Letter | Published:

New subclass of birds from the Cretaceous of South America

Nature volume 292, pages 5153 (02 July 1981) | Download Citation



Current classification of birds recognizes three subclasses which are morphologically distinct: the Archaeornithes for Archaeopteryx, the Odontornithes for the Hesperornithiformes and the Ichthyornithiformes, and the Neornithes for all modern birds and their extinct immediate relatives. (Some authorities1 prefer different names for some of these taxa.) I have examined new material recently discovered in the Upper Cretaceous rocks of Argentina which indicates the existence of a group of birds having features so different from those of the currently recognized subclasses that they seem to represent a fourth subclass, here named the Enantiornithes (‘opposite birds’). I describe unique features of the Enantiornithes which include a reduced outer metatarsal, in some forms an extreme modification of the remaining elements of the tarsometatarsus, a highly modified pectoral girdle, and sometimes a characteristic perforation in the proximal end of the humerus.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1.

    Bull. Fla St. Mus. biol. Sci. 7, 180 (1963).

  2. 2.

    & Mém. Soc. Géol. Fr. 139, 19–28 (1980).

  3. 3.

    Smithsonian Contr. Palaeobiol. 27, 1–21 (1976).

  4. 4.

    Smithsonian Contr. Palaeobiol. 27, 67–73 (1976).

  5. 5.

    & Zool. J. Linn. Soc. 69, 149–182 (1980).

Download references

Author information


  1. Department of Palaeontology, British Museum (Natural History), Cromwell Rd, London SW7 5BD, UK

    • C. A. Walker


  1. Search for C. A. Walker in:

About this article

Publication history






Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.