Anchiornis

Phylogeny: Dinosauria > Saurischia > Theropoda > Neotheropoda > Tetanurae > Avetheropoda > Coelurosauria > Maniraptora > Pennaraptora > Paraves > Anchiornithidae

Overview: Fossil specimens of Anchiornis, potentially numbering in the hundreds, all originate from the Tiaojishan Formation, in the Chinese province of Liaoning. Similar to the Early Cretaceous-aged Yixian Formation in the same region, the Tiaojishan is known for its well preserved fossils. Many of those referred to Anchiornis have been found with highly detailed feather impressions around the main skeleton. Said skeleton was small and lightly constructed, with Anchiornis usually measuring about sixty centimeters long. If a living specimen were around today, it would probably be mistaken for a modern bird. Indeed, Anchiornis has in the past been classified very close to birds, as well as to the famous Archaeopteryx. Others suggested it may’ve been a basal troodontid, however. Most recent studies classify Anchiornis within the family Anchiornithidae, as basal paravians.

Anchiornis retained a lot of typical theropod traits that distinguished it from true birds. This would include its toothed jaws, relatively long tail and distinct, clawed fingers. However, these traits were combined with more derived, highly birdlike features, which is the cause of the confusion over how it should be classified. Within the proposed Anchiornithidae, Anchiornis was closely related to taxa like Aurornis, Serikornis, Caihong, Eosinopteryx, and possibly Xiaotingia. Some of these genera have been suggested to be junior synonyms of Anchiornis, or in other words, the same animal. Fossils of said genera are also often found in the Tiaojishan, lending some support for this, but there were at least some traits that set them apart. Anchiornis was described as a genus in 2009. Its name refers to its relationship with birds; though studies suggest it itself was probably flightless.