Anchiornis huxleyi

Australia: The Land Where Time Began

Anchiornis huxleyi 'near-bird' Mid-Late Jurassic Troodontidae. Named after Thomas Huxley, the first to propose a relationship between dinosaurs and birds.

A feathered maniraptoran that is believed to be transitional between dinosaurs and birds, from a lacustrine deposit Tiaojishan Formation in Jianchang County, western Liaoning Province, China. It is from the Middle to Late Jurassic (Callovian or Oxfordian), but the age is uncertain. The age is believed to be between 161 and 151 million years ago. It was a small dinosaur with a triangular skull which had a number of features in common with other troodontids and, like other troodontids, had very long legs. It would normally be assumed that this indicated it was a fast runner, but the presence of feathers on the legs suggest the leg length may have been a vestigial characteristic. The forelimbs are very long, unlike those of other troodontids, but similar to those found in dromaeosaurids and early birds. The mixture of characteristics suggest it was a primitive form in the group. A second specimen was found at Daxishan in the same locality.

The specimen from Daxishan preserved an almost complete feather covering, sufficiently well preserved to allow the use of an electron microscope to determine the colours of the feathers. The arm and hand had pennaceous flight feathers attached to them, and flight feathers on its hind limbs, together forming fore-wings and hind-wings. It had 11 primary feathers and 10 secondary feathers on its forewing.

The authors of a letter to Nature (see below), Dongyu Hu et al., claim the well preserved specimen of the troodontid Anchiornis huxleyi from the earliest Late Jurassic of Tiaojishan Formation in Jianchang County, western Liaoning Province, China, refutes the 'temporal paradox'. According to this paradox, that has often been used to dispute a place for theropods in the evolution of birds, as most known bird-like feathered dinosaurs have been dated to the Cretaceous, after birds had evolved. They also claim their work provides significant information in relation to the framework of theropod divergence. This specimen has an extensive covering of feathers, with long pennaceous feathers attached to the pes. This species displays a complex distribution of skeletal and integumentary features that appear close to the dinosaur-bird transition.