Testing a time hypothesis in the biogeography of the arowana genus Scleropages (Osteoglossidae)

Aim To infer the timing of the early divergence of the freshwater arowana genus Scleropages and to determine whether it was contemporary with, or post‐dated, the latest possible freshwater route between Sundaland–Indochina and Australia–New Guinea through the drifting of India, estimated at a minimum of 115.0 Ma. Location Sundaland–Indochina and Australia–New Guinea. Methods Time‐calibrated phylogenetic reconstructions based on the mitogenome, a Bayesian method and a relaxed molecular clock, differing in how fossils were used to calibrate the clock and how the phylogenetic signal was corrected for saturation. Results The phylogenetic analyses supported the monophyly of Scleropages and its sister relationship with Osteoglossum . Within Scleropages , the Sundaland–Indochina species was the sister group of the two Australian species. After filtering the phylogenetic signal, the estimated mean ages of crown‐group Scleropages and their 95% credibility intervals (CI) ranged from 79.9 Ma (CI, 93.1–67.2 Ma) to 101.4 Ma (CI, 114.7–85.5 Ma). Main conclusions In all reconstructions, the ‘early freshwater origin’ hypothesis is rejected, because the age CI of Scleropages do not overlap with the final separation between India and Australia–Antarctica. The palaeontological evidence often presented in support of the ‘late marine origin’ hypothesis is inconclusive because none of the marine osteoglossid fossils are exclusively related to Scleropages , and Scleropages fossils are too fragmentary to be precisely classified. Altogether, there is evidence to reject the ‘early freshwater origin’ but no evidence favouring the ‘late marine origin’. Scleropages represents an additional case of trans‐oceanically distributed freshwater/terrestrial vertebrates that started to diversify during the Late Cretaceous, after the final separation between India and Australia–Antarctica.