Complex sentence: They were distinct to the Kangaroo Island Emu in a number of osteological details, including size, but the behaviour of the King Island Emu probably did not differ much from that of the mainland Emu.
Split into simpler sentences: They were distinct from the Kangaroo Island Emu in a number of osteological details, including size. The behaviour of the King Island Emu probably did not differ much from that of the mainland Emu.