Phylogeny of Living Parasitic Lampreys (Petromyzontiformes) Based on Morphological Data

• Published in: Copeia 2003-12, Vol.2003 (4), p.687-703
• Main Authors: Gill, Howard S, Renaud, Claude B, Chapleau, François, Mayden, Richard L, Potter, Ian C
• Format: Article
• Language: English
• Subjects: Fossils; Freshwater fishes; Genera; Monophyly; Northern hemisphere; Parasitism; Southern hemisphere; Taxa; Teeth; Velar consonants
• ISSN: 0045-8511; 1938-5110
• DOI: 10.1643/IA02-085.1

Relationships among the 18 extant species of parasitic lamprey (Petromyzontiformes) were determined using a cladistic analysis of 32 mainly morphological characters. Because previous analyses support all known fossils as phylogenetically older or the same age as living lampreys, a composite agnathan fossil was used as an outgroup. A consensus of three equally parsimonious trees revealed a trichotomy between a monophyletic northern hemisphere clade and the southern hemisphere genera Geotria and Mordacia. The monophyletic status of the northern hemisphere lampreys and their classification in a single family Petromyzontidae was corroborated. It is suggested that the two southern hemisphere lamprey genera be retained as distinct families. Among northern hemisphere species, Ichthyomyzon and Petromyzon form a monophyletic group sister to the remaining genera. Caspiomyzon is sister to Tetrapleurodon + Entosphenus + Lethenteron + Eudontomyzon + Lampetra, with Tetrapleurodon in turn being sister to a group comprising Entosphenus and a clade containing Lethenteron and its sister group Eudontomyzon + Lampetra. Differences in many characters are related to differences in modes of feeding and behavior. In a phylogenetic context, dentitional characters are resolved as related either to blood feeding (Petromyzon, Ichthyomyzon, and Mordacia) and hypothesized to be plesiomorphic, or to flesh feeding (Eudontomyzon, Lampetra, and Geotria).