Odorrana ishikawae ( Stejneger, 1901 )

Nakamura, Y & Ota, H, 2015, Late Pleistocene-Holocene amphibians from Okinawajima Island in the Ryukyu Archipelago, Japan: Reconfirmed faunal endemicity and the Holocene range collapse of forest-dwelling species, Palaeontologia Electronica 28 (6), pp. 1-26 : 8-10

Odorrana ishikawae ( Stejneger, 1901) —Ishikawa’s Frog

Figure 4.1–4.7

Occurrence (MNI). Sashiki (lower unit): 7.

Referred material. 10 female humeri (5 right and 5 left: RUMF-GF-04009), 3 male humeri (2 right and 1 left: RUMF-GF-04010), and 5 ilia (4 right and 1 left: RUMF-GF-04011).

Humerus. The humerus of this large-sized frog ( Figure 4.1–4.6 ) differs from those of other anurans examined (except O. splendida , see below) in having a series of character states: a robust shaft that is strongly waisted at the point proximal to the condylar part (in dorsoventral views); a weakly curved ventral edge of the crista ventralis, which is not parallel to the dorsal margin of the shaft (in mediolateral views); the distal edge of the crista ventralis that forms an oblique angle with the ventral outline of the shaft (in mediolateral views); a distinct crista paraventralis that extends proximally beyond the level of the ventrodistal corner of the crista ventralis; a developed spina tuberculi medialis; a depressed and flattened shaft at the area intervening between the spina tuberculi medialis and the crista ventralis; a usually distinct and shallowly concaved fossula dividens; a scarcely protruded epicondylus radialis; the distal part of the epicondylus ulnaris that protrudes medially (more than the proximal part in dorsoventral views); and a gently round outline of the proximal part of the olecranon scar (in dorsal view). In the female, the crista medialis and the crista lateralis are ridge-like ( Figure 4.1, 4.3 ), while in the male, the former is developed but the medial extent is less than the level of the medial edge of the epicondylus ulnaris, and the latter is much less developed than the former with a laterally convex edge ( Figure 4.4, 4.6 ). Nokariya (1984) did not provide useful observations on the humerus of this species.

Ilium. The ilium of this species ( Figure 4.7 ) differs from that of the other anurans examined (except O. splendida ) in having a series of character states: the tuber superior that is separated from the acetabular margin ( Nokariya, 1984); a comma shaped tuber superior that is usually anteroposteriorly longer than the height with a gently curved posterodorsal corner; a ridged margin of the tuber superior; a thick and low crista dorsalis (the height is less than that of the acetabulum); the crista dorsalis that is anteriorly tapered with a straight dorsal edge; a medial inclination of the crista dorsalis, except the posterior end; the pars ascendens with a posteriorly curved anterior edge; and a fused supracetabular fossa.

Remarks. The Amamioshima Island (Amami Island Group) population of this species has been described as O. splendida (see Kuramoto et al., 2011). These sibling species resemble each other osteologically, while O. ishikawae has more robust humeri and a more developed crista medialis in male humeri. The species-level identification of the fossil ilia discussed here is based on the species’ exclusive occurrence on the island.

Figures

FIGURE 4. Fossils referred to Odorrana ishikawae (1–7) and Odorrana narina (8–14), 1–3, right female humerus (one of 10 registered as RUMF-GF-04009) in ventral (1), medial (2), and dorsal (3) views; 4–6, right male humerus (one of three registered as RUMF-GF-04010) in ventral (4), medial (5), and dorsal (6) views; 7, right ilium lacking the anterior part with part of the ischium (one of five registered as RUMF-GF-04011) in lateral view; 8–10, right female humerus (one of eight registered as RUMF-GF-04014) in ventral (8), medial (9), and dorsal (10) views; 11–13, right male humerus lacking the proximal part of the shaft and the distal part of the epicondylus ulnaris (RUMF-GF-04015) in ventral (11), medial (12), and dorsal (13) views; and 14, pelvic girdle (fused right and left ilia [lacking anterior parts] with the ischium and the pubis: RUMF-GF-04016) in right lateral view. Abbreviations are the same as Figure 3. Arrows indicate the proximal ends of the crista paraventralis. Scale bars equal 5 mm.