ABSTRACT
The single most prominent and characteristic group of macrogastropods found within the Nicaraguan Subprovince is the genus Voluta (Volutidae-Volutinae), which has evolved an endemic radiation of at least 10 species on the isolated offshore banks and muddy coastal areas (several illustrated in Figures 7.2 and 7.3). Since these volutes have very large protoconchs and direct development, nonplanktonic larvae, they are easily trapped and isolated on offshore banks and seamounts and have produced a swarm of sibling species since the late Pliocene (Petuch, 1981b). During the heavy glaciations of the Gelasian Age of the earliest Pleistocene, lowered sea levels (as much as 250 m) allowed these shallowwater volutes to spread across the wide continental shelf and colonize previously unreachable offshore areas. During warm interglacial times, particularly during the Sangamonian Stage of the late Pleistocene, sea levels rose to their present height or higher (20 m or more in the Sangamonian) and ooded the wide shelf with much deeper water. Many of the shallow-water volutes became isolated on these offshore banks and island groups and quickly evolved a suite of closely related allopatric siblings. This unique species radiation, endemic to the Nicaraguan Subprovince, contains the following species:
Family Volutidae Subfamily Volutinae
Voluta demarcoi (coastal areas from Punta Patuca and Cabo Camaron to Puerto Cabezas) Voluta ernesti (coastal areas from Punta Gorda to the San Blas Islands, Panamá) Voluta hilli (endemic to the Gorda Bank and area of the Cajones and Bercero Cays) Voluta kotorai (Corn and San Andres Islands, and Gorda, Roncador, Quitasuen´o, and
Serrana Banks) Voluta lindae (endemic to the San Blas Islands area of Panamá) Voluta morrisoni (endemic to Rosalind and Serranilla Banks)
Voluta polypleura (endemic to the Caratasca and Vivorillo Cays) Voluta retemirabila (endemic to Misteriosa Bank) Voluta sunderlandi (endemic to Utila Island) Voluta new species (endemic to the Miskito Cays)
In an ongoing study of the genus Voluta, Anton Oleinik (Florida Atlantic University) and I recently discovered that the name Voluta polypleura, which Poppe and Goto (1992) applied to the shell previously known as Voluta demarcoi, was actually misapplied and incorrect. The real Voluta polypleura is a much smaller and more compact shell and, as pointed out by the species’ author (Crosse, 1876), completely lacks any “music lines or musical staff pattern” on the body whorl. The larger, more rectangular Voluta demarcoi (Figure 7.2C) always has strong color lines encircling the shell midbody, and its general appearance certainly does not match up with Crosse’s original description. Unfortunately,
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Crosse’s type specimen of Voluta polypleura was lost and could not be located in any museum in Europe. This apparent loss, however, was reversed by the rediscovery of the type locality of the true Voluta polypleura and by the collection of several live specimens. One of these so closely matched the illustration of Crosse’s species in color, shape, and size that it was decided to make this individual the neotype, thus preserving Crosse’s name and removing demarcoi from synonymy with polypleura.
