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Maniraptora is a clade used in phylogenetic taxonomy which covers the birds and the dinosaurs that were most closely related to them. It is a sister group to Arctometatarsalia and contains the major subgroups Deinonychosauria, Oviraptorosauria and Therizinosauria, and Aves. Maniraptors are characterized by elongated arms and hands, as well as a semi-lunate carpal bone in the wrist (carpus). Other basal traits common to all maniraptors include the presence of a furcula (wishbone), a distally shortened and stiffened tail, feathers, and an elongated, backwards-pointing pubis. The 'killer claw', which characterizes dromaeosaurs may also be a basal trait. Several of these traits, such as the furcula and backwards-pointed pubis, as well as a perforated acetabulum (a trait common to all dinosaurs) are apparently absent in the Scansoriopterygidae, though all known specimens are hatchlings, and their odd mix of "primitive" and "advanced" features could be due to ontogeny (i.e., their early stage of physical development). At least a few scientists consider them truly primitive, and hypothesize that maniraptorans may have branched off from theropods at a very early point, or may even have descended from pre-theropod dinosaurs (Czerkas & Yuan, 2002). Modern pennaceous feathers and remiges are present in almost all known maniraptoran subgroups, and powered flight is present in members of Aves and probably Dromaeosauridae.
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