theropod

Theropoda is a major clade of dinosaurs within the larger group Saurischia. Theropods are predominantly bipedal carnivores, although some lineages evolved diverse diets. In cladistic terms, Theropoda includes the most recent common ancestor of birds and all its descendants, making birds the only living members of the group. Theropods first appeared in the Late Triassic and rapidly diversified during the Jurassic and Cretaceous, occupying a wide range of ecological niches.

Anatomically, theropods are characterized by a generally upright posture, hollow limb bones, and three-toed hind feet. Many had sharp, laterally compressed teeth, though some lineages evolved beaks or tooth reduction. Forelimbs varied from long and grasping (as in some predatory dinosaurs) to short and stout (as in tyrannosaurs). Feathers or feather-like coverings are now known in a broad range of theropods, including several early taxa, and the presence of plumage is a standard feature in many later groups.

Among theropods, major subgroups include Ceratosauria, Tetanurae, and within Tetanurae Coelurosauria, which comprises tyrannosauroids, ornithomimids, maniraptorans, and their kin. Maniraptorans further split into groups such as dromaeosaurs, the avialans, and their close relatives. This culminated in the origin of birds (Avialae), the only surviving lineage of theropods. Some theropods, like the therizinosaurs, shifted toward omnivory or herbivory, illustrating the clade's ecological diversity.

Fossil evidence supports a feathered, often bird-like appearance in many theropods, and anatomical studies align birds with theropod dinosaurs. The transition from non-avian theropods to birds involved changes in locomotion, digestion, and reproductive biology, leading to modern avian diversity.