Osteolepis is an extinct genus of lobe-finned fish from the Devonian

Devonian

The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...

 period. It lived in the Orcadian Lakes

Orcadian Lakes

The Orcadian Lakes are a series of lakes which existed during the Devonian period in the region which is now northern Scotland, Orkney and Shetland. The sedimentary rocks they left behind have been studied since the 1830's...

 of northern Scotland

Scotland

Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

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Osteolepis was about 20 centimetres (7.9 in) long, and covered with large, square scales

Scale (zoology)

In most biological nomenclature, a scale is a small rigid plate that grows out of an animal's skin to provide protection. In lepidopteran species, scales are plates on the surface of the insect wing, and provide coloration...

. The scales and plates on its head were covered in a thin layer of spongy, bony material called cosmine. This layer contained canals which were connected to sensory cells deeper in the skin. These canals ended in pores on the surface, and were probably for sensing vibrations in the water.

Osteolepis was a rhipidistia

Rhipidistia

The Rhipidistia were lobe-finned fishes that are the ancestors of the tetrapods. Taxonomists traditionally considered the Rhipidistia a subgroup of Crossopterygii that described a group of fish that lived during the Devonian consisting of the Porolepiformes and Osteolepiformes...

n, having a number of features in common with the tetrapods (land-dwelling vertebrates and their descendants), and was probably close to the base of the tetrapod family tree.