The coelurosaur lineages most distant from birds had feathers that were relatively short and composed of simple, possibly branching filaments. This type of skin is best known in the ceratosaur Carnotaurus, which has been preserved with extensive skin impressions. In some species, these were interspersed with larger scales with bony cores, or osteoderms. Many larger theropods had skin covered in small, bumpy scales. However, outside the coelurosaurs, feathers may have been confined to the young, smaller species, or limited parts of the animal. Feathers or feather-like structures (filaments) are attested in most lineages of theropods (see feathered dinosaur). Mesozoic theropods were also very diverse in terms of skin texture and covering. Integument (skin, scales and feathers) Fossil of an Anchiornis, showing large preserved feather imprints The folds helped the teeth stay in place longer, especially as theropods evolved into larger sizes and had more force in their bite. An investigation in July 2015 discovered that what appeared to be "cracks" in their teeth were actually folds that helped to prevent tooth breakage by strengthening individual serrations as they attacked their prey. The morphology of the teeth is distinct enough to tell the major families apart, which indicate different diet strategies. Others are pachydont or phyllodont depending on the shape of the tooth or denticles. The majority of theropod teeth are blade-like, with serration on the edges, called ziphodont. Some theropods, such as Baryonyx, Lourinhanosaurus, ornithomimosaurs, and birds, are known to use gastroliths, or gizzard-stones. ĭiet is largely deduced by the tooth morphology, tooth marks on bones of the prey, and gut contents. Oviraptorosaurs, ornithomimosaurs and advanced troodontids were likely omnivorous as well, and some early theropods (such as Masiakasaurus knopfleri and the spinosaurids) appear to have specialized in catching fish. Several other lineages of early maniraptorans show adaptations for an omnivorous diet, including seed-eating (some troodontids) and insect-eating (many avialans and alvarezsaurs). Further study of maniraptoran theropods and their relationships showed that therizinosaurs were not the only early members of this group to abandon carnivory. Therizinosaurs possessed large abdomens for processing plant food, and small heads with beaks and leaf-shaped teeth. First thought to be prosauropods, these enigmatic dinosaurs were later proven to be highly specialized, herbivorous theropods. The first confirmed non-carnivorous fossil theropods found were the therizinosaurs, originally known as "segnosaurs". For example, a Compsognathus longipes fossil was found with a lizard in its stomach, and a Velociraptor mongoliensis specimen was found locked in combat with a Protoceratops andrewsi (a type of ornithischian dinosaur). Fossilized specimens of early theropods known to scientists in the 19th and early 20th centuries all possessed sharp teeth with serrated edges for cutting flesh, and some specimens even showed direct evidence of predatory behavior. All early finds of theropod fossils showed them to be primarily carnivorous. However, discoveries in the late 20th and early 21st centuries showed that a variety of diets existed even in more basal lineages. Strict carnivory has always been considered the ancestral diet for theropods as a group, and a wider variety of diets was historically considered a characteristic exclusive to the avian theropods (birds). Theropods exhibit a wide range of diets, from insectivores to herbivores and carnivores. In the Jurassic, birds evolved from small specialized coelurosaurian theropods, and are today represented by about 10,500 living species.īiology Diet and teeth Specimen of the troodontid Jinfengopteryx elegans, with seeds preserved in the stomach region Theropods first appeared during the Carnian age of the late Triassic period 231.4 million years ago ( Ma) and included the majority of large terrestrial carnivores from the Early Jurassic until at least the close of the Cretaceous, about 66 Ma. They were ancestrally carnivorous, although a number of theropod groups evolved to become herbivores and omnivores. Theropods are generally classed as a group of saurischian dinosaurs. Theropoda ( / θ ɪəˈr ɒ p ə d ə/ from Ancient Greek θηρίον ( thēríon) 'wild beast', and πούς, ποδός ( poús, podós) 'foot'), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Coelophysis bauri, one of the most well-known early theropods (mounted skeleton at Cleveland Museum of Natural History)
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