Centuriavis
Centuriavis is an extinct genus of phasianid landfowl from the Miocene of Nebraska. Known from a well preserved and articulated skeleton preserving the skull as well as much of the vertebral column, its name stems from the fact that it remained undescribed for nearly a hundred years. It is estimated that it weighed, which would make it comparable in size with the average female greater sage grouse. Centuriavis may be related to grouse and turkeys and only a single species has been described: Centuriavis lioae.
History and naming
The type material of Centuriavis consists of an articulated fossil preserving primarily the front of the body including the skull, pectoral girdle, wings and the vertebrae up to and including parts of the synsacrum. These remains were collected by the 1932 Skinner Expedition at the Machaerodus quarry, a locality within the Merritt Dam Member of the Ash Hollow Formation. The Machaerodus quarry is generally thought to be Clarendonian in age, with the overlying ash layer indicating a minimum age of 11.4 million years. The same locality also yielded an additional humerus about 88% the size of the holotype and a tarsometatarsus, both of which have been tentatively referred to Centuriavis by Ksepka and colleagues. They note that the size difference could potentially be explained by sexual dimorphism, with the type specimen belonging to a male while the referred humerus may have been that of a female. However, they also note that the material could also have belonged to a different, second type of galliform. Despite the relative completeness and preservation of the type specimen, the fossils of Centuriavis remained undescribed for nearly a century until being examined by Ksepka and colleagues.The massive time gap between the discovery and description of the bird is also the basis for the genus' scientific name, consisting of "centuria" and "avis". The species name derives from Suzanne Lio, managing director at the Bruce [Museum of Arts and Science] where the fossil was previously held.
Description
The beak of Centuriavis is proportionally shorter than in modern turkeys with a tip that's slightly downturned. The nares are small, resembling those of ptarmigans and prairie chickens. The skull roof is smooth, which differs from grouses and some individuals of the turkey which possess rugosities above the eyes. The lower jaw is more strongly curved than in turkeys with a short mandibular symphysis that lacks a fenestra. The preservation of the skull allowed for a detailed look at the neuroanatomy of Centuriavis, revealing that it possessed small olfactory bulbs, a trait typical for land fowl. The hyperpallium, also known as wulst, most closely resembles turkeys in its degree of projection. The well developed optic lobes likewise resemble turkeys and are located almost entirely behind the widest point of the endocast.As prior research has shown that the strongest indicator for body mass in landfowls was the length of the coracoid, Ksepka and colleagues were able to estimate the weight of Centuriavis. They concluded that the animal may have reached a bodymass of, which is close to the average weight reported in female greater sage-grouse. This would render Centuriavis larger than most extant grouse species, but still smaller than the largest modern grouse species and modern turkeys.