Stenornis

Last updated

Stenornis
Temporal range: Oligocene
~33–22  Ma
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Suliformes
Family: Plotopteridae
Genus: Stenornis
Ohashi & Hasegawa, 2020
Type species
Stenornis kanmonensis
Ohashi & Hasegawa, 2020

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. [1]

Contents

History and Etymology

The first remain associated with Stenornis, an isolated left coracoid, was collected in 1976 by Ota Masamichi on the Japanese island of Hikoshima, and described in 1979 as an indeterminate new species of plotopterid by Ota and Hasegawa Yoshikazu. [2] In 1986, while describing the new genus Copepteryx , Hasegawa and Storrs L. Olson tentatively referred that coracoid to the North American genus Tonsala , of which the coracoid was then badly known, based on similarities found in then undescribed Japanese plotopterids. [3] In 2020, a new analysis of the coracoid (KMNH VP 200003) from Hikoshima by Ohashi Tomoyuki and Hasegawa Yoshikazu led to the removal of the specimen from Tonsala and the creation of the new genus and species Stenornis kanmonensis, using the Hikoshima coracoid as holotype and another coracoid, found on Ainoshima by Sato Masahiro, as paratype. [1]

Etymology

The genus name, Stenornis, is formed from the Ancient Greek prefix "steno-", meaning "strait", and the suffix "-ornis", meaning "bird". The species name, kanmonensis, refers to the Kanmon Strait, where the holotype of the genus was discovered. [1]

Description

Stenornis is only known from two isolated coracoid bones. Size estimates based on comparison of these bones with those of other plotopterids indicates that it was roughly the size of its contemporary relative Copepteryx hexeris . Given the paucity of its remains, Stenornis is mainly differentiated from its relatives by osteological details of its coracoid, including the presence of a sulcus elongated craniocaudally on the ventral surface of the shaft, a processus lateralis located toward the cranial portion of the shaft, and a face where the coracoid articulates with the clavicle broader than all other plotopterids and bean-shaped. Despite being similarly sized with its relative Copepteryx, found in the same deposits, the coracoid was slightly smaller, although much larger than that of Tonsala , [1] more gracile, with a narrower sternal end and a broader and proximally situated lateral process. [3] [1]

The distinctive presence of a small depression on the middle of the face where the coracoid would articulate with the humerus. Although this depression was much less visible than for its relative Empeirodytes , it is speculated that the supracoracoideus muscle would have been attached to it. [1] The supracoracoideus muscle was responsible for the efficiency of plotopterids at wing-propelled diving, and was enlarged compared to those of non-diving birds. [4] The presence of this attachment depression on the coracoid might indicate that Stenornis and Empeirodytes were more powerful swimmers than most other plotopterids. [1]

Palaeoecology

During the Oligocene period, the prehistoric seas that are preserved today in the geological formations that compose the Ashiya Group were populated by at least four species of plotopterids : Empeirodytes okazakii , Stenornis kanmonensis, Copepteryx hexeris and Copepteryx titan. Fossil remains of sharks, pelagornithid seabirds, and early whales like the eomysticetid Yamatocetus have also been recovered in Oligocene sediments belonging to the group. [1]

Related Research Articles

<span class="mw-page-title-main">Plotopteridae</span> Extinct family of sea birds

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.

Megapaloelodus is an extinct genus of stem flamingo of the family Palaelodidae. Megapaloelodus is primarily known from Miocene America, from South Dakota and Oregon in the north to Argentina in the south, but the species Megapaloelodus goliath was found in Europe. Additionally, one unnamed species was discovered in Miocene sediments from Namibia. Due to a lack of skull material, little can be said about the ecology of Megapaloelodus. Species of this genus are typically larger than those of Palaelodus and appear to have inhabited similar brackish lake environments. Additionally, they may have been capable of "locking" their legs in a standing position.

<span class="mw-page-title-main">Pelagornithidae</span> Extinct family of seabirds

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.

Douglas Ralph Emlong was an amateur fossil collector from the Oregon Coast in the northwestern United States. His collections contributed to the discovery and description of numerous extinct marine mammal species, many of which are ancestral to extant groups. Described as an 'indefatigable' fossil collector with 'Promethian prowess in discovery of unprecedented vertebrate fossils', he contributed substantially to the field from the age of fourteen. The ancestral pinniped Enaliarctos emlongi was named in his honor by Annalisa Berta in 1991.

<i>Copepteryx</i> Extinct genus of birds

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.

<i>Andrewsornis</i> Extinct genus of birds

Andrewsornis is an extinct genus of giant flightless predatory birds of the family Phorusrhacidae or "terror birds" that lived in Oligocene Argentina. Fossils have been found in the Sarmiento Formation, and possibly the Agua de la Piedra Formation.

<i>Pelagornis</i> Extinct genus of birds

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.

Tympanonesiotes is a somewhat doubtfully valid 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.

<i>Hokkaidornis</i> Extinct genus of birds

Hokkaidornis is an extinct genus of penguin-like plotopterid from the Late Oligocene of Hokkaido, Japan.

Pterodromoides is an extinct genus of fulmarine petrel dating from the Late Miocene. It contains a single species, P. minoricensis. Its fossil remains were first discovered at the Punta Nati palaeontological site on the island of Menorca in the Balearic archipelago of the western Mediterranean. An additional specimen from North Carolina, USA has also been referred to this species, suggesting it lived across the North Atlantic. It was described in 2001, with the authors justifying the creation of a new genus by the large orbitonasal opening and characters of the postcranial skeleton, despite the similarity of the cranial osteology to that of Pagodroma.

<i>Plotopterum</i>

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.

<i>Tonsala</i> Extinct genus of Plotopteridae

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.

<i>Phocavis</i> Extinct genus of Plotopteridae

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.

<i>Thiornis</i> Extinct water bird

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

<i>Olympidytes</i> Extinct genus of Plotopteridae

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.

<i>Klallamornis</i> Extinct genus of American flightless birds

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.

References

  1. 1 2 3 4 5 6 7 8 Ohashi, T; Hasegawa, Y (2020). "New species of Plotopteridae (Aves) from the Oligocene Ashiya Group of Northern Kyushu, Japan". Paleontological Research. 24 (4): 285–297. doi:10.2517/2020PR005.
  2. Hasegawa, Y. & Ota, M. (1979). "Preliminary notes on the Oligo-Miocene Penguin-like birds from Japan (Part V)". Bulletin of the Kitakyushu Museum of Natural History. 1: 41–60.
  3. 1 2 Olson, S.L.; Hasegawa, Y. (1996). "A New Genus and Two New Species of Gigantic Plotopteridae from Japan (Aves : Pelecaniformes)". Journal of Vertebrate Paleontology. 16 (4): 742–751. Bibcode:1996JVPal..16..742O. doi:10.1080/02724634.1996.10011362.
  4. Ando, T.; Fukata, K. (2018). "A well-preserved partial scapula from Japan and the reconstruction of the triosseal canal of plotopterids". PeerJ. 6: e5391. doi: 10.7717/peerj.5391 . PMC   6112113 . PMID   30155348.