Elopteryx

From Wikipedia, the free encyclopedia

Elopteryx
Fossil range: Late Cretaceous
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Sauropsida
Superorder: Dinosauria
Order: Saurischia
Suborder: Theropoda
(unranked) Maniraptora
Family: Elopterygidae (disputed)
Lambrecht, 1933
Genus: Elopteryx
Andrews, 1913
Species

E. nopcsai Andrews, 1913 (type)

Elopteryx is a genus of maniraptoran theropod dinosaur based on fragmentary fossils found in late Cretaceous Period rocks of Romania. These fossils date from the early-mid Maastrichtian (Begudian) faunal stage, c.71-68 million years ago. The single species, Elopteryx nopcsai, is known only from very incomplete material, and therefore is considered a nomen dubium ("dubious name") by most paleontologists. The genus name Elopteryx is from Ancient Greek elos (έλος) "marsh" + pteryx (πτερυξ) "wing". The specific name honors the famous Hungarian paleontologist Franz Nopcsa von Felső-Szilvás. The monotypic family Elopterygidae was set up for this genus, but such a move is considered premature by most current authorities.

Contents

[edit] History

Initially, Elopteryx was described from a proximal femur (specimen BMNH A1234). A distal tibiotarsus was also tentatively assigned to this taxon; it was initially classified with the same specimen number and was found in close proximity, but may not be from the same individual (see below). This has since been relabeled and is now specimen BMNH A4359. The animal was at first believed to be a pelecaniform seabird.[1]

The supposed family Elopterygidae was initially placed in the Pelecaniformes suborder Sulae by Pierce Brodkorb in his fossil bird catalogue, and the Cenozoic genera Argillornis and Eostega were moved to it.[2] These two are unequivocal modern birds and the latter indeed seems to be an ancient sulid whereas the relationships of Argillornis are less well resolved. Reconstruction attempts like this are based on this presumed hypothesis. But more recent studies have indicated radically different results.

Other material had been assigned to E. nopcsai, including the proximal femur BMNH A1235 and the distal tibiotarsi BMNH A1528 and BMNH A1588. These two together with A4359 were eventually removed from Elopteryx, redescribed as Bradycneme draculae and Heptasteornis andrewsi, and used to establish a supposed family of gigantic owls.[1] Today however, they are generally accepted as non-avian dinosaurs, at least one of which seems to be an alvarezsaurid.[3] Brodkorb had changed his opinion after the supposed Elopteryx material was divided among three species in total, and was actually the first scholar in modern times to suggest that the Mesozoic bones were not of birds.[4]

Later, a supposed distal femur (FGGUB R.351) was for some years added to the proximal parts of that bone which remained assigned to Elopteryx, but was eventually identified as a hadrosaurid distal metatarsal. Likewise a skull (FGGUB 1007) supposedly belonging to Elopteryx turned out to be from a sauropod.[3]

In 1992, it was proposed that Bradycneme and Heptasteornis should be synonymized with E. nopcsai again, and a femur (MDE-D203), an anterior dorsal vertebra (MDE-D01), a posterior sacral vertebra (MDE collection, unnumbered) and some dorsal rib fragments from the Jurassic Grès à Reptiles Formation of France were described as indeterminate species of Elopteryx; that study placed all this material in the Dromaeosauridae or a family or subfamily (Elopteryginae) very close to these. The vertebrae were eventually separated again and assigned to a new dromaeosaurid, Variraptor mechinorum.[5]

The new femur does not appear to belong to Elopteryx either; while similar in general appearance it differs in details. And neither the ribs nor the tibiotarsi can be compared to the type specimen. In recent years, yet another (distal) femur piece, FGGUB R.1957, has been placed with Elopteryx, and although this cannot be compared directly either, it does not appear as if any other known animal had a femur that was proximally like A1234 and distally like FGGUB R.1957.[3]

Bradycneme and Heptasteornis have meanwhile been synonymized and split from each other and Elopteryx many times, and various solutions were proposed for this dilemma.[6] Among more recent studies, Elopteryx was considered an eumaniraptoran incertae sedis,[3] possibly either a non-ornithuran "pygostylian" bird[7] or a troodontid.[8] Thus E. nopcsai seems to be some sort of birdlike eumaniraptoran, but not related to modern birds.[3] While little can be said about BMNH A1588 - the Bradycneme specimen - Heptasteornis does indeed seem to belong to a more ancient lineage of theropods, which is interesting given that its holotype bone BMNH A4359 was believed to be from the very same individual as the Elopteryx holotype when they were dug up (see also Rahonavis and Vorona).

With the exception of Heptasteornis, which seems quite robustly identified as an alvarezsaurid of subfamily Mononykinae,[9] these taxa will be subject to continuing debate.

[edit] Footnotes

  1. ^ a b Harrison & Walker (1975)
  2. ^ Brodkorb (1963): pp.248-249
  3. ^ a b c d e Mortimer (2004)
  4. ^ Brodkorb (1978): pp.223-224
  5. ^ Le Loeuff et al. (1992), Le Loeuff and Buffetaut (1998)
  6. ^ E.g. Le Loeuff et al. (1992), Csiki & Grigorescu (1998)
  7. ^ Most of these - like Confuciusornis or Enantiornithes - are only known since the late 20th century.
  8. ^ Paul (1988), Weishampel et al. (1991), Naish & Dyke (2004)
  9. ^ Mortimer (2004), Naish & Dyke (2004)

[edit] References

  • Andrews, C.W. (1913): On some bird remains from the Upper Cretaceous of Transylvania. Geological Magazine 5: 193-196.
  • Brodkorb, Pierce (1963): Catalogue of fossil birds. Part 1 (Archaeopterygiformes through Ardeiformes). Bulletin of the Florida State Museum, Biological Sciences 7(4): 179-293. PDF fulltext
  • Brodkorb, Pierce (1978): Catalogue of fossil birds, Part 5 (Passeriformes). Bulletin of the Florida State Museum, Biological Sciences 23(3): 139-228.
  • Csiki, G. & Grigorescu, D. (1998): Small theropods from the Late Cretaceous of the Hateg Basin (western Romania) - an unexpected diversity at the top of the food chain. Oryctos 1: 87-104.
  • Harrison, Colin James Oliver & Walker, Cyril Alexander (1975): The Bradycnemidae, a new family of owls from the Upper Cretaceous of Romania. Palaeontology 18(3): 563-570. PDF fulltext
  • Le Loeuff, J. & Buffetaut, E. (1998): A new dromaeosaurid theropod from the Upper Cretaceous of Southern France. Oryctos 1: 105-112.
  • Le Loeuff, J.; Buffetaut, E.; Méchin, P. & Méchin-Salessy, A. (1992): The first record of dromaeosaurid dinosaurs (Saurischia, Theropoda) in the Maastrichtian of southern Europe: palaeobiogeographical implications. Bulletin de la Société géologique de la France 163(3): 337-343.
  • Mortimer, Michael (2004): The Theropod Database: Phylogeny of taxa. Retrieved 2007-NOV-04.
  • Naish, Darren & Dyke, Gareth J. (2004): Heptasteornis was no ornithomimid, troodontid, dromaeosaurid or owl: the first alvarezsaurid (Dinosauria: Theropoda) from Europe. Neues Jahrbuch für Geologie und Paläontologie Monatshefte 7: 385-401.
  • Paul, Gregory S. (1988): Predatory Dinosaurs of the World. New York, Simon & Schuster. ISBN 0-671-61946-2
  • Weishampel, D.B.; Grigorescu, D. & Norman, D.B. (1991): The dinosaurs of Transylvania. National Geographic Research and Exploration 7(2): 196-215. PDF fulltext

[edit] External links

Dinosaurs Portal