Presbyornithidae - Systematics

Systematics

Three genera are unequivocally accepted to belong to the Presbyornithidae:

• Presbyornis
• Headonornis
• Telmabates

There is one species generally accepted in Headonornis and Telmabates each. Presbyornis contains 2 or 3 described species. The genus Nautilornis is today considered a synonym of Presbyornis, which is found in a wide range of Late Paleocene to Early Oligocene deposits in North America and Europe. Additionally, most of the bones referred to Headonornis have been found to belong to Presbyornis, and the remaining coracoid may do so too. Telmabates lived in today's Patagonia during the Eocene.

Apart from these unequivocal presbyornithids, there are some genera which are tentatively assigned to this family pending the discovery of more complete material. As many fossils from the Early Palaeogene show somewhat ambiguous characters, it is not easy to place these early modern birds unequivocally into one lineage or another. That they were ecologically generalized and are usually known from very few fossil remains only serves to worsen this situation.

Possible genera of presbyornithids include:

• Teviornis
• Proherodius
• Zhylgaia

of which the first is known from Late Cretaceous deposits in Mongolia, the second latter from the Early Eocene of England, and the third is an enigmatic Late Cretaceous or Paleogene form from Central Asia. There are some other, undescribed, presbyornithid or possible presbyornithid remains, such as the partial right scapula BMNH PAL 4989, which was considered part of Headonornis hantoniensis, but cannot be positively refererred to a known taxon, or the Early Cretaceous remains from the Mongolian Barun Goyot Formation at Uday Sayr and the Nemegt Formation of Tsagaan Kushu.

Vegavis from the Late Cretaceous of Antarctica was in all likelihood not a presbyornithid, but rather about equally close to these and the living ducks, geese and swans.