Hesperornithiformes
| Hesperornithiformes | ||||||||||
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Skeletal reconstruction of Hesperornis regalis |
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| Temporal occurrence | ||||||||||
| Cretaceous period | ||||||||||
| 100 to 66 million years | ||||||||||
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| Systematics | ||||||||||
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| Scientific name | ||||||||||
| Hesperornithiformes | ||||||||||
| Sharpe , 1899 |
The Hesperornithiformes are a group of toothed flightless diving birds whose fossils are found in sedimentary rocks of the Cretaceous Period in North America , Eurasia and Antarctica .
The oldest of the known genera is Enaliornis from the Lower Cretaceous ( Albium ) of Cambridge Greensand near Cambridge . The majority of the species lived in the Upper Cretaceous. Hesperornis has been found in marine deposits in western North America from the Coniacium to the Campan and is thus the longest-lived of the previously discovered genera of the Hesperornithiformes. In Maastricht , at the end of the Chalk, the group died out.
As diving birds that swam with their legs, Enaliornis , Hesperornis, and Baptornis had rudimentary wings. In Hesperornis the forelimbs consisted only of a splint-like upper arm . Some smaller species of the Hesperornithiformes, which reached the size of cormorants , were possibly still able to fly. On land, hesperornithiform birds, like the recent loons, are likely to have been rather clumsy. There are finds from estuarine and continental deposits that show that they inhabited not only marine but also other aquatic habitats.
The largest known representatives to date belong to the species Canadaga arctica, described in 1999 . They could reach lengths of over 1.5 meters.
Family relationships
The representatives of the Hesperornithiformes, like many other birds of the Cretaceous period, had rows of simple, sharp teeth in their beak, which were suitable, for example, for grasping fish prey. Marsh described Ichthyornis and Hesperornis from the Niobrara Formation as members of the group Odontornithes ("chalk toothed birds") in 1880 . However, it turned out that the seagull-like Ichthyornithiformes are more closely related to the modern birds ( Neornithes ) than to the Hesperornithiformes.
| Aves ("Avialae" after Fastovsky and Weishampel 2005) |
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(Cladogram simplified based on Zhou 2004, within the Hesperornithiformes according to Martin 1984, see Feduccia 1999)
Familys
literature
- Alan Feduccia : The Origin and Evolution of the Birds. 2nd Edition. Yale University Press, New Haven / London 1999, ISBN 0-300-07861-7 .
- Peter M. Galton, Larry D. Martin: Enaliornis, an Early Cretaceous Hesperornithiform Bird from England, with Comments on Other Hesperornithiformes. In: Luis M. Chiappe, Lawrence M. Witmer: Mesozoic Birds: Above the Heads of the Dinosaurs. University of California Press, Berkeley / Los Angeles / London 2002, ISBN 0-520-20094-2 , pp. 317-338.
