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GERALD MAYR* Forschungsinstitut Senckenberg, Division of Ornithology, Senckenberganlage 25, D-60325 ... - page 2 / 10

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wing elements of a single specimen only. Scania- cypselus szarskii (Peters 1985) occurs in the Middle Eocene deposits of Messel, Germany (Peters 1985; Mayr & Peters 1999) and is represented by several articulated skeletons. There is also one specimen in which the feathering is excellently preserved (Mayr & Peters 1999). Like its recent relatives, S. szarskii had greatly elongated primaries; the tail was short and hardly forked.

MlíkovskY (1989) described an isolated tibiotarsus from the Quercy as a new species of the recent genus Cypseloides (Apodidae), C. mourerchauvireae. How- ever, the validity of this new taxon, let alone its assignment to Cypseloides, needs further confirma- tion. At least judging from the illustrations, the bone closely resembles the tibiotarsus of Aegialornis, with which it has not been compared in the original description (in size it corresponds to the tibiotarsus of A. gallicus; see Mourer-Chauviré 1988).

Other fossil Apodidae are known from Miocene deposits and were assigned to the Cypseloidinae (Collins 1976) and Apodinae (Ballmann 1976). Only the latter assignment, however, was supported by derived characters, and the similarity of lower Miocene swifts to the Cypseloidinae might well be plesiomorphic.

Among the most enigmatic taxa of swift-like birds are the members of the extinct family Jungornithi- dae. The first species assigned to this family was Jungornis tesselatus Karhu 1988 from the Lower Oligocene of the Northern Caucasus (Karhu 1988). Karhu (1988, 1992) noted several derived features in which Jungornis differs from recent swifts and corresponds with hummingbirds. Recently, Karhu (1999) described a second species of the Jungorni- thidae, Argornis caucasicus, from the Upper Eocene of the Northern Caucasus, which exhibits a less specialized wing morphology than J. tesselatus. Both Jungornis and Argornis are known only from wing elements of single specimens. An isolated coracoid from the Upper Eocene of the Quercy, which was assigned to Cypselavus gallicus by Mourer-Chauviré (1978), was described by Karhu (1988) as a new species of the Jungornithidae, Palescyvus escampensis (see Discussion below).

I herein describe a new apodiform bird from the Middle Eocene (49 million years ago) deposits of Messel (Hessen, Germany), which closely resembles Argornis caucasicus in skeletal morphology. In the new taxon the feathering is excellently preserved and strikingly different from that of recent swifts. It reveals that there was a high diversity among apodiform birds in the early Tertiary, and that the

A new Eocene swift-like bird

383

evolution of apodiform birds is more complicated than previously thought.

A survey of the fossil avifauna of Messel was given by Mayr (2000),and general information on the site can be found in Schaal and Ziegler (1988) and Mayr (2001).

MATERIAL AND METHODS

Dimensions are given in millimetres and refer to the greatest length along the longitudinal axis of the bone. For claws, the distance between the tuberculum extensorium and the apex phalangis was measured. The phalanges of the toes are numbered from the proximal to the distal, thus dI p2 means the distal (second) phalanx of the first toe. The wing area was measured following Pennycuick (1985, p. 223). If not indicated otherwise, the anatomical terminol- ogy follows Baumel and Witmer (1993). The fossil specimens are deposited in the Hessisches Landes- museum (HLMD), Darmstadt, Germany.

SYSTEMATIC PALAEONTOLOGY

Apodiformes Peters 1940 ?Jungornithidae (sensu Karhu 1999)

An assignment of the new taxon to the Apodi- formes is supported by the following characters, which I consider to be derived within neognathous birds: beak wide and very short, with a pointed tip and long narial openings; extremitas omalis of coracoid hooked; processus lateralis of coracoid strongly reduced; humerus greatly abbreviated and with large, ventrally protruding proximal end; manus longer than humerus; phalanx proximalis digiti majoris with distinct processus internus indicis; distal end of tibiotarsus with small condyli and wide incisura intercondylaris. A presumably plesiomor- phic feature shared with recent Apodiformes is the presence of a foramen nervi supracoracoidei, which is absent in most other ‘higher’ landbirds.

In overall morphology, the new taxon from Messel is very similar to Argornis; it shares the following combination of characters with this genus and with Jungornis: (1) humerus with very large and tapering crista deltopectoralis; (2) processus supracondylaris dorsalis (humerus) very small; (3) ventro-proximal edge of cotyla ventralis (ulna) weakly pronounced and tuberculum ligamenti collateralis ventralis very large; (4) facies articulares coracoidei (sternum) widely separated; (5) processus lateralis of coracoid protruding beyond the level of the angulus lateralis.

© 2003 British Ornithologists’ Union, Ibis, 145, 382–391

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