First species of Leptochelia Dana, 1849 (Crustacea: Tanaidacea) from the Eastern Pacific, with an annotated checklist and identification keys for the genus.

Forty three species of leptocheliids are known worldwide. In the American region only eight species have been described from the Western Atlantic, while for the Eastern Pacific none have been described, suggesting that the diversity of this family has been severely underestimated in this region. Here we describe the first species of Leptochelia from the Eastern Pacific, Leptochelia mexicana n. sp., which is characterized by the males having a spiniform seta on the second segment of uropodal endopod, a novel feature for the genus. In addition, the first annotated checklist and a taxonomic key with illustrations for Leptochelia species are included. The list includes the type locality, type depository, distribution, habitat and, in some cases, remarks.

Revision of Lepidonopsis humilis (Augener, 1922) and description of L. barnichae sp. nov. (Annelida: Polychaeta: Polynoidae) based upon morphological and molecular characters.

Lepidonopsis humilis (Augener, 1922) has been considered as an amphiamerican species, widely recorded in both the Grand Caribbean region and the Tropical Eastern Pacific. Based on type material and additional materials, L. humilis is redescribed herein and its distribution clarified and restricted. Furthermore, the identity of specimens from the Mexican Pacific is clarified and a new species L. barnichae sp. nov. is described. This species is characterized by conical macrotubercles with slightly curved tips; all elytra with a tuft of papillae on the surface, isolated from the marginal papillae; and the second segment dorsally projecting over the prostomium as a small lobe. Additionally, there is a 17.6% genetic divergence in the nucleotide sequence variation of COI between L. humilis and L. barnichae sp. nov., which supports the morphological differences observed. Thus, L. humilis does not have an amphiamerican distribution but is restricted to the Gran Caribbean region; whereas the specimens from the Tropical Eastern Pacific belong to the newly described species L. barnichae sp. nov. A key to the three known species of Lepidonopsis is included.

Reestablishment of Notopygos megalops McIntosh, description of N. caribea sp. n. from the Greater Caribbean and barcoding of "amphiamerican" Notopygos species (Annelida, Amphinomidae).

The species of the genus Notopygos Grube, 1855 are characterized by an ovate body, a prominent caruncle with three lobes, dendritic branchiae, and double dorsal cirri. Twenty-two species belonging to Notopygos have been described, mostly from the Indo-Pacific region. In America, few species are frequently recorded: Notopygos crinita Grube, 1855 from St. Helena Island (Atlantic) and Notopygos ornata Grube and Ørsted in Grube 1857 from Costa Rica (Pacific). Notopygos crinita is a widely distributed species in the Western Atlantic with additional reports in the Mediterranean Sea (as a questionable alien species) and in the Pacific Ocean. However, only the genus features have been considered, consequently some records could be misidentifications. During a revision of materials from collections and the barcode project, 'Mexican Barcode of Life, MEXBOL', we found specimens of Notopygos megalops and an undescribed species from reef zones in the Caribbean; the former had been considered a junior synonym of Notopygos crinita. Herein, Notopygos megalops is reestablished and Notopygos caribeasp. n. is described. A morphological and DNA barcode approach was used to explain the records of Notopygos ornata in the Atlantic and to show the differences with the new species, since both species share features such as complex pigmentation patterns, and circular projections in the median lobe of the caruncle.