Typhlotanais : G. O. Sars 1882

Genus: Typhlotanais G.O. Sars, 1882

Tanais: Lilljeborg (1864) (in part): 12.

Typhlotanais: G.O. Sars (1882a) 7: 52; Sieg (1986a) 94–95; Larsen (2005) 209–210.

Diagnosis (new): Body long (seven times as long as wide). All pereonites wider than long, lateral edges parallel (not rounded in dorsal view). Antennule shorter than carapace. Labrum hood-shaped, sparsely setose. Mandible lacinia mobilis delicately crenulated, molar with numerous, regular, blunt denticles. Maxilla with nine spines. Maxilliped basis as long as wide, with short seta; endites with two setae and two tubercles. Labium bilobed, sparsely setose distally. Cheliped slender; chela almost as long as carpus, three times as long as wide. Pereopods 1–3 coxa without spurs; pereopod-1 with regular setae (eight, two, and five on basis, merus and carpus respectively) on dorsal margin; pereopods 2 and 3 with spiniform setae on carpus and propodus; pereopods 4–6 carpus with prickly tubercles of moderate size (less than half of carpus length), unguis with bifid tip, propodus distal seta (-ae) reaching end of dactylus. Uropod rami one-articled; exopod little shorter than endopod, tipped with two simple setae (one seta robust).

Male: Unknown.

Gender of generic name: Masculine.

Type species: Typhlotanais (= Tanais) aequiremis (Lilljeborg, 1864).

Species included: Typhlotanais aequiremis (see remarks).

Remarks: The first step toward rationalizing typhlotanaid taxonomy was taken by Sieg (1984). In considering the ornamentation of the first three pairs of pereopods, he separated typhlotanaids from leptognathiids, primarily as a subfamily (op. cit.) and later as a family (Sieg, 1986b) judging them as an apomorphic group. His conclusions were based mainly on the presence of fully developed ‘spines’ (‘spiniform’ setae in presently accepted terminology) on the anterior pereopods in Leptognathiidae, while pereopod spines are strongly reduced or completely absent in typhlotanaids. In contradiction to the diagnosis given by Sieg 1986a, there are minute spiniform setae occuring on pereopods 2–3 of most typhlotanaids, including the type species— T. aequiremis. They are absent in a few species only. Two of these (Typhlotanais parvus Sieg, 1986 and T. grahami Błażewicz-Paszkowycz, 2004) have reduced setation on all pereopods and indeed the carpus of their pereopods 2 and 3 is armed with two regular setae only. This feature differs in the new genus Pulcherella described below, which has 3–5 setae on the pereopod 2–3 carpus. If Sieg’s concept that spiniform setae on these pereopods is an apomorphic character is correct, the regular and relatively numerous setae in Pulcherella should be considered plesiomorphic, while reduced setation, including the reduction of spiniform setae, should be an apomorphy.

Sieg (1986a) suggested two phylogenetic trends within Typhlotanais and created the subgenera Typhlotanais and Monosmerinx. His preliminary system was based on the number of terminal seta on the uropodal exopod (one in Monosmerinx and two in Typhlotanais) and the absence or presence of a proximal seta in the endopod of the pleopod. However, these two characters need to be entirely re-assessed. My initial observations reveal that there is only one seta on exopod of the uropods in just two typhlotanaids (T. parvus and T. grahami), while the lack of the proximal setae on the pleopods may be an artifact due to frangible character of pleopod setation.

At the moment Typhlotanais sensu stricto comprises only the type species (T. aequiremis). Consequently all other species must remain Typhlotanais sensu lato. It is recognized that further studies may place other Typhlotanais sensu lato species into Typhlotanais sensu stricto, but such a transfer is not possible now owing to the scarcity or poor condition of the material available for the study.

Morphological studies of Typhlotanais sensu lato have shown a variety of characters: the proportionate length of pereonite-1, the setation of the dorsal edge of the cheliped carpus, the morphology of the mandible molar process, the shape of the basis of pereopods 1–3, and the character of the clinging apparatus of pereopods 4–6. These characters can be used to provisionally split Typhlotanais into coherent morpho-groups and that may provide the basis for distinguishing new genera in the future.