Snail Spears and Scimitars: A Character Analysis of Conus Radular Teeth

Knowledge of the attributes of the venom-injecting radular teeth of Conus can enhance understanding of the functional biology of feeding and the systematics of this large and taxonomically difficult genus of gastropods. We define and provide a scheme for coding the states of Conus radular tooth characters, in order to facilitate their use in taxonomic and phylogenetic studies. To exemplify these characters, we describe and illustrate teeth of putatively primitive species and of species representing generalized, vermivorous, molluscivorous and piscivorous feeding groups within the genus. We define and address the intraspecific and interspecific variation of ten presence-absence characters and 15 continuous characters, of which at least five and ten, respectively, are present in most species. Some continuous characters are bimodally distributed among the species sampled. If this distribution still obtains when additional species are examined, these characters could also be coded unambiguously as having two states. We also review the several previously proposed classification schemes of Conus radular teeth and of species according to tooth characters. As Troschel suggested in 1866, a tooth length:width ratio greater than or less than 20 separates the genus into two distinct species groups, now known to comprise the molluscivorous and piscivorous species in the former, and vermivorous and generalized species in the latter. Important subsidiary characters are the number of barbs, presence/absence of blade, cusp, and spur, length of serrations, relative width of base, and tooth length:shell length ratio.