. 1996. Loncosaurus argentinus Ameghino, 1899 (Ornithischia, Ornithopoda): a revised description with comments on its phylogenetic relationships. Ameghiniana 33(4):373-376.
  9. Glut, D.F. (1997). Dinosaurs: The Encyclopedia. Mcfarland & Company, Inc., xi-1076. ISBN 0-89950-917-7
  10. Coria, R.A. 1999. Ornithopod dinosaurs from the Neuquén Group, Patagonia, Argentina: phylogeny and biostratigraphy. In Tomida, Y., Rich, T.H., and Vickers-Rich, P. (eds.) Proceedings of the Second Gondwanan Dinosaur Symposium, National Science Museum Monographs 15:47-60.
  11. The Paleobiology Database)
  12. von Huene, F. 1909. Skizze zu einer Systematik und Stammesgeschichte der Dinosaurier. Centralblatt für Mineralogie, Geologie und Paläontologie 1909:12-22. [German]
  13. von Zittel, K.A.. 1911. Grundzüge der Paläontologie (Paläozoologie). II. Abteilung. Vertebrata. Druck und Verlag von R. Oldenbourg:München, 1-598. [German]
  14. Molnar, R.E. 1980. Australian late Mesozoic continental tetrapods: some implications. Mémoires de la Société Géologique de France, Nouvelle Série 139:131-143.
  15. Lessem, D., and Glut, D.F. 1993. The Dinosaur Society Dinosaur Encyclopedia. Random House, Inc.:New York, 533 p. ISBN 0-679-41770-2
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