| Plotopterum | |
|---|---|
 | |
| Holotype coracoid of P. joaquinensis | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Suliformes |
| Family: | † Plotopteridae |
| Genus: | † Plotopterum Howard, 1969 |
| Type species | |
| Plotopterum joaquinensis Howard, 1969 | |
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.
The future holotype of Plotopterum was discovered in 1961 in the Pyramid Hill Sand member of the Jewett Sand Formation, in the San Joaquin Valley of California, by Dick Bishop and Ed Mitchell. The remains were presented by Bishop to the Natural History Museum of Los Angeles County in 1964. In 1969, Hildegarde Howard, at the time retired from her work of chief curator of science at the museum, described the remains, LACM 8927, the upper end of a left coracoid, as a new genus and species, Plotopterum joaquinensis, which she ascribed to a new, monotypic family, Plotopteridae, due to its unique characteristics and adaptations towards swimming. [1]
In 1977, Hasegawa, Okumura and Okazaki described an almost complete bird femur, collected in 1976 in the Akeyo Formation in Honshu, Japan, and dated from the Early Miocene, as an indeterminate member of the family Phalacrocoracidae. [2] Less than a decade later, in 1985, Hasegawa himself, with Storrs L. Olson, redescribed the Japanese remains as belonging to the genus Plotopterum, as Plotopterum sp. [3]
The genus name, Plotopterum, is formed from the prefix Plot-, meaning "swimming", and the suffix "-pterum", meaning wing. [1]
The holotype associated with Plotopterum, the humeral end of a left coracoid, was roughly the size of those of the extant Brandt's cormorant, but narrower and more rounded. Several of its characteristics, such as the outline of the head, the shape of the bone, the scapular facet and its adjacent shaft were described as reminiscent of cormorants and anhingas. However, other characteristics, such as the head hanging over the shaft and the shape of the triosseal region, were more typical of diving birds, like penguins and auks, unrelated groups presenting flipper-like wings well adapted for swimming. The shape of the triosseal area, swollen in its lower portion and narrowed anteroposteriorly, was presumably occupied by the pectoral tendon, and strengthened the wing when the animal was swimming. Contrary to its distant relative, the flightless cormorant, the wings of Plotopterum were not reduced by the lack of use, but were heavily specialized in swimming, [1] although flightlessness can only be inferred due to the lack of well-preserved remains. [4]
The almost complete femur tentatively attributed to the genus in 1985, MFM 1800, shared similarities with Anhingidae, and the individual it belonged to was probably smaller than those of its Oligocene relatives, approximately the size of a great cormorant. [3]
Plotopterum is an outlier compared to other plotopterids. Despite being stratigraphically the youngest genus of plotopterid, most of its larger relatives going extinct at the end of the Oligocene, it seems to have kept primitive characteristics and was not as specialized for wing-propelled diving than other, older but more derived plotopterids. It has been suggested that the isolation of the ghost lineage limited to the Miocene of California and Japan to which belong Plotopterum, sister taxon to all other plotopterids from the Oligocene of the Pacific Northwest and Japan, may have permitted the preservation of basal traits. [4]
The Pyramid Hill Sand member of the Jewett Sand Formation, where the first remains of Plotopterum were discovered, was, during the Miocene, covered by the Pacific Ocean, and has yielded, alongside the holotype of Plotopterum, numerous fossils of cetaceans, fish, turtles, and molluscs. [1] Plotopterum and its close relative Stemec are found in coastal deposits, and were possibly limited to coastal waters, while the larger Tonsalinae such as Tonsala and Copepteryx had a more pelagic lifestyle. [5]
It has been suggested that the diversification of marine mammals occurring in the Pacific Ocean during the Late Paleogene and the Early Neogene may have concurrenced the plotopterids, and participated in their extinction. During the Early Miocene, the only forms of Plotopteridae known in the fossil record, like Plotopterum, were smaller and less derived than their Oligocene counterparts, and those forms probably went extinct shortly later. [3] [6]
While other genus of Plotopterids were disappearing during the Late Oligocene, Plotopterum survived well into the Miocene. This survival might be explained by the preservation into the Miocene of the offshore islands needed by plotopterids as secure breeding sites along the coast of California, when they disappeared along the coast of the Pacific Northwest during the Late Oligocene. [7]
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.
Osteodontornis is an extinct seabird genus. It contains a single named species, Osteodontornis orri, which was described quite exactly one century after the first species of the Pelagornithidae was. O. orri was named after Santa Barbara Museum of Natural History paleontologist Phil C. Orr, for his recognition of the importance of the specimen.
The Pelagornithidae, commonly called pelagornithids, pseudodontorns, bony-toothed birds, false-toothed birds or pseudotooth birds, are a prehistoric family of large seabirds. Their fossil remains have been found all over the world in rocks dating between the Early Paleocene and the Pliocene-Pleistocene boundary.
Paleontology or palaeontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 1996.
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.
Cyphornis is a genus of the prehistoric pseudotooth birds. These 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.
Pelagornis is a widespread genus of prehistoric pseudotooth birds. These were probably rather close relatives of either pelicans and storks, or waterfowl, and are placed here 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.
Hokkaidornis is an extinct genus of penguin-like plotopterid from the Late Oligocene of Hokkaido, Japan.
The Keasey Formation is a geologic formation in northwestern Oregon. It preserves fossils dating back to the Paleogene period.
Spheniscus muizoni is an extinct species of banded penguins that lived during the early Late Miocene in what is now Peru, South America. The species, the earliest member of the extant genus, was described in 2007 by Ursula B. Göhlich based on fossils found in the fossiliferous Pisco Formation of the Pisco Basin, southwestern Peru.
Giganhinga is a genus of giant darter that lived during the Late Miocene to Early Pleistocene in what is now Uruguay and Argentina. The largest species of anhinga known to science, estimates suggest it may have weighed around 17.7 kg (39 lb) and was likely flightless. Its weight likely helped it dive for prey and the anatomy of the pelvis indicates that it was a good and maneuverable swimmer. Only a single species is currently recognized, G. kiyuensis.
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.
Stemec 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 Sooke Formation of British Columbia
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.
Empeirodytes is an extinct genus of Plotopteridae, a family of large flightless bird known from the Late Eocene to the Early Miocene of the West Coast of the United States, British Columbia and Japan. Remains associated with Empeirodytes have been found in Oligocene rocks of the Ashiya Group, on the islands of Ainoshima and Kaijima, near Kitakyushu, Japan.
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 Jinnobaru Formation on Hikoshima and the Ashiya Group on Ainoshima, Japan.
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.
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