The chromosomes of 14 species of amphisbaenians (Amphisbaenia, Reptilia).

The chromosomes of 14 species belonging to eight amphisbaenian genera are here reported. The karyotypes of nine species all comprise 6 pairs of metacentric macrochromosomes (M) and 7 to 12 pairs of microchromosomes (m). The M in these species are similar to one another in morphology. One species, Geocalamus acutus, has 7 pairs of M and 12 pairs of m; two of the M are telocentric, perhaps as a result of centric fission of one pair of metacentric M. The remaining four species, Bipes biporus, Amphisbaena alba, A. fuliginosa, and A. innocens, had higher diploid numbers and wide variations in morphology. B. biporus had 10 pairs of biarmed M and 11 pairs of m. A. alba had 11 pairs of M, 7 biarmed and 4 telocentric, and 8 pairs of m. A. fuliginosa had 11 pairs of M, only 3 biarmed and 8 telocentric, and 13 pairs of m. A. innocens also had 11 pairs of M, 4 biarmed and 7 telocentric, and 14 pairs of m. The karyotypes of these four species are so different from one another and from those of the remainder of the group that it was not possible to assess their cytogenetic relationships. A distinct and independent sequence of chromosomal evolution was presumably involved in each case. No heteromorphic pair or monosomy was observed in either male or female amphisbaenians.