Cenozoic Typhinae (Mollusca: Gastropoda) of the Western Atlantic Region

Abstract

Twenty-six genus-group names have been proposed for the muricid subfamily Typhinae. This study shows that four genera and 17 subgenera are valid, with approximately 125 fossil and Recent species. Of these, three genera, nine subgenera, and 36 species are known from the Cenozoic of the western Atlantic region, including three species from the Eocene, two from the Oligocene, 22 from the Miocene, one from the Pliocene, and four from the Pleistocene and Recent. In addition, four species are known only from the Recent fauna. In this paper, all of the species are treated systematically, including ten new species: Typhis (Typhina) palmerae, from the early middle Eocene Weches and Wautubbee formations of Texas and Mississippi, respectively; T. (Typhina) mississippiensis, from the lower Oligocene Red Bluff Clay of Mississippi; T. ( Rugotyphis) keenae, T. (Typhinellus) chipolanus, Pterotyphis (Pterotyphis) calhounensis, and P. (Tripterotyphis) vokesae, all from the late lower Miocene Chipola Formation of northwestern Florida; Typhis (Talityphis) carmenae, from the upper Miocene Agueguexquite Formation of Mexico; Siphonochelus (Pilsbrytyphis) darienensis and S. (P.) woodringi, both from the middle Miocene of Panama; and Siphonochelus (Laevityphis) bullisi, from the Pleistocene Moin Formation of Costa Rica and the Recent Caribbean. The oldest known typhine in the world is referred to Siphonochelus (Laevityphis), reported from the lower Eocene of England and France. This earliest form is a well developed typhine, from which it is concluded that the group must have evolved at an earlier time. Among the first Typhinae in the western Atlantic is also a representative of Siphonochelus (Laevityphis), occurring in the late middle Eocene of Alabama. The oldest reported typhine in the western Atlantic region is T. (Typhina) palmerae, n. sp., from the early middle Eocene of Mississippi and Texas. Typhinae have shells of less than 50 mm length with a protoconch of one and one-half to five whorls. Tubes are present at the shoulder, either alternating with, or within the varices. The number of varices may vary from two to six, but most forms have four varices and four tubes per whorl. The aperture is ovate and surrounded by a raised rim. The anterior canal is closed in all but one group. Generic and subgeneric units are based primarily upon the nature of the varices, the number of varices per whorl, the placement of the tubes with respect to the varices (just behind the varix, just in front of the varix, midway between the varices, or within the varix), and the direction in which the tubes point. A summary of the reported ecological data shows that the Typhinae live, for the most part, in shallow water in tropical and subtropical areas.