Coeluridae is a historically polyphyletic (unnaturally grouped) family of generally small, carnivorous

Carnivore

A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...

 dinosaur

Dinosaur

Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

s from the late Jurassic

Jurassic

The Jurassic is a geologic period and system that extends from about Mya to  Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...

 Period. For many years, any small Jurassic or Cretaceous theropod

Theropoda

Theropoda is both a suborder of bipedal saurischian dinosaurs, and a clade consisting of that suborder and its descendants . Dinosaurs belonging to the suborder theropoda were primarily carnivorous, although a number of theropod groups evolved herbivory, omnivory, and insectivory...

 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 Laevisuchus

Laevisuchus

Laevisuchus is a genus of abelisauroid theropod dinosaur from the Late Cretaceous.Its remains were discovered by Charles Alfred Matley near Jabalpur in Maastrichtian deposits in the Lameta Formation in India, and named and described by paleontologists Friedrich von Huene and Matley in 1933. The...

(a noasaurid

Noasauridae

Noasaurids were a group of theropod dinosaurs from the Cretaceous Period . They were generally small in size...

) and Microvenator

Microvenator

Microvenator is a genus of dinosaur from the Early Cretaceous Cloverly Formation in what is now south central Montana. Microvenator was an oviraptorosaurian theropod. The holotype fossil is an incomplete skeleton, most likely a juvenile, with a living length of about four feet. The adult size of...

(a close relative of oviraptorids

Oviraptoridae

Oviraptoridae is a group of bird-like, herbivorous and omnivorous maniraptoran dinosaurs. Oviraptorids are characterized by their toothless, parrot-like beaks and, in some cases, elaborate crests. They were generally small, measuring between one and two metres long in most cases, though some...

). Although they have been traditionally included in this family, there is no evidence that primitive coelurosaurs like Ornitholestes

Ornitholestes

Ornitholestes was a small theropod dinosaur of the late Jurassic of Western Laurasia . To date, it is known only from a single partial skeleton, and badly crushed skull found at the Bone Cabin Quarry near Medicine Bow, Wyoming, in 1900...

, Proceratosaurus

Proceratosaurus

Proceratosaurus is a genus of small-sized carnivorous theropod dinosaur from the Middle Jurassic of England. It was originally thought to be an ancestor of Ceratosaurus, due to the similar small crest on its snout...

and Scipionyx

Scipionyx

Scipionyx is a genus of theropod dinosaur from the Early Cretaceous of Italy, around 113 million years ago. There has been only one skeleton discovered, which is notable for the preservation of soft tissue and internal organs. It is the fossil of a juvenile only half a metre long...

form a clade with Coelurus

Coelurus

Coelurus is a genus of coelurosaur dinosaur from the Late Jurassic period . The name means "hollow tail", referring to its hollow tail vertebrae...

to the exclusion of other traditional coelurosaur families. Other traits that potentially define Coeluridae are uncertain because the genus Coelurus

Coelurus

Coelurus is a genus of coelurosaur dinosaur from the Late Jurassic period . The name means "hollow tail", referring to its hollow tail vertebrae...

is still incompletely known.

In 2003, O.W.M. Rauhut, using a cladistic analysis, found Coeluridae to include Coelurus

Coelurus

Coelurus is a genus of coelurosaur dinosaur from the Late Jurassic period . The name means "hollow tail", referring to its hollow tail vertebrae...

(Late Jurassic

Late Jurassic

The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago , which is preserved in Upper Jurassic strata. In European lithostratigraphy, the name "Malm" indicates rocks of Late Jurassic age...

, North America), Compsognathus

Compsognathus

Compsognathus was a small, bipedal, carnivorous theropod dinosaur. The animal was the size of a turkey and lived around 150 million years ago, the early Tithonian stage of the late Jurassic Period, in what is now Europe. Paleontologists have found two well-preserved fossils, one in Germany...

(Late Jurassic, Europe), Sinosauropteryx

Sinosauropteryx

Sinosauropteryx was the first genus of dinosaur outside of Avialae to be found with evidence of feathers. They were covered with "furry" coats of very simple filament-like feathers...

(Early Cretaceous

Early Cretaceous

The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...

, Asia) and an unnamed Compsognathus

Compsognathus

Compsognathus was a small, bipedal, carnivorous theropod dinosaur. The animal was the size of a turkey and lived around 150 million years ago, the early Tithonian stage of the late Jurassic Period, in what is now Europe. Paleontologists have found two well-preserved fossils, one in Germany...

-like form (Early Cretaceous, South America; this dinosaur has since been placed in the new genus Mirischia

Mirischia

Mirischia is a small extinct genus of compsognathid dinosaur from the Albian stage of Brazil. Though presently known only from a pelvis and incomplete hind limbs, it preserves enough information to show that it should be recognized as a distinct species...

). Rauhut considered coelurids to be a monophyletic group of basal coelurosaurs

Coelurosauria

Coelurosauria is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs. In the past, it was used to refer to all small theropods, although this classification has been abolished...

, 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

Tyrannosauroidea

Tyrannosauroidea is a superfamily of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent beginning in the Jurassic Period...

.