Key to the species of the Melanophryniscus stelzneri group

1 a. Dorsum uniformly brown. ................................................ Melanophryniscus krauczuki

1 b. Dorsum black. .................................................................................................................. 2

2 a. Dorsum black with many small and/or few large yellow spots; at least one pair of yellow blotches on the suprascapular region............................................................ 3

2 b. Dorsum uniformly black or with red middorsal line, without yellow spots on middorsum or suprascapular region (however, yellow blotches may be present laterally). .......................................................................................................................... 6

3 a. One yellow stripe between the eyes or 2-3 large yellow blotches forming a distinct interocular band. Dorsal and ventral surfaces with large and small, irregularly formed, yellow spots, sometimes with a black center (Figs. 10A, B). .................................................................................... Melanophryniscus klappenbachi

3 b. Without distinct yellow interocular band. Dorsal surface with numerous small, or few mid-sized yellow spots without black center. .................................................... 4

4 a. Dorsum and venter with numerous small, irregularly arranged yellow spots; yellow blotches on suprascapular region not enlarged (Figs. 10C, D). Skin densely granular.......................................................... Melanophryniscus fulvoguttatus

4 b. Dorsum and venter with larger, symmetrically arranged blotches; at least one pair of distinct yellow blotches on suprascapular region. Skin scarcely granular or nearly smooth. ............................................................................................................ 5

5 a. Dorsal surface uniformely black with a pair of distinct large, copper-coloured blotches on suprascapular region (Figs. 10E, F). .............................................................................. Melanophryniscus cupreuscapularis

5 b. Dorsal surface black with two large yellow blotches on suprascapular region and additional smaller and larger yellow spots on dorsum (Fig. 11). ............................................................................................. Melanophryniscus stelzneri

6 a. Dorsum usually with a distinct red (brown in preservative) middorsal line which is rarely absent but often interrupted or present only as a small trace behind the eyes and/or above anus. Without yellow lateral blotches and yellow line on posterior region of arms (sometimes there are few reddish spots). Ventral surface with red (not orange or yellow) blotches (Figs. 5, 6). .............................................................................................. Melanophryniscus dorsalis

6 b. Dorsum without red middorsal line; uniformly black, with or without yellow lateral spots. Distinct yellow stripe on posterior region of the arms. Ventral surface black, with red, orange and yellow spots (yellow colouration at least present on throat). ........................................................................................................... 7

7 a. Dorsum uniformly black, without yellow lateral blotches (Fig. 9). Skin texture warty and granular. Distribution in rocky habitats; does not occurr in sandy areas on the coast............................................................. Melanophryniscus atroluteus

7 b. Dorsum usually with yellow lateral spots (Figs. 7, 8), but sometimes uniformly black. Skin texture less granular. Exclusively in sandy habitats on the coast. ................................................................................... Melanophryniscus montevidensis