A new species of Thaisella (Neogastropoda: Muricidae) from Caribbean Guatemala, with accounts on the anatomy and taxonomy of the genus in the Western Atlantic

Thaisella guatemalteca is a new species with type locality in Puerto Barrios, Department of Izabal, Caribbean (Atlantic) coast of Guatemala. Its anatomical attributes are described. The main intention is to provide data for a future re-evaluation of a possible complex of species that inhabit different estuarine regions along the Western Atlantic, of which this species is part. The new species can be easily distinguished by its small size, well-developed anal canal, simple sculpture, stubby periumbilical keel, and an orange aperture bearing poorly developed riblets. Anatomically, the set of distinctive features include an anal flap at the mantle edge, elongated radular teeth, strong asymmetry of salivary glands, a lack of accessory salivary glands, a pair of gastric ducts to the digestive gland, a relatively small and simple penis, and a pallial oviduct lacking a bursa and other chambers. The significance of these findings is still obscure because these characters are unknown in allied species, but provisionally, the genus Thaisella appears to be exclusively American (mostly Atlantic), always associated with an estuarine environment, and possessing geographically restricted species.