Table 3.

Dating of ancient mammalian divergences

Lineage	MYBP
	Amino acid	2nd codon position
Marsupials plus monotremes, eutherians	130 ± 9.7	143 ± 16.8
Marsupials, montremes	116 ± 9.0	126 ± 15.9
Myomorph rodents, remaining eutherians	115 ± 9.0	125 ± 15.6
Guinea pig, remaining eutherians	98 ± 7.9	103 ± 13.4
Primates, ferungulates	95 ± 7.3	101 ± 12.2
Wallaroo, opossum	75 ± 7.1	76 ± 11.8

Datings were based on ML distances of amino acids according to the mtREV-22 matrix, and ML distances of the 2nd codon positions based on the TN model of sequence evolution (63) with the parameters of the model estimated from the data set by the puzzle program (transition/transversion parameter = 1.60 and purine transition/pyrimidine transition parameter = 1.66). As a calibration point, the artiodactyl/cetacean divergence set at 60 MYBP (A/C-60) was applied. The 95% confidence intervals were estimated according to Possion expectations of numbers of amino acid or nucleotide substitutions. The phylogenetic analysis generally joined the rabbit and the ferungulates. With that topology the dating of the divergence between the rabbit and the ferungulates is tentatively given at ≈90 MYBP.