Living animals for comparison in studies of Mesozoic fossils

Abstract

Lungfish are timeless, starting in the Devonian and still found today. Unfortunately this does not mean that biologists and palaeontologists agree about the functional anatomies of dipnoans. Most lungfish that are sufficiently well preserved have an enlarged rib behind the head, known as the occipital or cranial rib. Biologists describe this rib in living lungfish as an aid to the suctorial activities of the fish, involving feeding, burrowing in the mud or drawing a current of air or water into the oral cavity, activities important to both groups of extant lungfish. The arrangement of the occipital rib in lungfish differs in neoceratodonts and lepidosirenids, because the morphology of the oral cavity and the throat differs in the two groups. Suctorial activities are important in most if not all lungfish, for feeding, breathing in air or water, or digging a hole in the substrate. However, presence of an occipital rib does not mean that the fish would have been an air breather.