Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species

Olmecadrilus gen. nov. an acanthodrilid meroic earthworm genus is described from the states of Oaxaca and Veracruz, Mexico. The new genus is characterized by a single gizzard, calciferous glands in segments 9–14 of the lamellar type, meronephridia (tufts in first segments, several closed parietal micronephridia in most of the body and paired medial open megameronephridia in last segments), last hearts in segment 13, tubular prostates in segments 17 and 19, spermathecae with diverticula and without genital nor penial setae.

The genus included now five species, two formerly described in Ramiellona (Olmecadrilus mexicanus (Gates 1962) and Olmecadrilus wilsoni (Righi 1972 )) and three new species described in this paper and sampled from tropical rain forests of Los Tuxtlas mountains, Veracruz. The new species Olmecadrilus tuxtlensis gen. et sp. nov., Olmecadrilus ocarinus sp. nov. and Olmecadrilus titepetlensis sp. nov., are separated by size, pigment, pattern of genital marks, shape of the spermatheca, and the position of seminal vesicles.

We discuss the relationship of Olmecadrilus gen. nov. with other meroic (Ramiellona) and holoic genera (Kaxdrilus, Balanteodrilus) that present a single gizzard and calciferous glands, including comments on its relation with other meroic genera with multiple gizzards (Dichogaster, Eutrigaster, Zapatadrilus) also present in Mexico. Finally, a brief discussion is provided on the relationships of the meroic monogiceriat Mexican genera and other similar genera from India, Australia and New Zealand.