Abstract
A new genus of Itaquasconinae, Meplitumengen. nov., and a new species, Meplitumenalunasp. nov., are described. The new genus has characters present in other genera of Itaquasconinae but in a unique combination. The spiral thickening of the bucco-pharyngeal tube is also present anteriorly to the insertion point of the stylet supports, excluding only the short portion where the apophyses for the insertion of the stylet muscles (AISM) are present. This character is similar to Astatumen Pilato, 1997 but Meplitumengen. nov. differs from this genus as stylet furcae are shaped differently and as stylet supports and placoids are present. The presence of a spiral thickening in a portion of the buccal tube anterior to the stylet supports distinguishes the new genus from Mesocrista Pilato, 1987, Platicrista Pilato, 1987 and Itaquascon de Barros, 1939. Meplitumengen. nov. also differs from Mesocrista, in having the caudal processes of the AISM pointing laterally (instead of postero-laterally), and the apices of the caudal processes of the stylet furcae unswollen. From Itaquascon the new genus also differs by having more robust stylet supports, pharyngeal bulb with placoids, stylet furcae differently shaped. Meplitumengen. nov. also differs from Platicrista in having caudal processes of the AISM more robust and not flexible, and more slender stylet supports. The new species, Meplitumenalunasp. nov., has a cuticle with a very faint roughness at the caudal extremity of the body, and eyes probably absent. The pharyngeal bulb is long, with two long, narrow, rod-shaped macroplacoids; a microplacoid and septulum are absent. The claws are well developed with main branches provided with accessory points, and at the base of the claws, a structure interpretable as a very thin lunule is present. Other cuticular thickenings on the legs are absent.
Highlights
In the study of systematics and phylogeny is one so fortunate to encounter a taxon with characters that sheds light on phylogenetic directions within a group
The spiral thickening of the bucco-pharyngeal tube is present anteriorly to the insertion point of the stylet supports, excluding only the short portion where the apophyses for the insertion of the stylet muscles (AISM) are present. This character is similar to Astatumen Pilato, 1997 but Meplitumen gen. nov. differs from this genus as stylet furcae are shaped differently and as stylet supports and placoids are present
Meplitumen gen. nov. differs from Mesocrista, in having the caudal processes of the AISM pointing laterally, and the apices of the caudal processes of the stylet furcae unswollen
Summary
In the study of systematics and phylogeny is one so fortunate to encounter a taxon with characters that sheds light on phylogenetic directions within a group. While studying Colombian tardigrades, from the Sierra Nevada de Santa Marta, we found eight specimens and two exuviae with eggs of a new species of Hypsibiidae (Itaquasconinae), for which it is necessary to erect a new genus that we name Meplitumen gen. This discovery is further confirmation of the biodiversity richness of this Neotropical region (Myers et al 2000, Rull 2007), which, at least with regards to the tardigrades, is still far from being thoroughly investigated. Our new genus shows characters that are present in these other genera but in a unique combination. This encouraged us to hypothesise possible evolutionary pathways that connect these five Itaquasconinae genera, which appear to constitute a homogeneous group within the subfamily
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