Xenotarsosaurus
Encyclopedia
Xenotarsosaurus is a genus
of abelisaurid theropod dinosaur
that lived during the Late Cretaceous
of Argentina
.
In 1980 geologist Juan Carlos Sciutto discovered a rich fossil site six kilometres north of the Ocho Hermanos ranch in Chubut
province. Among the fossils found there were some theropod remains. Later, a team led by Argentinian paleontologist
José Fernando Bonaparte recovered some more theropod bones, possibly from the same individual.
In 1986, Ricardo 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 bonapartei honours Bonaparte.
The type specimens (and only known fossils of Xenotarsosaurus) were found in the Bajo Barreal Formation
. In 1986 this formation was seen as Campanian
; today it is thought to date to the earlier Cenomanian
–Turonian
. The bones consist of two cotypes: UNPSJB PV 184, a series of two anterior dorsal vertebrae, and PVL 612, a right hind limb including the 611 millimetres (24.1 in) long femur
, the tibia
, fibula and astragalocalcaneum of the ankle. The exceptional complete fusion, without sutures, of the astragalus
and calcaneum, forming an element that is again fused to the widened lower end of the tibia, occasioned the generic name.
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 neoceratosaurian of uncertain affinities.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of abelisaurid theropod dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
that lived during the Late Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
of Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
.
In 1980 geologist Juan Carlos Sciutto discovered a rich fossil site six kilometres north of the Ocho Hermanos ranch in Chubut
Chubut Province
Chubut a province in the southern part of Argentina situated between the 42nd parallel south and the 46th parallel south , the Andes range separating Argentina from Chile, and the Atlantic ocean...
province. Among the fossils found there were some theropod remains. Later, a team led by Argentinian paleontologist
Paleontology
Paleontology "old, ancient", ὄν, ὀντ- "being, creature", and λόγος "speech, thought") is the study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments...
José Fernando Bonaparte recovered some more theropod bones, possibly from the same individual.
In 1986, Ricardo Martínez
Ricardo Martinez
Ricardo José Martinez Mora is an electric bass guitar player. He has been in the music industry for more than two decades, working as a session bassist, performer, arranger, songwriter, music producer, music director, banjo player , among other music related activities.He is highly regarded by...
, Olga Giménez, Jorge Rodríguez
Jorge Rodríguez
Jorge Rodríguez may refer to:* Jorge Rodriguez-Gerada, Cuban-American artist* Jorge Rodríguez , Mexican football player* Jorge Marcelo Rodríguez, Uruguayan football player* Jorge Rodríguez , former Vice President of Venezuela...
and Graciela Bochatey described the theropod fossils and coined the genus and species Xenotarsosaurus bonapartei for them. The generic name is derived from Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
xenos, "strange", tarsos, "tarsus
Tarsus (skeleton)
In tetrapods, the tarsus is a cluster of articulating bones in each foot situated between the lower end of tibia and fibula of the lower leg and the metatarsus. In the foot the tarsus articulates with the bones of the metatarsus, which in turn articulate with the bones of the individual toes...
", and sauros, "lizard", a reference to the exceptional build of the ankle. The specific name bonapartei honours Bonaparte.
The type specimens (and only known fossils of Xenotarsosaurus) were found in the Bajo Barreal Formation
Bajo Barreal Formation
The Bajo Barreal Formation is a geological formation in Chubut, Argentina whose strata date back to the Late Cretaceous.-Dinosaurs:Dinosaur remains are among the fossils that have been recovered from the formation...
. In 1986 this formation was seen as Campanian
Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...
; today it is thought to date to the earlier Cenomanian
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 stratigraphic column deposited during the corresponding...
–Turonian
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 93.5 ± 0.8 Ma and 89.3 ± 1 Ma...
. The bones consist of two cotypes: UNPSJB PV 184, a series of two anterior dorsal vertebrae, and PVL 612, a right hind limb including the 611 millimetres (24.1 in) long femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
, the tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
, fibula and astragalocalcaneum of the ankle. The exceptional complete fusion, without sutures, of the astragalus
Talus bone
-External links:* *...
and calcaneum, forming an element that is again fused to the widened lower end of the tibia, occasioned the generic name.
The remains show some similarities to Carnotaurus
Carnotaurus
Carnotaurus was a large predatory dinosaur. Only one species, Carnotaurus sastrei has been described so far.Carnotaurus lived in Patagonia, Argentina during the Campanian or Maastrichtian stage of the Late Cretaceous...
sastrei, causing the describers to assign Xenotarsosaurus to the Abelisauridae
Abelisauridae
Abelisauridae is a family of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous Period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are found on the modern continents of Africa and South America, as well as on the Indian...
, which has remained a common determination. However, it has also been proposed that Xenotarsosaurus is a neoceratosaurian of uncertain affinities.