Table 1.

Published estimates of echidna–platypus divergence times, including our relaxed molecular clock estimates (bottom three rows)

Date	Data/method
17–25 Ma (10)	Immunoglobulin IgM
18–27 Ma (4)	Molecular clock estimates based on Protamine P1 genes (290 bp for platypus, 311 bp for echidna)
20–45 Ma (6)	Molecular estimates based on mitochondrial ND1 protein sequences and assuming that the echidna-platypus split is 20–30% as old as the monotreme-marsupial split
25 Ma (7)	Molecular clock estimate based on single copy DNA–DNA hybridization data
25–30 Ma (5)	Molecular clock estimates based on partial mitochondrial 12S rRNA gene sequences
28–73 Ma (2)	Molecular clock estimates based on myoglobin, α-globin, and β-globin protein sequences
34 Ma (9)	Molecular clock estimate based on amino acid sequences for 12 mitochondrial proteins
54 Ma (1)	Molecular clock estimate based on α-and β-haemoglobin and myoglobin protein sequences
50–57 Ma (8)	Molecular clock estimate based on α-lactalbumin protein sequences
63.6 Ma (11)	Molecular clock estimate based on 66 nDNA, mDNA, tRNA genes
>63.2 - 61.8 Ma (13)	Fossil (Monotrematum), paleomagnetic date
64–80 Ma (3)	Molecular clock estimates based on single copy DNA–DNA hybridization data
63.7 (95.0–39.7) Ma	Relaxed molecular clock estimate based on Woodburne et al. IGF2 data (41)
79.5 (110.4–51.6) Ma	Relaxed molecular clock estimate based on van Rheede et al. Dataset I DNA data (29)
88.9 (130.8–55.6) Ma	Relaxed molecular clock estimate based on van Rheede et al. Dataset I amino acid data (29)