A remarkable diversity of waterfowl (Aves: Anseriformes) from the upper Eocene and lower Oligocene of Kazakhstan

ABSTRACT

Evolutionarily advanced waterfowl (the modern family Anatidae and its stem members in the order Anseriformes) are a successful bird group, well represented in faunas globally since the late Oligocene. However, the pre-late Oligocene history of the evolutionary lineage of Anatidae remains largely unexplored, as these birds are very rare in earlier faunas. This paper describes a remarkable diversity of waterfowl from the lower Oligocene of Kazakhstan (Central Asia), which includes two members of Anatidae, as well as stem-anatids referred to Romainvilliidae and Paranyrocidae. The latter family is represented by the enigmatic swan-sized Cygnopterus, the genus revised here, with new materials confirming its ordinal and familiar assignment. Anatidae are represented by the globally oldest diagnosable taxa for this family, including species in the fossil genus Mionetta, previously known from upper Oligocene–Middle Miocene strata. The paper further addresses two upper Eocene anseriform taxa from Kazakhstan. These data show that diverse assemblages of advanced anseriforms existed in Asia as early as early Oligocene. The presence of several stem-anatid taxa in the late Eocene faunas of Central Asia supports the hypothesis of a possible Eurasian (or Northern Continents) origin of Anatidae, although the subsequent diversification of the group could have occurred in the Australian region.

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the author(s).

ACKNOWLEDGMENTS

The author thanks T. W. Worthy, an anonymous reviewer and the editor V. L. De Pietri for valuable comments on the earlier version of the manuscript. This work was supported by the Russian Science Foundation, https://rscf.ru/en/project/24-24-00470/.

DATA AVAILABILITY STATEMENT

The author confirms that the data supporting the findings of this study are available within the article.