A new group of species of the genus Megalothorax (Collembola, Neelidae) with Gondwanan distribution, and introducing an open interactive identification key of Megalothorax species Author Schneider, Clément Abteilung Bodenzoologie, Senckenberg Gesellschaft f ¸ r Naturforschung, Görlitz, Germany. Author Minor, Maria A. School of Natural Sciences, Massey University, Palmerston North, New Zealand. Author D’Haese, Cyrille A. MECADEV, UMR 7179 CNRS MNHN, Muséum national d’Histoire naturelle, Paris, France. text Zootaxa 2023 2023-01-12 5228 2 101 121 journal article 226125 10.11646/zootaxa.5228.2.1 819e7189-366e-4967-8cc9-60bcf42615ee 1175-5326 7532173 07D486F0-D44C-4F4B-B625-557442893DF2 Megalothorax tasmanterolenis sp. nov. Figs 4 , 5 , 8A, B , 9A–D 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 TAS001d. 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 TAS001d (same as holotype ), 28S rDNA: OP942370 (806bp), 16S rDNA: OP942367 (468bp). Voucher could not be recovered. Diagnosis. Yellow-orange in ethanol, labrum a1 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 s2 globular, s3 absent on the abdomen, tenaculum with 4 + 4 teeth, posterior lamellae of the mucro moderately enlarged, internal lamella serrated, external lamella irregular. Description. General aspect. Habitus and segmentation typical of the genus. Length from labrum to anus: up to 500µm. 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. 4A ); 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. 4A, 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. 4A, 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. 4B ). Ventrally, 3 + 3 chaetae in the sub-labial region. Diagram of head chaetotaxy provided in Fig. 8A, 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 a1 and a2 thicker than chaetae m0-2 ; a1 shorter than a2 ; m0-2 smooth ( Fig. 4D ); apex of a1 with bifurcate tip ( Fig. 4C ); apex of a2 acuminate, with inward curvature, subtly serrated ( Fig. 4C ). Organisation of the labral anterior process not studied in detail. Two small teeth near the ridge of the labrum ( Fig. 4C ). Other mouthparts. Oral fold with 2 + 2 chaetae ( Fig. 4E ). Maxilla outer lobe with two chaetae (apical and basal) and with a strong bifurcate hair in subapical internal position ( Fig. 4E ). Sub-lobal plate without hair, with two lobes on the anterior ridge ( Fig. 4E ). Mandibula ordinary ( Fig. 4F ). Maxilla with a well developed apical lamella ( Fig. 4G ). Antenna. As in Fig. 5A , 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 Sb6 above S2 , S3 . Sa2 with a swollen aspect in comparison to the other Sa and Sb chaetae. Thoracic and abdominal tergites. As in Fig. 4A , same observations as in M. anterolenis sp. nov. , but with schaetae s3 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. 5E ). Dens ordinary ( Fig. 5E ): 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. 5E ). Ventral tube with 2 + 2 apical chaetae, retinaculum with 4 + 4 teeth. FIGURE 4. Megalothorax tasmanterolenis sp. nov. (A) Chaetotaxy of trunk tergites from Th. I to Abd. IV, area of repartition of the secondary granulation represented in grey, (B) Head dorsal side. (C, D) anterior side of the labrum anterior process, (D) labrum posterior side. (E) Maxillary outer lobe. (F) Mandibula. (G) Maxilla. 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. 5B–D ; with external basal lamellae short. Differential diagnosis. Very similar to M. anterolenis sp. nov. , but differs from the latter by the shape of the labral chaetae a1 , 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 s3 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 ).