Plotopteridae

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Extinct family of sea birds

title: "Plotopteridae" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["plotopteridae", "extinct-flightless-birds", "paleogene-birds-of-north-america", "extinct-animals-of-the-united-states", "taxa-named-by-hildegarde-howard", "prehistoric-bird-families"] description: "Extinct family of sea birds" topic_path: "geography/united-states" source: "https://en.wikipedia.org/wiki/Plotopteridae" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Extinct family of sea birds ::

| name = Plotopterids | fossil_range = Eocene – Miocene ~ | image = Fossil of sternum of Copepteryx from Kitahata Karatsu Japan.JPG | image_caption = Copepteryx | taxon = Plotopteridae | authority = Howard, 1969 | subdivision_ranks = Genera | subdivision =

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.

Their fossils have been found in California, Oregon, Washington, British Columbia, Hokkaido, Tōhoku, Chūbu, Kyushu. They seem to have evolved on arctic islands during the mid-Eocene, spreading southwards with the formation of kelp forests They ranged in size from that of a large cormorant (such as a Brandt's cormorant), to very large size, with femur length two times longer than emperor penguin. They had shortened wings optimised for underwater wing-propelled pursuit diving (like penguins or the now extinct great auk), and a body skeleton similar to that of the darter. ::figure[src="https://upload.wikimedia.org/wikipedia/commons/d/d4/Tonsala_hildegardae.png" caption="''Tonsala hildegardae'' fossils"] ::

The second species to be named from rocks along the eastern Pacific Ocean was Tonsala hildegardae from the late Oligocene lower part of the Pysht Formation in Washington State. More fossils of T. hildegardae have since been described and included some of the first known examples of borings made by the marine bone-eating worm Osedax in bird bones. The hallux was more similar to that of frigatebirds rather than that of darters, sulids and cormorants, suggesting they evolved from a highly aerial ancestor.

::figure[src="https://upload.wikimedia.org/wikipedia/commons/e/ee/Copepteryx_hexeris.jpg" caption="Reconstruction of ''[[Copepteryx]]''."] ::

The earliest known member of the family, Phocavis maritimus lived in the late Eocene, but most of the known species lived during Oligocene time, becoming extinct in the early to mid-Miocene. That they became extinct at the same time as the giant penguins of the Southern Hemisphere, which also coincided with the radiation of the seals and dolphins, has led to speculation that the expansion of marine mammals was responsible for the extinction of the Plotopteridae, though this has not been formally tested.

References

References

  1. Howard, H.. (1969). "A new avian fossil from Kern County, California". [[Condor (journal).
  2. (2021). "Early Plotopteridae Specimens (Aves) from the Itanoura and Kakinoura Formations (Latest Eocene to Early Oligocene), Saikai, Nagasaki Prefecture, Western Japan". Paleontological Research.
  3. Olson, Storrs L.. (1979). "Fossil Counterparts of Giant Penguins from the North Pacific". [[Science (journal).
  4. (1996). "A new genus and two new species of gigantic Plotopteridae from Japan (Aves: Pelecaniformes)". [[Journal of Vertebrate Paleontology.
  5. Tatsuro et al., New Skeletal Remains of Plotopterids from Japan, SVP 2015
  6. (2014). "Enigmatic affinity in the brain morphology between plotopterids and penguins, with a comprehensive comparison among water birds". Zoological Journal of the Linnean Society.
  7. (2015-07-04). "Oligocene plotopterid skulls from western North America and their bearing on the phylogenetic affinities of these penguin-like seabirds". Journal of Vertebrate Paleontology.
  8. (2021). "Comparative osteology of the penguin-like mid-Cenozoic Plotopteridae and the earliest true fossil penguins, with comments on the origins of wing-propelled diving". Journal of Zoological Systematics and Evolutionary Research.
  9. Goedert, James L.. (1988). "A new late Eocene species of Plototpteridae (Aves: Pelecaniformes) from northwestern Oregon". Proceedings of the California Academy of Sciences.
  10. (2016). "New late Eocene and Oligocene remains of the flightless, penguin-like plotopterids (Aves, Plotopteridae) from western Washington State, U.S.A.". Journal of Vertebrate Paleontology.
  11. (2018). "First record of a tarsometatarsus of ''Tonsala hildegardae'' (Plotopteridae) and other avian remains from the late Eocene/early Oligocene of Washington State (USA)". Geobios.
  12. (2015). "A new member of the family Plotopteridae (Aves) from the late Oligocene of British Columbia, Canada". Palaeontologia Electronica.
  13. (2020-08-18). "西海市から発見された世界最古級のペンギンモドキの化石について". 西海市教育委員会、蒲郡市教育委員会、[[Fukui Prefectural Dinosaur Museum.
  14. (2021). "New late Eocene and Oligocene plotopterid fossils from Washington State (USA), with a revision of ''"Tonsala" buchanani'' (Aves, Plotopteridae)". Journal of Paleontology.
  15. Olson, Storrs L.. (1980). "A new genus of penguin-like pelecaniform bird from the Oligocene of Washington (Pelecaniformes: Plotopteridae)". Contributions in Science.
  16. (2002). "A preliminary report on the diversity and stratigraphic distribution of the Plotopteridae (Pelecaniformes) in Paleogene rocks of Washington State, USA". Proceedings of the 5th Symposium of the Society of Avian Paleontology and Evolution, Beijing.
  17. (2017). "First record of a tarsometatarsus of ''Tonsala hildegardae'' (Plotopteridae) and other avian remains from the late Eocene/early Oligocene of Washington State (USA)". Geobios.
  18. (2011). "''Osedax'' borings in fossil marine bird bones". Naturwissenschaften.
  19. Mayr, Gerald, Goedert, James L., "An unusual new species and additional fossils of the penguin-like Plotopteridae from the Paleogene of Washington State, USA", Received 29 May 2025, Accepted 01 Jul 2025, Published online: 21 Jul 2025

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plotopteridaeextinct-flightless-birdspaleogene-birds-of-north-americaextinct-animals-of-the-united-statestaxa-named-by-hildegarde-howardprehistoric-bird-families