comparable, its proximal end resembles the proximal ulna of Argornis caucasicus. As in the latter, the olecranon is more strongly developed than in Aegial- ornis and recent Hemiprocnidae (HLMD Be 163, right side). In recent Apodidae, the olecranon is pro- nounced in Apodinae and Chaeturinae but short in the Cypseloidinae (Collins 1976). As in Jungornis, Argornis and recent Trochilidae, the ventro-proximal edge of the cotyla ventralis is weakly pronounced (HLMD Be 163, right side), and the tuberculum ligamenti collateralis ventralis very large (in recent swifts it is distinctly smaller).
The carpometacarpus (Fig. 6) resembles that of Argornis caucasicus too, but is somewhat shorter than the humerus (in Argornis it is slightly longer). The processus extensorius strongly protrudes craniad. The os metacarpale minus runs parallel to the os metacarpale majus.
The phalanx digiti alulae lacks a claw, which is present in recent Apodidae but absent in the Hemiprocnidae.As in most recent swifts but contrary to Argornis, the phalanx proximalis digiti majoris is not fenestrated, and like in all other swift-like birds it bears a well-developed processus internus indicis (terminology after Stegmann 1963). On both sides of the skeleton, the distal part of the phalanx distalis digiti majoris is strongly deflected. I consider this peculiar morphology to be of taphonomic origin, otherwise it would distinguish Parargornis from all other avian taxa (in Argornis, this phalanx is straight).
The pelvis is poorly preserved but appears to have had similar proportions to that of recent swifts. As in the latter, the alae ischii are very narrow.
Details of the femur cannot be discerned. The tibiotarsus is long and slender, much longer than in Scaniacypselus szarskii. The condyli are small and of similar size, the incisura intercondylaris is wide.The trochlea cartilaginis tibialis is not as deeply grooved as in recent Hemiprocnidae and Apodinae; in the Cypseloidinae as well as in the Aegialornithidae it is also shallow.
The tarsometatarsus has similar proportions to that of the Aegialornithidae, in most recent Apodi- formes it is more abbreviated.The hypotarsus exhib- its three cristae of similar height, whereas in most recent Apodidae only a crista medialis is present. The foramen vasculare distale appears to have been rather small. Concerning the morphology of its distal end, the bone most closely resembles the tarsometa- tarsus of recent Hemiprocnidae. As in the latter, the trochlea metatarsi II is very large and strongly
A new Eocene swift-like bird
protrudes medially. The trochlea metatarsi III is small and medio-laterally narrow.
The toes (Fig. 7) are fairly long, the third toe is the longest and exceeds the tarsometatarsus in length. The pedal phalanges have the usual number, as in recent Hemiprocnidae, the three proximal phalanges of the fourth toe are somewhat shorter than the fourth phalanx. In some recent Apodidae (e.g. Apus, Panyptila and Cypsiurus), the proximal pedal phalanges of the three anterior toes are greatly abbreviated, and the most proximal phalanges of the third and fourth toe are completely reduced.The hallux is of similar length to that of recent Hemi- procnidae. The claws of the three anterior toes are robust, only slightly curved and resemble those of recent Hemiprocnidae, too. As in the latter, but con- trary to recent Apodidae, the tubercula flexoria are weakly developed. The claw of the hallux is longer and more straight than those of the anterior toes.
The specimen exhibits well-preserved feather remains (Fig. 8), and even the barbulae can be dis- cerned. Whereas all recent swifts have very long, narrow and pointed wings, those of Parargornis are short, broad and rounded. In hummingbirds also the wing is very short, but much narrower than in Parar- gornis and pointed, too. The approximate length of the four outermost primaries is as follows (the length of the primaries of the equally sized ‘Messel-swift’ Scaniacypselus szarskii is given in parentheses): ?P10: ~25 (~74); ?P9: ∼37 (~72); ?P8: ∼43 (~72); ?P7: ∼45 (~62); the innermost (?) primary (?P1) measures ∼46 (~31). Hence contrary to what is seen in recent swifts and hummingbirds, in Parargornis the outer- most primaries are shorter than the proximally adja- cent ones. Furthermore, the primaries of Parargornis are only slightly asymmetric, and the secondaries are distinctly longer than in recent swifts and hummingbirds. Wing coverts are preserved on the left wing of HLMD Be 193 and measure about 15 mm.
Two long, broad and fairly symmetric tail feathers are preserved which measure about 65 mm. A third one is situated between these feathers and is about 35 mm long. Apart from these three feathers, only a fourth, growing tail feather can be discerned, which might indicate that the specimen is a moulting individual. In all recent swifts with elongated tail feathers (Panyptila, Hemiprocne), these are narrow and tapering, not broad and symmetric as in Parargornis. A similar tail (at least in shape) is, however, found among some recent hummingbirds (Lesbia nuna, Sappho sparganura).
© 2003 British Ornithologists’ Union, Ibis, 145, 382–391