page_title: Theropoda
section_title: Forelimb morphology
hierarchical_section_title: Theropoda / Biology / Forelimb morphology
caption_attribution_description: English: SR X-ray lCT reconstructions of osteology in DIP-V-15100 and DIP-V-15101. (a) Mummified DIP-V-15100, showing rachises, skin, muscle and claws. (b) Skeletal morphology of DIP-V-15100, using different density threshold. (c) Mummified DIP-V-15101, showing rachises, skin, muscle and claws. (d) Skeletal morphology of DIP-V-15101. (e) Reconstruction of osteology based on the CT data. al, alular digit; am, alular metacarpal; ma, major digit; mam, major metacarpal; mi, minor digit; mim, minor metacarpal; ra, radius; ul, ulna. Scale bars, 5 mm
context_page_description: Theropoda or theropods are a dinosaur clade that is characterized by hollow bones and three-toed limbs. They are generally classed as a group of saurischian dinosaurs. Theropods were ancestrally carnivorous, although a number of theropod groups evolved to become herbivores, omnivores, piscivores, and insectivores. Theropods first appeared during the Carnian age of the late Triassic period 231.4 million years ago and included the sole large terrestrial carnivores from the Early Jurassic until at least the close of the Cretaceous, about 66 Ma. In the Jurassic, birds evolved from small specialized coelurosaurian theropods, and are today represented by about 10,500 living species.
context_section_description: Shortened forelimbs in relation to hind legs was a common trait among theropods, most notably in the abelisaurids (such as Carnotaurus) and the tyrannosaurids (such as Tyrannosaurus). This trait was, however, not universal: spinosaurids had well developed forelimbs, as did many coelurosaurs. The relatively robust forelimbs of one genus, Xuanhanosaurus, led Dong Zhiming to suggest that the animal might have been quadrupedal. However, this is no longer thought to be likely.
  The hands are also very different among the different groups. The most common form among non-avian theropods is an appendage consisting of three fingers; the digits I, II and III (or possibly II, III and IV), with sharp claws. Some basal theropods (e.g. Herrerasaurus, Eoraptor) had four digits, and also a reduced metacarpal V. Ceratosaurians usually had four digits, while most tetanurans had three.
  The forelimbs' scope of use is also believed to have also been different among different families. The spinosaurids could have used their powerful forelimbs to hold fish. Some small maniraptorans such as scansoriopterygids are believed to have used their forelimbs to climb in trees. The wings of modern birds are used primarily for flight, though they are adapted for other purposes in certain groups. For example, aquatic birds such as penguins use their wings as flippers.
caption: Mummified enantiornithean wing (of an unknown genus) from Cenomanian amber from Myanmar
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