ハタネズミ亜科のねずみ3種における臼歯の大きさの比率および変異

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In this paper the author examined the size proportion and the variation of the molar in three species of voles (Microtinae), Clethrionomys andersoni, Eothenomys smithi and Microtus montebelli. 1. Relative molar series length as against the total skull length is the smallest in C. andersoni and the largest in M. montebelli. M. montebelli is the most specialized of the three species of herbivores within the present treatment. 2. Relative sizes of the 2nd and the 3rd molar as against the 1st are called the degeneration index (Fujita, 1950). There arre no interspecific defferences in the degeneration indices of the upper 2nd molar. But, in the lower 2nd, upper and lower 3rd molar, the indices decrease from C. andersoni to E. smithi and M. montebelli (Table 1). The smaller indices in the crown length of the lower 2nd and 3rd molar of M. montebelli is due to the development of the lower 1st molar (Table 2). The degenerative trend is greater in the 3rd molar than in the 2nd in every species (Table 1). 3. Variation coefficient of molar sizes is the highest in the 3rd molar in every species (Table 3). 4. Crown-breadth and molar-length relative to crown-length conform to allometry formula, y=bx^α. There are recongnized four allometric tribes in double logarithmic plots in each relations (Fig. 2 and 3). The values of α and log b are shown in Table 4.
社団法人日本動物学会の論文
1964-09-15