''Xenotarsosaurus'' 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 ...
of
abelisaurid
Abelisauridae (meaning "Abel's lizards") is a family (or clade) of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are foun ...
theropod
Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...
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 ...
that lived during the Late
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...
of
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 ...
.
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
Chubut ( from Tehuelche language, Tehuelche 'transparent'; ) is a provinces of Argentina, province in southern Argentina, situated between the 42nd parallel south (the border with Río Negro Province), ...
province. Among the fossils found there were some theropod remains. Later, a team led by Argentinian
paleontologist
Paleontology, also spelled as palaeontology or palæontology, is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use fossils as a means to classify organisms, measure geolo ...
José Fernando Bonaparte 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
Greek may refer to:
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group
*Greek language, a branch of the Indo-European language family
**Proto-Greek language, the assumed last common ancestor of all kno ...
''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 wikt:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to ancho ...
s (and only known fossils of ''Xenotarsosaurus'') were found in the
Bajo Barreal Formation
The Bajo Barreal Formation is a geological Formation (geology), formation in the Golfo San Jorge Basin of Chubut Province, Chubut and Santa Cruz Province, Argentina, Santa Cruz, Argentina whose strata date back to the Cenomanian, Middle Cenomanian ...
. In 1986 this formation was seen as
Campanian
The Campanian is the fifth of six ages of the Late Cretaceous epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campa ...
; today it is thought to date to the earlier
Cenomanian
The Cenomanian is, in the International Commission on Stratigraphy's (ICS) geological timescale, the oldest or earliest age (geology), age of the Late Cretaceous epoch (geology), Epoch or the lowest stage (stratigraphy), stage of the Upper Cretace ...
–
Turonian
The Turonian is, in the International Commission on Stratigraphy, ICS' geologic timescale, the second age (geology), age in the Late Cretaceous epoch (geology), Epoch, or a stage (stratigraphy), stage in the Upper Cretaceous series (stratigraphy), ...
. 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 associated. In other words, a type is an example that serves to anchor or centralizes t ...
s: UNPSJB PV 184, a series of two anterior dorsal
vertebra
Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spina ...
e, and PVL 612, a right hind limb including the long
femur
The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg.
The Femo ...
, the
tibia
The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...
,
fibula
The fibula (: fibulae or fibulas) 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. ...
and astragalocalcaneum of the ankle. The exceptional complete fusion, without
sutures, of the
astragalus
Astragalus may refer to:
* ''Astragalus'' (plant), a large genus of herbs and small shrubs
*Astragalus (bone)
The talus (; Latin for ankle or ankle bone; : tali), talus bone, astragalus (), or ankle bone is one of the group of foot bones known ...
and
calcaneum
In humans and many other primates, the calcaneus (; from the Latin ''calcaneus'' or ''calcaneum'', meaning heel; : calcanei or calcanea) or heel bone is a bone of the tarsus of the foot which constitutes the heel. In some other animals, it is t ...
, forming an element that is again fused to the widened lower end of the tibia, occasioned the generic name.
Description
In 2010
Gregory S. Paul
Gregory Scott Paul (born December 24, 1954) is an American freelance researcher, author and illustrator who works in paleontology. He is best known for his work and research on theropoda, theropod dinosaurs and his detailed illustrations, both l ...
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).
Classification
The remains show some similarities to ''
Carnotaurus
''Carnotaurus'' (; ) is a genus of Theropoda, theropod dinosaur that lived in South America during the Late Cretaceous period, probably sometime between 72 and 69 million years ago. The only species is ''Carnotaurus sastrei''. Known from a si ...
sastrei'', causing the describers to assign ''Xenotarsosaurus'' to the
Abelisauridae
Abelisauridae (meaning "Abel's lizards") is a family (or clade) of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are fou ...
, 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.
In 2021, ''Xenotarsosaurus'' was placed as an abelisaurid more derived than ''
Eoabelisaurus
''Eoabelisaurus'' () is a genus of abelisauroid theropod dinosaur from the Lower Jurassic Cañadón Asfalto Formation of the Cañadón Asfalto Basin in Argentina, South America. The generic name combines a Greek ἠώς, (''eos''), "dawn", with t ...
'' based on phylogenetic analyses. A 2022 phylogenetic analysis also recovered the genus as an abelisaurid.
See also
*
Timeline of ceratosaur research
This timeline of ceratosaur research is a chronological listing of events in the History of paleontology, history of paleontology focused on the ceratosaurs, a group of relatively primitive, often horned, predatory theropod dinosaurs that became ...
Notes
External links
''Xenotarsosaurus'' at DinoData
{{Taxonbar, from=Q135103
Abelisauridae
Dinosaur genera
Cenomanian dinosaurs
Turonian dinosaurs
Bajo Barreal Formation
Dinosaurs of Argentina
Fossil taxa described in 1986