A new Eocene swift-like bird
The scapula bears a short acromion.As far as pres- ervation allows comparison, it resembles the scapula of Jungornis and Argornis.
Figure 6. Parargornis messelensis, holotype (HLMD Be 163), right wing in ventral view. Coated with ammonium chloride to enhance contrast; scale bar equals 10 mm.
The extremitas omalis of the furcula (HLMD Be 193, left side; Fig. 5) is of similar shape to that of Argornis. As in the latter genus and Jungornis, but contrary to recent Apodiformes, the transition between the scapus claviculae and the processus acromialis is not pronounced (see Karhu 1988: Fig. 5). The extremitas sternalis (HLMD Be 193) is slightly wider than in Argornis.
The sternum appears to have been of similar rela- tive length to that of Jungornis and recent Hemiproc- nidae, and is not as elongated as in Apodidae and Trochilidae. As preserved, the sternal ends of the coracoids are widely separated, which indicates that the facies articulares coracoidei of the sternum are also widely separated, as in Jungornis (in recent Apodiformes they are situated close together). As in Jungornis, the carina sterni is somewhat lower than in recent Apodiformes (the sternum of Argornis is too fragmentarily preserved to allow meaningful comparisons). The caudal margin of the sternum appears to bear a small incisura lateralis (HLMD Be 193, right side; HLMD Be 163, right side), whereas in recent Hemiprocnidae and Apodidae, as well as in recent hummingbirds, there are no incisions at all (although recent swifts often exhibit foramina in various parts of the corpus sterni). In Jungornis there is a fenestra lateralis.
The humerus of Parargornis messelensis (Figs 5 and 6) has similar proportions to that of Argornis cauca- sicus, Cypselavus gallicus and recent Hemiprocne lon- gipennis. It is less abbreviated than the corresponding bone of Jungornis, the Trochilidae, and recent and fossil Apodidae.The proximal end is large and strongly
Figure 7. Parargornis messelensis, holotype (HLMD Be 163), detail of the feet. The arrow indicates the large claw on the hind toe. Coated with ammonium chloride to enhance contrast; scale bar equals 10 mm.
© 2003 British Ornithologists’ Union, Ibis, 145, 382–391