Orcaptor
| Orcaptor | ||||||||||||
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Artist's impression (the feathers are theoretically possible, but not proven by fossil records) |
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| Temporal occurrence | ||||||||||||
| Cenomanium to Santonium ( Upper Cretaceous ) | ||||||||||||
| 100.5 to 83.6 million years | ||||||||||||
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Patagonia |
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| Systematics | ||||||||||||
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| Orcaptor | ||||||||||||
| Novas , Ezcurra & Lecuona , 2008 | ||||||||||||
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Orkoraptor is a genus of the Megaraptoridae from the theropod group . The only known species of the so far monotypical genus is Orkoraptor burkei from the Middle Mata Amarilla Formation (formerly Pari Aike Formation, Upper Cretaceous , Cenomanium to Santonium , approx. 100.5 to 83.6 million years old) in the province of Santa Cruz in the Argentine part of Patagonia .
Etymology and history of research
The generic name is derived from the Tehuelch Orr-Korr , ("toothed river"), which designates the river La Leona , which is near the place of discovery and the Latin raptor ("robber"). The species addition burkei honors the amateur paleontologist Coleman Burke , who supported the expedition that found the fossils. The species name can roughly be translated as "Burke's robbers from the toothed river".
The type specimen of the genus, MPM-Pv 3457, was found in 2001 in the Middle Mata Amarilla Formation in southern Patagonia. It was first described in 2008 by Fernando Novas and co-authors .
In 2010, Benson , Carrano and Brusatte placed the genus in the newly established clade of Megaraptora . In 2013, Novas et al. the Megaraptora originating from the area of Gondwana , including Orkoraptor , in the subgroup of the Megaraptoridae within the Megaraptora.
Fossil record
The fossil material of the holotype MPM-Pv 3457 includes a right postorbital , a right quadratojugal , a bone of the lower jaw, which is possibly a right coronoid , eight isolated individual teeth, parts of the atlas vertebra , two proximal caudal vertebrae, the proximal half of a right one Tibia , fragments of a total of eight ribs and three incomplete chevron bones . The remains of the holotype come from a single site with a diameter of about 1.5 m in the Middle Mata Amarilla Formation. In addition, there are three more individual teeth (MPM-Pv 3458) from the same find layer.
features
Orkoraptor was a bipedal theropod about 6–7 meters long with an estimated body mass of about 500 kilograms.
Orkoraptor's teeth are flattened labiolingually and strongly curved backwards. A deep groove that runs along the longitudinal axis of the teeth, both on the labial side and on the ligual side, gives the teeth a characteristic figure-of-eight cross-section. The mesial side is smooth (imperforate) and relatively wide. Only the distal side of the teeth is provided with sawtooth-like denticles, a feature that Orkoraptor shares with some representatives of the Compsognathidae and the Deinonychosauria .
As in most diapsidae , the three-rayed postorbital shows a broad zygomatic process and the edge to the eye socket is blunt and without a suborbital flange. The rostral process is inclined anterodorsally (forward and upward), a feature that Orkoraptor shares with some representatives of the Maniraptora . The quadratojugale, however, has only a short zygomatic process. The proximal caudal vertebrae show small pleurocoels (lateral openings for weight reduction), a rare feature of a theropod that is otherwise known only from a few other representatives of the tetanurae .
Age rating
The sediments of the Middle Mata Amarilla Formation were originally assigned to the Upper Cretaceous ( Maastrichtian ) and the first descriptors followed this approach. Later U-Pb dates on zirconia from a tuff layer, however, show a somewhat older age of the find layers, which are now classified in the Cenomanium to Santonium of the Upper Cretaceous.
Systematics
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| Systematic position of Orkoraptor in the sense of Benson et al., 2010; within the allosauroid according to Carrano et al., 2012 |
The characteristics found led the first person to suspect that it was a representative of the Coelurosauria . In order to test their hypothesis, they integrated Orkoraptor into a corresponding, already existing phylogenetic data matrix and added two further characteristics that were taken into account. The analysis showed Orkoraptor to be a representative of the Maniraptora . A more precise classification within this group was not possible. The authors found it remarkable that the inclusion of Orkoraptor in the data matrix caused the long and well-established clades of the Compsognathidae and the Dromaeosauridae to collapse in their status as monophyletic groups. This and other results of the analysis prompted them to cautiously classify the new genus as the representative of the coelurosaurs in question. However, they also did not rule out the possibility that orcoraptor belonged to a previously unknown group of large tetanurae from the Upper Cretaceous South America.
In 2010, Benson, Carrano and Brusatte published the results of a second attempt to clarify the systematic position of Orkoraptor and three other theropods ( Aerosteon , Australovenator and Shaochilong ). This time a data matrix was used and expanded that Benson had already put together in order to clarify the relationships between the basal tetanurae. It turned out that Orkoraptor with Aerosteon , Australovenator , Neovenator , Chilantaisaurus , Fukuiraptor and Megaraptor formed a monophyletic group, which the authors called Neovenatoridae and compared to the Carcharodontosauridae as a sister group within the Carcharodontosauria . The authors interpreted the group as a representative of the Allosauroidea . In addition, Benson and his coauthors identified within the Neovenatoridae another monophyletic subgroup of Aerosteon , Australovenator , Fukuiraptor , Megaraptor and Orkoraptor which they called Megaraptora. Orcoraptor could be assigned to this subgroup, but the position within the clade remained unclear due to the very fragmentary fossil record.
In a more comprehensive phylogenetic analysis of the Tetanurae, Carrano et al. 2012 this assessment. Orkoraptor is explicitly mentioned in this work as a representative of the Megaraptora, but was not part of the data matrix used for the analysis. The cladogram above shows the systematic position of Orkoraptor according to the interpretation of Benson et al., 2010 and Carrano et al., 2012 as a representative of the Megaraptora (subgroup of the Neovenatoridae) within the Allosauroidea.
| Systematic position of Orkoraptor within the Megaraptoridae (Tyrannosauroidea, Neotetanurae) according to Porfiri et al., 2014. |
In 2013, a working group around two of the first descriptors (Novas and Ezcurra) published a further attempt based on a phylogenetic analysis to prove that the Megaraptora, and thus Orkoraptor , belong to the Coelurosaurs. The authors confirmed the Megaraptora as a monophyletic group, but located them in the group of the Tyrannosauroidea , i.e. deep within the clade of the Coelurosauria and not within the Allosauroidea. In addition, they distinguished within the Megaraptora the subgroup of Megaraptoridae in which they summarized all representatives of the Megaraptora from the former southern continent Gondwana and compared Fukuiraptor from Laurasia . Porfiri et al. Followed this assessment in 2014 . based on new evidence for the genus Megaraptor .
In summary, it can be said that the systematic position of the orcoraptor , and the megaraptora in general, is still unclear (as of March 2018).
Paleecology
For Orkoraptor can from a carnivorous be assumed diet.
The Middle Mata Amarilla Formation (formerly Pari Aike Formation) is made up of sandstones and clay / siltstones that are deposited in an interwoven to anastomosing or meandering river system at the edge of the Austral Basin (also known as the Rocas Verdes Basin or Magellan Basin) were.
Mineralogical and geochemical analyzes of paleo soils within the sediment sequence allow conclusions to be drawn about the paleoclimatological conditions. The data speak for a subtropical climate with an annual mean temperature of 12 ± 2.1 ° C and an average annual rainfall of 1404 ± 108 mm with pronounced seasonal rainy seasons.
Numerous plant fossils show a dense vegetation cover. At the base of the Middle Mata Amarilla Formation, numerous tree trunks and rhizomes of a Petrified Forest (María Elena Petrified Forest) have been preserved. The tree society is dominated by representatives of the Podocarpaceae . Subordinate also occur Araucariaceae and occasionally Cycadales in appearance. Fossil tree trunks from the higher parts of the Middle Mata Amarilla Formation can only be assigned as representatives of the conifers , but there are also find horizons that are dominated by leaf prints of covered plants . Iglesias and co-authors differentiate 12 different morphotypes for the latter , which indicates a relatively high diversity of the moths in this ecosystem. Since fossil tree trunks and leaf prints can be clearly assigned to different groups of seed plants, the authors suspect that the cover-seeded plants do not represent large trees, but rather parts of the shrub and herb layer .
Orkoraptor shared this habitat among others, the Abelisauroiden austrocheirus isasii , the Iguanodontier Talenkauen santacrucensis and the sauropods puertasaurus reuili . There are also remains of crocodiles and turtles.
Individual evidence
- ↑ a b c d e f g h i F. E. Novas, MD Ezcurra & A. Lecuona: Orkoraptor burkei nov. gen. et sp., a large theropod from the Maastrichtian Pari Aike Formation, Southern Patagonia, Argentina. In: Cretaceous Research , Vol. 29, pp. 468-480, 2008. doi: 10.1016 / j.cretres.2008.01.001 , (digitized version )
- ↑ a b c d A. N. Varela, DG Poiré, T. Martin, A. Gerdes, FJ Goin, JN Gelfo & S. Hoffmann: U-Pb zircon constraints on the age of the Cretaceous Mata Amarilla Formation, Southern Patagonia, Argentina: its relationship with the evolution of the Austral Basin. In: Andean Geology , Vol. 39, No. 3, pp. 359–379, 2012. doi: 10.5027 / andgeoV39n3-a01 , (available)
- ↑ a b c d e R. BJ Benson, MT Carrano & SL Brusatte: A new clade of archaic large-bodied predatory dinosaurs (Theropoda: Allosauroidea) that survived to the latest Mesozoic. In: Naturwissenschaften , Volume 97, Issue 1, pp. 71–78, 2010 (online 2009). doi: 10.1007 / s00114-009-0614-x , (digitized version) , (Appendix)
- ^ A b F. E. Novas, FL Agnolín, MD Ezcurra, J. Porfiri & JI Canale: Evolution of the carnivorous dinosaurs during the Cretaceous: The evidence from Patagonia. In: Cretaceous Research , Vol. 45, pp. 174–215, 2013. (digitized version )
- ↑ a b c J. D. Porfiri, FE Novas, JO Calvo, FL Agnolín, MD Ezcurra & IA Cerda: Juvenile specimen of Megaraptor (Dinosauria, Theropoda) sheds light about tyrannosauroid radiation. In: Cretaceous Research , Vol. 51, pp. 35–55, 2014. doi: 10.1016 / j.cretres.2014.04.007 , (digitized version )
- ^ GS Paul: The Princeton Field Guide to Dinosaurs. 2nd edition, p. 108, 2016. (extract)
- ^ FE Novas, AV Cambiaso & A. Ambrosio: A new basal iguanodontian (Dinosauria, Ornithischia) from the Upper Cretaceous of Patagonia. In: Ameghiniana , Vol. 41, No. 1, pp. 75–82, 2004. (digitized version )
- ↑ a b c M. T. Carrano, RBJ Benson & SD Sampson: The phylogeny of Tetanurae (Dinosauria: Theropoda). In: Journal of Systematic Palaeontology , Vol. 10, No. 2, pp. 211–300, 2012. (digitized version )
- ^ PJ Makovicky, S. Apesteguía & FL Agnolín: The earliest dromaeosaurid theropod from South America - Supplementary Notes. In: Nature , Vol. 437, pp. 1007-1011, 2005. (available)
- ↑ JD Porfiri, RDJ Valieri, DDD Santos & MC Lamanna: A new megaraptoran theropod dinosaur from the Upper Cretaceous Bajo de la Carpa Formation of northwestern Patagonia. In: Cretaceous Research , Vol. 89, pp. 302-319, 2018. (manuscript version )
- ↑ a b A. N. Varela, MS Raigemborn, S. Richiano, T. White, DG Poiré & S. Lizzoli: Late Cretaceous paleosols as paleoclimate proxies of high-latitude Southern Hemisphere: Mata Amarilla Formation, Patagonia, Argentina. In: Sedimentary Geology , Vol. 363, pp. 83-95, 2018. doi : 10.1016 / j.sedgeo.2017.11.001
- ↑ LCA Martínez, A. Iglesias, AE Artabe, AN Varela & S. Apesteguía: A new Encephalarteae trunk (Cycadales) from the Cretaceous of Patagonia (Mata Amarilla Formation, Austral Basin), Argentina. In: Cretaceous Research , Vol. 72, pp. 81–94, 2017. (digitized version )
- ^ A. Iglesias, AB Zamuner, DG Poiré & F. Larriestra: Diversity, Taphonomy and Palaeoecology of an Angiosperm Flora from the Cretaceous (Cenomanian – Coniacian) in Southern Patagonia, Argentina. In: Palaeontolgy , Vol. 50, Part 2, pp. 445–466, 2007. (digitized version )
- ↑ MD Ezcurra, FL Agnolin & FE Novas: At abelisauroid dinosaur with a non-atrophied manus from the Late Cretaceous Pari Aike Formation of southern Patagonia. In: Zootaxa , No. 2450, pp. 1–25, 2010. (digitized version)