Archaeorhynchus

2025-06-27T04:11:11Z

45.182.57.78:

{{Short description|Extinct genus of dinosaurs}}
{{distinguish|text=the prehistoric weevil genus [[Archaeorrhynchus]]}}
{{speciesbox
| image = Archaeorhynchus-Paleozoological Museum of China.jpg
| image_caption = Fossil specimen, [[Paleozoological Museum of China]]
| fossil_range = [[Early Cretaceous]], {{fossilrange|125|120}}
| display_parents = 3
| species = spathula
| genus = Archaeorhynchus
| parent_authority = Zhou & Zhang, 2006
| authority = Zhou & Zhang, 2006
}}

'''''Archaeorhynchus''''' (meaning "ancient snout") is a genus of beaked [[Avialae|avialans]] from the early [[Cretaceous]] period. A fossil of its only known species, '''''Archaeorhynchus spathula''''', was first reported in 2005 by Zhou & Zhang to have been found in [[Yixian Formation]] rocks at Yixian, [[Liaoning province]], [[China]], showing a well-preserved and essentially complete skeleton.<ref name="2006 paper">{{cite journal|last=Zhou|first=Z|author2=Zang.F.C.|title=A beaked basal ornithurine bird (Aves, Ornithurae) from the Lower Cretaceous of China|journal=Zoologica Scripta|year=2006|volume=35|issue=4|pages=363–373|doi=10.1111/j.1463-6409.2006.00234.x|s2cid=85222311}}</ref> Two more complete specimens were found in Lower Cretaceous deposits of [[Jianchang]], Liaoning, northeastern China, preserving new anatomical information. These deposits are 120 million years old, whereas the original specimen was 125 million years old, meaning the age range for this species is 125-120Ma.<ref name="2013 paper">{{cite journal|last=Zhou|first=S|title=Anatomy of the basal ornithuromorph bird Archaeorhynchus spathula from the early Cretaceous of Liaoning, China|journal=Journal of Vertebrate Paleontology|year=2013|volume=33|issue=33|pages=141–152|display-authors=etal|doi=10.1080/02724634.2012.714431|s2cid=86035166}}</ref>

''Archaeorhychus'' is one of the earliest avialans known to have had a beak, and represents one of the most basal [[Ornithuromorpha|ornithuromorph]] avialans.<ref name="2006 paper"/> The fossils preserved feathers associated with the neck, head and tail regions. The fossils also show grooves and openings/ holes (foramina) on the tips of the upper and lower jaws, suggesting that it supported a horny bill. Other features present suggest powerful flight capability similar to that of some modern birds.<ref name="2013 paper"/> It has also been suggested that it had an herbivorous diet based on preserved gizzard stones found in its stomach.<ref name="2006 paper"/>

==Description==
''Archaeorhynchus'' was a medium-sized avialan,<ref name="2006 paper"/> measuring about {{convert|20|cm|in}} long, hip height of {{cvt|15.5|cm}}, and weight of {{cvt|275|g}}.<ref>{{cite book
| isbn = 9780691190594
| url = https://books.google.com/books?id=WnZyDwAAQBAJ&dq=avisaurus+size&pg=PA281
| title = Dinosaur Facts and Figures: The Theropods and Other Dinosauriformes
| publisher = Princeton University Press
| date = June 25, 2019
| access-date = 29 August 2022
| pages = 281
| author = Rubén Molina-Pérez, Asier Larramendi, David Connolly, Gonzalo Ángel Ramírez Cruz, Andrey Atuchin
}}</ref> The three specimens have well-preserved skulls showing important anatomical information, including: slender [[maxilla]] and premaxilla, short nasals and discrete [[mandible]] elements.<ref name="2013 paper"/> The skull bones of the [[holotype]] were slightly dislocated due to transportation.<ref name="2006 paper"/> All three known fossil specimens have a preserved vertebrae column, although they are not entirely complete. However, when combining the three specimens together, the whole spine could be reconstructed. Based on reconstruction of the vertebrae, it was estimated that the backbone had 9 or 10 neck vertebrae and 9 or 10 tail vertebrae. The back vertebrae were not preserved.<ref name="2013 paper"/> ''Archaeorhynchus'' had slender and curved vertebral ribs (ribs that do not attach to the breastbone) with robust and strong bases.<ref name="2013 paper"/> The pectoral girdle had a robust and U-shaped wishbone, a slightly curved shoulder blade, a short and robust [[coracoid]] and a broad and deeply notched breastbone. The hips had an unfused [[ilium (bone)|ilium]], a slender and curved [[pubis (bone)|pubis]] with a small pubic foot and a strap like [[ischium]] which is shorter than the pubis.<ref name="2013 paper"/>

The hind limb was shorter than the forelimb. The forelimbs had a [[humerus]] and a [[radius (bone)|radius]] which were straighter and shorter than the [[ulna]]. The forelimbs also preserved the major and minor [[metacarpals]] as well as the finger bones showing a [[phalangeal formula]] of 2-3-2. The hind limbs have a robust and bowed [[femur]], a [[tibia]] which is slightly longer than the femur, and a slender [[fibula]]. They also preserve four [[metatarsals]] (metatarsal V is not preserved) where metatarsals II-IV, are not fused to each other and where metatarsal III is the longest and widest, while the others are equal in length <ref name="2013 paper"/>

Feathers are preserved in the holotype and one of the two most recent finds, where they are associated with the neck, wing and tail regions.<ref name="2013 paper"/>

==Relationships==
Phylogenetic analysis conducted by Zhou & Zhang indicated that ''Archaeorhynchus'' was most closely related to ornithurines. This is based on the fact that the ''Archaeorhynchus'' shared advanced features with other ornithurines such as a U-shaped wishbone, a "keel" for flight muscle attachments along the full length of the breastbone, and a compressed and expanded first finger bone of the major manual digit. Nonetheless, ''Archaeorhynchus'' also retained primitive features including the lower jaw not being strongly forked at the back, and deep posterior notches in the sternum.<ref name="2013 paper"/> The holotype specimen also showed features which suggest powerful flight capability similar to modern birds.<ref name="2006 paper"/>

==Diet==
Scientists have hypothesized that the ''Archaeorhynchus'' had an herbivorous diet, due to the large numbers of [[gastroliths]] (stomach stones) found in the gut of all known specimens. High numbers of these gastroliths suggest that they were not swallowed accidentally.<ref name="2013 paper"/> These stones would have been eaten to help break down food that the animal would not have been able to chew because it was toothless.

==Life cycle==
A 2021 study on a juvenile specimen shows that, much like [[Enantiornithes]] and [[megapode]]s, ''Archaeorhynchus'' probably demonstrated flight soon after birth.<ref>Foth, C.; Wang, S.; Spindler, F.; Lin, Y.; Yang, R. (2021) "A Juvenile Specimen of ''Archaeorhynchus'' Sheds New Light on the Ontogeny of Basal Euornithines". Frontiers in Earth Science. 9: Article 604520 https://doi.org/10.3389/feart.2021.604520</ref>

==References==
{{Reflist}}


==External links==
* oficina.cienciaviva.pt: [https://web.archive.org/web/20070701014235/http://oficina.cienciaviva.pt/~pw011/jazidas/archaeorrhynchus.gastrolitos.zhou.2006.coppy.jpg Photo of holotype]. Note gastroliths (indicated "GS"). Retrieved 2007-NOV-2.

{{Paraves|B.}}
{{Taxonbar|from=Q3014381}}

[[Category:Euornithes]]
[[Category:Early Cretaceous dinosaurs of Asia]]
[[Category:Yixian fauna]]
[[Category:Fossil taxa described in 2006]]

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Archaeorhynchus