''Grabauornis'' is an extinct genus of

enantiornithean The Enantiornithes, also known as enantiornithines or enantiornitheans in literature, are a group of extinct avialans ("birds" in the broad sense), the most abundant and diverse group known from the Mesozoic era. Almost all retained teeth and cl ...

s from the

Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...

of China. The

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

, ''Grabauornis lingyuanensis'', was named and described in 2014 by Johan Dalsätt, Per Ericson and

Zhou Zhonghe Zhonghe Zhou (; born 19 January 1965 in Jiangdu, Jiangsu province) is a Chinese palaeontologist. He described the ancient bird '' Confuciusornis''.. Zhonghe graduated from Nanjing University and earned a Ph.D. in Biology in 1999 from the Univer ...

. The genus name combines a reference to

Amadeus William Grabau Amadeus William Grabau (January 9, 1870 – March 20, 1946) was an American geologist, teacher, stratigrapher, paleontologist, and author who worked in the United States and China. Biography Grabau's grandfather, J.A.A. Grabau, led a group of ...

with the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

word , which means bird. The specific name refers to the place where it was found; the city of

Lingyuan Lingyuan () is a city in the west of Liaoning province in Northeast China, bordering Hebei province and Inner Mongolia. It is under the administration of Chaoyang City, which lies to the east-northeast. Administrative Divisions There are eight ...

in the Lianoning province of China. Dalsät already referred to the descriptive article in 2012, before it was published, in his dissertation and the name ''Grabauornis'' was mentioned with it. However it was still an invalid ''nomen ex dissertatione''. In addition, he explicitly stated that he did not want to perform naming acts, if they are not performed validly. The fossil,

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

IVPP V14595, was found in a layer of the

Yixian Formation The Yixian Formation (; formerly Romanization of Chinese, transcribed as Yihsien Formation or Yixiang Formation) is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans the Barremian stage of the Early Cretaceous. I ...

which dates to the

Aptian The Aptian is an age (geology), age in the geologic timescale or a stage (stratigraphy), stage in the stratigraphic column. It is a subdivision of the Early Cretaceous, Early or Lower Cretaceous epoch (geology), Epoch or series (stratigraphy), S ...

, at an age of 125 million years. The holotype consists of a well-preserved skeleton, compressed onto a single plate. ''Grabauornis'' shows a unique combination of differentiating traits. The center of the back of the sternum plate extends further back than the side wings, the latter are fan-shaped. It also has a relatively short head with small, conical teeth. As for the arms and hands; the second and third phalanges of the second finger are quite robust, the third metacarpal extends further than the second and the hand is shorter than the ulna. Besides that, the shoulder blade is long and narrow and tapers towards the top. ''Grabauornis'' has a humerus that is 95% of the length of the ulna. In most enantiornitheans the values are between 77 and 125%, so ''Grabauornis'' has an average ratio. According to the descriptors, this indicates a good ability to fly; only above 130% the animal would have to remain on the ground. This ability would be confirmed by the possession of an

alula The alula , or bastard wing, (plural ''alulae'') is a small projection on the anterior edge of the wing of modern birds and a few non-avian dinosaurs. The word is Latin and means "winglet"; it is the diminutive of ''ala'', meaning "wing". The a ...

, a thumb feather that could serve as a nose vane. The hypocleidium of the wishbone is also well developed.

References

Further reading