Olympidytes | |
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Femur and distal end of the tibiotarsus of Olympidytes | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Class: | Aves |
Order: | Suliformes |
Family: | † Plotopteridae |
Subfamily: | † Tonsalinae |
Genus: | † Olympidytes Mayr & Goedert, 2016 |
Type species | |
Olympidytes thieli Mayr & Goedert, 2016 |
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, in what is today the State of Washington and Japan. [1]
The first specimen attributed to Olympidites, a partial postcranial skeleton, was collected in 2012 by Bruce Thiel in Late Eocene to Early Oligocene sediments from the Lincoln Creek Formation. Another specimen attributed to the genus was collected by James L. Goedert in 2012, from Late Eocene or Early Oligocene rocks from the Jansen Creek member of the Makah Formation, in the southwest of the State of Washington. In 2016, those remains were identified by Goedert and Gerald Mayr as belonging to a new genus and species of plotopterid, which they named Olympidytes thieli, based on the holotype SMF Av 608, the fragmentary skeleton found by Thiel. [1] In 2021, Mori Hirotsugu and Miyata Kazunori tentatively referred to the genus, as cf. Olympidytes sp., a fragmentary right tibiotarsus found in Early Oligocene deposits belonging to the lower member of the Kakinoura Formation near Saikai, Japan. [2] With the redescription of the Japanese remains of Tonsala from Japan as the new genus Stenornis , [3] Olympidytes is the only genus of tonsalin plotopterid known from both sides of the Pacific Ocean. [2] In 2021, a specimen once referred to Tonsala (now Klallamornis ) buchanani was redescribed as an indeterminate new species of plotopterid potentially belonging either to the genus Olympidytes or Klallamornis. [4]
The genus name, Olympidytes, is formed from the prefix "Olymp-", referring to the Olympic Peninsula in which the paratype was discovered, and the Ancient Greek "-dytes", meaning "diver". The species name, thieli, was given to honour Bruce Thiel, the collector and donator of the holotype. [1]
Olympidytes was a comparatively small plotopterid, comparable in size with its relative Tonsala . The pygostyle was more typical of that of leg-propelled diving birds like penguins, rather than the elongated shape typical of modern wing-propelled divers, although this can be explained by the function held by the tail in terrestrial locomotion for the modern penguins, absent in plotopterids. The 111.2 cm long femur was intermediate in its stoutness between Tonsala and its larger Japanese relatives Hokkaidornis and Copepteryx . The complete tibiotarsus of the holotype, unique among all plotopterids, was similar but stouter than that of Tonsala. The referred tarsometatarsus, although damaged, lacked a foramen vasculare distale, as in its relative Klallamornis , possibly suggesting that they were sister taxa. [1]
Cf Olympidytes sp., based on the specimen SM-SKT-1153 from Japan, likely represent a new species different from O. thieli. While very similar in size and in shape to the type species, the tibiotarsus lacked a deep groove located on the lateral side of the pons supratendineus where the tandon of the fibularis brevis muscle would attach, a distinctive trait of the genus Olympidytes. [2]
Like its relative Klallamornis and modern penguins, [5] Olympidytes is known to swallow pebbles, recovered as gastroliths in association with the holotype. [1]
The presence of a well-developed trochlea cartiginalis tibialis, an adaptation usually present in hindlimb-propelled diving birds, and unusual for the wing-propelled plotopterid, may indicate that Olympidytes and its relative Hokkaidornis were well adapted for both forms of propulsions. [2]
In the Late Eocene to Early Oligocene ocean preserved by the Jansen Creek member of the Makah Formation, Olympidytes coexisted with at least two other species of plotopterids, Klallamornis abyssa and ?Klallamornis clarki. [1] With remains assigned tentatively to Olympidytes discovered in Japan, it is currently the only known genus of plotopterid known from both sides of the Pacific. [2] The diversity of plotopterid on both sides of the Pacific during the Late Eocene and Early Oligocene ; the group may have benefited from the global cooling event occurring during the Eocene-Oligocene boundary, which increase the presence of nutrients and the diversity of phytoplankton in seas worldwide. [2]
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 penguins. That they lived in the North Pacific, the other side of the world from the penguins, has led to them being described at times as the Northern Hemisphere's penguins, though they were not closely related. More recent studies have shown, however, that the shoulder-girdle, forelimb and sternum of plotopterids differ significantly from those of penguins, so comparisons in terms of function may not be entirely accurate. Plotopterids are regarded as closely related to Anhingidae (darters) and Phalacrocoracidae (cormorants). On the other hand, there is a theory that this group may have a common ancestor with penguins due to the similarity of forelimb and brain morphology. However, the endocast morphology of stem group Sphenisciformes differs from both Plotopteridae and modern penguins.
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Copepteryx is an extinct genus of flightless bird of the family Plotopteridae, endemic to Japan during the Oligocene living from 28.4 to 23 mya, meaning it existed for approximately 5.4 million years.
Dasornis is a genus of prehistoric pseudotooth birds. These were probably close relatives of either pelicans and storks or waterfowl; they are placed in the order Odontopterygiformes to account for this uncertainty.
Pseudodontornis is a rather disputed genus of the prehistoric pseudotooth birds. The pseudotooth birds or pelagornithids were probably rather close relatives of either pelicans and storks, or of waterfowl, and are here placed in the order Odontopterygiformes to account for this uncertainty. Up to five species are commonly recognized in this genus.
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Plotopterum is an extinct genus of flightless seabird of the family Plotopteridae, native to the North Pacific during the Late Oligocene and the Early Miocene. The only described species is Plotopterum joaquinensis.
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 Washington and Japan.
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.
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Klallamornis is an extinct genus of Plotopteridae, a family of large, flightless birds related to modern cormorants, darters, gannets, and boobies. This genus included the largest North American plotopterids. Its remains can be found in Late Eocene to Late Oligocene rocks from the Makah Formation, the overlying Pysht Formation and the Lincoln Creek Formation of the State of Washington. During its existence, Klallamornis was the largest plotopterid on the North American continent. The first fossil remains attributed to the taxon were collected in 1983, although the genus wasn't described until 2016.