Portaratrum, Guerrero-Kommritz, Jürgen, 2003

Guerrero-Kommritz, Jürgen, 2003, Portaratrum, a new genus of deep­sea Tanaidacea (Crustacea) with description of two new species, Zootaxa 282, pp. 1-14 : 3-4

Portaratrum n. gen.

Diagnosis: Antennula with four articles, antenna with six articles, basis of cheliped fused to cephalothorax, uropods biarticled, uropod exopod uniarticled, pleonal spur directed downwards.

Description: Adult female: body long and slender about eight times longer than broad, cephalothorax oval. Pereon composed of 6 free pereonites, pleon composed of 5 free pleonites and a pleotelson, ventral pleonal spur on pleonite 5. Antennula composed of four articles. Antenna composed of six articles, article 2 with a row of setules. Labrum hoodshaped with distal setules, mandibles well calcified, pars molaris not acute, with several terminal spinules. Maxillule endite with nine terminal spines. Maxilliped basis oval, endites not fused. Labium composed of 2 triangular lobes with distal setules. Cheliped basis fused to cephalothorax. Pereopods 1–3 with a simple stout seta on merus. No coxae on pereopods. Pleopods biramous. Uropods endopodite composed of two articles, endopod uniarticled.

Neuter: As female except pleopods not well developed.

Males: Unknown.

Type species: Portaratrum afer n. sp., here designated.

Included species: In addition to the type species, Portaratrum fascinatus n. sp.

Etymology: The name is derived from the Latin words portare (to carry) and aratrum (the plough), with reference to the pleonal spur, meaning the one who carries a plough.

Distribution: Abyssal plains of the tropical South Atlantic and tropical South Pacific Oceans.

Remarks: Although some Tanaidacea possess ventral spiniform projections on their body, those located on the pereon, called hyposphenia, are very variable and have little taxonomic value ( Lang 1953; Guerrero­Kommritz et al. 2002). Ventral spines located on pleonite 5 are stable and taxonomically valid. This character is present in Portaratrum and also in the genus Chauliopleona and in the species Leptognathia tuberculata Hansen, 1913 , L. armata Hansen, 1913 , L. hastata Hansen, 1913 and L. amdrupii Hansen, 1913 . Portaratrum can easily be differentiated from Chauliopleona and Leptognathia by the basis of the chelipeds being fused to the cephalothorax. In addition, the new genus has a heavily calcified cuticle that resembles that of the Agathotanaidae . In Chauliopleona and Leptognathia , the cheliped is inserted into to the cephalothorax via a sclerite, the basis of the cheliped is not fused to the cephalothorax and the body is weakly calcified as in Portaratrum . In Chauliopleona , Leptognathia armata , L. hastata and L. amdrupii the pleonal spur is directed backwards rather than downwards. The uropod exopod is biarticled in Chauliopleona , and the Leptognathia species but uniarticled in Portaratrum . The form of the pleonal process in Portaratrum is quite similar to that of L. tuberculata . However, Portaratrum can be differentiated by the absence of the carpal shield of the cheliped which is present in L. tuberculata .

This genus is here assigned provisionally to the family Colletteidae . The rigid body calcification and the cheliped attachment are more similar to that of the Agathotanaidae , but the form of the molar process and the presence of pleopods on females shows clearly that it does not belongs to that family. The absence of coxa, the form of the mandible and molar process, endites of the maxilliped not fused, place this genus close to Colletteidae . Further analysis will show if this genus belongs to the Colletteidae or a new not yet defined family.