Abelisauridae

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Abelisauridae
Skeletal reconstruction of Aucasaurus garridoi

Skeletal reconstruction of Aucasaurus garridoi

Temporal occurrence
Lower to Upper Cretaceous ( Aptian to Maastrichtian )
126.3 to 66 million years
Locations
Systematics
Dinosaur (dinosauria)
Lizard dinosaur (Saurischia)
Theropoda
Ceratosauria
Abelisauroidea
Abelisauridae
Scientific name
Abelisauridae
Bonaparte & Novas , 1985

The Abelisauridae are a group of theropod dinosaurs within the Ceratosauria . They were medium-sized to large, two-legged carnivores, which were characterized by relatively short arms and a short and high, heavily ornamented skull.

Fossils come from the Lower and Upper Cretaceous ( Aptian to Maastrichtian ) of Africa, Madagascar, South America and India.

features

skull

Overall, the skull was robustly built, with different skull bones fused together to a greater extent, such as the paired nasal bones (nasals) and the paired frontal bones (frontal). The skull was proportionally tall and short. This feature was extremely developed in Carnotaurus , where the skull was almost as high as it was long. The intermaxillary bone (premaxillary), a bone located in front of the upper jaw (maxillary), was relatively high, making the snout appear blunt when viewed from the side. Seen from above, the snout was relatively broad and rounded, and not tapered as in many other theropods.

The surface of the facial skull was heavily ornamented with numerous pits and protrusions, which indicates that the integument was horny. Above the eye socket (orbit) there was a thickened browbone, which is formed by the tearbone (lacrimale) and the postorbital . Different genera show horns or appendages emanating from the top of the skull: Rajasaurus and Majungasaurus have a single, low horn, which is formed by the nasal bone and the frontal bone and is reminiscent of the skull domes of the Pachycephalosauria . Aucasaurus, on the other hand, has a pair of small protrusions that extend from the frontal bone, while Carnotaurus has a pair of very large frontal horns.

As with other theropods, the skull had multiple skull windows . The infratemporal window , which is located behind the eye sockets (orbita), was large, as with other representatives of the ceratosauria - this skull window was often twice as large as the eye socket. The lower jaw is characterized by a large mandibular window , which is formed by the dental, the anterior and tooth-bearing part of the lower jaw, as well as by the posterior jawbone. This enlarged skull window went hand in hand with a reduction in the contact points between the dentate and the posterior jawbone and presumably led to an increased mobility of the bones of the lower jaw towards one another. The eye sockets appear teardrop-shaped, while the antorbital window , the cranial window between the eye socket and the nostril, was shortened.

The teeth were relatively small, flattened on the sides and show sawn cutting edges. While the pair of intermaxillary bones in all Abelisaurids has four teeth on each side, the number of teeth in the upper jaw varies from 12 in Carnotaurus to 19 in Rugops .

Postcranial skeleton

The neck was built robustly. The neck ribs exhibited rod-like, rearwardly directed extensions which - in combination with an enlarged occiput served as a cam surface for a comparatively strong neck muscles - (occiput) in the skull back. The caudal vertebrae of some representatives of the Abelisauridae had a unique morphology : the transverse processes - lateral outgrowths of the vertebrae - were long and pointed upwards. This presumably provided space for an enlarged caudofemoralis muscle - the main drive muscle of the legs. The transverse processes were also connected to the transverse processes of the neighboring vertebrae, which indicates that the tail was more immobile than that of other theropods. Indications of these specialized tail features can be found in South American representatives of the abelisaurids, such as Carnotaurus , Aucasaurus , Scorpiovenator and Ilokelesia , but are absent in abelisaurids from Madagascar and India.

The arms are only known from Aucasaurus , Carnotaurus and Majungasaurus . In these genera, the arms were only rudimentary . In Aucasaurus and Carnotaurus, the humerus is only about 30% of the length of the thigh bone. The forearm was no more than a third of the length of the upper arm, making it extremely short. The arm was always kept straight because the elbow joint was immobile. The metacarpals (metacarpals) steered directly with the forearm; Carpal bones (carpalia) were missing. As with other representatives of the Ceratosauria, the hand consisted of four rays, but had an extremely unusual anatomy for theropods: Finger bones were missing on the first and fourth rays - only the two central rays show two extremely shortened fingers. The nerve fibers leading to the arms, which are responsible for the transmission of stimuli , were similarly reduced as in recent emus and kiwis , where the arms have become functionless.

The pelvis was characterized by an elongated ilium . In various representatives of the Abelisauridae, a backward-directed bony branch of the iliac bone was directed with the transverse process of the first caudal vertebra - an unusual feature for theropods. The hind legs resemble those of basal theropods such as Ceratosaurus and were proportionally short and stocky in most genera. Usually that was shin (tibia) and the calf bone (fibula) and the upper tarsal bones (the talus and the calcaneus ) to a so-called Tibiotarsus merged - the Tibiotarsus was there shorter than the thigh bone (femur).

Systematics

External system and definitions

External classification of the Abelisauridae.
 Theropoda 

Coelophysoidea


   

Tetanurae


 Ceratosauria 

Ceratosaurus


 Abelisauroidea 

Noasauridae


   

Abelisauridae






Template: Klade / Maintenance / Style
simplified after Wilson and colleagues, 2003:

The Abelisauridae are counted among the Ceratosauria, a group that split off from the lineage leading to the birds early on and thus occupies a basal (original) position within the theropods. The Abelisauridae are the most strongly derived (advanced) group of the Ceratosauria. Within the Ceratosauria, the Abelisauridae is the sister group of the Noasauridae - these two groups as well as various basic representatives are combined in the Abelisauroidea group.

There are various phylogenetic definitions for the Abelisauridae . Initially this group was as a node-based taxon ( node-based definition defined): So this taxon, according to Sereno includes, for example, (1998) the last common ancestor of Abelisaurus and Carnotaurus and all descendants of that ancestor. However, this definition excludes representatives from the Abelisauridae, such as the rugops described only in 2004 , which are classified as basal as Abelisaurus . Wilson and colleagues (2003) therefore published a new stem-based definition : According to this definition, the Abelisauridae include all taxa that were more closely related to Carnotaurus sastrei than to Noasaurus leali (a member of the Noasauridae).

The definition of this group through commonly derived characteristics ( synapomorphies ) - characteristics by which this taxon differs from all related taxa - is difficult. Most of the representatives are only known from very fragmentary skeletal finds, and it is unclear whether certain features were really limited to the Abelisauridae, or whether they already appeared in more basal forms outside this group. Probable synapomorphies are mainly found on the skull bones and include, for example, the short and deep intermaxillary bone, the thick paired frontal bone and the reduced contacts between the bones of the lower jaw.

Internal system

Internal systematics of the Abelisauridae
 Abelisauridae 

Rugops


   

Abelisaurus


 Carnotaurinae 

Majungasaurus


 Brachyrostra 
 Carnotaurini 

Carnotaurus


   

Aucasaurus



   

Ilokelesia


   

Scorpiovenator


   

Ekrixinatosaurus






Template: Klade / Maintenance / 3

Template: Klade / Maintenance / Style
simplified according to Canale and colleagues, 2009:

There is currently no consensus on the relationships within the Abelisauridae. In most phylogenetic analyzes, however, Abelisaurus is regarded as a basic representative of the group, while Carnotaurus occupies a derived position. To summarize the derived representatives of the Abelisauridae, the group Carnotaurinae is often used, which includes all Abelisaurids that are more closely related to Carnotaurus than to Abelisaurus . Carrano and Sampson (2008), however, come to the conclusion that Abelisaurus was not a basal, but a derivative of the Abelisauridae.

Juan Canale and colleagues (2009) propose a new group within the Carnotaurinae, the Brachyrostra . This group should include all carnotaurines that have a proportionally very short snout ( Carnotaurus , Aucasaurus , Ilokelesia , Skorpiovenator and Ekrixinatosaurus ) and excludes Majungasaurus as a basal representative, which shows a proportionally longer snout. Other researchers, however, see Majungasaurus as the closest relative of Carnotaurus and thus as a very derivative representative.

Temporal distribution and paleobiogeography

Previous finds are limited to the Cretaceous period - the oldest find is cryptops from the late Lower Cretaceous ( Aptian ) Africa. However, Simone Maganuco and colleagues (2004) describe teeth from the Central Jurassic of Madagascar, which, according to these researchers, may be attributed to the Abelisauridae. The last known representatives of the Abelisauridae come from the late Upper Cretaceous ( Maastrichtian ) of India , Madagascar and Morocco , here with Chenanisaurus from the Ouled Abdoun Basin , and only died in the Cretaceous-Paleogene mass extinction together with all other non-avian dinosaurs out.

Geographically, indubitable finds are limited to South America, India, Madagascar and continental Africa. These land masses once formed the major southern continent of Gondwana , which gradually broke up into its present-day components during the Cretaceous period. The exact course of this break-up is the subject of numerous debates to this day, with the Abelisaurids - as one of the groups that distinguish the fauna of Gondwana from the fauna of the northern continent of Laurasia - play an important role in the argumentation of the competing hypotheses. A widespread hypothesis, the so-called Africa-first hypothesis, assumes that Africa was already completely separated from the other land masses of Gondwana during the Lower Cretaceous, while the latter were still connected by land bridges into the Upper Cretaceous. An important argument in support of this hypothesis was the distribution of the Abelisaurids, the remains of which were often found in India, Madagascar and South America, but were absent in Africa for a long time, which indicated that the Abelisauridae only emerged after Africa separated from the rest of Gondwana to have. This argument has recently been questioned, since with Rugops an Abelisaurid was discovered in continental Africa and since particularly old finds from South America appeared, which are dated to a time when Africa was not yet separated. Supporters of the hypothesis note, however, that Rugops was a very basic representative of the Abelisauridae, and that the derived representatives of the group typical for the rest of Gondwana are still missing.

Research history

In 1985, Jose Bonaparte and Fernando Novas described a skull discovered in Argentina as an Abelisaurus . Since Abelisaurus differed significantly from all other theropods known at the time, these researchers created a new group, the Abelisauridae, which initially contained Abelisaurus as the only genus. The names Abelisaurus and Abelisauridae honor Roberto Abel, director of the Museo de Cipolleti and discoverer of the skull. The Abelisauridae were initially classified within the Carnosauria , a group to which almost all major theropods were assigned at the time. It was not until the early 1990s that today's classification within the Ceratosauria was established.

Shortly after the group was described, other representatives were discovered. In the same year (1985), Bonaparte described the new genus Carnotaurus as the second known representative of this group. Carnotaurus is based on a well-preserved, almost complete skeleton that was also discovered in Argentina. A year later, Martinez and colleagues described a much more fragmentary find, also from Argentina, as Xenotarsosaurus . In a publication, also published in 1986, Bonaparte suspects that the Indosuchus discovered in India could also be an Abelisaurid. Although known only from two skulls , this find indicated that the Abelisauridae were not restricted to South America.

Numerous other representatives of the Abelisauridae have been described to date. Although a large part of these genera is only known from very fragmentary remains, two skeletons, the Aucasaurus and the Scorpiovenator , have recently been described that are as well preserved as that of the Carnotaurus . Excavations that have been taking place in Madagascar since 1993 have uncovered numerous skeletons of the Abelisaurid Majungasaurus - today this genus is one of the best known theropods of the southern land masses (Gondwana).

literature

  • Juan I. Canale, Carlos A. Scanferla, Federico L. Agnolin, Fernando E. Novas : New carnivorous dinosaur from the Late Cretaceous of NW Patagonia and the evolution of abelisaurid theropods. In: The natural sciences . Vol. 96, No. 3, 2009, pp. 409-414, doi : 10.1007 / s00114-008-0487-4 .
  • 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 .
  • Philip Senter: Vestigial skeletal structures in dinosaurs. In: Journal of Zoology. Vol. 280, No. 1, 2010, ISSN  0022-5460 , pp. 60-71, doi : 10.1111 / j.1469-7998.2009.00640.x .
  • 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.
  • Scott D. Sampson, Lawrence M. Witmer : Craniofacial Anatomy of Majungasaurus Crenatissimus (Theropoda: Abelisauridae) From the Late Cretaceous of Madagascar. In: Journal of Vertebrate Paleontology. Vol. 27, Supplement to No. 2, ZDB -ID 1313684-7 = Society of Vertebrate Paleontology. Memoir. 8: Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar , 2007, pp. 32-104, doi : 10.1671 / 0272-4634 (2007) 27 [32: CAOMCT] 2.0.CO; 2 .
  • Jeffrey A. Wilson, Paul C. Sereno, Suresh Srivastava, Devendra K. Bhatt, Ashu Khosla, Ashok Sahni: A new abelisaurid (Dinosauria, Theropoda) from the Lameta Formation (Cretaceous, Maastrichtian) of India (= The University of Michigan. Contributions from the Museum of Paleontology. Vol. 31, No. 1, 2003, ISSN  0097-3556 ). The University of Michigan - Museum of Paleontology, Ann Arbor MI 2003, online .
  • Rodolfo A. Coria , Luis M. Chiappe , Lowell Dingus : A new close relative of Carnotaurus sastrei Bonaparte 1985 (Theropoda: Abelisauridae) from the Late Cretaceous of Patagonia. In: Journal of Vertebrate Paleontology. Vol. 22, Vol. 2, 2002, pp. 460-465, doi : 10.1671 / 0272-4634 (2002) 022 [0460: ANCROC] 2.0.CO; 2 .
  • Fernando E. Novas: The age of dinosaurs in South America. Indiana University Press, Bloomington IN 2009, ISBN 978-0-253-35289-7 .
  • W. Scott Persons IV, Philip J. Currie: Dinosaur Speed ​​Demon: The Caudal Musculature of Carnotaurus sastrei and Implications for the Evolution of South American Abelisaurids. In: PLoS ONE . Vol. 6, No. 10, 2011, e25763, doi : 10.1371 / journal.pone.0025763 .
  • Paul C. Sereno, Jeffrey A. Wilson, Jack L. Conrad: New dinosaurs link southern landmasses in the Mid-Cretaceous. In: Proceedings of the Royal Society. Series B: Biological Sciences. Vol. 271, No. 1546, 2004, ISSN  0950-1193 , pp. 1325-1330, doi : 10.1098 / rspb.2004.2692 .
  • Simone Maganuco, Andrea Cau, Giovanni Pasini: First description of theropod remains from the Middle Jurassic (Bathonian) of Madagascar. In: Atti della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale in Milano. Vol. 146, No. 2, 2005, ISSN  0037-8844 , pp. 165-202.
  • José F. Bonaparte , Fernando E. Novas: Abelisaurus comahuensis, ng, n.sp., Carnosauria del Crétacico Tardio de Patagonia. In: Ameghiniana. Vol. 21, No. 2/4, 1985, pp. 259-265, (Translated into English by Matthew Carrano, 1998: Abelisaurus comahuensis, ng, n.sp., Carnosauria from the Late Cretaceous of Patagonia. Online (PDF; 31.2 kB) ).
  • José F. Bonaparte: The Gondwanian Theropod Families Abelisauridae and Noasauridae. In: Historical Biology. Vol., No. 1, 1991, ISSN  0891-2963 , pp. 1-25, doi : 10.1080 / 10292389109380385 .
  • David W. Krause, Scott D. Sampson, Matthew T. Carrano, Patrick M. O'Connor: Overview of the History of Discovery, Taxonomy, Phylogeny, and Biogeography of Majungasaurus Crenatissimus (Theropoda: Abelisauridae) From the Late Cretaceous of Madagascar. In: Journal of Vertebrate Paleontology. Vol. 27, Supplement to No. 2, = Society of Vertebrate Paleontology. Memoir. 8: Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar , 2007, pp. 1-20, doi : 10.1671 / 0272-4634 (2007) 27 [1: OOTHOD] 2.0.CO; 2 .

Individual evidence

  1. ^ A b Gregory S. Paul : The Princeton Field Guide To Dinosaurs. Princeton University Press, Princeton NJ et al. 2010, ISBN 978-0-691-13720-9 , pp. 78-82, online .
  2. ↑ a b c d Paul Sereno: Abelisauridae. (No longer available online.) In: Taxon Search. Archived from the original on October 23, 2007 ; accessed on August 2, 2014 .
  3. ↑ a b Sampson and Witmer 2007 , pp. 95–96
  4. ↑ a b Bonaparte et al. 1990 , p. 3
  5. ↑ Tykoski and Rowe 2004 , p. 52
  6. ↑ a b c d e f Novas 2009 , pp. 253–266
  7. ↑ a b Tykoski and Rowe 2004 , p. 51
  8. ↑ Wilson et al. 2003 , pp. 4-9
  9. ↑ a b Coria et al. 2002
  10. ↑ Persons and Currie 2011 , pp. 1–7
  11. ↑ a b c Senter 2010 , p. 64
  12. ↑ Novas 2009 , pp. 262-264
  13. ↑ Tykoski and Rowe 2004 , p. 66
  14. ↑ a b Wilson et al. 2003 , p. 25
  15. ↑ a b Novas 2009 , pp. 252-253
  16. ↑ Wilson et al. 2003 , p. 30
  17. ↑ Novas 2009 , pp. 272-273
  18. ↑ a b c Canale et al. 2009
  19. ^ Paul Sereno: Carnotaurinae. (No longer available online.) In: Taxon Search. Archived from the original on May 16, 2012 ; accessed on August 2, 2014 .
  20. ↑ a b Carrano and Sampson , p. 202
  21. ↑ a b Sereno et al. 2004
  22. ↑ Tykoski and Rowe 2004 , p. 65
  23. ↑ Sereno et al. 2004 , pp. 165, 195
  24. ↑ Nicholas R. Longrich, Xabier Pereda Suberbiola, Nour-Eddine Jalil, Fatima Khaldoune, Essaid Jourani: An abelisaurid from the latest Cretaceous (late Maastrichtian) of Morocco, North Africa. In: Cretaceous Research: Vol. 76, 2017, pp. 40-52, doi: 10.1016 / j.cretres.2017.03.021 .
  25. ↑ Carrano and Sampson , pp. 212-214
  26. ^ Bonaparte and Novas 1985
  27. ↑ a b Bonaparte 1991 , pp. 1-2
  28. ↑ Krause et al. 2007 , p. 1

Web links

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