Asteriornis maastrichtensis

from Wikipedia, the free encyclopedia
Asteriornis maastrichtensis
Temporal occurrence
Maastrichtium (Upper Cretaceous)
66.8 to 66.9 million years
Locations
Systematics
Birds (aves)
Neornithes
New-jawed birds (Neognathae)
Pangalloanserae
Genre : Asterioris
Type : Asteriornis maastrichtensis
Scientific name of the  genus
Asterioris
Field , Benito , Chen , Jagt & Ksepka 2020
Scientific name of the  species
Asteriornis maastrichtensis
Field et al. 2020

Asteriornis maastrichtensis is one of the oldest known birds from their crown group , the Neornithes . Asteriornis maastrichtensis shows a previously undocumented combination of the characteristics of hen birds (Galliformes) and geese birds (Anseriformes). The fossil record is of great value to the history of the evolution of birds and closes a knowledge gap on the evolution of birds. The occurrence of Asteriornis maastrichtensis in the northern hemisphere callsinto questionthe hypotheses of a Gondwanian origin of the crown group birds, until the discovery it was assumed that modern birds have developed in the southern hemisphere.

features

Asteriornis maastrichtensis is a small species of the Pangalloanserae with an estimated body weight of 394 g, derived from the length of the hind legs. Most of the important skull components are in their original anatomical position. In general, the premaxillary part of the upper beak resembles the recent Galliformes , in particular the slightly downwardly curved tip and the delicate construction without ossified connections between the rostral parts. The tip of the beak is hookless , which distinguishes Asteriornis from most Galloanserae with the exception of certain ducks and Presbyornithidae .

Find and location

The fossil comes from the find layer of the Maastricht Formation, which is around 66.8 to 66.7 million years old. This is roughly the time that dinosaurs and numerous other groups of living things became extinct. The almost complete skull and associated postcranial parts including the incomplete femur , tibiotarsus , tarsometatarsus and radius have been preserved . It is one of the few fossils of the Vogel Crown Group from the Mesozoic Era and the first of the Vogel Crown Group with a well-preserved skull. The ratio of tibiotarsus length (lower leg) plus tarsometatarsus length (barrel bone) to femur (thigh bone) exceeds that of most tree-dwelling birds. The tarsometatarsus and tibiotarsus suggest that they were originally longer than the preserved parts, so that the "hind leg index" falls within the range of variation of long-legged ground birds.

The location of the holotype ( Natuurhistorisch Museum Maastricht (NHMM) 2013 008) is the Cimenterie Belge Réunie (CBR) -Romontbos quarry ( outcrop 61H-45) west of Eben-Emael, Province of Liège , Belgium. The finds were located directly above the contact between the uppermost Lanaye subformation (member) of the Gulpen Formation and the Valkenburg subformation of the Maastricht Formation above. They were preserved in a matrix of comparatively fine-grain, soft, light yellow biocalcarenite with a low macrofossil content, which corresponds to the typical lithology of the lower part of the Maastricht Formation (Valkenburg and Gronsveld subformation).

etymology

Asteriornis refers to the titanide Asteria and the Greek word for bird, ornis . In Greek mythology , Asteria is the goddess of shooting stars , a reference to the meteorite impact on the Cretaceous-Paleogene border . She transformed into a quail , a chicken bird , which reflects the relationship between Asteriornis and the Galloanserae . The additional species maastrichtensis refers to the origin of the holotype , the Maastricht formation.

Individual evidence

  1. ↑ a b c d Daniel J. Field, Juan Benito, Albert Chen, John WM Jagt, Daniel T. Ksepka: Late Cretaceous neornithine from Europe illuminates the origins of crown birds. In: Nature 579, 2020, pp. 397-401. doi: 10.1038 / s41586-020-2096-0
  2. ^ A b Daniel J. Field, Juan Benito, Albert Chen, John WM Jagt, Daniel T. Ksepka: Supplementary information - Late Cretaceous neornithine from Europe illuminates the origins of crown birds. In: Nature , pp. 14-15. ( Online )

Web links