''Empeirodytes'' 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 ...

Plotopteridae 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 ...

, a family of large

flightless bird Flightless birds are birds that cannot Bird flight, fly, as they have, through evolution, lost the ability to. There are over 60 extant species, including the well-known ratites (ostriches, emus, cassowary, cassowaries, Rhea (bird), rheas, an ...

known from the

Late Eocene The Priabonian is, in the International Commission on Stratigraphy, ICS's geologic timescale, the latest age (geology), age or the upper stage (stratigraphy), stage of the Eocene epoch (geology), Epoch or series (stratigraphy), Series. It spans ...

to the

Early Miocene The Early Miocene (also known as Lower Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages: the Aquitanian age, Aquitanian and Burdigalian stages. The sub-epoch lasted from 23.03 ± 0.05 annum, Ma to ...

of the

West Coast of the United States The West Coast of the United States, also known as the Pacific Coast and the Western Seaboard, is the coastline along which the Western United States meets the North Pacific Ocean. The term typically refers to the Contiguous United States, contig ...

British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...

and

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 ...

. Remains associated with ''Empeirodytes'' have been found in

Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

rocks of the Ashiya Group, on the islands of Ainoshima and Kaijima, near

Kitakyushu is a Cities of Japan, city located in Fukuoka Prefecture, Japan. As of June 1, 2019, Kitakyushu has an estimated population of 940,978, making it the second-largest city in both Fukuoka Prefecture and the island of Kyushu after the city of Fuk ...

History and Etymology

In 2020, Ohashi Tomoyuki and Hasegawa Yoshikazu first described the remains of ''Empeirodytes okazakii'', assigning 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 ...

KMNH VP 600011, a partial left

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 ...

found in

-aged rocks of the Ashiya Group on the island of Ainoshima,

. They referred as

paratype In zoology and botany, a paratype is a specimen of an organism that helps define what the scientific name of a species and other taxon actually represents, but it is not the holotype (and in botany is also neither an isotype (biology), isotype ...

a right coracoid from the same horizon, discovered on the nearby Kaijima.

Etymology

The genus name, ''Empeirodytes'', is formed from 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 ...

prefix "''Empeiros''", meaning "proficient", and the suffix "-''dytes''", meaning "diver", referencing the adaptation towards wing-propelled diving exhibited by plotopterids. The species name, "''okazakii''", honours Okazaki Yoshihiro, another

vertebrate Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...

researcher who worked on

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 preserve ...

s from the Ashiya Group.

Description

The genus ''Empeirodytes'' is only known from two isolated

s. It is assumed from the size of those remains that the bird was a medium-sized plotopterid, smaller than the large genera of Japanese tonsalin plotopterids ''

Copepteryx ''Copepteryx'' is an extinct genus of flightless bird, flightless bird of the family Plotopteridae, endemic to Japan during the Oligocene living from 28.4 to 23 Annum, mya, meaning it existed for approximately . History and Etymology Remains of ...

'' and ''

Hokkaidornis ''Hokkaidornis'' is an extinct genus of Sphenisciformes, penguin-like plotopterid from the Late Oligocene of Hokkaido, Japan. History and etymology The first ''Hokkaidornis'' remains were discovered in sediments dated from the Late Oligocene of ...

'', but larger than the derived '' Plotopterum''. ''Empeirodytes'' is mostly differentiated from other genera of plotopterids by the presence of a high and sharp ridge on the caudal margin of the labrum internum, and of a clear depression on the ventral surface of the portion where the shaft of the coracoid articulates with 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 ...

. The presence of that depression may indicate the attachment of the supracoracoideus muscle, used by plotopterids to propel themselves through water, potentially indicating that ''Empeirodytes'' and its relative ''

Stenornis ''Stenornis'' is an extinct genus of Plotopteridae, a family of large-sized, flightless seabirds native from the North Pacific during the Paleogene and the earliest Neogene. The remains of ''Stenornis'' have been found in Oligocene rocks of the ...

'' had better swimming abilities than most other plotopterids.

Palaeobiology

During the

, the sea that composes today the

Yamaga Formation The Yamaga Formation is a palaeontological formation located in Japan. It dates to the Upper Oligocene period. See also * List of fossil sites This list of fossil sites is a worldwide list of localities known well for the presence of foss ...

and the Jinnobaru Formation of the Ashiya Group was home to at least four species of plotopterids, the medium-sized ''Empeirodytes'', the large-sized '' Stenornis kanmonensis'' and '' Copepteryx hexeris'', and the giant ''Copepteryx titan''. Alongside these, those waters were also populated by the eomysticetid

whale Whales are a widely distributed and diverse group of fully Aquatic animal, aquatic placental mammal, placental marine mammals. As an informal and Colloquialism, colloquial grouping, they correspond to large members of the infraorder Cetacea ...

Yamatocetus, sharks and

pelagornithid The Pelagornithidae, commonly called pelagornithids, pseudodontorns, bony-toothed birds, false-toothed birds or pseudotooth birds, are a prehistoric family (biology), family of large seabirds. Their fossil remains have been found all over the wor ...

seabird Seabirds (also known as marine birds) are birds that are adaptation, adapted to life within the marine ecosystem, marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent ...

References

{{Taxonbar, from=Q112733081 Fossil taxa described in 2020 Paleogene Japan Plotopteridae Extinct flightless birds Prehistoric bird genera