Squalus acanthius fetus.
Title: The Biological bulletin
Authors: Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual report 1907/08-1952; Lillie, Frank Rattray, 1870-1947; Moore, Carl Richard, 1892-; Redfield, Alfred Clarence, 1890-1983
Subjects: Biology; Zoology; Biology; Marine Biology
Source: https://commons.wikimedia.org/wiki/File:The_Biological_bulletin_(19751334684).jpg

The spiny dogfish, spurdog, mud shark, or piked dogfish (Squalus acanthias) is one of the best known species of the Squalidae (dogfish) family of sharks, which is part of the Squaliformes order. It is found mostly in shallow waters and further offshore in most parts of the world, especially in temperate waters.