Apus sp.

Watanabe, Junya, Matsuoka, Hiroshige & Hasegawa, Yoshikazu, 2018, Pleistocene non-passeriform landbirds from Shiriya, northeast Japan, Acta Palaeontologica Polonica 63 (3), pp. 469-491 : 476-478

Apus sp.

Fig. 6A, C, D .

Material.—Loc. 3, Shiriya, Aomori Prefecture, Japan; Late Pleistocene (~MIS 5e): NSMT PV 24548, left coracoid; NSMT PV 24549, left carpometacarpus; NSMT PV 24550, proximal phalanx of right major wing digit.

Measurements.—See Table 3 and Fig. 7.

Description.—One left coracoid with a worn angulus lateralis was recovered ( Fig. 6A ). The fossil differs from the members of Cypseloidinae ( Streptoprocne and Cypseloides ) in the narrowness of a notch on the dorsal part of the sternal margin of the tuberculum brachiale (the notch being dorsoventrally broad and often deep in Cypseloidinae ). It differs from Collocaliini ( Collocalia and Aerodramus ) and agrees with Apodini ( Aeronautes , Tachornis , Cypsiurus , Tachymarptis , and Apus ) and to a lesser extent with Chaeturini ( Hirundapus and Chaetura ) in an elongated and slit-like medioventral opening of the foramen n. supracoracoidei (which is omo-sternally narrower in Collocaliini ). It also differs from Chaeturini in the absence of a strong constriction of the neck (in Chaeturini, the neck is constricted and the processus acrocoracoideus is slanted medially). Within Apodini, the fossil agrees with Tachornis , Tachymarptis , and Apus and differs from Aeronautes , Panyptila , and Cypsiurus in a relatively omal position of the dorsal opening of the foramen n. supracoracoidei (which is distinctly offset sternally from the omal margin of the processus supracoracoidei in the latter genera). The fossil has a characteristic profile of the sternal articulation surface, where the medioventral margin is strongly produced, the dorsal flange is lying rather medially ( Fig. 6B 2 ), and the dorsolateral margin is strongly concave. This condition is apparently unique to Tachymarptis and Apus within Apodidae . The single coracoid of Tachymarptis examined ( T. melba, USNM 559068) is distinct from the fossil in the presence of a prominent ridge on the ventral margin of the shaft leading from the lateral part of the sternal end to the ventral margin of the sulcus supracoracoideus. The fossil is indistinguishable from A. apus and A. pacificus in both dimensions and qualitative characters.

One complete left carpometacarpus was recovered ( Fig. 6C ). The fossil differs from Cypseloidinae in a cranially lying sulcus tendinosus in dorsal view ( Fig. 6C 2 , B 3 ); which is lying on the caudal half of the distal shaft in Cypseloidinae ) and the absence of a constriction of the distal shaft of the os metacarpale minor (the constriction is present around the distal one-fifth in Cypseloidinae ). It differs from Collocaliini and Chaeturini and agrees with Apodini in a strong expansion of the os metacarpi minor near the distal symphysis. Collocaliini further differ in a deeper distal part of the fossa supratrochlearis, and Hirundapus differs in a cranially positioned processus pisiformis. Within Apodini, the fossil agrees with Tachymarptis and Apus in a relatively small processus alularis whose proximal margin is not slanted proximally. The fossil carpometacarpus is consistent in size with the coracoid described above, thus is referred to the same species with it.

A distal phalanx of the major wing digit lacking the distal articular surface was recovered ( Fig. 6D ). Although relatively few taxonomically useful characters were detected for this element, the fossil differs from Streptoprocne in the absence of a strong convexity on the cranial surface of the proximal shaft, from Cypseloides in the absence of a prominent swell on the middle part on the cranial surface, from Aerodramus in the absence of a strong constriction at the base of the distal extension of the caudal margin, from Chaeturini on one hand and Aeronautes , Tachornis , and Panyptila on the other in a moderately developed depression on the ventral surface (which is deeper and narrower in the former group and shallower in the latter), and from most genera of the family except Hirundapus , Tachymarptis , and Apus in the broadness of the tip of the distal extension of the caudal margin. Therefore, the fossil is consistent only with Tachymarptis and Apus among the genera compared. Its size is consistent with the carpometacarpus described above.

Remarks.—The genus Apus is distributed throughout the OldWorld(chieflyinAfrica),andincludesc.15modernspecies. Although recent authors tend to separate Tachymarptis from it ( Päckert et al. 2012; Dickinson and Remsen 2013; del Hoyo and Collar 2014), there seems to be relatively few osteological differences between the two genera, as far as concerning the elements known for the Shiriya material (but see the feature of the coracoid mentioned above).

Only two species of the genus occur on Japanese islands today: A. pacificus and A. nipalensis . The Shiriya material is larger than the latter species and consistent in size with the former ( Table 3; Fig. 7). However, the fossils cannot be distinguished from other modern species of the genus, including A. apus whose modern range spans over northern China.

The fossil record of Apodidae was reviewed by Mlíkovský (1989, 2002) and Boev (2000). Several extinct species/subspecies of Apus have been described from Neogene deposits in Europe. Apus wetmorei Ballmann, 1976 , and A. gaillardi ( Ennouchi, 1930) are known from the upper Miocene of Italy and France, respectively. The former species was described as a species in size of modern A. caffer , and the latter was estimated to be smaller than modern A. apus (according to dimensions given by Harrison 1984). Therefore, these species would be smaller than the species represented by the Shiriya material, although no elements are known in common.

Apus apus palapus Jánossy, 1974 , known from the Lower Pleistocene of Austria ( Jánossy 1974) and possibly of Hungary ( Jánossy 1978), is a temporal subspecies of A. apus which differs from the modern form in osteometric proportions. On its original description ( Jánossy 1974), it was only compared with modern A. apus and A. pallidus . As such, despite Jánossy’s (1974) conjecture, it is not certain if that subspecies can be osteologically differentiated from modern A. pacificus . Apus baranensis Jánossy, 1978 , is known from the upper Miocene–Lower Pleistocene of Hungary and Bulgaria ( Jánossy 1978; Boev 2000; Kessler 2010). Being smaller than A. affinis , it is unlikely to be represented by the Shiriya material (see also Fig. 7). Although A. baranensis was synonymized with A. wetmorei by Mlíkovský (2002) based on the putative similarity of size alone, this act has been doubted by Zelenkov (2017) who mentioned the actual difference in size. Apus submelba Jánossy, 1972 , known from several Middle–Late Pleistocene localities in Europe ( Jánossy 1972, 1978; Mourer-Chauviré1975; Tyrberg 2008a), is considered closely related to modern Tachymarptis (formerly Apus ) melba , and indeed has been considered synonymous with the modern species by Mlíkovský (2002). The species might be better moved to Tachymarptis , if it is a distinct species and that genus deserves separation from Apus . In any way, published dimensions ( Jánossy 1972) indicate that it was larger than the Shiriya material. Apart from these extinct forms, remains of modern species of the genus are known from numerous Quaternary localities throughout the Old World (e.g., Tyrberg 1998, 2008a; Harvati et al. 2013; Val 2016).

Figures

Fig. 6. Apodid bird Apus sp. from the upper Pleistocene of Shiriya, Japan (A, C, D), compared with Recent Apus pacificus (Latham, 1801) from Russia (B). A. NSMT PV 24548, left coracoids in ventral (A1) and dorsal (A2) views. B. UWBM 46958, left coracoid, in ventral (B1) and dorsal (B2) views; left carpometacarpus in dorsal view (B3); proximal phalanx of left major wing digit in dorsal view (B4). C. NSMT PV 24549, left carpometacarpus in ventral (C1) and dorsal (C2) views. D. NSMT PV 24550, proximal phalanx of right major wing digit in ventral (D1) and dorsal (D2) views. Fossils coated with ammonium chloride.

Fig. 2. Phasanid bird Syrmaticus sp. from the upper Pleistocene of Shiriya, Japan (A, B, E, F, H–L), compared with Recent Syrmaticus soemmerringii (Temminck, 1830) (C) and Recent Phasianus colchicus Linnaeus, 1758 (D). A. NSMT PV 24535, left humerus in cranial (A1) and caudal (A2) views. B. NSMT PV 24536, right humerus in cranial (B1) and caudal (B2) views. C. MVZ 49764, left humerus in caudal view (C1), left coracoid in dorsal (C2) and omal (C3) views, right carpometacarpus in dorsal view (C4). D. MVZ 68327, left humerus in caudal view (D1), left coracoid in dorsal (D2) and omal (D3) views. E, F. NSMT PV 24541 and NSMT PV 24542, respectively, right carpometacarpi in dorsal view. G. NSMT PV 24540, premaxilla in ventral (G1) and left lateral (G2) views. H. NSMT PV 24539, proximal phalanx of right major wing digit in dorsal (H1) and ventral (H2) views. I. Right ulnare (NSMT PV 24538), in distal (I1) and proximal (I2) views. J. Left coracoid (NSMT PV 24531), in ventral (J1), dorsal (J2), and omal (J3) views. K. Left coracoid (NSMT PV 24532), in ventral (K1) and dorsal (K2) views. Fossils coated with ammonium chloride.

Fig. 3. Bivariate scatter plots of Recent and fossil species of Syrmaticus: proximal (A) and distal (C) humeral, humeral shaft (B), and carpometacarpal (D) measurements.