Abelisauridae

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Abelisaurids
Temporal range: Middle Jurassic-Late Cretaceous, 170–66Ma
Aucasaurus.jpg
Reconstructed skeleton of Aucasaurus garridoi
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Suborder: Theropoda
Clade: Abelisauria
Family: Abelisauridae
Bonaparte & Novas, 1985
Type species
Abelisaurus comahuensis
Bonaparte & Novas, 1985
Subgroups

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 found on the modern continents of Africa and South America, as well as on the Indian subcontinent and the island of Madagascar. Abelisaurids first appear in the fossil record of the early middle Jurassic period, and at least one species (Majungasaurus crenatissimus) survived until the end of the Mesozoic era 66 million years ago.

Like most theropods, abelisaurids were carnivorous bipeds. They were characterized by stocky hindlimbs and extensive ornamentation of the skull bones, with grooves and pits. In many abelisaurids, like Carnotaurus, the forelimbs are vestigial, the skull is shorter and bony crests grows above the eyes. Most of the known abelisaurids would have been between 5 to 9 meters (17 to 30 ft) in length, from snout to tip of tail, with a new and as yet unnamed specimen from northwestern Turkana in Kenya, Africa reaching a possible length of 11–12 meters (36 to 39 feet).[2] Before becoming well known, fragmentary abelisaurid remains were occasionally misidentified as possible South American tyrannosaurids.[3]

Description[edit]

Reconstructed Abelisaurus skull, "Dinosaurs of Patagonia" exhibit. Note the rough bone surfaces and projections from the lacrimal and postorbital bones into the eye socket
Carnotaurus skeleton, Natural History Museum, London

Skull[edit]

Although skull proportions varied, abelisaurid skulls were generally very tall and very short in length. In Carnotaurus, for example, the skull was nearly as tall as it was long. The premaxilla in abelisaurids was very tall, so the front of the snout was blunt, not tapered as seen in many other theropods.[2]

Two skull bones, the lacrimal and postorbital bones, projected into the eye socket from the front and back, nearly dividing it into two compartments. The eye would have been located in the upper compartment, which was tilted slightly outwards in Carnotaurus, perhaps providing some degree of binocular vision. The lacrimal and postorbital also met above the eye socket, to form a ridge or brow above the eye.[2]

Sculpturing is seen on many of the skull bones, in the form of long grooves, pits and protrusions. Like other ceratosaurs, the frontal bones of the skull roof were fused together. Carnotaurines commonly had bony projections from the skull. Carnotaurus had two pronounced horns, projecting outward above the eyes, while its close relative Aucasaurus had smaller projections in the same area. Majungasaurus and Rajasaurus had a single bony horn or dome, projecting upwards from the skull. These projections, like the horns of many modern animals, might have been displayed for species recognition or intimidation.[4][5][6]

Forelimbs and hands[edit]

The forelimb of Aucasaurus

Data for the abelisaurid forelimbs are known from Eoabelisaurus and the carnotaurines Aucasaurus, Carnotaurus and Majungasaurus. All had small forelimbs which seems to have been vestigial.[7] The bones of the forearm (radius and ulna) were extremely short, only 25% of the length of the upper arm (humerus) in Carnotaurus and 33% in Aucasaurus. The entire arm was held straight, and the elbow joint was immobile.[7]

As is typical for ceratosaurs, the abelisaurid hand had four basic digits. However, it is there that any similarity ends. No wrist bones existed, with the four palm bones (metacarpals) attaching directly to the forearm. There were no finger bones on the first or fourth digits, only one on the second digit and two on the third digit. These two external fingers were extremely short and immobile. Manual claws were very small in Eoabelisaurus, and totally absent in carnotaurines.[7]

More primitive relatives such as Noasaurus and Ceratosaurus had longer, mobile arms with fingers and claws.[8]

Hind limbs[edit]

Abelisaurid hindlimbs were more typical of ceratosaurs, with the astragalus and calcaneum (upper ankle bones) fused to each other and to the tibia, forming a tibiotarsus. The tibia was shorter than the femur, giving the hindlimb stocky proportions. There were three functional digits on the foot (the second, third, and fourth), while the first digit, or hallux, did not contact the ground.[4]

Distribution[edit]

Restored skeleton of an abelisaur in Brazil

Abelisauroids are typically regarded as a Cretaceous group, though the earliest abelisaurid remains are known from the Middle Jurassic of Argentina (classified as the species Eoabelisaurus mefi) and possibly Madagascar (fragmentary remains of an unnamed species);[9][10] a possible abelisaurid remains (an isolated left tibia, right femur and right tibia) were also discovered in Late Jurassic Tendaguru Beds in Tanzania.[11] Abelisaurid remains have only been found in the southern continents, which once made up the supercontinent of Gondwana. When first described in 1985, only Carnotaurus and Abelisaurus were known, both from the Late Cretaceous of South America. Abelisaurids were then located in Late Cretaceous India (Indosuchus and Rajasaurus) and Madagascar (Majungasaurus), which were closely connected for much of the Cretaceous. It was thought that the absence of abelisaurids from continental Africa indicated that the group evolved after the separation of Africa from Gondwana, around 100 million years ago.[12] However, the discovery of Rugops and other abelisaurid material from the middle of the Cretaceous in northern Africa disproved this hypothesis.[13][14] Mid-Cretaceous abelisaurids are now known from South America as well, showing that the group existed prior to the breakup of Gondwana.[15][16][17]

Classification[edit]

A comparison of Abelisaurid skulls (not to scale) 1. Rajasaurus, 2. Rugops, 3. Abelisaurus, 4. Majungasaurus, 5. Aucasaurus, and 6. Carnotaurus

Paleontologists Jose Bonaparte and Fernando Novas coined the name Abelisauridae in 1985 when they described the eponymous Abelisaurus. The name is formed from the family name of Roberto Abel, who discovered Abelisaurus, as well as from the Greek word σαυρος/sauros meaning 'lizard'. The very common suffix -idae is usually applied to zoological family names and is derived from the Greek suffix -ιδαι/-idai, which indicates a plural noun.[18]

Abelisauridae is a family in rank-based Linnaean taxonomy, within the infraorder Ceratosauria and the superfamily Abelisauroidea, which also contains the family Noasauridae. It has had several definitions in phylogenetic taxonomy. It was originally defined as a node-based taxon including Abelisaurus, Carnotaurus, their common ancestor and all of its descendants.[19][20]

Later it was redefined as a stem-based taxon, including all animals more closely related to Abelisaurus (or the more complete Carnotaurus) than to Noasaurus.[6] The node-based definition would not include animals like Rugops or Ilokelesia, which are thought to be more basal than Abelisaurus and would be included by a stem-based definition.[21] Within Abelisauridae is the subgroup Carnotaurinae, and among carnotaurines, Aucasaurus and Carnotaurus are united in Carnotaurini.[13]

Shared characteristics[edit]

Size comparison between abelisaurid genera and human.

Complete skeletons have been described only for the most advanced abelisaurids (such as Carnotaurus and Aucasaurus), making it difficult to establish defining features of the skeleton for the family as a whole. However, most are known from at least some skull bones, so known shared features come mainly from the skull.[4]

Many abelisaurid skull features are shared with carcharodontosaurids. These shared features, along with the fact that abelisaurids seem to have replaced carcharodontosaurids in South America, have led to suggestions that the two groups were related.[19] However, no cladistic analysis has ever found such a relationship and, aside from the skull, abelisaurids and carcharodontosaurids are very different, more similar to ceratosaurs and allosauroids, respectively.[4]

Phylogeny[edit]

A 2004 phylogenetic analysis, performed by Paul Sereno of the University of Chicago and several colleagues, obtained the following results:[13]

 Abelisauroidea 

Noasauridae


 Abelisauridae 

?Ilokelesia



Rugops


unnamed

Abelisaurus


 Carnotaurinae 

Rajasaurus


unnamed

Majungasaurus


 Carnotaurini 

Aucasaurus



Carnotaurus








Restoration of Rugops, a basal Abelisaur

Ilokelesia was originally described as a sister group to Abelisauroidea.[15] However, Sereno tentatively places it closer to Abelisaurus than to noasaurids, a result which agrees with several other recent analyses.[4][16][22] If a stem-based definition is used, Ilokelesia and Rugops are therefore basal abelisaurids. However, as they are more basal than Abelisaurus, they are outside of Abelisauridae if the node-based definition is adopted. Ekrixinatosaurus was also published in 2004, so it was not included in Sereno's analysis. However, an independent analysis, performed by Jorge Calvo and colleagues, shows it to be an abelisaurid.[16]

Some scientists include Xenotarsosaurus from Argentina and Compsosuchus from India as basal abelisaurids,[23][24] while others consider them to be outside Abelisauroidea.[25] The French Genusaurus and Tarascosaurus have also been called abelisaurids but both are fragmentary and may be more basal ceratosaurians.[4]

With the description of Skorpiovenator in 2008, Canale et al. published another phylogenetic analysis focusing on the South American abelisaurids. In their results, they found that all South American forms, including Ilokelesia (except Abelisaurus), grouped together as a sub-clade of carnotaurines, which they named Brachyrostra.[26] In the same year Matthew T. Carrano and Scott D. Sampson published new large phylogenetic analysis of ceratosaurian.[27] With the description of Eoabelisaurus, Diego Pol and Oliver W. M. Rauhut (2012) combined these analyses and added ten new characters. The following cladogram follows their analysis.[28]

Ceratosauria 

Berberosaurus



Deltadromeus





Spinostropheus




Limusaurus



Elaphrosaurus




 Neoceratosauria 
 Ceratosauridae 

Ceratosaurus



Genyodectes



 Abelisauroidea 
 Noasauridae 

Laevisuchus



Masiakasaurus



Noasaurus



Velocisaurus



 Abelisauridae 

Eoabelisaurus




Rugops




Abelisaurus


 Carnotaurinae 


Majungasaurus



Indosaurus



Rajasaurus



 Brachyrostra 


Ilokelesia



Ekrixinatosaurus



Skorpiovenator



 Carnotaurini 

Carnotaurus



Aucasaurus












The description of Arcovenator in 2013 introduces a new abelisaurid subfamily, Majungasaurinae.[1]

Abelisauridae

Kryptops



Rugops



Genusaurus



MCF-PVPH-237 ("Bayosaurus")



Xenotarsosaurus



Tarascosaurus



La Boucharde abelisaurid



 Majungasaurinae 

Pourcieux abelisaurid



Arcovenator



Majungasaurus



Indosaurus



Rahiolisaurus



Rajasaurus



 Brachyrostra 

Ilokelesia




Ekrixinatosaurus




Skorpiovenator


 Carnotaurini 

Abelisaurus



Aucasaurus



Pycnonemosaurus



Quilmesaurus



Carnotaurus








Timeline[edit]

21st century in paleontology 20th century in paleontology 19th century in paleontology 2090s in paleontology 2080s in paleontology 2070s in paleontology 2060s in paleontology 2050s in paleontology 2040s in paleontology 2030s in paleontology 2020s in paleontology 2010s in paleontology 2000s in paleontology 1990s in paleontology 1980s in paleontology 1970s in paleontology 1960s in paleontology 1950s in paleontology 1940s in paleontology 1930s in paleontology 1920s in paleontology 1910s in paleontology 1900s in paleontology 1890s in paleontology 1880s in paleontology 1870s in paleontology 1860s in paleontology 1850s in paleontology 1840s in paleontology 1830s in paleontology 1820s in paleontology Aucasaurus Carnotaurus Skorpiovenator Ekrixinatosaurus Ilokelesia Rajasaurus Indosaurus Majungasaurus Abelisaurus Rugops Arcovenator 21st century in paleontology 20th century in paleontology 19th century in paleontology 2090s in paleontology 2080s in paleontology 2070s in paleontology 2060s in paleontology 2050s in paleontology 2040s in paleontology 2030s in paleontology 2020s in paleontology 2010s in paleontology 2000s in paleontology 1990s in paleontology 1980s in paleontology 1970s in paleontology 1960s in paleontology 1950s in paleontology 1940s in paleontology 1930s in paleontology 1920s in paleontology 1910s in paleontology 1900s in paleontology 1890s in paleontology 1880s in paleontology 1870s in paleontology 1860s in paleontology 1850s in paleontology 1840s in paleontology 1830s in paleontology 1820s in paleontology

References[edit]

  1. ^ a b Tortosa, Thierry; Eric Buffetaut; Nicolas Vialle; Yves Dutour; Eric Turini; Gilles Cheylan (2013). "A new abelisaurid dinosaur from the Late Cretaceous of southern France: Palaeobiogeographical implications". Annales de Paléontologie (In press). doi:10.1016/j.annpal.2013.10.003. Retrieved 13 December 2013. 
  2. ^ a b c "October/November 2013, Abstracts Of Papers, 73rd Annual Meeting". Society of Vertebrate Paleontology. 2013. Retrieved 2013-10-27. 
  3. ^ "Abelisaurus." In: Dodson, Peter & Britt, Brooks & Carpenter, Kenneth & Forster, Catherine A. & Gillette, David D. & Norell, Mark A. & Olshevsky, George & Parrish, J. Michael & Weishampel, David B. The Age of Dinosaurs. Publications International, LTD. p. 105. ISBN 0-7853-0443-6.
  4. ^ a b c d e f Tykoski, R.S. & Rowe, T. (2004). "Ceratosauria". In: Weishampel, D.B., Dodson, P., & Osmolska, H. (Eds.) The Dinosauria (2nd edition). Berkeley: University of California Press. Pp. 47–70 ISBN 0-520-24209-2
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  6. ^ a b Wilson, J.A.; Sereno, P.C.; Srivastava, S.; Bhatt, D.K.; Khosla, A.; Sahni, A. (2003). "A new abelisaurid (Dinosauria, Theropoda) from the Lameta Formation (Cretaceous, Maastrichtian) of India". Contributions of the Museum of Palaeontology of the University of Michigan 31: 1–42. 
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  8. ^ Agnolin, Federico L.; Chiarelli, Pablo (2009). "The position of the claws in Noasauridae (Dinosauria: Abelisauroidea) and its implications for abelisauroid manus evolution". Paläontologische Zeitschrift 84: 293. doi:10.1007/s12542-009-0044-2. 
  9. ^ Pol, D. and Rauhut, O.W.M. (2012). "A Middle Jurassic abelisaurid from Patagonia and the early diversification of theropod dinosaurs." Proceedings of the Royal Society B, published ahead of print May 23, 2012: 1471-2954.
  10. ^ Maganuco, S.; Cau, A.; Pasini, G. (2005). "First description of theropod remains from the Middle Jurassic (Bathonian) of Madagascar". Atti della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale in Milano 146 (2): 165–202. 
  11. ^ Rauhut, Oliver W. M. (2011). "Theropod dinosaurs from the Late Jurassic of Tendaguru (Tanzania)". Special Papers in Palaeontology 86: 195–239. doi:10.1111/j.1475-4983.2011.01084.x. 
  12. ^ Sampson, S.D.; Witmer, L.M.; Forster, C.A.; Krause, D.A.; O'Connor, P.M.; Dodson, P.; Ravoavy, F. (1998). "Predatory dinosaur remains from Madagascar: implications for the Cretaceous biogeography of Gondwana". Science 280 (5366): 1048–1051. doi:10.1126/science.280.5366.1048. PMID 9582112. 
  13. ^ a b c Sereno, P.C.; Wilson, J.A.; Conrad, J.L. (2004). "New dinosaurs link southern landmasses in the mid-Cretaceous". Proceedings of the Royal Society B 271: 1325–1330. doi:10.1098/rspb.2004.2692. PMC 1691741. PMID 15306329. 
  14. ^ Mahler, L. (2005). "Record of Abelisauridae (Dinosauria: Theropoda) from the Cenomanian of Morocco".". Journal of Vertebrate Paleontology 25 (1): 236–239. doi:10.1671/0272-4634(2005)025[0236:ROADTF]2.0.CO;2. 
  15. ^ a b Coria, R.A. & Salgado, L. "A basal Abelisauria Novas 1992 (Theropoda- Ceratosauria) from the Cretaceous Period of Patagonia, Argentina". In: Perez-Moreno, B, Holtz, T.R., Sanz, J.L., & Moratalla, J. (Eds.). Aspects of Theropod Paleobiology. Gaia 15:89–102. [not printed until 2000]
  16. ^ a b c Calvo, J.O.; Rubilar-Rogers, D.; Moreno, K. (2004). "A new Abelisauridae (Dinosauria: Theropoda) from northwest Patagonia". Ameghiniana 41 (4): 555–563. 
  17. ^ Lamanna, M.C.; Martinez, R.D.; Smith, J.B. (2002). "A definitive abelisaurid theropod dinosaur from the early Late Cretaceous of Patagonia".". Journal of Vertebrate Paleontology 22 (1): 58–69. doi:10.1671/0272-4634(2002)022[0058:ADATDF]2.0.CO;2. 
  18. ^ Bonaparte, J.F. & Novas, F.E. (1985). ["Abelisaurus comahuensis, n.g., n.sp., Carnosauria of the Late Cretaceous of Patagonia".] Ameghiniana. 21: 259–265. [In Spanish]
  19. ^ a b Novas, F.E. (1997). "Abelisauridae". In: Currie, P.J. & Padian, K.P. Encyclopedia of Dinosaurs. San Diego: Academic Press. Pp. 1–2 ISBN 0-12-226810-5.
  20. ^ Sereno, P.C. (1998). "A rationale for phylogenetic definitions, with applications to the higher-level taxonomy of Dinosauria". Neues Jahrbuch fur Geologie und Palaontologie: Abhandlungen 210: 41–83. 
  21. ^ Sereno, P.C. (2005). Abelisauridae. TaxonSearch. 7 November 2005. Retrieved 19 September 2006.
  22. ^ Coria, R.A.; Chiappe, L.M.; Dingus, L. (2002). "A close relative of Carnotaurus sastrei Bonaparte 1985 (Theropoda: Abelisauridae) from the Late Cretaceous of Patagonia". Journal of Vertebrate Palaeontology 22: 460–465. doi:10.1671/0272-4634(2002)022[0460:ANCROC]2.0.CO;2. 
  23. ^ Novas, F.E.; Agnolin, F.L.; Bandyopadhyay, S. (2004). "Cretaceous theropods from India: a review of specimens described by Huene and Matley (1933)".". Revista del Museo Argentino del Ciencias Naturales 6 (1): 67–103. 
  24. ^ Rauhut, O.W.M. (2003). "The interrelationships and evolution of basal theropod dinosaurs". Special Papers in Palaeontology 69: 1–213. 
  25. ^ Martínez, R.D. and Novas, F.E. (2006). "Aniksosaurus darwini gen. et sp. nov., a new coelurosaurian theropod from the early Late Cretaceous of central Patagonia, Argentina". Revista del Museo Argentino de Ciencias Naturales, nuevo serie 8(2):243-259
  26. ^ Canale, Juan I.; Scanferla, Carlos A.; Agnolin, Federico L.; Novas, Fernando E. (2008). "New carnivorous dinosaur from the Late Cretaceous of NW Patagonia and the evolution of abelisaurid theropods". Naturwissenschaften 96 (3): 409–14. doi:10.1007/s00114-008-0487-4. PMID 19057888. 
  27. ^ Carrano, M. T.; Sampson, S. D. (2007). "The Phylogeny of Ceratosauria (Dinosauria: Theropoda)". Journal of Systematic Palaeontology 6 (02). doi:10.1017/S1477201907002246.  edit
  28. ^ Diego Pol & Oliver W. M. Rauhut (2012). "A Middle Jurassic abelisaurid from Patagonia and the early diversification of theropod dinosaurs". Proceedings of the Royal Society B: Biological Sciences (in press). doi:10.1098/rspb.2012.0660.  edit

External links[edit]