The oldest diving anseriform bird from the late Eocene of Kazakhstan and the evolution of aquatic adaptations in the intertarsal joint of waterfowl

A specialized diving lifestyle has repeatedly evolved in several lineages of modern and fossil waterfowl (Anseriformes), with the oldest previously known representative being the late Oligocene Australian oxyurine ducks Pinpanetta. However, diving specializations have never been previously documente...

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Main Author: Nikita Zelenkov
Format: Article
Language:English
Published: Institute of Paleobiology PAS 2020-12-01
Series:Acta Palaeontologica Polonica
Subjects:
Online Access:http://www.app.pan.pl/archive/published/app65/app007642020.pdf
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author Nikita Zelenkov
author_facet Nikita Zelenkov
author_sort Nikita Zelenkov
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description A specialized diving lifestyle has repeatedly evolved in several lineages of modern and fossil waterfowl (Anseriformes), with the oldest previously known representative being the late Oligocene Australian oxyurine ducks Pinpanetta. However, diving specializations have never been previously documented for any of the primitive Paleogene anseriforms ( “stem-anatids”), and thus may be associated with the origin of modern anatid-like body plan. Here I describe a tarsometatarsus of a new duck-sized diving anseriform bird from the latest Eocene (late Priabonian) Kusto Svita in Eastern Kazakhstan, which predates the previously reported occurrence of diving specialization in Anseriformes by at least 6 MA. The new taxon Cousteauvia kustovia gen. et sp. nov. has an unusual and previously undocumented morphology, but partly resembles the stem-anatids Paranyrocidae and Romainvilliidae, thus representing the first known occurrence of diving adaptations in primitive non-anatid anseriforms. The evolutionary appearance of specialized waterfowl taxa in the late Eocene of Central Asia supports a view that this region might have played an important role in the evolution of morphologically derived Anseriformes. The structure of the intertarsal joint in basal and modern anseriforms is here further discussed in relation with adaptations for aquatic locomotion. The presence of elongate and evenly narrow condyles of the tibiotarsus in Anatidae and other swimming/diving birds allows a firm contact with the hyperprotracted tarsometatarsus at the initial phase of the propulsion. This morphology contrasts with the restricted condyles of Presbyornithidae, which indicate a different, strictly wading locomotory specialization. Cousteauvia obviously evolved diving specializations on the basis of a more primitive structure of the intertarsal joint.
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spelling doaj.art-c185281bab5249989fe46eda4f5507132022-12-21T21:33:19ZengInstitute of Paleobiology PASActa Palaeontologica Polonica0567-79201732-24212020-12-0165473374210.4202/app.00764.2020The oldest diving anseriform bird from the late Eocene of Kazakhstan and the evolution of aquatic adaptations in the intertarsal joint of waterfowlNikita Zelenkov0Borissiak Paleontological institute of Russian Academy of Sciences, Profsoyuznaya 123, Moscow, RussiaA specialized diving lifestyle has repeatedly evolved in several lineages of modern and fossil waterfowl (Anseriformes), with the oldest previously known representative being the late Oligocene Australian oxyurine ducks Pinpanetta. However, diving specializations have never been previously documented for any of the primitive Paleogene anseriforms ( “stem-anatids”), and thus may be associated with the origin of modern anatid-like body plan. Here I describe a tarsometatarsus of a new duck-sized diving anseriform bird from the latest Eocene (late Priabonian) Kusto Svita in Eastern Kazakhstan, which predates the previously reported occurrence of diving specialization in Anseriformes by at least 6 MA. The new taxon Cousteauvia kustovia gen. et sp. nov. has an unusual and previously undocumented morphology, but partly resembles the stem-anatids Paranyrocidae and Romainvilliidae, thus representing the first known occurrence of diving adaptations in primitive non-anatid anseriforms. The evolutionary appearance of specialized waterfowl taxa in the late Eocene of Central Asia supports a view that this region might have played an important role in the evolution of morphologically derived Anseriformes. The structure of the intertarsal joint in basal and modern anseriforms is here further discussed in relation with adaptations for aquatic locomotion. The presence of elongate and evenly narrow condyles of the tibiotarsus in Anatidae and other swimming/diving birds allows a firm contact with the hyperprotracted tarsometatarsus at the initial phase of the propulsion. This morphology contrasts with the restricted condyles of Presbyornithidae, which indicate a different, strictly wading locomotory specialization. Cousteauvia obviously evolved diving specializations on the basis of a more primitive structure of the intertarsal joint.http://www.app.pan.pl/archive/published/app65/app007642020.pdfavesanseriformesdivingevolutionintertarsal jointeocenekazakhstancentral asia
spellingShingle Nikita Zelenkov
The oldest diving anseriform bird from the late Eocene of Kazakhstan and the evolution of aquatic adaptations in the intertarsal joint of waterfowl
Acta Palaeontologica Polonica
aves
anseriformes
diving
evolution
intertarsal joint
eocene
kazakhstan
central asia
title The oldest diving anseriform bird from the late Eocene of Kazakhstan and the evolution of aquatic adaptations in the intertarsal joint of waterfowl
title_full The oldest diving anseriform bird from the late Eocene of Kazakhstan and the evolution of aquatic adaptations in the intertarsal joint of waterfowl
title_fullStr The oldest diving anseriform bird from the late Eocene of Kazakhstan and the evolution of aquatic adaptations in the intertarsal joint of waterfowl
title_full_unstemmed The oldest diving anseriform bird from the late Eocene of Kazakhstan and the evolution of aquatic adaptations in the intertarsal joint of waterfowl
title_short The oldest diving anseriform bird from the late Eocene of Kazakhstan and the evolution of aquatic adaptations in the intertarsal joint of waterfowl
title_sort oldest diving anseriform bird from the late eocene of kazakhstan and the evolution of aquatic adaptations in the intertarsal joint of waterfowl
topic aves
anseriformes
diving
evolution
intertarsal joint
eocene
kazakhstan
central asia
url http://www.app.pan.pl/archive/published/app65/app007642020.pdf
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