Janavis

Source: Wikipedia, the free encyclopedia.

Janavis
Temporal range: Late
Ma
↓
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Clade: Avialae
Clade: †Ichthyornithes
Genus: †Janavis
Benito et al. 2022
Type species
†Janavis finalidens
Benito et al. 2022

Janavis (from the Roman god

modern bird,[4] it provides information on the evolution and divergence of basal and modern birds, especially on the evolutionary modifications of bird skulls.[5]

Fossil

The fossil of Janavis,

computed tomography in 2021 revealed additional structures inside the rock including neck bones (six cervical vertebrae), an additional four dorsal vertebrae, the first phalanx of the second digit of the forelimb, the left scapula, a humerus and a bit of the upper right femur.[3]

History

The fossil of Janavis was collected in 2000

Eben Emael (Bassenge), Belgium. It was collected and partly prepared by Dutch amateur palaeontologist Rudi W. Dortangs. A team of American and Dutch palaeontologists reported the first identification as "Europe's last Mesozoic bird" in 2002 from which it was assigned as a species of the ancestral group (as a basal member of the clade Ornithurae) of modern birds. The sediments on which the fossil was laid were estimated to be 66.8 million years old, from the Late Cretaceous. The researchers concluded: "This fossil is the youngest non-neornithine (= non-modern) bird known to date from anywhere in the world–it was collected just 40 m below (equivalent to about 800,000 years before) the K-T boundary."[2]

The fossil was donated by Dortangs to the Natuurhistorisch Museum Maastricht (Maastricht Natural History Museum) in Maastricht, the Netherlands, from where it was sent to Daniel J. Field's team at the University of Cambridge in 2018.[7] Field's PhD student, Juan Benito, was assigned for the analysis.[8] Hoping that a CT scan could give the parts remaining in the rocks, he made a series of observations, but was disappointed. All he could see was "just a bunch of vertebrae and rib."[9] Two years later, Benito, then a post-doctoral scholar, re-examined the specimen. Field's team subsequently made more elaborate CT scans and came to the conclusion that the specimen was of an ancient bird species not known to science. They published a new description in Nature in 2022, giving it the name Janavis finalidens.[10] The genus name was derived from the Roman god Janus, the god of beginnings and endings, and the Latin word avis for bird; the specific name from the Latin finalis, meaning ending or final, and dens, for tooth, reflecting that the specimen is among the latest-known toothed birds.[3]

Description

Janavis is a relatively large bird, with an estimated wingspan of about five feet. The humerus has a length of 134.8 millimeters compared to 71.5 millimeters for the largest known Ichthyornis upper arm bone, specimen YPM 1742. Extrapolation from the humerus shaft circumference results in a weight estimate for Janavis of 1504 grammes. Extrapolation from the humerus length indicates 1604 grammes but was deemed less reliable as this element is broken in the fossil. The minimal weight estimate is 1120 grammes.[3]

Apart from its size, Janavis can be distinguished from all other known

pneumatisation of the dorsal vertebrae and ribs, especially by the presence of large pneumatic openings in the underside of the front thoracic vertebrae and paired fenestrated tubercles on the lower outer edge of the fifteenth presacral vertebra. The shoulder blade lacks an acromion. This is shared with some modern euornithean groups but these are all much more derived.[3]

The pterygoid is not fused to the

plesiomorphy inherited from the most basal birds.[3]

References

  1. ^ Davis, Nicola (2022-11-30). "CT scans of toothed bird fossil leads to jaw-dropping discovery". The Guardian. Retrieved 2022-12-07.
  2. ^
    S2CID 2704882
    .
  3. ^
    S2CID 254099216
    .
  4. ^ Davis, Nicola (2020-03-18). "'Wonderchicken': oldest fossil of modern bird discovered". The Guardian. Retrieved 2022-12-07.
  5. ^ "Cambridge University: Fossil overturns knowledge about origin of birds". BBC News. 2022-11-30. Retrieved 2022-12-07.
  6. doi:10.1126/science.adg0662
    .
  7. ^ Cockburn, Harry (2022-12-01). "Fossil 'overturns more than a century of knowledge' about evolution of birds". The Independent. Retrieved 2022-12-08.
  8. ^ Collins, Sarah (2022-11-30). "Bird beak evolved before end of dinosaurs, fossil reveals". University of Cambridge. Retrieved 2022-12-08.
  9. ^ Lesté-Lasserre, Christa (2022-11-30). "Ancient bird with a movable beak rewrites the story of avian evolution". New Scientist. Retrieved 2022-12-08.
  10. S2CID 254124520
    .
Retrieved from "https://en.wikipedia.org/w/index.php?title=Janavis&oldid=1220377151"