Accipitridae, Vigors, 1824

Watanabe, Junya, Matsuoka, Hiroshige & Hasegawa, Yoshikazu, 2018, Pleistocene non-passeriform landbirds from Shiriya, northeast Japan, Acta Palaeontologica Polonica 63 (3), pp. 469-491 : 483-484

Accipitridae gen. et sp. indet.

Fig. 10 .

1988 Buteo buteo ( Linnaeus, 1758) ; Hasegawa et al. 1988: pl. 7: 6.

Material.—Loc. 3, Shiriya, Aomori Prefecture, Japan; Late Pleistocene (~ MIS 5e): NSMT PV 19003, right femoral shaft; NSMT PV 24598, terminal phalanx of pedal digit (right second?). Locality unrecorded, Shiriya, Aomori Prefecture, Japan; Middle–Late Pleistocene (~ MIS 9/5e): NSMT PV 24599, left distal ulna.

Measurements.—See Table 5; no formal measurement was possible for the pedal phalanx.

Description.—One moderately worn distal ulna was recovered ( Fig. 10B ). In the fossil, the proximal margin of the trochlea carpalis is strongly elevated from the shaft, agreeing with Nisaetus , Kaupifalco , Melierax , Circus , Accipiter , and Buteo (and perhaps with Butastur , to a lesser extent). Concerning these genera, the fossil differs from Melierax in a proximally elongated trochlea carpalis, from Kaupifalco and Accipiter in the absence of a deep fossa ventral to the trochlea carpalis. In addition, the ulna of Accipiter differs in a long, sharp, and longitudinally oriented tip of the tuberculum carpale. Therefore, the fossil probably represents a species of Nisaetus , Circus , or Buteo , but further identification does not seem feasible.

One fragmentary shaft of the femur preserving a foramen pneumaticum ( Fig. 10A ) and one terminal pedal phalanx, probably of the right second toe ( Fig. 10C ), were recovered. The only notable feature of these fossils is the presence of a depression just proximal to the foramen pneumaticum medial to the crista trochanteris of the femur ( Fig. 10A ). This feature is observed in Macheiramphus , Kaupifalco , Melierax , Circus , and Buteo .

Remarks.—It is obvious that the three specimens represent one or more species much smaller than Haliaeetus sp. described above. Although the femur, NSMT PV 19003, was figured as Buteo buteo by Hasegawa et al. (1988), it is too fragmentary and not diagnostic enough to allow identification to the generic level. Even assuming that the ulna and femur represent the same species, they may possibly represent either Circus or Buteo , each of which includes several modern species distributed on the central Japanese islands today. Therefore, it seems reasonable to retract the record of B. buteo from the Shiriya local fauna.

Figures

Fig. 10. Accipitridae gen. et sp. indet. from the upper Pleistocene of Shiriya, Japan. A. NSMT PV 19003, left femur in cranial (A1) and lateral A2) views. B. NSMT PV 24599, left ulna in craniodorsal (B1) and ventral B2) views. C. NSMT PV 24598, terminal phalanx of (right second?) pedal digit in lateral (C1) and medial (C2) views. Fossils coated with ammonium chloride. Scale bar 10 mm. Abbreviation: d, depression proximal to foramen pneumaticum (see text).