Identification of the sharks of the genus Etmopterus Rafinesque, 1810 (Elasmobranchii: Etmopteridae) from the upper slope of southern Brazil, with comparison between the species E. bigelowi Shirai & Tachikawa, 1993 and E. pusillus Lowe, 1839. Braz. j. oceanogr. 2008;56(2):139-143. doi:10.1590/S1679-87592008000200006