Journal of Ornithology

, Volume 156, Issue 2, pp 441–450 | Cite as

Skeletal morphology of the middle Eocene swift Scaniacypselus and the evolutionary history of true swifts (Apodidae)

  • Gerald MayrEmail author
Original Article


New specimens of Scaniacypselus szarskii, a stem group representative of the Apodidae (true swifts) from the middle Eocene Messel oilshale in Germany, are described. These fossils show that Scaniacypselus differs from crown group Apodidae in a number of distinct and previously unrecognized osteological features. Notably, the sternum of Scaniacypselus is shorter than that of extant true swifts, the ulna proportionally longer, the carpometacarpus shorter, and the internal index process on the proximal phalanx of the major wing digit less developed. In details of its humerus morphology, Scaniacypselus is distinguished from all extant apodiform birds. Scaniacypselus further has a much shorter tarsometatarsus than most crown group Apodidae. It is hypothesized that short legs are plesiomorphic for Apodidae as a total group (stem group and crown group representatives), but that crown group Apodidae primitively have an elongated tarsometatarsus as an adaptation for clinging to vertical surfaces. The less specialized wing and pectoral girdle morphology suggests that Scaniacypselus was probably not as aerial as extant Apodidae. The differences in foot morphology indicate that it was more arboreal than its living relatives and had different breeding and roosting habits. Crown group Apodiformes probably diverged well after the middle Eocene, and the derived nesting behavior may have contributed to their evolutionary success.


Apodiformes Character evolution Fossil birds Messel Scaniacypselus szarskii 


Skelettmorphologie des mitteleozänen Seglers Scaniacypselus und die Evolutionsgeschichte echter Segler (Apodidae)

Es werden neue Fossilfunde von Scaniacypselus beschrieben, einem mitteleozänen Stammgruppenvertreter der Apodidae (Segler) aus Messel. Die neuen Belege zeigen, dass sich Scaniacypselus in einigen Skelettmerkmalen deutlich von heutigen Apodidae unterscheidet. Insbesondere ist das Brustbein von Scaniacypselus kürzer als das heutiger Segler, die Ulna länger, der Carpometacarpus kürzer und der Processus internus indicis der proximalen Phalanx des Hauptfingerstrahls des Flügels weniger stark entwickelt. In einigen Details der Morphologie des Humerus unterscheidet sich Scaniacypselus von allen rezenten apodiformen Vögeln. Der Tarsometatarsus von Scaniacypselus ist zudem viel kürzer als derjenige der meisten Kronengruppen-Vertreter der Apodidae. Vermutlich sind kurze Läufe plesiomorph für Pan-Apodidae (Stammgruppe und Kronengruppe), während eine Verlängerung des Tarsometatarsus primitiv für die Kronengruppe ist und eine Anpassung an das Klammern an vertikalen Oberflächen darstellt. Die weniger spezialisierte Flügelmorphologie von Scaniacypselus legt nahe, dass das Taxon weniger an das Leben in der Luft angepasst war als heutige Segler. Die Unterschiede in der Morphologie der Füße weisen darauf hin, dass Scaniacypselus in höherem Maße baumbewohnend war und von heutigen Seglern und Baumseglern abweichende Brut- und Ruhegewohnheiten hatte. Die Kronengruppenvertreter der Apodidae spalteten sich vermutlich erst weit nach dem mittleren Eozän ab, und das abgeleitete Brutverhalten dieser Vögel dürfte zu ihrem evolutionären Erfolg beigetragen haben.



I thank E. Brahm and S. Schaal for the loan of the fossils and S. Tränkner for taking the photographs. I am further indebted to C. Mourer-Chauviré and two anonymous reviewers for comments, which improved the manuscript.


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Copyright information

© Dt. Ornithologen-Gesellschaft e.V. 2014

Authors and Affiliations

  1. 1.Ornithological SectionSenckenberg Research Institute and Natural History Museum FrankfurtFrankfurt Am MainGermany

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