The grass squid Pickfordiateuthis vossi Brakoniecki, 1996 is a dwarf species distributed along the northwest coast of Mexico. In the eastern Pacific, little is known about its distribution and life cycle. Two specimens, which are considered the smallest individuals of the genus collected to date, were caught in zooplankton trawls during 2 oceanographic cruises (January and March 1998) carried out in the central Mexican Pacific. The paralarval and juvenile stages are described and represent a new record in the area, with a range extension of 600 km southwest from the nearest previous record.

Pelagic nudibranchs exemplify evolutionary convergences towards streamlined, transparent body forms adapted for life in the planktonic environment. Here, we describe a new genera and species, designated as Pleuropyge melaquensis gen. et sp. nov. This species belongs to the family Phylliroidae and is distinguished by key diagnostic characters, including a laterally positioned anus approximately one-third of the body length from the head, the absence of a cephalic disc, and an anterior hepatic caecum that is longer than the intestine. The description of P. melaquensis contributes to the classification of a third genus and a fourth species within the Phylliroidae family. This study offers novel insights into the functional and structural traits that have enabled nudibranchs to transition from benthic to pelagic environments.

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