Avisaurus

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Avisaurus
Temporal range: Late Cretaceous (Maastrichtian), 68–66  Ma
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Avisaurus.jpg
Holotype tarsometatarsus of A. archibaldi
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Clade: Avialae
Clade: Enantiornithes
Family: Avisauridae
Genus: Avisaurus
Brett-Surman & Paul, 1985
Type species
Avisaurus archibaldi
Brett-Surman & Paul, 1985
Species
  • A. archibaldiBrett-Surman and Paul, 1985 (type)
  • A. darwiniClark et al., 2024

Avisaurus (meaning "bird lizard") is a genus of enantiornithine avialan from the Late Cretaceous of North America. [1]

Contents

Discovery

Avisaurus archibaldi was discovered in the Late Cretaceous Hell Creek Formation of North America (Maastrichtian, from c.70.6-66 million years ago), making it one of the last enantiornithids. It was collected in 1975 in the UCMP locality V73097, in Garfield County, Montana, USA. The holotype is represented by a single fossil of a tarsometatarsus in the collection of the University of California Museum of Paleontology. It has the catalog number UCMP 117600. The species name honors J. David Archibald, its discoverer, from The University of California, Berkeley. It was initially described as the left tarsometatarsus of a non-avian theropod by Brett-Surman and Paul in 1985. It was later redescribed as the right tarsometatarsus of an enantiornithine bird by Chiappe in 1992. [2]

Avisaurus gloriae Varricchio and Chiappe 1995, [3] discovered in the late Campanian Upper Two Medicine Formation of Glacier County, Montana, USA, was renamed Gettyia by Atterholt et al. (2018). [4] In 2024, another species of Avisaurus from the Hell Creek Formation was named as Avisaurus darwini, with the specific name in honor of Charles Darwin. [5]

Description

Size (lower right) compared to contemporary birds, pterosaurs, and a human Pterosauria journal.pbio.2001663.g020.png
Size (lower right) compared to contemporary birds, pterosaurs, and a human

Avisaurus was a large enantiornithine, with A. darwini weighing up to 1.2 kilograms (2.6 lb) and A. archibaldi weighing up to 1.7 kilograms (3.7 lb). [5] The type specimen of A. archibaldi has a maximum length of 73.9 mm (2.91 in), making it one of the largest known tarsometatarsi of an enantiornithine. [3]

Classification

This genus belongs to the enantiornithine family Avisauridae, which also contains similar animals from South America such as Soroavisaurus , Neuquenornis and Intiornis . [5]

Brett-Surman and Paul (1985) explicitly considered the possibility that A. archibaldi was an enantiornithine. The authors described and named UCMP 117600 formally, but they looked at other enantiornithine material, including the "metatarsus" PVL 4690 from Argentina. The authors assigned this latter fossil to Avisaurus sp. From this they concluded that members of the genus Avisaurus existed in both North and South America in the Late Cretaceous. Moreover, the authors concluded that the length/width ratio and degree of metacarpal fusion of these bones were more like those of non — avian dinosaurs. A terrestrial dinosaur genus in both continents would then support Brett — Surman's theory that there had been a land connection between the two continents. [6]

Further discoveries and further study by Chiappe showed that all of the material belonged to enantiornithine birds, and PVL 4690 was given its own genus Soroavisaurus . [2]

Paleoenvironment and paleobiology

Avisaurus remains fossilized in the humid low-lying swamps, lakes, and river basins of the western shore of the Western Interior Seaway, Hell Creek Formation. [5]

Inwardly curved claws of the Avisaurus tarsis resemble those of eudromaeosaurs, indicating that it was predatory. It likely preyed on other vertebrates, with similarity to some modern raptors. [7] [5]

Related Research Articles

<span class="mw-page-title-main">Enantiornithes</span> Extinct clade of dinosaurs

The Enantiornithes, also known as enantiornithines or enantiornitheans in literature, are a group of extinct avialans, the most abundant and diverse group known from the Mesozoic era. Almost all retained teeth and clawed fingers on each wing, but otherwise looked much like modern birds externally. Over seventy species of Enantiornithes have been named, but some names represent only single bones, so it is likely that not all are valid. The Enantiornithes became extinct at the Cretaceous–Paleogene boundary, along with Hesperornithes and all other non-avian dinosaurs.

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

Yungavolucris is a genus of enantiornitheans. It contains the single species Yungavolucris brevipedalis, which lived in the Late Cretaceous. The fossil bones were found in the Lecho Formation at estancia El Brete, Argentina."Yungavolucris brevipedalis" means "Short-footed Yungas bird". The generic name, Yungavolucris is after the Yungas region + the Latin volucris, which translates to "bird". The specific name brevipedalis is from the Latin brevis, which means "short", + pedalis, from the Latin pes, meaning "foot".

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

Lectavis is a genus of enantiornithine avialan. Their fossil bones have been recovered from the Late Cretaceous Lecho Formation at estancia El Brete, Argentina. The genus contains a single species, Lectavis bretincola.

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<i>Magnusavis</i> Genus of enantiornithine birds

Magnusavis is an extinct genus of large enantiornithine birds from the Late Cretaceous (Maastrichtian-aged) Hell Creek Formation of Montana, United States. The genus contains a single species, M. ekalakaensis, known from an incomplete right tarsometatarsus and toe bone.

References

  1. PaleoBiology Database: Avisaurus, basic info
  2. 1 2 Chiappe, Luis M. (1992) "Enantiornithine (Aves) Tarsometatarsi and the Avian Affinities of the Late Cretaceous Avisauridae" "Journal of Vertebrate Paleontology" September 3, 1992, Volume 12 no. 3 pp. 344-350
  3. 1 2 Varricchio, David J., Chiappe, Luis M. (1995) "A New Enantiornithine Bird From the Upper Cretaceous Two medicine Formation of Montana" " Journal of Vertebrate Paleontology" March 14, 1995, Vol. 15, no. 1, pp. 201 - 204
  4. Atterholt, Jessie; Hutchison, J. Howard; O’Connor, Jingmai K. (2018-11-13). "The most complete enantiornithine from North America and a phylogenetic analysis of the Avisauridae". PeerJ. 6: e5910. doi: 10.7717/peerj.5910 . ISSN   2167-8359. PMC   6238772 . PMID   30479894.
  5. 1 2 3 4 5 Clark, Alexander D.; Atterholt, Jessie; Scannella, John B.; Carroll, Nathan; O’Connor, Jingmai K. (2024-10-09). "New enantiornithine diversity in the Hell Creek Formation and the functional morphology of the avisaurid tarsometatarsus". PLOS ONE. 19 (10): e0310686. doi: 10.1371/journal.pone.0310686 . ISSN   1932-6203. PMC   11463745 . PMID   39383133.
  6. Brett-Surman, Michael K., Paul, Gregory S. (1985) "A new family of bird-like dinosaurs linking Laurasia and Gondwanaland." "Journal of Vertebrate Paleontology" 5(2): 133-138.
  7. Matthew P. Martyniuk (2012). A Field Guide to Mesozoic Birds and Other Winged Dinosaurs. Pan Aves. p. 142. ISBN   9780988596504 . Retrieved 29 August 2022.

Further reading