''Eosinopteryx'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

s known to the late

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...

period of

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

. It contains a single

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

, ''Eosinopteryx brevipenna''.

Discovery and naming

''E. brevipenna'' is known from a single fossil specimen recovered from the

Tiaojishan Formation The Tiaojishan Formation is a geological formation in Hebei and Liaoning, People's Republic of China, dating to the middle-late Jurassic period (Bathonian- Oxfordian stages). It is known for its exceptionally preserved fossils, including those of ...

of western

Liaoning Province Liaoning () is a coastal provinces of China, province in Northeast China that is the smallest, southernmost, and most populous province in the region. With its capital at Shenyang, it is located on the northern shore of the Yellow Sea, and i ...

, China, which has been dated to the late Jurassic period ( Oxfordian age), about 160 million years ago. The name ''Eosinopteryx'' is derived from the Greek ''eos'' ("daybreak" or "dawn"), the Latin ''Sinae'' ("Chinese"), and the Greek ''pteryx'' ("feather"). The specific name ''brevipenna'' (from the Latin ''brevis'', "short", and ''penna'', "feather") refers to the reduced plumage preserved in the

type specimen In biology, a type is a particular wiktionary:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to a ...

, YFGP-T5197.

Description

''Eosinopteryx brevipenna'' is known from a single

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

specimen representing the nearly complete skeleton of a subadult or adult individual. The specimen is very small for a non-

avialan Avialae ("bird wings") is a clade containing the only living dinosaurs, the birds. It is usually defined as all theropod dinosaurs more closely related to birds (Aves) than to deinonychosaurs, though alternative definitions are occasionally used ...

dinosaur, measuring about long. Unlike most troodontids, the snout was very short, shorter than the diameter of the eye socket. The wings were about the same size as those of the related ''

Anchiornis huxleyi ''Anchiornis'' is a genus of small, four-winged paravian dinosaurs, with only one known species, the type species ''Anchiornis huxleyi'', named for its similarity to modern birds. The Latin name ''Anchiornis'' derives from a Greek word meaning " ...

'', with the primary wing feathers being longer than the humerus (upper arm bone). An unusual arrangement of the wing bones would have prevented any flapping motion. The tail was very short compared to most troodontids and

dromaeosaurids Dromaeosauridae () is a family of feathered theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek ('), meaning ...

and also unlike members of those groups, the feet and toes were very slender, lacking highly curved claws for predation or climbing. Unusually, the tail of the only known fossil does not show signs of the presence of complex vaned feathers (

rectrices Flight feathers (''Pennae volatus'') are the long, stiff, asymmetrically shaped, but symmetrically paired pennaceous feathers on the wings or tail of a bird; those on the wings are called remiges (), singular remex (), while those on the tail ...

), and the lower tarsals and feet appear to have been featherless, unlike many related species with "hind wings" on the lower legs and feet. A researcher from the

University of Southampton , mottoeng = The Heights Yield to Endeavour , type = Public research university , established = 1862 – Hartley Institution1902 – Hartley University College1913 – Southampton University Coll ...

said in 2013 the discovery of ''Eosinopteryx'' suggests "that the origin of flight was much more complex than previously thought". A 2017 study describing new specimens of ''Anchiornis'' found ''Eosinopteryx'' only distinguishable from ''Anchiornis'' in the length of the tail, but the tail of ''Eosinopteryx'' is incomplete, rendering this distinction invalid. This led some researchers to consider ''Eosinopteryx'' a junior synonym of ''Anchiornis.''

Classification

Though initially classified as a

troodontid Troodontidae is a clade of bird-like theropod dinosaurs. During most of the 20th century, troodontid fossils were few and incomplete and they have therefore been allied, at various times, with many dinosaurian lineages. More recent fossil discov ...

, a more comprehensive analyses of its relationships have found it to be either a primitive

paravian Paraves are a widespread group of theropod dinosaurs that originated in the Middle Jurassic period. In addition to the extinct dromaeosaurids, troodontids, anchiornithids, and possibly the scansoriopterygids, the group also contains the aviala ...

or an

. In 2017 re-evaluation of the Harlem ''

Archaeopteryx ''Archaeopteryx'' (; ), sometimes referred to by its German name, "" ( ''Primeval Bird''), is a genus of bird-like dinosaurs. The name derives from the ancient Greek (''archaīos''), meaning "ancient", and (''ptéryx''), meaning "feather" ...

'' specimen, ''Eosinopteryx'' is found to be an anchiornithid.

External links

A photograph of the type specimen, published by David Evans' twitter accountA close-up view of the skull, from the same source

References

Late Jurassic dinosaurs of Asia Prehistoric paravians Fossil taxa described in 2013 Feathered dinosaurs Taxa named by Pascal Godefroit Paleontology in Liaoning Jurassic birds {{Theropod-stub