''Fukuipteryx'' is an extinct genus of basal

avialan Avialae ("bird wings") is a clade containing the only living dinosaurs, the birds, and their closest relatives. It is usually defined as all theropod dinosaurs more closely related to birds (Aves) than to deinonychosaurs, though alternative defi ...

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

s found in

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 ...

deposits from

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

Kitadani Formation The Kitadani Formation ( ''Kitadani-sō'') is a unit of Lower Cretaceous sedimentary rock which crops out near the city of Katsuyama in Fukui Prefecture, Japan, and it is the primary source of Cretaceous-aged non-marine vertebrate fossils in Jap ...

. It contains one species, ''Fukuipteryx prima''.Imai, T., Azuma, Y., Kawabe, S., Shibata, M., Miyata, K., Wang, M., & Zhou, Z. (2019)
An unusual bird (Theropoda, Avialae) from the Early Cretaceous of Japan suggests complex evolutionary history of basal birds
Communications Biology, 2(1). doi: 10.1038/s42003-019-0639-4

Discovery and naming

In 2013, the first associated skeleton of an Early Cretaceous avialan from Japan was collected at the Kitadani Dinosaur Quarry in Katsuyama, Fukui, central Japan. The specimen is three-dimensionally preserved, and exhibits several autapomorphies, which led to the creation of a new taxon. In 2019, 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 ...

''Fukuipteryx prima'' was named and described by Takuya Imai, Yoichi Azuma, Soichiro Kawabe, Masateru Shibata, Kazunori Miyata, Wang Min and Zhou Zhonghe. The genus name combines a reference to Fukui with the

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

''pteryx'', meaning "feather". The specific name means "the first" in

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

and refers to its basal position on the avialan phylogenetic tree. The

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 ...

, FPDM-V-9769, was found in a layer of green sandstone from the Kitadani Formation that dates from 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 ...

, about 120 million years old. It consists of a partial skeleton with a lower jaw. In total, a right surangular, two cervical vertebrae, four back vertebrae, two sacral vertebrae, five tail vertebrae, the pygostyle, ribs, a wishbone, both coracoid pelvis bones, the right ilium bone, the left upper arm bone, the ulna and radius of both forearms, the second right metacarpal, the left hand and both lower hindlimbs minus the calf bones and toes are preserved. The skeleton is not articulated but is preserved three-dimensionally. It is a subadult animal, less than one year old. It is part of the collection of the

Fukui Prefectural Dinosaur Museum The , located in Katsuyama, Fukui, Japan, is one of the leading dinosaur museums in Asia that is renowned for its exhibits of fossil specimens of dinosaurs and paleontological research. It is sited in the Nagaoyama Park ( Katsuyama Dinosaur Fore ...

. The fossil was not fully prepared from its matrix and the bones were reconstructed via a

CAT-scan A computed tomography scan (CT scan), formerly called computed axial tomography scan (CAT scan), is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers or ...

Description

''Fukuipteryx'' was about the size of a modern

pigeon Columbidae is a bird family consisting of doves and pigeons. It is the only family in the order Columbiformes. These are stout-bodied birds with small heads, relatively short necks and slender bills that in some species feature fleshy ceres. ...

. ''Fukuipteryx'' shows several

autapomorphies In phylogenetics, an autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or outgroup taxa, not even those most closely related to ...

(unique derived characters) that indicate that it was not a very basal species, in the sense that it would be outside of Avialae. A

pygostyle Pygostyle is a skeletal condition in which the final few caudal vertebrae are fused into a single ossification, supporting the tail feathers and musculature. In modern birds, the rectrices attach to these. The pygostyle is the main component o ...

, a fusion of the posterior tail vertebrae, is present, suggesting that the loss of a long tail was a less important step in the evolution of flight than was previously thought. The pygostyle is robust with rudiments of

neural spine Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal ...

s still visible, while the rear end has a paddle-shaped structure. The

furcula The (Latin for "little fork"; : furculae) or wishbone is a forked bone found in most birds and some species of non-avian dinosaurs, and is either an interclavicle or formed by the fusion of the two clavicles. In birds, its primary function is ...

is robust and U-shaped, but the angle between the branches is not very large. The

coracoid A coracoid is a paired bone which is part of the shoulder assembly in all vertebrates except therian mammals (marsupials and placentals). In therian mammals (including humans), a coracoid process is present as part of the scapula, but this is n ...

is a long strut, not fused to the shoulder blade. The

humerus The humerus (; : humeri) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius (bone), radius and ulna, and consists of three sections. The humeral upper extrem ...

is the largest bone of the limbs. The humerus has a round depression on the front top of its head. The shaft of the humerus is bent upwards (with the wing in a horizontal position). The

ulna The ulna or ulnar bone (: ulnae or ulnas) is a long bone in the forearm stretching from the elbow to the wrist. It is on the same side of the forearm as the little finger, running parallel to the Radius (bone), radius, the forearm's other long ...

and

radius In classical geometry, a radius (: radii or radiuses) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The radius of a regular polygon is th ...

are longer than the

femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...

Phylogeny

cladistic Cladistics ( ; from Ancient Greek 'branch') is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is ...

analysis recovered ''Fukuipteryx'' as an early-diverging avialan closer to modern birds than to ''

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 (''archaîos''), meaning "ancient", and (''ptéryx''), meaning "feather" ...

'', but more basal than ''

Jeholornis ''Jeholornis'' (meaning "Jehol bird") is a genus of avialan dinosaurs that lived between approximately 122 and 120 million years ago during the early Cretaceous Period in China. Fossil ''Jeholornis'' were first discovered in the Jiufotang Formati ...

''. Below is a

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

following that analysis:

References

{{Taxonbar, from=Q75218540 Avialae Aptian genera Early Cretaceous dinosaurs of Asia Cretaceous Japan Dinosaurs of Japan Fossil taxa described in 2019 Taxa named by Zhou Zhonghe