|European eel, Anguilla anguilla|
The shoulder bones are separate from the skull. The scales have smooth edges or are absent.
Eels hatch from eggs. Baby (larval) eels are flat and transparent (clear). They are called leptocephalus (Greek for "thin head"). A young eel is called an elver. For a long time people did not know where eels came from, because baby eels look very different from adults. They thought the babies were a different species.
Most eels prefer to live in the shallowest parts of the ocean. They live at the bottom of the ocean, sometimes in holes. Eels in the Anguillidae family come to fresh water to live there. Eels in the Nemichthyidae family swim about 500 m below the ocean surface. Eels in the Synaphobranchidae family live as deep as 4000 m below the surface.
This order has 4 suborders (smaller groups) called Anguilloidei, Nemichthyoidei, Congroidei, and Synaphobranchoidei.
There are 400 species of eels in all.