Megalothorax tasmanterolenis

Description. General aspect. Habitus and segmentation typical of the genus. Length from labrum to anus: up to 500 µm. Specimens whitish (in 96 % ethanol). All typical chaetal types of the genus are accounted for, without any remarkable development. Integument. Distribution of the secondary granulation identical to M. anterolenis sp. nov. (Fig. 4 A); the speckle of enlarged primary granules on the clypeal area is present but subtle on our available specimens. Integumentary channels moderately developed on the head (Fig. 4 A, B). On each side of the head, the basal channel splits nine times successively. First the two external branches extend to the antero-dorsal region of the head, then up to five branches extend to the latero-posterior part of the head, finally the five most posterior branches reaching the dorsoposterior part of the head. Head channels connection with linea ventralis circular. Channels absent on trunk. Sensory fields and wax rods. Same observation as in M. anterolenis sp. nov. (also see Fig. 4 A, B). Head chaetotaxy. Postero-dorsal chaetae without remarkable thickening, only subtly stronger than antero-dorsal chaetae. Number of chaetae: 12 + 12 in the postero-dorsal region, 9 + 9 and 2 unpaired in the antero-dorsal region, 2 + 2 in the antero-lateral region (Fig. 4 B). Ventrally, 3 + 3 chaetae in the sub-labial region. Diagram of head chaetotaxy provided in Fig. 8 A, B. Labium. Basomedian fields of labium with 1 + 1 chaetae, basolateral fields of labium with 1 + 1 chaetae on a small papilla. Labial palps ordinary. Labrum. Chaetae a 1 and a 2 thicker than chaetae m 0 - 2; a 1 shorter than a 2; m 0 - 2 smooth (Fig. 4 D); apex of a 1 with bifurcate tip (Fig. 4 C); apex of a 2 acuminate, with inward curvature, subtly serrated (Fig. 4 C). Organisation of the labral anterior process not studied in detail. Two small teeth near the ridge of the labrum (Fig. 4 C). Other mouthparts. Oral fold with 2 + 2 chaetae (Fig. 4 E). Maxilla outer lobe with two chaetae (apical and basal) and with a strong bifurcate hair in subapical internal position (Fig. 4 E). Sub-lobal plate without hair, with two lobes on the anterior ridge (Fig. 4 E). Mandibula ordinary (Fig. 4 F). Maxilla with a well developed apical lamella (Fig. 4 G). Antenna. As in Fig. 5 A, same observations as M. anterolenis sp. nov., but with 9 to 10 normal chaetae on Ant. III (either 4 or 5 chaetae in the apical whorl) and Sb 6 above S 2, S 3. Sa 2 with a swollen aspect in comparison to the other Sa and Sb chaetae. Thoracic and abdominal tergites. As in Fig. 4 A, same observations as in M. anterolenis sp. nov., but with schaetae s 3 absent. Pseudopores not studied. Abd. VI. Ordinary, with nine chaetae on tergites, a small chaetae on each anal valves, and with 10 + 10 chaetae on sternites. Genital plate. Female with 2 + 2 chaetae, male not seen. Abd. IV sternites. With 2 + 2 usual neosminthuroid chaetae and 2 + 2 ordinary chaetae, the internal chaetae longer than the external ones. Abdominal appendages. Manubrium with 2 + 2 posterior chaetae (Fig. 5 E). Dens ordinary (Fig. 5 E): basal part of dens with 1 + 1 posterior chaetae, apical part of dens with 1 + 1 posterior chaetae and 7 + 7 small spines; basal spines with blunt apex, apical spines with filamentous apex. Mucro elliptical, with moderately wide lamellae; internal posterior lamella with around seven teeth (but could not precisely studied), external lamella without hardened teeth, but with an irregular aspect (Fig. 5 E). Ventral tube with 2 + 2 apical chaetae, retinaculum with 4 + 4 teeth. Legs. Chaetal composition on legs (subcoxa 1, 2, coxa, trochanter, femur and tibiotarsus): leg I, 1, 0, 1, 2, 8, 12 chaeta (e); leg II, 1, 1, 1, 3, 8, 12 chaeta (e); leg III, 2, 1, 1, 4, 8, 10 chaeta (e). Claws ordinary, as in Fig. 5 B – D; with external basal lamellae short.

Figs 4, 5, 8 A, B, 9 A – D

Diagnosis. Yellow-orange in ethanol, labrum a 1 chaetae with bifurcate tip, maxillary palp with an internal bifurcate hair, basomedian and basolateral fields of labium each with 1 + 1 chaetae, secondary granulation limited to the abdominal I – IV tergites, s-chaeta s 2 globular, s 3 absent on the abdomen, tenaculum with 4 + 4 teeth, posterior lamellae of the mucro moderately enlarged, internal lamella serrated, external lamella irregular.

Differential diagnosis. Very similar to M. anterolenis sp. nov., but differs from the latter by the shape of the labral chaetae a 1, the morphology of posterior lamellae of the mucro, the number of teeth on the retinaculum, and dorsally on the forehead by the additional pair of chaetae and the additional integumentary channel branch. After much scrutinization, we concluded on the absence of s 3 on the abdomen (present in M. anterolenis sp. nov.). Name etymology. Derived from the name of M. anterolenis sp. nov. combined with the region of discovery (Tasmania).

Material examined. Holotype. Female on slide (CSCOL _ 98), Australia, Tasmania, Ida Bay, 26. iii. 2015, 43.5070 ° S, 146.8755 ° E, mosses on the ground and rotten branches, sample number TAS 001 d. Paratype. Female on slide (CSCOL _ 99), same data as the holotype. All material collected by C. D’Haese. Material deposit. The holotype will be deposited at the Senckenberg Museum für Naturkunde, Görlitz, Germany. Paratype will be deposited at the Muséum National d’Histoire Naturelle, Paris, France. Obtained molecular data. One specimen from TAS 001 d (same as holotype), 28 S rDNA: OP 942370 (806 bp), 16 S rDNA: OP 942367 (468 bp). Voucher could not be recovered.