''Hokkaidornis'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

penguin Penguins are a group of aquatic flightless birds from the family Spheniscidae () of the order Sphenisciformes (). They live almost exclusively in the Southern Hemisphere. Only one species, the Galápagos penguin, is equatorial, with a sm ...

-like

plotopterid Plotopteridae is an extinct family of flightless seabirds with uncertain placement, generally considered as member of order Suliformes. They exhibited remarkable convergent evolution with the penguins, particularly with the now extinct giant peng ...

from the

Late Oligocene The Chattian is, in the geologic timescale The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the pro ...

Hokkaido is the list of islands of Japan by area, second-largest island of Japan and comprises the largest and northernmost prefectures of Japan, prefecture, making up its own list of regions of Japan, region. The Tsugaru Strait separates Hokkaidō fr ...

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 ...

History and etymology

The first ''Hokkaidornis'' remains were discovered in sediments dated from the Late Oligocene of the Tokoro Formation, near the city of

Abashiri is a city located in Okhotsk Subprefecture, Hokkaido, Japan. Abashiri is known as the site of the Abashiri Prison, a Meiji-era facility used for the incarceration of political prisoners. The old prison has been turned into a museum, but the ...

, in the Japanese island of

, and had been identified as the remains of a yet-unidentified genus and species of plotopterid in 1998. In 2008, Kazuhiko Sakurai, Masaichi Kimura and Takayuki Katoh described the new genus and species ''Hokkaidornis abashiriensis'', using as

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 ...

the specimen AMP 44, a semi-complete skeleton lacking the skull.

Etymology

The genus name, ''Hokkaidornis'', is constructed from

, the island in which the holotype was discovered, and 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 ...

suffix ''-ornis'', meaning "bird". The species name, ''abashiriensis'', refers to the town of

, near which it was found; the city name itself meaning "to be discovered in rock" in the native

Ainu language Ainu (, ), or more precisely Hokkaido Ainu (), is a language spoken by a few elderly members of the Ainu people on the northern Japanese island of Hokkaido. It is a member of the Ainu language family, itself considered a language family isola ...

Description

''Hokkaidornis'' was a large-bodied plotopterid, with estimated height of and length of , roughly the size of its relative '' Copepteryx hexeris''. The anterior ends of 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 ...

are more reminiscent of those found in ''

Anhinga The anhinga (; ''Anhinga anhinga''), sometimes called snakebird, darter, American darter, or water turkey, is a water bird of the warmer parts of the Americas. The word ''anhinga'' comes from ''a'ñinga'' in the Brazilian Tupi language and means ...

'' than those of

Phalacrocoracidae Phalacrocoracidae is a family of approximately 40 species of aquatic birds commonly known as cormorants and shags. Several different classifications of the family have been proposed, but in 2021 the International Ornithologists' Union (IOU) ado ...

. The sternal end of 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 ...

, only part of the coracoid preserved in the holotype specimen, had a more angular sterno-coracoidal process, differing it from ''Copepteryx'' and ''

Tonsala ''Tonsala'' is an extinct genus of Plotopteridae, a family of flightless seabird similar in biology with penguins, but more closely related to modern cormorants. The genus is known from terrains dated from the Late Oligocene of the State of Washi ...

''. The well-preserved

scapula The scapula (: scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on either side ...

was similar to that of ''Tonsala''. The partially preserved

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 ...

was more elongated than that of ''Tonsala'', and had a shaft more sinuous than that of ''Copepteryx'', and similar to that of ''Tonsala''. The

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 ...

was flattened like in other plotopterid, while 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 ...

was the largest known for plotopterids. The

pelvis The pelvis (: pelves or pelvises) is the lower part of an Anatomy, anatomical Trunk (anatomy), trunk, between the human abdomen, abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also c ...

shared similarities with those of modern anhingas. 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 ...

was more robust than that of Tonsala, and had a more bowed shaft and a more bulbous head than those of both species of ''Copepteryx'', although it resembled, as well than the

tibiotarsus The tibiotarsus is the large bone between the femur and the tarsometatarsus in the leg of a bird. It is the fusion of the proximal part of the tarsus with the tibia. A similar structure also occurred in the Mesozoic Heterodontosauridae. These ...

, those of some specimens referred tentatively to ''Copepteryx'' by Olson and Hasegawa. The

patella The patella (: patellae or patellas), also known as the kneecap, is a flat, rounded triangular bone which articulates with the femur (thigh bone) and covers and protects the anterior articular surface of the knee joint. The patella is found in m ...

was remarkably heavy. The

tarsometatarsus The tarsometatarsus is a bone that is only found in the lower leg of birds and some non-avian dinosaurs. It is formed from the fusion of several bird bones found in other types of animals, and homologous to the mammalian tarsus (ankle bones) a ...

was more robust and less elongated than in ''

Phocavis ''Phocavis'' is an extinct genus of flightless seabird, belonging to the family Plotopteridae, and distantly related with modern cormorants. Its fossils, found in the Keasey Formation in Oregon, are dated from the Late Eocene. History and Etymol ...

'', but was nearly undistinguishable to that of the paratype of ''C. hexeris'', and quite similar to those of modern-day

Paleobiology

''Hokkaidornis'' had a well-developed trochlea cartilaginis tibialis on its

, a character mostly known from hindlimb-propelled marine birds. That development may indicate that ''Hokkaidornis'' was not only adapted towards wing-propelled swimming like most other plotopterids, but also able to propel itself through water with its hindlimbs, a characteristic also present in its relative ''

Olympidytes ''Olympidytes'' is an extinct genus of Plotopteridae, a family of large, flightless marine bird superficially similar to modern penguins but more closely related to cormorants and gannets. It lived during the Late Eocene or the Early Oligocene, i ...

''. The preservation of ripple marks on sandstones found in the vicinity of the holotype and the presence of the

bivalve Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...

s '' Periploma yokoyamai'' and ''

Yoldia ''Yoldia'' is a genus of marine bivalve mollusks in the family (biology), family Yoldiidae. Some former members of the genus are now known as ''Portlandia (bivalve), Portlandia''. The genus was named after , Conde de Yoldi (1764–1852), a Spani ...

'', the

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

Turritella ''Turritella'' is a genus of medium-sized sea snails with an operculum, marine gastropod mollusks in the family Turritellidae.Vos, C.; Gofas, S. (2013). Turritella Lamarck, 1799. Accessed through: World Register of Marine Species at http://www. ...

and the

scaphopod Scaphopoda (plural scaphopods , from Ancient Greek σκᾰ́φης ''skáphē'' "boat" and πούς ''poús'' "foot"), whose members are also known as tusk shells or tooth shells, are a class (biology), class of shelled Marine life, marine inve ...

Dentalium Dentalium may refer to: * ''Dentalium'' (genus), a genus of tooth shells * Dentalium shell The word dentalium, as commonly used by Native American artists and anthropologists, refers to tooth shells or tusk shells used in indigenous jewelry, ad ...

'' in association with the specimen indicates that ''Hokkaidornis'' lived in a shallow marine environment.

References

{{Taxonbar, from=Q5878136 Pelecaniformes Oligocene birds of Asia Fossil taxa described in 2008 Fossils of Japan