Ichthyornithes

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Ichthyornitheans
Temporal range:
Ma
Cast of an
Ichthyornis dispar skeleton, Rocky Mountain Dinosaur Resource Center
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Clade: Avialae
Clade: Ornithurae
Clade: †Ichthyornithes
Marsh, 1873
Subgroups[2]

And see text

Synonyms

Ichthyornithiformes Furbringer, 1888[2]

Ichthyornithes is an extinct group of toothed avialan dinosaurs very closely related to the common ancestor of all modern birds. They are known from fossil remains found throughout the late Cretaceous period of North America, though only two genera, Ichthyornis and Janavis, are represented by complete enough fossils to have been named. Ichthyornitheans became extinct at the Cretaceous–Paleogene boundary, along with enantiornitheans, all other non-avian dinosaurs, and many other animal and plant groups.

Origin and evolution

The earliest known ichthyornitheans appear in the fossil record about 95 million years ago, during the

Mesozoic era. The last ichthyornithean fossils are found in the Hell Creek Formation very close (within 300,000 years at least) of the K-Pg boundary, dated to 66 million years old.[4]

The study describing

Galloanserae and Neoaves, but does note that this link is worth investigating and that the pelagornithid palate is not known.[5]

A study on an Ichthyornis endocast reveals that it had a relatively "primitive" brain compared to modern birds, similar to that of Archaeopteryx and other non-avian theropods. Conversely, it had a palate remarkably convergent with that of modern neognaths.[6]

Classification

Ichthyornitheans were close to the ancestry of modern birds, the

phylogenetic taxonomy as all descendants of the most recent common ancestor of Ichthyornis dispar and modern birds.[2]

Species

Ichthyornis dispar from North America and

Cretaceous-Paleogene extinction event 66 million years ago.[4] Another unnamed species similar to Ichthyornis is known from isolated remains found in Campanian-age rocks from Alberta. Two more species also represented only by fossil shoulder bones are known from the Cenomanian-age Ashville Formation near Carrot River, Saskatchewan. Though originally thought to be species of Ichthyornis,[3] they probably represent one or more new genera.[4] Additional ichthyornithean remains have been described from Russia, suggesting that this group ranged across much of the northern hemisphere in the Cenomanian.[7]

Relationships

The cladogram below is the result of a 2014 analysis by Michael Lee and colleagues that expanded on data from an earlier study by O’Connor & Zhou in 2012, showing the relationship of Ichthyornis to other ornithurines. The clade names are positioned based on their definitions.[8]

Ornithurae

†Ichthyornis

†Hesperornithes

†Limenavis

Aves
(modern birds)

References

  1. ^
    S2CID 254099216
    .
  2. ^
    S2CID 84035285
    .
  3. ^
    doi:10.1080/02724634.1997.10010961
    .
  4. ^
    PMID 21914849
    .
  5. ^ G. Mayr, V. L. De Pietri, L. Love, A. Mannering, and R. P. Scofield. 2019. Oldest, smallest, and phylogenetically most basal pelagornithid, from the early Paleocene of New Zealand, sheds light on the evolutionary history of the largest flying birds. Papers in Palaeontology
  6. PMID 34330706
    .
  7. ^ Nikita V. Zelenkov, Alexander O. Averianov & Evgeny V. Popov (2017) An Ichthyornis-like bird from the earliest Late Cretaceous (Cenomanian) of European Russia. Cretaceous Research, 75: 94-100.
  8. PMID 24449041
    .
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