Comparison of the skeletal features of two sympatric tree frogs (Hylidae: Hyla) —Hyla japonica and H.suweonensis—using 3D micro-CT

ABSTRACT We used 3D micro-computed tomography to compare the skeletal features of two species of male tree frogs with similar morphologies: the globally prevalent Hyla japonica and critically endangered Hyla suweonensis. One of the most prominent differences between the two species was the angle of the alary processes of the premaxilla. In H. suweonensis, the alary processes were inclined posteriorly at an angle of 77.05°, whereas in H. japonica they were deflected at an angle of 93.27° (a difference of more than 16°). This difference accounts for the more protruded shape of H. suweonensis compared to that of H. japonica. Sizes and proportions related to skeletal compartments (e.g., skull, forelimb, vertebrae, and hindlimb) also differed between the two species, which is consistent with the general exterior observation that compared to H. japonica, H. suweonensis has a more acuminate snout and a more slender body. The full skeletal configuration could provide classification keys for the two sympatric species that will be applicable to ecological field surveys and conservation activities.