Fossil range: Late Jurassic, 153-150 million years ago
Coeluridae is an historically paraphyletic (unnaturally grouped) family of generally small, carnivorous dinosaurs from the late Jurassic Period. For many years, any small Jurassic or Cretaceous theropod that did not belong to one of the more specialized families recognized at the time was classified with the coelurids, creating a confusing array of 'coelurid' theropods that were not closely related. Some dinosaurs mistakenly assigned to Coeluridae in the past include Stenonychosaurus (a troodontid) and Microvenator (a close relative of oviraptorids). Although they have been traditionally included in this family, there is no evidence that primitive coelurosaurs like Ornitholestes, Proceratosaurus and Scipionyx form a clade with Coelurus to the exclusion of other traditional coelurosaur families. Other traits that potentially define Coeluridae are uncertain because the genus Coelurus is still incompletely known.
In 2003, O.W.M. Rauhut, using a cladistic analysis, found Coeluridae to include Coelurus (Late Jurassic, North America), Compsognathus (Late Jurassic, Europe), Sinosauropteryx (Early Cretaceous, Asia) and an unnamed Compsognathus-like form (Early Cretaceous, South America; this dinosaur has since been placed in the new genus Mirischia). Rauhut considered coelurids to be a monophyletic group of basal coelurosaurs, characterized by evolutionary reversals in some aspects of the vertebrae to the more primitive theropod condition. However, he and other authors have not since found this result. Phil Senter proposed in 2007 that Coelurus and Tanycolagreus were the only coelurids, and were actually tyrannosauroids.