Anchisauridae

Skeletal reconstruction of Anchisaurus

• North America

The Anchisauridae is a group of sauropodomorphen dinosaurs, which was first proposed in 1885 by Othniel Charles Marsh. This family includes Anchisaurus and his next of kin; according to the most recent definition of the group Anchisaurus and Ammosaurus includes with. Both species are from the Early Jurassic of North America.

Validity, definition and history of research

The validity of this group is controversial; in the current literature it is only used occasionally. Paul Sereno (1999) considers the type of material for Anchisaurus not diagnostic, that is, that there are no features available by which one can distinguish the genus from other genera, such as the related Ammosaurus. Consequently he considers the Anchisauridae as invalid. Peter Galton and Paul Upchurch ( 2004) present the Anchisauridae Meanwhile, as a valid group and define it as all species that are more closely related than Anchisaurus with Melanorosaurus.

Various authors assigned to next Anchisaurus other genera of this group, however, these assignments vary depending on the author. Othniel Charles Marsh asked this group initially as monotypical taxon to which only contained the Anchisaurus same time as described by him. Initially awarded Marsh the name Amphisauridae name for this group, Anchisaurus itself he initially Amphisaurus. As it turned out later that the name was already taken Amphisaurus, both names have been changed in Anchisaurus and Anchisauridae. Galton (1990 ) also led Anchisaurus the only genus of this group. Parking (1970 ), meanwhile, wrote the group next Anchisaurus to the genera Thecodontosaurus and Massospondylus. The recent study, which recognizes the Anchisauridae as valid, comes from Galton and Upchurch ( 2004). These authors you assign the two genera Anchisaurus and Ammosaurus. Ammosaurus has already been discovered by Marsh, however, described this as the other kind of Anchisaurus.

Features

Galton and Upchurch (2004) give several common features derived at ( synapomorphies ), by which the group is to distinguish them from other groups. So is the length- to-height ratio of the longest postaxial cervical vertebrae at least 3.0. Deltopectoralkamm of a bone crest of the upper arm bone ( humerus), terminates on the half of the length of the humerus. The Präacetabularprozess the ilium ends of the distal end of the pubis process; both bone combs are also viewed from the side in a narrow angle.

System

Traditionally, this group is counted among the prosauropods, which are considered as the precursor group or sister group of sauropods. Currently, it is debatable whether the prosauropods are a monophyletic group. A recent study by Adam Yates concludes that Anchisaurus was actually closely related to the sauropods, much closer than prosauropods such as Plateosaurus.