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'Maniraptora' ("hand snatchers") is a clade of coelurosaurian dinosaurs used in phylogenetic taxonomy which covers the birds and the dinosaurs that were most closely related to them. It contains the major subgroups Deinonychosauria, Oviraptorosauria and Therizinosauria, and Aves. It It is a sister group to Ornithomimosauria, together with which it comprises the more inclusive clade Maniraptoriformes. Maniraptors first appear in the fossil record during the Jurassic Period, and survive today in the over 9,000 species of living birds.

Contents

Characteristics

Phylogeny

References

Characteristics

Maniraptors are characterized by elongated arms and hands, as well as a "half-moon shaped" (semi-lunate) bone in the wrist (carpus). Other traits common to all maniraptors include the presence of a wishbone (furcula), a stiffened tail, feathers, and an elongated, backwards-pointing pubic bone. The 'killer claw', which characterizes dromaeosaurs may also be a primitive trait for the group, though if this is the case several maniraptor lineages lost it secondarily.
Several of these traits, such as the furcula and backwards-pointed pubis, as well as a ''perforated acetabulum'' (the hole in the hip socket that allows an upright stance, 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.^[1]
Modern pennaceous feathers and remiges are present in almost all known maniraptoran subgroups, and powered flight is present in members of Aves and possibly Dromaeosauridae.

Phylogeny

The Maniraptora was originally named by Jacques Gauthier in 1986, for a branch-based clade defined as all dinosaurs closer to modern birds than to the ornithomimids. Gauthier noted that this group could be easily characterized by their long forelimbs and hands, which he interpreted as adaptations for grasping (hence the name Maniraptora, which means "hand snatchers" in relation to their 'seizing hands'). In 1994, Thomas R. Holtz attempted to define the group based on the characteristics of the hand and wrist alone (an ''apomorphy-based'' definition), and included the long, thin fingers, bowed, wing-like forearm bones, and half-moon shaped wrist bone as key characters. Most subsequent studies have not followed this definition, however, prefering the earlier branch-based definition.
The branch-based definition usually includes the major groups Deinonychosauria, Oviraptorosauria, Therizinosauria, and Aves. Other taxa often found to be maniraptorans include the alvarezsaurids, ''Ornitholestes'' and, less frequently, the compsognathids. Several taxa have been assigned to the maniraptora more definitively, though their exact placement within the group remains uncertain. These forms include the scansoriopterygids, ''Pedopenna'', and ''Yixianosaurus''.
The following cladogram follows Norell ''et al.'' 2006, with clade names after the definitions by Sereno, 2005.^[2][3]

References

1. Czerkas, S.A., and Yuan, C. (2002). "An arboreal maniraptoran from northeast China." Pp. 63-95 in Czerkas, S.J. (Ed.), ''Feathered Dinosaurs and the Origin of Flight.'' The Dinosaur Museum Journal '1'. The Dinosaur Museum, Blanding, U.S.A. PDF abridged version
2. Norell, M.A., Clark, J.M., Turner, A.H., Makovicky, P.J., Barsbold, R., and Rowe, T. (2006). "A new dromaeosaurid theropod from Ukhaa Tolgod (Omnogov, Mongolia)." ''American Museum Novitates'', '3545': 1-51.
3. Sereno, P. C., McAllister, S., and Brusatte, S. L. (2005). "TaxonSearch: a relational database for suprageneric taxa and phylogenetic definitions." ''PhyloInformatics'', '8': 1-21.[1]