抄録
Lamniform sharks (Chondrichthyes: Elasmobranchii) are common in the fossil record but are represented mainly by isolated teeth. A phylogenetic analysis of 15 extant lamniform species based on 42 morphological characters using Scytiorhinus (Carcharhiniformes) as an outgroup produces a consensus tree with the following generic relationships: [Mitsukurina + [Carcharias + Odontaspis + Pseudocarcharias + Megachasma + [Alopias + [Cetorhinus + [[Isurus + Carcharodon] + Lamna]]]]]. When an extinct form, Cretoxyrhina mantelli, is added to the analysis, the fossil taxon occurs within the Alopias clade. Comparisons among the cladogram based on 29 non-dental characters alone, that based on 19 dental characters, and that based on combined (48) characters, suggest that dental characters provide at least some phylogenetic signal. Mapping of quantitative dental data on the cladogram based on non-dental characters suggests 1) a decrease in the number of tooth rows through lamniform phylogeny, 2) possible relationships between the crown heights and food types or feeding habits, and 3) that narrower crowns are plesiomorphic in lamniforms.
