Complex sentence: The flooding of Sundaland separated species that had once shared the same environment such as the river threadfin ("Polydactylus macrophthalmus ", Bleeker 1858), that had once thrived in a river system now called"North Sunda River " or"Molengraaff river".
Split into simpler sentences: The flooding of Sundaland separated species that had once shared the same environment. One example is the river threadfin ("Polydactylus macrophthalmus ", Bleeker 1858), which once thrived in a river system now called"North Sunda River " or"Molengraaff river".