Abelisauridae

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Abelisaurids
Temporal range:
Ma
Majungasaurus crenatissimus skeleton, Stony Brook University
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Clade: †
Abelisauria
Family: †Abelisauridae
Bonaparte & Novas
, 1985
Type species
†
Abelisaurus comahuensis

Bonaparte & Novas, 1985
Subgroups

Abelisauridae (meaning "Abel's lizards") is a

subcontinent and the island of Madagascar. Isolated teeth were found in the Late Jurassic of Portugal,[2] and the Late Cretaceous genera Tarascosaurus and Arcovenator have been described in France.[1] Abelisaurids first appear in the fossil record of the early middle Jurassic period, and at least three genera (the Moroccan Chenanisaurus, the South American Carnotaurus and the Madagascan Majungasaurus) survived until the end of the Mesozoic era 66 million years ago.[3]

Like most theropods, abelisaurids were

tyrannosaurids.[5]

Description

Size comparison of five abelisaurids; Carnotaurus, Ekrixinatosaurus, Skorpiovenator, Aucasaurus, and Majungasaurus

Abelisaurid hind limbs were more typical of ceratosaurs, with the

hallux, did not contact the ground.[6]

Skull

Skull of Abelisaurus.

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.[4]

Two skull bones, the

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.[4]

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.[6][7][8] In Arcovenator, the dorsal margin of the postorbital (and probably also the lacrimal) is thickened dorsolaterally, forming a strong and rugose bony brow ridge rising above the level of the skull roof.[1] Possibly, this rugose brow ridge supported a keratinous or scaly structure for displays.

Fore limbs and hands

Drawing of the hand bones of Carnotaurus
Hand bones of Carnotaurus, as interpreted by Ruiz and colleagues (2011)[9]

Data for the abelisaurid fore limbs are known from Eoabelisaurus and the carnotaurines Aucasaurus, Carnotaurus, and Majungasaurus. All had small fore limbs, which seem to have been vestigial.[10] 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.[10]

As is typical for ceratosaurs, the abelisaurid

metacarpals) attaching directly to the forearm. No phalanges (finger bones) were 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.[10]

More primitive relatives such as Noasaurus and Ceratosaurus had longer, mobile arms with fingers and claws.[11] Paleobiologist Alexander O. Vargas suggested a major reason for the evolution towards vestigial fore limbs in the group was because of a genetic defect; the loss of function in HOXA11 and HOXD11, two genes that regulate the fore limbs' development.[12]

Distribution

Illustration of Abelisaurus

Abelisauroids are typically regarded as a Cretaceous group, though the earliest abelisaurid remains are known from the Middle

Arcovenator escotae from southern France provided the first indisputable evidence of the presence of Abelisaurids in Europe. Arcovenator presents strong similarities with the Madagascan Majungasaurus and Indian abelisaurids, but not with the South American forms. Arcovenator, Majungasaurus, and Indian forms are united in the new clade Majungasaurinae.[1]

Classification

Illustration of Carnotaurus

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, and 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) meaning 'descendants'.[22]

Abelisauridae is a family in rank-based

phylogenetic taxonomy. It was originally defined as a node-based taxon including Abelisaurus, Carnotaurus, their common ancestor, and all of its descendants.[23][24]

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.[8] The node-based definition would not include animals such as Rugops or Ilokelesia, which are thought to be more basal than Abelisaurus and would be included by a stem-based definition.[25] Within the Abelisauridae is the subgroup Carnotaurinae, and among carnotaurines, Aucasaurus and Carnotaurus are united in Carnotaurini.[17]

Shared characteristics

Skeletal diagram of the known material of Carnotaurus

Complete skeletons have been described only for the most advanced abelisaurids (such as Carnotaurus and

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.[6]

Phylogeny

Known material of Majungasaurus

Below is a cladogram generated by Tortosa et al. (2014) in the description of Arcovenator and creation of a new subfamily Majungasaurinae.[1]

Abelisauridae

Ilokelesia was originally described as a sister group to the Abelisauroidea.[19] However, Sereno tentatively places it closer to Abelisaurus than to noasaurids, a result which agrees with several other recent analyses.[6][20][26] 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 the 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.[20]

Some scientists include Xenotarsosaurus from Argentina and Compsosuchus from India as basal abelisaurids,[27][28] while others consider them to be outside the Abelisauroidea.[29] The French Genusaurus and Tarascosaurus have also been called abelisaurids but both are fragmentary and may be more basal ceratosaurians.[6]

Skeleton of Eoabelisaurus, a close relative of the Abelisauridae

With the description of

Brachyrostra.[30] In the same year Matthew T. Carrano and Scott D. Sampson published new large phylogenetic analysis of ceratosaurian.[31] With the description of Eoabelisaurus, Diego Pol and Oliver W. M. Rauhut (2012) combined these analyses and added 10n new characters. The following cladogram follows their analysis.[32]

Ceratosauria 

Paleobiology

Feeding

Fossil teeth found amid the bones of a titanosaur from the Allen Formation of Argentina suggest that abelisaurids preyed upon or at least scavenged titanosaurs.[33]

Ontogeny and growth

Studies of the abelisaurid Majungasaurus indicate that it was a much slower-growing dinosaur than other theropods, taking nearly 20 years to reach adult size. Similar studies on other abelisaurid genera indicate that this slow maturation may have been a common trait to the whole of the Abelisauridae.[34]

See also

References

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  4. ^ a b c "October/November 2013, Abstracts Of Papers, 73rd Annual Meeting" (PDF). Society of Vertebrate Paleontology. 2013. Archived from the original (PDF) on 2013-10-29. Retrieved 2013-10-27.
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  7. ^ Bonaparte, J.F.; Novas, F.E.; Coria, R.A. (1990). "Carnotaurus sastrei Bonaparte, the horned, lightly built carnosaur from the middle Cretaceous of Patagonia". Contributions in Science of the Natural History Museum of Los Angeles County. 416: 1–42.
  8. ^ 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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  12. ^ Magazine, Smithsonian. "Need a Hand? Don't Ask an Abelisaurid". Smithsonian Magazine. Archived from the original on 2015-07-23. Retrieved 2015-07-23.
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  14. ^ 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.
  15. ^ Rauhut, Oliver W. M. (2011). "Theropod dinosaurs from the Late Jurassic of Tendaguru (Tanzania)". Special Papers in Palaeontology. 86: 195–239. Archived from the original on 2020-02-01. Retrieved 2020-02-01.
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  17. ^
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  19. ^ 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]
  20. ^ 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.
  21. S2CID 86153297
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  22. ^ 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]
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  24. doi:10.1127/njgpa/210/1998/41
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  25. ^ Sereno, P.C. (2005). Abelisauridae Archived 2007-10-23 at the Wayback Machine. TaxonSearch. 7 November 2005. Retrieved 19 September 2006.
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  27. doi:10.22179/REVMACN.6.74
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  28. ^ Rauhut, O.W.M. (2003). "The interrelationships and evolution of basal theropod dinosaurs". Special Papers in Palaeontology. 69: 1–213.
  29. ^ 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
  30. S2CID 23619863
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  31. S2CID 30068953. Archived
    (PDF) from the original on 2018-07-20. Retrieved 2018-08-06.
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  33. ^ "Isolated theropod teeth associated with a sauropod skeleton from the Late Cretaceous Allen Formation of Río Negro, Patagonia, Argentina - Acta Palaeontologica Polonica". Archived from the original on 2021-06-09. Retrieved 2021-06-30.
  34. ^ "Fearsome Malagasy Dinosaur Remained a Pipsqueak Most of Its Life". Live Science. 16 November 2016. Archived from the original on 2016-11-22. Retrieved 2016-11-22.

External links

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