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 ...
from the Upper
Pliocene
The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58black-necked grebe.
History
The specimens were collected in the summer of 1951 from Kansas, United States by Claude W. Hibbard and the species was named in 1967 by Bertram G. Murray. The species name "discors" refers to how different it is from other members of ''
Podiceps
''Podiceps'' is a genus of birds in the grebe family. The genus name comes from Latin , "rear-end" and ', "foot", and is a reference to the placement of a grebe's legs towards the rear of its body.
It has representatives breeding in all contine ...
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 ...
, which is comparable in size to tarsometatarsi of the black-necked grebe and of the females of the
horned grebe
The horned grebe or Slavonian grebe (''Podiceps auritus'') is a relatively small and Threatened species, threatened species of waterbird in the family Podicipedidae. There are two subspecies, ''P. a. auritus'' (Slavonian grebe), which breed ...
(''P. auritus''). It differs from them by its internal
is not internally flared, and the head is small relative to the length of the bone. Further when viewed at the medial perspective, the tarsometatarsus of ''P. discors'' is not as long or it is directed so far anteriorly as seen in other species of the genus. Additional material has been found in Idaho which represent a complete
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 ...
(UMMP 52423), an almost complete
carpometacarpus
The carpometacarpus is a bone found in the hands of birds. It results from the fusion of the carpal and metacarpal bone, and is essentially a single fused bone between the wrist and the knuckles. It is a smallish bone in most birds, generally fla ...
(UMMP 49653), three
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 (UMMP 49590, UMMP 52277, and UMMP 52585), two
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 ...
e (UMMP 45289 and UMMP 49589) and two distal end fragments of two
tibiotarsi
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 sm ...
(UMMP 52432 and 52448). They are all similar to those of the same bone elements in the black-necked grebe with some overlap, though the bones are more slender in form by comparison.
A femur from California (SDSNH 23836) has been recovered that is identical to UMMP 52423.
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 ...
, all dating to 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 ...
. This suggests this species was widely distributed in western North America which would have been similar to the range of the black-necked grebe.