''Aechmophorus elasson'' is an extinct species of

grebe Grebes () are aquatic diving birds in the order (biology), order Podicipediformes (). Grebes are widely distributed freshwater birds, with some species also found in sea, marine habitats during Bird migration, migration and winter. Most grebes f ...

recovered from the

Piacenzian The Piacenzian is in the international geologic time scale the upper stage (stratigraphy), stage or latest age (geology), age of the Pliocene. It spans the time between 3.6 ± 0.005 year#SI prefix multipliers, Ma and 2.58 Ma (million years ago). T ...

age of the United States.

History

The specimens were collected in the summer of 1962 from Idaho, United States by Claude W. Hibbard and the species was named in 1967 by Bertram G. Murray. Material was later described from California, United States by Robert M. Chandler (1990).

Description

The material overall resembles those of extant species of ''

Aechmophorus ''Aechmophorus'' is a genus of birds in the grebe family. Species It has two living representatives breeding in western North America. One prehistoric species has been described from fossil remains: *'' Aechmophorus elasson'' (Late Plio ...

'', although slightly smaller in dimensions. The holotype are the distal end of 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 ...

and a slightly worn left

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 ...

. Other referred material from the

Hagerman Fossil Beds National Monument Hagerman Fossil Beds National Monument is a Pliocene-age site near Hagerman, Idaho, Hagerman, Idaho. The Monument is internationally significant because it protects one of the richest known fossil deposits from the Blancan North American Land Ma ...

include several fragmentary remains of the humeri, ulnae and a proximal of a

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 ...

, as well as two complete and two distal portions of

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 ...

s. Murrary (1967) did not provide a detailed osteological diagnosis on the Idaho material. Chandler (1990) would provide one for both the Idaho and California specimens. The California material includes a right ulna that is missing a quarter of its distal end, a right femur, left

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 ...

missing its cnemial crests, and tarsometatarsi (a complete left tarsometatarsus and a right one missing their distal end). As noted from Murrary (1967), Chandler (1990) finds the osteological diagnosis to be similar to extant ''Aechmophorus''.

Classification

''A. elasson'' is an extinct species of ''Aechmophorus'' and possibly the ancestral species to both

Clark's grebe Clark's grebe (''Aechmophorus clarkii'') is a North American waterbird species in the grebe family. Until the 1980s, it was thought to be a pale morph of the western grebe, which it resembles in size, range, and behavior. Intermediates between ...

(''A. clarkii'') and

western grebe The western grebe (''Aechmophorus occidentalis'') is a species in the grebe family of water birds. Folk names include "dabchick", "swan grebe" and "swan-necked grebe". Western grebe fossils from the Late Pleistocene of southwest North America we ...

(''A. occidentalis'').

Paleobiology

''A. elasson'' is known from the

Glenns Ferry Formation The Glenns Ferry Formation is a Pliocene stratigraphic unit in the western United States. Outcrops of the formation in Hagerman Fossil Beds National Monument preserve the remains of seven fish species, five of which are extinct. These include the t ...

and the

San Diego Formation The San Diego Formation is a geological formation in southwestern San Diego County, California, United States, and northwestern Baja California, Mexico. Geology It is a coastal transitional marine and non-marine pebble and cobble conglomerat ...

. One of the handful fossil species of an extant genus of North American grebe, ''A. elasson'' is relatively smaller in comparison to both Clark's grebe and western grebe, and fossil evidence of

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

specimens of the latter genus suggest a size increased occurred in the genus.

References

{{Taxonbar, from=Q107340305

elasson Elassona (; Katharevousa: ) is a town and a municipality in the Larissa regional unit in Greece. During antiquity Elassona was called Oloosson (Ὀλοοσσών) and was a town of the Perrhaebi tribe. It is situated at the foot of Mount Olympus. ...

Fossil taxa described in 1967 Piacenzian species Birds described in 1967