''Pedopenna'' (meaning "foot feather") is a

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 ...

of small, feathered,

maniraptora Maniraptora is a clade of coelurosaurian dinosaurs which includes the birds and the non-avian dinosaurs that were more closely related to them than to ''Ornithomimus velox''. It contains the major subgroups Avialae, Deinonychosauria, Oviraptoros ...

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 ...

from the

Daohugou Beds The Haifanggou Formation (), also known as the Jiulongshan Formation (), is a fossil-bearing rock deposit located near Daohugou () village of Ningcheng County, in Inner Mongolia, northeastern China. The formation consists of coarse conglomerates ...

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 is possibly older than ''

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" ...

'', though the age of the

where it was found is debated. A majority of studies suggest that beds probably date from between the late

Middle Jurassic The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from about 174.1 to 163.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relatively rare, but geological formations co ...

(168 million years ago) and early

Late Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the name ...

Period (164-152 million years ago). The name ''Pedopenna'' refers to the long pennaceous feathers on the metatarsus; ''daohugouensis'' refers to the locality of Daohugou, where the

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

was found. ''Pedopenna daohugouensis'' probably measured 1 meter (3 ft) or less in length, but since this species is only known from the hind legs, the actual length is difficult to estimate. ''Pedopenna'' was originally classified as a

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 ...

, the group of

n dinosaurs that includes both

deinonychosaurs Deinonychosauria is a clade of paravian dinosaurs which lived from the Late Jurassic to the Late Cretaceous periods. Fossils have been found across the globe in North America, Europe, Africa, Asia, South America, and Antarctica,Case, J.A., Marti ...

and

avialans 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 use ...

(the lineage including modern birds), but some scientists have classified it as a true avialan more closely related to modern birds than to deinonychosaurs. More recently, it has been recovered as a

scansoriopterygid Scansoriopterygidae (meaning "climbing wings") is an extinct family of climbing and gliding maniraptoran dinosaurs. Scansoriopterygids are known from five well-preserved fossils, representing four species, unearthed in the Tiaojishan Formation f ...

.Hartman, Scott; Mortimer, Mickey; Wahl, William R.; Lomax, Dean R.; Lippincott, Jessica; Lovelace, David M. (2019). "A new paravian dinosaur from the Late Jurassic of North America supports a late acquisition of avian flight". PeerJ. 7: e7247. doi:10.7717/peerj.7247. PMC 6626525. .

Description

The feet of ''Pedopenna'' resembled those of the related

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 disco ...

s and

dromaeosaurid 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 ...

s (which together form the group

Deinonychosauria Deinonychosauria is a clade of paravian dinosaurs which lived from the Late Jurassic to the Late Cretaceous periods. Fossils have been found across the globe in North America, Europe, Africa, Asia, South America, and Antarctica,Case, J.A., Mar ...

), though were overall more primitive. In particular, the second toe of ''Pedopenna'' was not as specialized as in deinonychosaurs. While ''Pedopenna'' did have an enlarged claw and slightly shortened second toe, it was not as highly developed as the strongly curved, sickle-like claws of its relatives. Xu Xing and Zhang Fucheng, who interpreted the

Daohugou The Haifanggou Formation (), also known as the Jiulongshan Formation (), is a fossil-bearing rock deposit located near Daohugou () village of Ningcheng County, in Inner Mongolia, northeastern China. The formation consists of coarse conglomerates ...

fossil beds where ''Pedopenna'' was found as mid to 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 ...

in age, used the presence of such a primitive member of the avian lineage, in combination with many primitive members of closely related lineages there, to support the idea that birds originated in

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...

Feathers

The bird-like characteristics of ''Pedopenna'' are further evidence of the dinosaur-bird evolutionary relationship. Apart from having a very bird-like skeletal structure in its legs, ''Pedopenna'' was remarkable due to the presence of long

pennaceous feather The pennaceous feather is a type of feather present in most modern birds and in some other species of maniraptoriform dinosaurs. Description A pennaceous feather has a stalk or quill. Its basal part, called a ''calamus'', is embedded in the skin ...

s on the

metatarsus The metatarsal bones, or metatarsus, are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the med ...

(foot). Some deinonychosaurs are also known to have these 'hind wings', but those of ''Pedopenna'' differ from those of animals like ''

Microraptor ''Microraptor'' (Greek, μικρός, ''mīkros'': "small"; Latin, ''raptor'': "one who seizes") is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China. They ...

''. ''Pedopenna'' hind wings were smaller and more rounded in shape. The longest

feather Feathers are epidermal growths that form a distinctive outer covering, or plumage, on both avian (bird) and some non-avian dinosaurs and other archosaurs. They are the most complex integumentary structures found in vertebrates and a premier ...

s were slightly shorter than the metatarsus, at about 55 mm (2 in) long. Additionally, the feathers of ''Pedopenna'' were symmetrical, unlike the asymmetrical feathers of some

deinonychosaur Deinonychosauria is a clade of paravian dinosaurs which lived from the Late Jurassic to the Late Cretaceous periods. Fossils have been found across the globe in North America, Europe, Africa, Asia, South America, and Antarctica,Case, J.A., Mar ...

s and birds. Since asymmetrical feathers are typical of animals adapted to flying, it is likely that ''Pedopenna'' represents an early stage in the development of these structures. While many of the feather impressions in the fossil are weak, it is clear that each possessed a

rachis In biology, a rachis (from the grc, ῥάχις [], "backbone, spine") is a main axis or "shaft". In zoology and microbiology In vertebrates, ''rachis'' can refer to the series of articulated vertebrae, which encase the spinal cord. In this c ...

and barbs, and while the exact number of foot feathers is uncertain, they are more numerous than in the hind-wings of ''Microraptor''. ''Pedopenna'' also shows evidence of shorter feathers overlying the long foot feathers, evidence for the presence of

covert Secrecy is the practice of hiding information from certain individuals or groups who do not have the "need to know", perhaps while sharing it with other individuals. That which is kept hidden is known as the secret. Secrecy is often controvers ...

s as seen in modern birds. Since the feathers show fewer aerodynamic adaptations than the similar hind wings of ''Microraptor'', and appear to be less stiff, suggests that if they did have some kind of aerodynamic function, it was much weaker than in deinonychosaurs and birds. Xu and Zhang, in their 2005 description of ''Pedopenna'', suggested that the feathers could be ornamental, or even vestigial. It is possible that a hind wing was present in the ancestors of deinonychosaurs and birds, and later lost in the bird lineage, with ''Pedopenna'' representing an intermediate stage where the hind wings are being reduced from a functional gliding apparatus to a display or insulatory function. this theory may be confirmed by the recent discovery of ''

Serikornis ''Serikornis'' is a genus of small, feathered anchiornithid dinosaur from the Upper Jurassic Tiaojishan Formation of Liaoning, China. It is represented by the type species ''Serikornis sungei''. Discovery ''Serikornis'', first described in A ...

'', an anchiornithid with soft, symmetrical feathers and filaments on parts of the body that were similar to Pedopenna's.

References

{{Taxonbar, from=Q220431 Prehistoric paravians Jurassic dinosaurs of Asia Fossil taxa described in 2005