Devonian Fossil Fish Osteolepis – Ancient Tetrapod Ancestor

Osteolepis macrolepidotus

Class Sarcopterygi, Infraclass Tetrapodomorpha, Superorder Osteolepidida, Order Osteolepiformes, Family Osteolepidae

Geologic Time: Middle Devonian

Size: 140 mm in length on 130 mm by 155 mm matrix

Fossil Site: Caithness Flagstones, Cruday Quarry, Orkney, Scotland

Devonian Fossil Fish OsteolepisDescription: The Osteolepiform fish are thought to be the ancestors of the Tetrapoda due to their paired lobed fins being homologous to the limbs, and the choanae (posterior nostril). Osteolepis possessed two rounded dorsal fins placed posteriorly, and a heterocercal tail with a larger lower lobe. They have thick rhombic scales covered with a cosmine layer (hence the shine). This ancient group of fish is thought to have given rise to the Tetrapod bauplan as animals colonized the land.

Also see: Paleozoic Fish Fossils

click to enlarge fossil pictures

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