''Clasmodosaurus'' (meaning "fragmentary tooth reptile") is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

titanosauria Titanosaurs (or titanosaurians; members of the group Titanosauria) were a diverse group of Sauropoda, sauropod dinosaurs, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with tax ...

sauropod Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their b ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...

from the

Mata Amarilla Formation The Mata Amarilla Formation is a List of fossiliferous stratigraphic units of Argentina, fossiliferous formation of the Magallanes Basin, Austral Basin in southern Patagonia, Argentina. The formation consists of sediments deposited during the Ceno ...

and the

Cerro Fortaleza Formation The Cerro Fortaleza Formation, in older literature described as Pari Aike Formation, is a Late Cretaceous geologic formation of Campanian to Maastrichtian age (although it has formerly been reported to be Cenomanian to Santonian) of the Austra ...

. It lived during the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

in what is now

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

. It is known from five fossilized and assorted teeth, but is diagnosed by a unique combination of characters.

History

''Clasmodosaurus'' was named by

Florentino Ameghino Florentino Ameghino (born Giovanni Battista Fiorino Giuseppe Ameghino; September 19, 1853 – August 6, 1911) was an Argentine naturalist, paleontologist, anthropologist and zoologist, whose fossil discoveries on the Argentine Pampas, especial ...

in 1898, but remained largely unknown for decades after its discovery. It was originally considered a sauropod, but

Friedrich von Huene Baron Friedrich Richard von Hoyningen-Huene (22 March 1875 – 4 April 1969) was a German nobleman paleontologist who described a large number of dinosaurs, more than anyone else in 20th-century Europe. He studied a range of Permo-Carbonife ...

suggested that it could be a

coelurosaur Coelurosauria (; from Greek, meaning "hollow-tailed lizards") is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs. Coelurosauria is a subgroup of theropod dinosaurs that includes compsognathids, ty ...

or synonymous with ''

Loncosaurus ''Loncosaurus'' (meaning uncertain; either Araucanian "chief" or Greek "lance" "lizard"Norman, D.B., and Weishampel, D.B. 1990. Iguanodontidae and related ornithopods. In: Weishampel, D.B., Dodson, P., and Osmólska, H. (eds.). ''The Dinosauria ...

'', which he considered to be a

carnosaur Carnosauria is an extinct group of carnivorous theropod dinosaurs that lived during the Jurassic and Cretaceous periods. While Carnosauria was historically considered largely synonymous with Allosauroidea, some recent studies have revived Carn ...

. Like ''Loncosaurus'', its taxonomy remained unclear with it regarded as a theropod on the rare occasions it was mentioned. However,

Jaime Powell Jaime Eduardo Powell (January 13, 1953 – February 1, 2016) was an Argentine paleontologist who described the titanosaur sauropod dinosaur taxa ''Aeolosaurus'' and found evidence that titanosaurs have osteoderms. Research Powell described the f ...

suggested that it was a dubious genus of sauropod in 1986, an identification which has been accepted since. Like diplodocoids and titanosaurs, it had narrow tooth crowns, and it is typically regarded as a titanosaur like most Late Cretaceous sauropods. More recently, a revision of Ameghino's collection and new discoveries in the Cerro Fortaleza Formation find the taxon to also hail from this formation.

Description

The teeth of ''Clasmodosaurus spatula'' were polygonal in cross section rather than round, an unusual trait also found in the

titanosaur Titanosaurs (or titanosaurians; members of the group Titanosauria) were a diverse group of sauropod dinosaurs, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with taxa still thr ...

'' Bonitasaura salgadoi.'' However, these teeth are much larger and more robust than those of ''Bonitasaura,'' with well-defined longitudinal ridges and grooves, resembling diamantinasaur teeth in some aspects.

References

{{Taxonbar, from=Q1768702 Titanosauria Dinosaur genera Late Cretaceous dinosaurs Fossil taxa described in 1898 Taxa named by Florentino Ameghino Dinosaurs of Argentina