Haliaeetus sp.

Watanabe, Junya, Matsuoka, Hiroshige & Hasegawa, Yoshikazu, 2018, Pleistocene non-passeriform landbirds from Shiriya, northeast Japan, Acta Palaeontologica Polonica 63 (3), pp. 469-491 : 478-483

Haliaeetus sp.

Fig. 8A, D, E–R.

1988 Haliaeetus cf. pelagicus ( Pallas, 1811) ; Hasegawa et al. 1988: pl. 7: 13.

Material.—Loc. 1, Shiriya, Aomori Prefecture, Japan; Late Pleistocene (~ MIS 5e): NSMT PV 24554, right humeral shaft and NSMT PV 24555, terminal phalanx of left first toe (?). Loc. 2, Shiriya, Aomori Prefecture, Japan; middle Pleistocene (~ MIS 9): NSMT PV 24556, left coracoid without sternal end; NSMT PV 24557, sternal end of right coracoid; NSMT PV 24558, left distal humerus; NSMT PV 24559– 24561, right ulnar shafts; NSMT PV 24562, left distal ulna; NSMT PV 24563, 24564, left distal carpometacarpi; NSMT PV 24565, left alular phalanx; NSMT PV 24566, 24567, fragmentary right tibiotarsal shafts; NSMT PV 24568, right distal tibiotarsus, NSMT PV 24569–24580, terminal pedal phalanges. Loc. 3, Shiriya, Aomori Prefecture, Japan; Late Pleistocene (~ MIS 5e): NSMT PV 24581, incomplete cranium; NSMT PV 24582, right humeral shaft; NSMT PV 24583, right distal humerus; NSMT PV 24584,left proximal ulna; NSMT PV 24585, left distal radius; NSMT PV 24586, left ulnare; NSMT PV 24587, left femoral shaft; NSMT PV 19010, right distal tibiotarsus; NSMT PV 24588,terminal phalanx of right first toe (?). Locality unrecorded, Shiriya, Aomori Prefecture, Japan; Middle–Late Pleistocene (~ MIS 9/5e): NSMT PV 24589, left coracoidal shaft; NSMT PV 24590, 24591, left and right distal tibiotarsi, respectively; NSMT PV 24592–24597, terminal pedal phalanges.

Measurements.—See Table 4 and Fig. 9 .

Description.—One cranium preserving a part of the frontals, the dorsal margin of the foramen magnum, and both tympanic cavities was recovered ( Fig. 8A). In the fossil, there is only a shallow depression rostral to the tympanic cavity, ventral to the fossa temporalis, where a prominent excavation, from which the quadratic articulations are distinctly elevated, is present in most accipitrids ( Fig. 8A 3, B 3, C 3 ). This feature is apparently unique to Haliaeetus and Haliastur , as well as to some Gypaetinae ( Pernis , Aviceda , Polyboroides , and Gypaetus ). The crania in the latter group are much deeper dorsoventrally for its width (except Gypaetus ) and characterized by a narrower fossa temporalis. In addition, the fossil differs from some other large-bodied accipitrid genera, including Aquila and Aegypius , in weaker lateroventral extension of the cranial roof over the laterocaudal margin of the cotyla quadratica squamosi.

Three coracoidal shafts, the most complete one of which preserves the dorsal part of the processus acrocoracoideus and entire processus procoracoideus ( Fig. 8D, E), are referred to the same species as the cranium. The fossils have a stocky profile compared to most accipitrids, while lacking extensive pneumatization along the entire cranial margin of the sulcus supracoracoideus (which is seen in Gypini), agreeing with Harpia , Aquila , Haliastur , Milvus , Butastur , Haliaeetus , and Icthyophaga . Among those genera, the fossils differ from Harpia and Aquila and agree with the others in weak development of the sternal margin of the facies articularis clavicularis, which is developed as a prominent ridge on the medial surface of the processus acrocoracoideus in the former group ( Fig. 8B 4, C 4 ). The fossils differ from the coracoid of Butastur in having a single pneumatic fovea caudal to the dorsal tip of the tuberculum brachiale (whereas Butastur has a pair of foveae in the same position).

One moderately worn proximal part of the ulna, with the olecranon broken away, was recovered ( Fig. 8H). The shaft is relatively shallow craniocaudally, agreeing only with some species of Haliaeetus , including H. albicilla , H. leucocephalus , and H. pelagicus . Other qualitative features, including a strong constriction of the cotyla dorsalis in its ventral part (less apparent in, e.g., Harpia , Stephanoaetus , and Aquila ) and the lack of pneumatic foramina in the proximal end (foramina pneumatica are present caudal to the proximal articular surfaces and/or around the impressio m. brachialis in Gypini), are consistent with the assignment to Haliaeetus .

Two distal ends of carpometacarpi, one of which preserves the distal part of the os metacarpi minor near the distal symphysis, are referred to this species ( Fig. 8N). So far as observed in the better preserved specimen, the spatium intermetacarpale is craniocaudally narrow, as characteristically observed in Elanus , Kaupifalco , Butastur , and Haliaeetus ( Fig. 8B 9 , C 5 ). The fossils further differ from Gypini in the absence of foramina pneumatica at or around the distal symphysis.

Five distal ends of the tibiotarsus are referred to this species ( Fig. 8O, P). In the fossils, the sulcus extensorius is lying near the lateral margin of the distal shaft, and almost restricted to the lateral half of the bone, agreeing with Circus , Accipiter , Haliaeetus (except H. leucogaster ), Icthyophaga , and perhaps Aquila (the condition is less clear in the last genus; Fig. 8B 10 , C 6 ). Among these genera, the fossils differ from Circus , Accipiter , and Aquila and agree with Haliaeetus and Icthyophaga in weak proximal extension of the medial margin of the condylus medialis on the caudal surface; in the former group, the margin clearly extends past the proximal margin of the condyle on the cranial side ( Fig. 8C 7), whereas it fades more distally in the latter

D. NSMT PV 24556, left coracoid in medial (D 1), ventral (D 2), and dorsal (D 3) views. E. NSMT PV 24557, right coracoid in dorsal view. F, G. NSMT PV 24582 and NSMT PV 24558, respectively, right and left humeri in cranial view. H, I. NSMT PV 24584 and NSMT PV 24562, respectively, left ulnae in ventral (H 1, I 1), cranial (H 2), and dorsal (I 2) views. J. NSMT PV 24586, left ulnare in proximal (J 1) and distal (J 2) views. K. NSMT PV 24565, left alular phalanx in dorsal (K 1) and ventral (K 2) views. L. NSMT PV 24587, left femur in caudal (L 1) and cranial (L 2) views. M. NSMT PV 24585, left radius in caudal (M 1) and cranial (M 2) views. N. NSMT PV 24564, left carpometacarpus in dorsal (N 1) and ventral (N 2) views. O. NSMT PV 24591, right tibiotarsus in cranial view. P. NSMT PV 19010, left tibiotarsus in cranial (P 1) and caudal (P 2) views. Q, R. NSMT PV 24570 and NSMT PV 24571, respectively, terminal phalanges of right second and third pedal digits in medial view. Fossils coated with ammonium chloride. Abbreviations: cm, (proximal extent of the caudal margin of) condylus medialis; e, excavation rostral to the tympanic cavity (see text); fac, (sternal margin of) facies articularis clavicularis; se, sulcus extensorius; si, spatium intermetacarpale.

group ( Fig. 8B 11). The tibiotarsus of Aquila further differs in a much deeper incisura intercondylaris ( Fig. 8C 6 , C 7). The tibiotarsus of Icthyophaga differs in a distinctly deeper, wider sulcus extensorius.

Two shafts and two distal fragments of the humerus ( Fig. 8F, G), one distal end of the ulna ( Fig. 8I), three ulnar shafts, one distal end of the radius ( Fig. 8J), one complete ulnare ( Fig. 8J), one alular phalanx lacking the distal tip ( Fig. 8K), one distal shaft of the femur ( Fig. 8L), one basal phalanx of the third toe, and 19 terminal phalanges of various toes ( Fig. 8Q, R) are tentatively referred to this species based on their large size. Although the preserved parts carry little taxonomic information, some of these elements can be differentiated at least from other large accipitrids. In the fossil humerus, the proximal part of the condylus dorsalis does not possess a sharp, straight ventral margin (which is observed in Aegypius ). The fossil distal ulna, radius, ulnare, and alar phalanx differ from the corresponding elements of Gypini in the absence of extensive pneumatization. From Aquila , the radius differs in a ventrally positioned caudal knob of the distal articular surface, the ulnare does in strongly convex distal margin of the facies articularis ulnaris, the alular phalanx in a relatively proximal position of the tubercle on the ventrocaudal margin near the proximal end (in Aquila , the tubercle is elongated distally), and the femur in a more strongly developed impressio ansae m. iliofibularis near the proximal extent of the condylus lateralis.

Remarks.—The material examined here includes the specimen figured as H. cf. pelagicus ( NSMT PV 19010) by Hasegawa et al. (1988). The size variation within the material seems to be consistent with the presence of only one species, although the possibility that more species are represented cannot be ruled out. With 35 identifiable specimens, the species is the most common landbird species represented in the Shiriya material (minimum number of individuals being three for Loc. 2 and one for each of Locs. 1 and 3). As far as concerning the elements preserved, it was difficult to find unambiguous osteological features that allow assignment to certain clades within the family. Nevertheless, most elements of the Shiriya material could be differentiated from those of other large eagles, Aquila and Gypini, thus they most likely represent a sea eagle of the genus Haliaeetus . Three modern species of Haliaeetus occur on the central Japanese islands today ( The Ornithological Society of Japan 2012): H. albicilla , H. pelagicus , and H. leucocephalus (although the last species has only been recorded as an accidental visitor). Partly due to the small size of the comparative material, it is at best difficult to assign the material to any of these three species (see Fig. 9 ). Hence, it seems justified to leave the specific identification open rather than designating a particular species as was done by Hasegawa et al. (1988), pending further study.

The oldest putative records of the genus include a large accipitrid from the lower Oligocene of Egypt ( Accipitridae genus and species indeterminate, aff. Haliaeetus in Rasmussen et al. 1987) and Haliaeetus (?) sp. from the middle Miocene of Florida ( Becker 1987a, b), whose true affinities are difficult to evaluate from the evidences provided. Neogene records include H. piscator Milne-Edwards, 1871 , from the upper Miocene of France ( Milne-Edwards 1867 –1871), and H. fortis Kurochkin, 1985 , from the upper Miocene–lower Pliocene of Mongolia ( Kurochkin 1985; Zelenkov 2013). It should be noted that the placement of the former species within Haliaeetus has been doubted by Mlíkovský (2002). According to published dimensions and illustrations, both H. piscator and H. fortis seem to have been smaller than the species represented by the Shiriya material.

A putative Early Pleistocene species from Czech Republic, H. angustipes Jánossy, 1983 , has been shown to be inseparable from modern H. albicilla by Mlíkovský (1997). An extinct species H. australis ( Harrison and Walker, 1973) is known from the Holocene of the Chatham Islands ( Dawson 1961; Harrison and Walker 1973; Olson 1984; Millener 1999). Published dimensions of that species ( Harrison and Walker 1973) suggest that it might be comparable in size with the Shiriya material, but it is not feasible to make a comparison because the latter lacks the tarsometatarsus, the most intensively described element of H. australis ( Harrison and Walker 1973; Olson 1984). A genetically distinct lineage which is most closely related to H. albicilla is known from Holocene deposits of Hawaiian Islands ( Olson and James 1991; Fleischer et al. 2000; Hailer et al. 2015). Published dimensions of the Hawaiian material ( Olson and James 1991) indicate that it is smaller than the Shiriya material.

Occurrence of modern species of the genus has been recorded from various Pleistocene localities. Haliaeetus albicilla and H. leucogaster are known from numerous localities in the Old World (e.g., Hou 1993; Tyrberg 1998, 2008a; Guerra et al. 2013; Huguet et al. 2017) and North America (e.g., Brodkorb 1964; Guthrie 1992; Emslie 1998), respectively. Haliaeetus vocifer has been recorded from a few localities in Africa, whereas H. vociferoides has been recorded from Madagascar ( Lambrecht 1933; Phillips 1988). Baird (1991) mentioned the occurrence of cf. H. leucogaster from Quaternary cave deposits in Australia. Apparently, H. pelagicus does not have a definitive fossil record, apart from Holocene archaeological occurrences (e.g., Friedman 1935). Although Rich et al. (1986) cited the occurrence of H. cf. pelagicus from the Pleistocene of Yage, central Honshu Island, the original report of the site ( Tomida 1978) designated the relevant species as Haliaeetus sp. indet. Further work with larger comparative material would be required to verify the identifications of the putative records of the last species, whose breeding range is largely restricted around the Sea of Okhotsk today.

Figures

Fig. 9. Bivariate scatter plots of Recent and fossil species of Haliaeetus: cranial (A), coracoidal (B), humeral (C), ulnar (D), radial (E), and tibiotarsal (F) measurements. Abbreviations: CNT, crista nuchalis transversa; FT, fossa temporalis.

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.

Fig. 4. Coturnicini gen. et sp. indet. from the upper Pleistocene of Shiriya, Japan. A. NSMT PV 24543, right humerus in cranial (A1) and ventral (A2) views. B. NSMT PV 24547, tarsometatarsus in dorsal (B1) and medial (B2) views. C. NSMT PV 24545, left tibiotarsus in cranial view. Fossils coated with ammonium chloride.Abbreviation: c, concavity on the ventral surface of epicondylus ventralis (see text).

Fig. 5. Columbidae gen. et sp. indet. from the upper Pleistocene of Shiriya, Japan. A. NSMT PV 24551, right humerus in dorsal (A1) and cranial (A2) views. B. NSMT PV 24552, left humerus in cranial view. C. NSMT PV 24553 sternum in ventral (C1) and cranial (C2) views. Fossils coated with ammonium chloride.

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).

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.