|Allosaurus: notice the arms, and the skull bones|
Carnosaurs are a subgroup of the theropod dinosaurs. They are the clade Carnosauria. The term was once used very widely, but is now defined more narrowly. It is called by some authorities the Allosauroidea.
The group includes some of the main carnivores of the Jurassic and Cretaceous periods, such as Allosaurus, Carcharodontosaurus and Neovenator. Modern cladistic analysis defines Carnosauria (or Allosauroidea) as those tetanurans which share a more recent common ancestor with Allosaurus than with modern birds.
Carnosaurs are characterized by several features. Some features must have been adaptations to their large size, such as their open skull, made of struts rather than solid bone. They had large eyes and a long, narrow skull. The femur ("thigh bone") is usually larger than the tibia ("shin bone"). This suggests close-to action was controlled by sight.
The legs are adapted for running, but not extremely so. They had strong arms, probably used to wrestle prey as the teeth bit in. The structure of an Allosaurus suggests a strongly-built general all-round predator. This is a different from a tyrannosaur like Albertosaurus, which was better adapted for running on open ground. Tyrannosaurs, with their small two-fingered hands, would use their heads for killing prey, and for head-butting rivals.
The idea that the group became extinct at the end of the Jurassic is refuted. It is now known that the Neovenatorid clade survived until the end of the Mesozoic. This group (see cladogram below) included Aerosteon, Australovenator, Fukuiraptor and Neovenator.
Classification[change | change source]
- Infraorder Carnosauria
- Superfamily Allosauroidea
- Family Allosauridae
- Family Carcharodontosauridae
- Family Sinraptoridae
Cladogram[change | change source]
References[change | change source]
- Sereno P.C. 1999. The evolution of dinosaurs. Science 284 (5423): 2137–2147.
- Sereno P.C. 1998. A rationale for phylogenetic definitions, with application to the higher-level taxonomy of Dinosauria. Neues Jahrbuch für Geologie und Paläontologie Abhandlungen 210: 41–83
- Benson, R.B.J; Carrano, M.T; Brusatte, S.L. (2010). "A new clade of archaic large-bodied predatory dinosaurs (Theropoda: Allosauroidea) that survived to the latest Mesozoic". Naturwissenschaften 97 (1): 71–78. doi:10.1007/s00114-009-0614-x. PMID 19826771.