Rana vertebralis Hewitt 1927

Identification of Rana vertebralis Hewitt, 1927

The two river frogs in question can be easily distinguished on the extensive webbing reaching the last phalanx of the fourth toe in the Maluti River Frog, but with up to three phalanges free in the Phofung River Frog, and small tympanum, less than the eye-tympanum distance in the Maluti River Frog, larger in the Phofung River Frog. The description (Hewitt 1927) is brief and incomplete, with an important error. Only four statements are diagnostic, and all four identify the Maluti River Frog—Tympanum width less than eye-tympanum distance; toes completely webbed in five types (the description refers to half-webbed toes, but examination of the holotype PEM A1550, and the paratypes PEM A1551, A1552, A1562 and A10562 shows this to be in error, only PEM A1555 has webbing that does not reach the tip of the fourth toe). Hewitt (1927) illustrates the type in Plate 24. The quality of the reproduction is too poor to make out useful features. The left foot of the type appears to show that three phalanges of the fourth toe are free of webbing (Fig. 3 A). This would identify the type as a Phofung River Frog, in contradiction to the small tympanum. Unfortunately the type is now in very poor condition, but it clearly shows the fourth toe to be completely webbed. It appears that Fig. 2 of Plate 24 of Hewitt (1927) was retouched, as the dark line along the margin of the webbing is not present in the type (Fig. 3 B). The webbing might have been invisible in the photograph if this retouching had not been done. Whoever did it, however, got it wrong. It also appears that Hewitt's photograph was flipped horizontally, as the right foot and right hand of the type show the same orientation as the left foot and left arm in the photograph (Fig. 3). The same specimen was illustrated by Tarrant et al. (2008: Fig. 2 A) to show the poor condition. Note that the Tarrant et al. Fig. 2 A is flipped horizontally.