Rana ulma Matsui, 2011

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 : 10-12

Rana ulma Matsui, 2011 (formerly known as R. okinavana Boettger, 1895 : see Matsui, 2007)— Ryukyu Brown Frog

Figure 5.1–5.7

Occurrence (MNI). Minatogawa: 49; Sashiki (lower unit): 152.

Referred material. Minatogawa: 89 female humeri (41 right and 48 left: YMHF-MA 007 ), 1 male humerus (left: YMHF-MA 008 ), and 17 ilia (8 right and 9 left: YMHF-MA 009 ); Sashiki (lower unit): 176 female humeri (108 right and 68 left: RUMF-GF-04019), 87 male humeri (44 right and 43 left: RUMF-GF-04020), and 93 ilia (46 right and 47 left: RUMF-GF-04021) .

Humerus. Correct observations on the humerus of this tiny, slender-bodied frog by Nokariya (1984; as Rana [ Rana ] okinavana ) are confined to a weak crista paraventralis and a distinct fossula dividens. The humerus of this species ( Figure 5.1–5.6 ) may be identified on the basis of having a series of character states (see also below): a slender and nearly straight shaft with an almost uniform diameter throughout the length; a proximodistally short crista ventralis (the distance between the ventrodistal corner and the eminentia capitata is at least 4.5 times longer than the length of the eminentia capitata); a straight ventral edge of the crista ventralis that is nearly parallel to the dorsal edge 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); the crista paraventralis that extends proximally to the level of the ventrodistal corner of the crista ventralis; a distinct spina tuberculi medialis; a scarcely protruded epicondylus radialis; the distal part of the epicondylus ulnaris that usually protrudes medially (more than the proximal part in dorsoventral views); and a tapered and pointed proximal part of the olecranon scar (in dorsal view). Female humeri usually lack the crista medialis and the crista lateralis, but some show a fringe-like crista medialis ( Figure 5.1–5.3 ). In male humeri, a well-developed crista medialis extends proximally to the midpoint of the shaft, while the proximal extent of the crista lateralis is more confined ( Figure 5.4–5.6 ).

Ilium. The ilium of this species ( Figure 5.7 ) can be diagnosed on the basis of having a series of character states (see also below): a spindle- or commashaped tuber superior, which is in contact with, or separated from, the acetabular margin (contra Nokariya, 1984); a thin and moderately high crista dorsalis, the height of which is almost the same as that of the acetabulum ( Nokariya, 1984); a gently arched dorsal edge of the crista dorsalis, which is highest at the point much anterior to the tuber superior; a posteriorly curved anterior edge of the pars ascendens; and an open supracetabular fossa.

Remarks. The humerus of this species is morphologically similar to those of closely related species, R. kobai (endemic to the Amami Island Group) and R. tsushimensis (endemic to Tsushima Island, north of Kyushu); the ilium is also similar to that of R. kobai . The fossils discussed here are referred to R. ulma on the basis of the exclusive occurrence on the island.

Figures

FIGURE 5. Fossils referred to Rana ulma (1–7) and Microhyla okinavensis (8). 1–3, right female humerus (one of 176 registered as RUMF-GF-04019) in ventral (1), medial (2), and dorsal (3) views; 4–6, right male humerus (one of 87 registered as RUMF-GF-04020) in ventral (4), medial (5), and dorsal (6) views; 7, right ilium (one of 93 registered as RUMF-GF-04021) in lateral view; and 8, right ilium (one of two registered as RUMF-GF-04023) in lateral view. Abbreviations are the same as Figure 3. Arrows indicate the proximal ends of the crista paraventralis. Scale bars equal 1 mm.