''Xenotarsosaurus'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of abelisaurid theropod

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

that lived during the Late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

Discovery

In 1980 geologist Juan Carlos Sciutto discovered a rich fossil site six kilometres north of the Ocho Hermanos ranch in

Chubut Chubut may refer to: * Chubut Province, Argentina * Chubut River in the Chubut Province * Chubut steamer duck The Chubut steamer duck or white-headed flightless steamer duck (''Tachyeres leucocephalus'') is a flightless duck endemic to Argenti ...

province. Among the fossils found there were some theropod remains. Later, a team led by Argentinian

paleontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...

José Fernando Bonaparte José is a predominantly Spanish and Portuguese form of the given name Joseph. While spelled alike, this name is pronounced differently in each language: Spanish ; Portuguese (or ). In French, the name ''José'', pronounced , is an old vernacul ...

recovered some more theropod bones, possibly from the same individual. In 1986, Rubén Martínez, Olga Giménez, Jorge Rodríguez and Graciela Bochatey described the theropod fossils and coined the genus and species ''Xenotarsosaurus bonapartei'' for them. The generic name is derived from Greek ''xenos'', "strange", ''tarsos'', " tarsus", and ''sauros'', "lizard", a reference to the exceptional build of the ankle. The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

''bonapartei'' honours Bonaparte. The

type specimen In biology, a type is a particular wiktionary:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to a ...

s (and only known fossils of ''Xenotarsosaurus'') were found in the

Bajo Barreal Formation The Bajo Barreal Formation is a geological formation in the Golfo San Jorge Basin of Chubut and Santa Cruz, Argentina whose strata date back to the Middle Cenomanian to Late Turonian. The formation was first described by Teruggi & Rossetto in ...

. In 1986 this formation was seen as Campanian; today it is thought to date to the earlier

Cenomanian The Cenomanian is, in the ICS' geological timescale, the oldest or earliest age of the Late Cretaceous Epoch or the lowest stage of the Upper Cretaceous Series. An age is a unit of geochronology; it is a unit of time; the stage is a unit in the s ...

–

Turonian The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous Epoch, or a stage in the Upper Cretaceous Series. It spans the time between 93.9 ± 0.8 Ma and 89.8 ± 1 Ma (million years ago). The Turonian is preceded by t ...

. The bones consist of two

cotype In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes th ...

s: UNPSJB PV 184, a series of two anterior dorsal

vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...

e, and PVL 612, a right hind limb including the long

femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with ...

, the

tibia The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...

fibula The fibula or calf bone is a leg bone on the lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones. Its upper extremity is ...

and astragalocalcaneum of the ankle. The exceptional complete fusion, without sutures, of the astragalus and

calcaneum In humans and many other primates, the calcaneus (; from the Latin ''calcaneus'' or ''calcaneum'', meaning heel) or heel bone is a bone of the tarsus of the foot which constitutes the heel. In some other animals, it is the point of the hock. St ...

, forming an element that is again fused to the widened lower end of the tibia, occasioned the generic name. In 2010 Gregory S. Paul estimated its length at 6 meters (19.7 ft), its weight at 750 kg (1,654 lbs). In 2016, its length was estimated to be . The same year Molina-Pérez & Larramendi gave a similar length of 5.4 meters (18 ft) and a weight of 430 kg (948 lbs). The remains show some similarities to '' Carnotaurus sastrei'', causing the describers to assign ''Xenotarsosaurus'' to the Abelisauridae, which has remained a common determination. However, it has also been proposed that ''Xenotarsosaurus'' is a

neoceratosauria Ceratosaurs are members of the clade Ceratosauria, a group of dinosaurs defined as all theropods sharing a more recent common ancestor with ''Ceratosaurus'' than with birds. The oldest known ceratosaur, ''Saltriovenator'', dates to the earliest ...

n of uncertain affinities.R.A. Coria and J. Rodríguez, 1993, "Sobre ''Xenotarsosaurus bonapartei'' Martínez, Giménez, Rodríguez y Bochatey, 1986; un problematico Neoceratosauria (Novas, 1989) del Cretácico de Chubut", ''Ameghiniana'' 30(3): 326-327

Notes

External links

''Xenotarsosaurus'' at DinoData
{{Taxonbar, from=Q135103 Abelisaurids Late Cretaceous dinosaurs of South America Cretaceous Argentina Fossils of Argentina Fossil taxa described in 1986 Cenomanian life

Discovery

See also

Notes

External links