Xenotarsosaurus
| Xenotarsosaurus | ||||||||
|---|---|---|---|---|---|---|---|---|
Lower leg of Xenotarsosaurus bonapartei with tibia (t), fibula (f), ankle bone (a) and heel bone (ca) |
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| Temporal occurrence | ||||||||
| Upper Cretaceous ( Cenomanium to Turonium ) | ||||||||
| 100.5 to 89.7 million years | ||||||||
| Locations | ||||||||
| Systematics | ||||||||
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| Scientific name | ||||||||
| Xenotarsosaurus | ||||||||
| Martínez et al., 1986 | ||||||||
| Art | ||||||||
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Xenotarsosaurus is a little-known genus of theropod dinosaurs from the Abelisauroidea group , whichlived in what is now South Americaduring the early Upper Cretaceous ( Cenomanium to Turonium ). The only find so far consists of a fragmentary hind leg and two vertebrae and comes from the Bajo Barreal Formation in the Argentine province of Chubut . The only species is Xenotarsosaurus bonapartei .
The name Xenotarsosaurus ( Gr. Xenos - "strange", tarsus - "foot", saurus - "lizard") means something like "lizard with strange foot" and indicates the unusual structure of the ankle. The second part of the species name, bonapartei , honors the paleontologist José Fernando Bonaparte .
features
It was a medium-sized theropod. The thigh bone measures 59.8 centimeters in length, which suggests a body length of about 5 meters. In the first description (Martínez and colleagues, 1986), Xenotarsosaurus was distinguished from other theropods by the eponymous structure of the ankle joint, which is characterized by the ankle bone (astragalus) fused with the heel bone (calcaneum) . Today, however, this amalgamation is no longer considered a unique feature of Xenotarsosaurus , but rather a common feature of the Ceratosauria group.
Systematics
The relationships of this genus are controversial because of the only sparse remains. In the first description of the genus she assigned Martínez to the Abelisauridae , which has been doubted by some later authors. Coria and Rodriguez (1993) propose to list Xenotarsosaurus only as a representative of the Neoceratosauria (= Ceratosauria) that cannot be classified further (Neoceratosauria incertae sedis ). Carrano and Sampson (2008) classify this genus as a representative of the Abelisauroidea, but consider a position within the Abelisauridae to be probable.
Find
The only find (holotype, copy number UNPSJB-Pv-184 and -612) comes from the lower strata of the Bajo Barreal Formation north of the Ocho Hermanos farm. This specimen was recovered along with the bones of the titanosaur Epachthosaurus . It includes two incomplete presacral vertebrae and a partial right leg (femur, shin, fibula, astragalus, calcaneum).
Two more fragmentary finds of Abelisaurids come from the Bajo Barreal Formation: an upper jaw and a postcranial skeleton . Both finds could possibly also belong to Xenotarsosaurus ; However, since these finds only slightly overlap with the Xenotarsosaurus skeleton, an assignment is currently not possible.
literature
- Matthew T. Carrano, Scott D. Sampson: The Phylogeny of Ceratosauria (Dinosauria: Theropoda). In: Journal of Systematic Palaeontology. Vol. 6, No. 2, 2008, ISSN 1477-2019 , pp. 183-236, doi : 10.1017 / S1477201907002246 .
- Rodolfo A. Coria : Nonavian Theropods. In: Zulma Gasparini, Leonardo Salgado , Rodolfo A. Coria (eds.): Patagonian Mesozoic reptiles. Indiana University Press, Bloomington et al. 2007, ISBN 978-0-253-34857-9 , 229-256.
- Rodolfo A. Coria, Jorge Rodríguez: Sobre Xenotarsosaurus bonapartei Martínez, Giménez, Rodríguez, y Bochatey, 1986; un problematico Neoceratosauria (Novas, 1989) del Cretacico de Chubut. In: Ameghiniana. Vol. 30, No. 3, 1993, ISSN 0002-7014 , pp. 326-327.
- Matthew C. Lamanna, Rubén D. Martínez, Joshua B. Smith: A Definitive Abelisaurid Theropod Dinosaur from the early Late Cretaceous of Patagonia. In: Journal of Vertebrate Paleontology. Vol. 22, No. 1, 2002, pp. 58-69, doi : 10.1671 / 0272-4634 (2002) 022 [0058: ADATDF] 2.0.CO; 2 .
- Ricardo D. Martínez, Olga Giménez, Jorge Rodriguez, Graciela Bochatey: Xenotarsosaurus bonapartei nov. gen. et sp. (Carnosauria, Abelisauridae), un nuevo Theropoda de la Formacion Bajo Barreal, Chubut, Argentina. In: Actas del 4 Congreso Argentino de Paleontologia y Bioestratigrafia. Mendoza, Noviembre 23-27, 1986. Volume 2: Evolucion de los Vertebrados Mesozoicos. Inca, Mendoza 1986, pp. 23-31.
- Ronald S. Tykoski, Timothy Rowe : Ceratosauria. In: David B. Weishampel , Peter Dodson , Halszka Osmólska (eds.): The Dinosauria . 2nd edition. University of California Press, Berkeley CA et al. 2004, ISBN 0-520-24209-2 , pp. 47-70.
Individual evidence
- ↑ a b Coria 2007 , pp. 237-238
- ↑ a b c Martínez et al. 1986 , pp. 23-24
- ↑ a b Lamanna et al. 2002 , p. 63
- ↑ Martínez et al. 1986 , p. 63
- ^ Coria and Rodríguez 1993
- ↑ a b Carrano et al. 2008 , p. 209