Syrmaticus sp.

Watanabe, Junya, Matsuoka, Hiroshige & Hasegawa, Yoshikazu, 2018, Pleistocene non-passeriform landbirds from Shiriya, northeast Japan, Acta Palaeontologica Polonica 63 (3), pp. 469-491 : 472-475

Syrmaticus sp.

Fig. 2A, B, E, F, G–K .

Material.—Loc. 3, Shiriya, Aomori Prefecture, Japan; Late Pleistocene(~MIS5e):NSMT PV24531,24532,left omal and sternal coracoids, respectively; NSMT PV 24533–24535, two right and one left proximal humeri, respectively; NSMT PV 24536, right distal humerus; NSMT PV 24537 left humeral shaft; NSMT PV 24538, right ulnare; NSMT PV 24539, worn proximal phalanx of the right major wing digit. Locality unrecorded, Shiriya, Aomori Prefecture, Japan; Middle–Late Pleistocene (~MIS 9/5e): NSMT PV 24540, tip of premaxilla; NSMT PV 24541, 24542, proximal and distal fragments of right carpometacarpus, respectively.

Measurements.—See Table 1 and Fig. 3 .

Description.—One well preserved proximal end of the humerus was recovered ( Fig. 2A ). The fossil is characterized by a narrow dorsal tricipital fossa (the fossa dorsal to the crus dorsale fossae), which is pointed proximally with a faint dorsal margin and only slightly excavates the distal margin of the caput humeri in its ventral part. The combination of these states is apparently unique to Phasianini the dorsal tricipital fossa is wider and excavates the caput humeri more deeply in Rollulinae and most other tribes within Phasianinae except Pavonini). The fossil differs from Pavonini in a proximodistally thinner tuberculum ventrale that lacks a distinct attachment scar just ventral to its tip (which is characteristically present at this position in Pavonini). Within Phasianini , the fossil agrees only with Syrmaticus (except S. reevesii ) in weak development of the incisura capitis (in Chrysolophus , Phasianus , Crossoptilon , Catreus , Lophura , and S. reevesii , the incisure is wider and deeper, and excavates the proximal margin of the tuberculum ventrale; Fig. 2C 1, D 1 ). Two other fragmentary proximal humeri are tentatively referred to the same species, based on the consistency of size and observable features.

Another phasianid humerus preserving the distal half of the bone ( Fig. 2B ) is referred to the same species as the proximal end with which it is roughly consistent in size. In the fossil, the processus flexorius is well developed distally, as in Coturnicini , Lophophorini, Phasianini , and Tetraonini (except Meleagris ). The fossil differs from Coturnicini in the absence of a concavity on the epicondylus ventralis just caudal to the pit for the m. pronator superficialis (see below), and from most members of Tetraonini (except Perdix and Meleagris ) in less craniocaudal compression of the body.

An omal end of the coracoid preserving the processus acrocoracoideus ( Fig. 2J ) and a sternal end of the coracoid with a worn angulus lateralis ( Fig. 2K ) are tentatively referred to this species, with which they are consistent in size. In the fossil, the impressio lig. acrocoracohumeralis is dorsoventrally thick and developed as a deep groove with distinct margins. This state is characteristic to some members of Phasianini and Tetraonini (except Perdix , Meleagris , and Bonasa ) among phasianids. The omal end differs from Tetraonini and agrees with Phasianini in a relatively straight profile of the tuberculum brachiale in medial view (in Tetraonini, its dorsal tip is produced sternally to give a concave profile to the tuberculum brachiale). The fossil differs from Phasianus and agrees with Syrmaticus in a relatively poorly developed ventral part of the processus acrocoracoideus (in Phasianus , it is strongly elevated from the shaft and produced medially, with the ventral margin of the tuberculum brachiale protruding as medially as the dorsal margin; Fig. 2C 3, D 3, J 3 ). The sternal protrusion of the processus lateralis observed in the fossil sternal end, the most sternal point of which is lying even sternally than the lateral end of the crista articularis sternalis ( Fig. 2K ), is apparently unique to Phasianini (in most other phasianids, the latter is the most sternal point in the coracoid). This feature is most pronounced in Syrmaticus within Phasianini , with which the fossil agrees ( Fig. 2C 2, D 2 ).

One carpometacarpus preserving the proximal symphysis and processus intermetacarpalis ( Fig. 2E ), another preserving the distal symphysis and articular surfaces ( Fig. 2F ), a proximal phalanx of major wing digit lacking the caudodistal part ( Fig. 2H ), one moderately worn ulnare ( Fig. 2I ), and a tip of premaxilla ( Fig. 2G ) are tentatively referred to this species. The fossils are too fragmentary for definitive identification, although they are consistent with modern species of the genus in size and proportions.

Remarks.—This genus includes several modern species of pheasants which are distributed in China, northern Indochina, Taiwan, and most central Japanese islands (except for Hokkaido Island). As far as observed in this study, few qualitative features observable in the Shiriya material were found useful in distinguishing species within the genus, except for the development of the incisura capitis of the humerus noted above; the incisure is deep and wide in S. reevesii and the other genera of the tribe Phasianini , whereas it is narrower and shallower in the other modern species of Syrmaticus . Although it is tempting to speculate that this character reflects the phylogenetic relationship e.g., the state observed in S. reevesii represents a primitive condition within Syrmaticus ), the available evidence is inconclusive; most recent molecular phylogenetic analyses

Zhan and Zhang 2005; Wang et al. 2013; Jiang et al. 2014; Hosner et al. 2016) recovered either S. soemmerringii or S. reevesii as the most basal divergences within the genus, but the branching orders for these species have not been well resolved. In any way, the Shiriya fossils clearly agree with the group including S. soemmerringii , S. mikado , S. ellioti , and S. humiae . Although most dimensions of the Shiriya material are consistent with those of modern S. soemmerringii , the only species that occur on the central Japanese islands today, the sample size is too small to allow definitive assignment to any of the modern species ( Fig. 3 ), let alone identification to the subspecific level.

Two extinct species of Syrmaticus have been named so far: S. phasianoides ( Jánossy, 1991) from the upper Miocene of Hungary ( Jánossy 1991; Zelenkov 2016) and S. kozlovae Kurochkin, 1985 , from the upper Miocene–lower Pliocene of Mongolia ( Kurochkin 1985; Zelenkov and Kurochkin 2010). According to published dimensions ( Zelenkov 2016), S. phasianoides is larger than any modern species of the genus, thus would be larger than the Shiriya material as well. According to published dimensions and descriptions ( Zelenkov and Kurochkin 2010), S. kozlovae is slightly smaller than the Shiriya material, and further differs from it in certain osteological features of the distal humerus, including a less distally protruding processus flexorius (see Zelenkov and Kurochkin 2010).

The fossil record of the modern species of the genus is scanty. Syrmaticus soemmerringii has been identified from several Pleistocene localities in the central Japanese islands ( Takai 1962; Nokariya and Ono 1980; Ono 1980), but little justifications were given in these previous reports. As S. soemmerringii had once been included in Phasianus in some past editions of the Check-list of Japanese Birds (e.g., The Ornithological Society of Japan 1974), this species may possibly be represented by identifications labeled as “ Phasianus sp. ” by Japanese authors (e.g., Ono in Rich et al. 1986). Although S. reevesii had been reported from the Pleistocene of Choukoutien (also known as Zhoukoudian), China ( Shaw 1935), a later, more comprehensive report of the paleoavifauna ( Hou 1993) did not mention this species.

Modern S. soemmerringii is the only species of the genus that naturally occurs in the central Japanese islands, where it is an endemic, resident breeder. Lying at the northeastern tip of Honshu Island, Shiriya is at the northern limit of the natural distribution of the species; it does not occur in Hokkaido Island except as an introduced breeder ( The Ornithological Society of Japan 2012). If the Shiriya material represents that species, the occurrence would indicate that the species had spread throughout Honshu Island by the Late Pleistocene (MIS 5e), assuming that the genus originated in the continental Asia as indicated by the distribution and phylogeny of modern and fossil species ( Zhan and Zhang 2005; Zelenkov and Kurochkin 2010).

Hasegawa et al. (1988) included Phasianus sp. in their faunal list for the Shiriya local fauna without designating any specimens. The examination of the entire avian material from Shiriya in this study could not identify specimens certainly referable to Phasianus rather than Syrmaticus . Although some fragmentary specimens within the material might possibly represent a species of the former genus, the absence of diagnostic specimens seems a sufficient reason to retract the occurrence of Phasianus sp. from the Shiriya local fauna.

Figures

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.

Fig. 1. Geographic location of Shiriya localities. Landmarks mentioned in the text are also indicated. Inset (41°24’N, 141°24’E) shows major fossil localities mentioned in the text (stars; after Hasegawa et al. 1988). Dark grey indicates distribution of limestone/limestone breccia bodies (after Tsushima and Takizawa 1977). Abbreviations: I., island; Is., islands.