Description: This lungfish fossil comes from the area around Caithness, Scotland that is famous for Devonian fishes. The genus Dipterus was also the first lungfish to described in the fossil record, circa 1828, notably by Adam Sedgwick (considered by some as a founder of modern geology) and Roderick Murchison, another early geologist.

The lungfish appear in the fossil record in the early Devonian, then radiated reaching maximum diversity by the end of the period. Early members of subclass Dipnoi were marine fish, while all those in the fossil record from Carboniferous lived in fresh water.

Lungfish along coelacanths are the jawed, lobe-finned and (mostly) bony fish that together with the tetrapods (amphibians, reptiles, birds and mammals) comprise Class Sarcopterygii. Lungfish are thus in the important lineage that would colonize and dominate the land, including humans, of course. Dipterus had lungs but no air bladder, as in still extant lungfishes; in contrast, its dorsal, caudal, and anal fins were separated, unlike modern descendants where they are fused together. Unique to these early lobe-finned fish were cosmoid scales that had shiny bony tissue that due to an external enameloid layer over a dentine layer and which had a vascular system. Fossils sometimes retain shininess due to this. Not surprisingly, the lobe-finned fish had numerous morphological characteristics that fostered land colonization, many of which have been throughout the evolution of land vertebrates.

The Sarcopterygii lobe-finned fishes and ray-finned fishes (Class Actinopterygii) both became common during the Devonian “Age of Fishes”. However, essentially all jawless fishes (Superclass Agnatha) excepting lampreys and hagfish, as well as the Placodermi armored fishes disappeared by the end of the Period. Extant lungfish are now only found in Africa, South America and Australia, so they continue their long run.

Also see: Paleobiology-Devonian Evolutionary Milestones Sarcopterygii Fish Fossils