| Hokkaidornis Temporal range: Late Oligocene ~ | |
|---|---|
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| Right scapula of Hokkaidornis abashiriensis | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Suliformes |
| Family: | † Plotopteridae |
| Subfamily: | † Tonsalinae |
| Genus: | † Hokkaidornis Sakurai et al. 2008 |
| Type species | |
| †Hokkaidornis abashiriensis Sakurai et al. 2008 | |
Hokkaidornis is an extinct genus of penguin-like plotopterid from the Late Oligocene of Hokkaido, Japan. [1]
The first Hokkaidornis remains were discovered in sediments dated from the Late Oligocene of the Tokoro Formation, near the city of Abashiri, in the Japanese island of Hokkaido, and had been identified as the remains of a yet-unidentified genus and species of plotopterid in 1998. In 2008, Kazuhiko Sakurai, Masaichi Kimura and Takayuki Katoh described the new genus and species Hokkaidornis abashiriensis, using as holotype the specimen AMP 44, a semi-complete skeleton lacking the skull. [1]
The genus name, Hokkaidornis, is constructed from Hokkaido, the island in which the holotype was discovered, and the ancient Greek suffix -ornis, meaning "bird". The species name, abashiriensis, refers to the town of Abashiri, near which it was found ; the city name itself meaning "to be discovered in rock" in the native Ainu language. [1]
Hokkaidornis was a large-bodied plotopterid, with estimated height of 1.3 metres (4.3 ft) and length of 1.7 metres (5.6 ft), [2] roughly the size of its relative Copepteryx hexeris . The anterior ends of the furcula are more reminiscent of those found in Anhinga than those of Phalacrocoracidae. The sternal end of the coracoid, only part of the coracoid preserved in the holotype specimen, had a more angular sterno-coracoidal process, differing it from Copepteryx and Tonsala . The well-preserved scapula was similar to that of Tonsala. The partially preserved humerus was more elongated than that of Tonsala, and had a shaft more sinuous than that of Copepteryx, and similar to that of Tonsala. The radius was flattened like in other plotopterid, while the ulna was the largest known for plotopterids. The pelvis shared similarities with those of modern anhingas. The femur was more robust than that of Tonsala, and had a more bowed shaft and a more bulbous head than those of both species of Copepteryx, although it resembled, as well than the tibiotarsus, those of some specimens referred tentatively to Copepteryx by Olson and Hasegawa. The patella was remarkably heavy. The tarsometatarsus was more robust and less elongated than in Phocavis , but was nearly undistinguishable to that of the paratype of C. hexeris, and quite similar to those of modern-day penguins. [1]
Hokkaidornis had a well-developed trochlea cartilaginis tibialis on its tarsometatarsus, a character mostly known from hindlimb-propelled marine birds. That development may indicate that Hokkaidornis was not only adapted towards wing-propelled swimming like most other plotopterids, but also able to propel itself through water with its hindlimbs, a characteristic also present in its relative Olympidytes . [3]
The preservation of ripple marks on sandstones found in the vicinity of the holotype and the presence of the bivalves Periploma yokoyamai and Yoldia , the gastropod Turritella and the scaphopod Dentalium in association with the specimen indicates that Hokkaidornis lived in a shallow marine environment. [1]
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.
Waimanu is a genus of early penguin which lived during the Paleocene, soon after the Cretaceous–Paleogene extinction event, around 62–60 million years ago. It was about the size of an emperor penguin. It is one of the most important bird fossils for understanding the origin and evolution of birds because of the time period it comes from, and the position of penguins near the base of the bird family tree.
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.
Cruschedula is an enigmatic bird genus considered to be nomen dubium which consists of the single species Cruschedula revola.
Majiashanosaurus is an extinct genus of pachypleurosaur or alternatively a basal eosauropterygian known from the Early Triassic of Anhui Province, eastern China. It contains a single species, Majiashanosaurus discocoracoidis.
Ozimek is a genus of sharovipterygid archosauromorph reptile, known from Late Triassic deposits in Poland and closely related to the Kyrgyzstani Sharovipteryx. It contains one species, O. volans, named in 2016 by Jerzy Dzik and Tomasz Sulej. Like Sharovipteryx, Ozimek had long, slender limbs with the hindlimbs longer than the forelimbs; the hindlimbs likely supported gliding membranes as fossilized in Sharovipteryx. Another unusual characteristic was the shoulder girdle, where the massive coracoids formed a shield-like structure covering the bottom of the shoulder region that would have limited mobility. In other respects, such as its long neck, it was a typical member of the non-natural grouping Protorosauria. Phylogenetic analysis has indicated that it, possibly along with Sharovipteryx, may have been an unusual member of the protorosaur group Tanystropheidae, although further study of its anatomy is needed to resolve its precise relationships.
Fukuipteryx is an extinct genus of basal avialan dinosaurs found in Early Cretaceous deposits from Japan's Kitadani Formation. It contains one species, Fukuipteryx prima.
Orienantius ritteri is an extinct genus of enantiornithine bird from the Lower Cretaceous of China.
Scaniacypselus is a genus of basal swift from the Eocene of Denmark, Germany and France. Many well preserved specimens still showing plumage were discovered in the Messel Pit near Darmstadt, Germany. Scaniacypselus had relatively broader wings than modern swifts and hindlimbs better adapted to perching on tree-branches, indicating that the bird wasn't as aerial as its extant relatives and likely nested in trees like hummingbirds and treeswifts. Two species are recognized, S. wardi and S. szarskii.
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.
Thiornis is a fossil genus of Middle Miocene grebe known from a nearly complete specimen from Libros, Spain. Originally classified as a type of moorhen, Thiornis has since been classified as a species of grebe. The overall anatomy of the bird is identical to modern grebes. It contains a single species, T. sociata.
Adelalopus is an extinct genus of palaelodid bird from the lowermost Oligocene of Belgium. It is the oldest member of its family and the largest known palaelodid from Europe, slightly larger than Megapaloelodus goliath. It contains a single species, Adelalopus hoogbutseliensis.
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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