Talenkauen

Taxobox
name = "Talenkauen"
fossil_range = Late Cretaceous
regnum = Animalia
phylum = Chordata
classis = Sauropsida
superordo = Dinosauria
ordo = Ornithischia
subordo = Ornithopoda
infraordo = Iguanodontia
unranked_familia = Elasmaria
genus = "Talenkauen"
genus_authority=Novas "et al.", 2004
subdivision_ranks=Species
subdivision=
*"T. santacrucensis" Novas "et al.", 2004 (type)

"Talenkauen" (meaning "small skull" in Aonikenk, referring to the proportionally small skull) is a genus of basal iguanodont dinosaur from the Maastrichtian-age Upper Cretaceous Pari Aike Formation of Lake Viedma, Santa Cruz, Argentina. It is based on MPM-10001, a partial articulated skeleton missing the rear part of the skull, the tail, and the hands. Its most unusual feature is the presence of several thin mineralized plates along the sides of the ribs.cite journal |last=Novas |first=Fernando E. |authorlink=Fernando Novas |coauthors=Cambiaso, Andrea V; and Ambrioso, Alfredo |year=2004 |title=A new basal iguanodontian (Dinosauria, Ornithischia) from the Upper Cretaceous of Patagonia |journal=Ameghiniana |volume=41 |issue=1 |pages=75–82 ]

Description

"Talenkauen" was rather like "Dryosaurus" in shape and build, but with a proportionally longer neck. The full length of the body is estimated at no more than 4 meters (13 ft). Unlike more derived iguanodontians, it still had teeth in the tip of the beak (premaxillary teeth), and a first toe. More derived iguanodonts lose this toe, retaining only the three middle toes. The humerus has reduced areas for muscle attachment, a featured shared with other South American ornithopods like "Notohypsilophodon" and "Anabisetia". This and other similarities to South American ornithopods suggests that there may have been a distinct Southern Hemisphere ornithopod group, but the authors cautioned that all of the evidence together does not permit such an interpretation. The authors, through cladistic analysis, found the new genus to be more basal than "Dryosaurus" and "Anabisetia", but more derived than "Tenontosaurus" and "Gasparinisaura". More recently, the describers of "Macrogryphosaurus" found their genus and "Talenkauen" to be related, and coined the clade Elasmaria for the two genera.cite journal |last=Calvo |first=J.O. |coauthors=Porfiri, J.D.; and Novas, F.E. |year=2007 |title=Discovery of a new ornithopod dinosaur from the Portezuelo Formation (Upper Cretaceous), Neuquén, Patagonia, Argentina. |journal=Arquivos do Museu Nacional |volume=65 |issue=4 |pages=471–483 ]

Mineralized plates

"Talenkauen"'s most distinct feature is a set of smooth, ovoid plates found along the side of the rib cage. These plates can be long (180 millimeters, or 7.1 in), but are very thin (only 3 millimeters thick [0.1 in] ). They were present with at least the first eight ribs, attaching along the middle portion of a rib and laying flat. Several other dinosaurs are know to have had similar plates, including "Hypsilophodon", "Othnielosaurus", "Parksosaurus", "Thescelosaurus",cite journal |last=Butler |first=Richard J. |coauthors=and Galton, Peter M. |date=2008 |title=The 'dermal armour' of the ornithopod dinosaur "Hypsilophodon" from the Wealden (Early Cretaceous: Barremian) of the Isle of Wight: a reappraisal |journal=Cretaceous Research |volume=29 |issue=4 |pages=636-642 |doi=10.1016/j.cretres.2008.02.002] and "Macrogryphosaurus" (also from Argentina, but from somewhat older rocks), which may have been related. Because of the fragility of the plates, and the fact that they may not have always turned to bone in the living animal, they may have been more widespread than currently known. Novas and colleagues suggested that the plates may be homologous to uncinate processes, strip-like bony projections found on the ribs of a variety of animals including the tuatara, crocodiles, birds, and some maniraptoran theropod dinosaurs. In birds, uncinate processes help to ventilate the lungs, working with rib cage muscles, and Novas and colleagues proposed a similar function for the plates of "Talenkauen". This homology was rejected in a more recent study by Richard Butler and Peter Galton because of the plates' form.cite journal |last=Butler |first=Richard J. |coauthors=and Galton, Peter M. |date=2008 |title=The 'dermal armour' of the ornithopod dinosaur "Hypsilophodon" from the Wealden (Early Cretaceous: Barremian) of the Isle of Wight: a reappraisal |journal=Cretaceous Research |volume=29 |issue=4 |pages=636-642 |doi=10.1016/j.cretres.2008.02.002] The plates were too thin and limited in location to have been very useful as defensive devices.

Paleobiology

"Talenkauen", as a basal iguanodont, would have been a small, bipedal herbivore.cite book |last= Norman|first=David B. |editor= Weishampel, D.B., Dodson, P., and Osmólska, H. (eds.)|title=The Dinosauria |edition=2nd |year= 2004|publisher=University of California Press |location=Berkeley |isbn=0-520-24209-2 |pages=pp. 413-437 |chapter=Basal Iguanodontia] Other dinosaurs from the same formation include the giant titanosaurid "Puertasaurus" and a large, derived, unnamed tetanuran theropod.cite journal |last=Novas |first=Fernando E. |authorlink=Fernando Novas |coauthors=Salgado, Leonardo; Calvo, Jorge; and Agnolin, Federico |year=2005 |title=Giant titanosaur (Dinosauria, Sauropoda)from the Late Cretaceous of Patagonia |journal=Revisto del Museo Argentino de Ciencias Naturales, n.s. |volume=7 |issue=1 |pages=37–41 |url=http://www.macn.secyt.gov.ar/cont_Publicaciones/Rns-Vol07-1_37-41.pdf |accessdate=2007-03-04 ]

References

External links

* [http://news.nationalgeographic.com/news/2004/04/0405_040405_dinodiscovery.html National Geographic news release] on "Talenkauen"; the National Geographic Society was one of the supporters of the research on this dinosaur.
* [http://dino.lm.com/images/display.php?id=1935 Restoration of "Talenkauen"] , by Gabriel Lio.