Megalothorax calvignacensis Panina, Bedos, Deharveng & Schneider, 2026, sp. nov.

Megalothorax calvignacensis sp. nov. urn:lsid:zoobank.org:act: 32125530-4756-461A-8102-B42D30F60B70 Figs 1A–C, 2–3, 8, Tables 1–2 Diagnosis Megalothorax calvignacensis sp. nov. belongs to the minimus -group (Schneider & D’Haese 2013). The peculiar feature of this species is the black-grey colour of the body, common in the incertus -group (M. nigropunctatus Schneider & D’Haese, 2013, M. perspicillum Schneider & D’Haese, 2013), but firstly seen in the minimus -group. Although the new species is morphologically similar to several species of the genus – namely M. granulosus Schneider & D’Haese, 2013, M. minimus Willem, 1900 sensu Schneider & D’Haese, 2013, M. willemi Schneider & D’Haese, 2013, it exhibits several distinctive features. In chaetotaxy, M. calvignacensis sp. nov. resembles M. granulosus, apart from the absence of chaetae β1, γ2, η4 (vs their presence in M. granulosus). In addition, the second pair of dorsal globular sensilla s3 is present in M. calvignacensis (vs absent in M. granulosus). Both species have a smooth mucro, 2+2 chaetae on the manubrium, an unpaired chaeta a0 on forehead and flame-shaped inner sensilla. Megalothorax calvignacensis sp. nov. is similar to M. minimus by its smooth mucro, an unpaired chaeta a0 and similar chaetotaxy. In M. calvignacensis present chaeta ζ1 (vs absent in M. minimus), but in M. calvignacensis absent chaeta β1 (vs present in M. minimus). In addition, M. calvignacensis has flame-shaped inner sensilla (vs T-shaped in M. minimus). Adult specimens can be easily recognized from M. minimus by the pigmentation, orange in M. minimus (Fig. 1B, D–E). With another widespread species, M. willemi, the new species shares the presence of flame-shaped inner sensilla, smooth mucro, an unpaired chaeta a0 and similar chaetotaxy. However, in M. calvignacensis sp. nov. the chaeta β1 is absent (vs present in M. willemi) and the chaeta ζ1 is present (vs absent in M. willemi); and M. willemi lacks pigmentation. Etymology Megalothorax calvignacensis sp. nov. is named after its type locality, the commune of Calvignac. Type material Holotype FRANCE • 1 ♀; Lot, Calvignac, mosses on rock face; 1.78475° E, 44.46041° N; 178 m a.s.l.; 25 Dec. 2023; Guy Bariviéra leg.; sample code nos 46-Q23-086, SMNG, slide no. SMNG-APT-AA04651. Paratypes (9 ♀♀) FRANCE • 5 ♀♀; Lot, Calvignac, mosses on rock face; 1.78475° E, 44.46041° N; 178 m a.s.l.; 25 Dec. 2023; Guy Bariviéra leg.; Apterygota collection SMNG, slides nos SMNG-APT-AA04652 to SMNG-APT-AA04655, tube no. SMNG-APT-EA-003-001 • 2 ♀♀; same data as for preceding; MSPU, slides nos LD 46-Q23-086-A, LD 46-Q23-086-B • 2 ♀♀; same data as for preceding; MNHN, slides nos 46-Q23-086A, 46-Q23-086B. Other material examined FRANCE • 6 specs in ethanol; Lot, Calvignac, mosses on rock face; 1.78475° E, 44.46041° N; 178 m a.s.l.; 25 Dec. 2023; Guy Bariviéra leg.; Apterygota collection SMNG, tube no. SMNG-APT-EA-003-001 • several specs in ethanol; same data as for preceding; MNHN. Description GENERAL ASPECT. Habitus and segmentation typical of the genus. Body length up to 500 µm. Specimens grey in alcohol (Fig. 1A–C). General chaetotaxy typical of the genus, trichobothria not studied. All chaetae ordinary, not lanceolate. INTEGUMENT. Secondary granulation made of the usual dorsal rough granule. Integumentary channels extending laterally and dorsally in anterior and posterior parts of head. Anterior canal branching. Channels connection with linea ventralis roundabout-like. SENSORY FIELDS AND WAX RODS (Fig. 2A). Sensory fields (sf 1–6) and their inner sensilla, as well as wax rod crypts wrc 1–7 with typical distribution of the genus. All inner sensilla of sensory fields are flame-shaped, the inner sensilla of sf 2 broad. MOUTHPARTS. Labrum as typical of the genus (Fig. 2C). Chaetae a1 pointing inward, with two teeth. Chaetae a2 with two small teeth. Labium with 4+4 proximal chaetae (Fig. 2D). Basomedian field with 3+ 3 chaetae. Labial palp (Fig. 2D) typical of the genus (A, B, C, D, E, b1, b2, d1, d 2, 2e, H, h1, h2). Oral fold and maxillary outer lobe typical of the genus, without sublobal hair (Fig. 2E). Maxillary head without strong modification. Mandibula ordinary (Fig. 2F). Head chaetotaxy. Forehead chaetotaxy as on Fig. 2B. Clypeal-labral formula: a0; 2, 4, 5, 4, 5, 4. Chaeta a0 present. Dorsal posterior area with 18 ordinary chaetae (Fig. 2B). Ventral side with three pairs of post-labial chaetae. Trend for posterior chaetae to be longer and stronger than anterior chaetae. ANTENNAL CHAETOTAXY (Fig. 3A–B). Ant. I and II with one and four chaetae, respectively. Ant. III with seven chaetae and two long S-chaetae (S1 and S4). Striations of Ant III sensory organ short sensilla (S2 and S3) distinguishable in light microscopy. Ant. IV with seven chaetae (X-chaeta present) and ten S-chaetae. Sensory organ with Sx, Sy, Or, a, Sa. Organite (Or) of Ant IV short, seems apically flared. Summary on antennal chaetotaxy provided in Table 1. BODY CHAETOTAXY. Th. II with 12 + 12 chaetae, 1+ 1 tubular and curved s1-sensilla (Fig. 2A). All chaetae ordinary. Th. III with 10 + 10 chaetae (some chaetae more lanceolate), 6+ 6 free wax-rods (wrc1–6). Chaeta a6 is longer and stronger than chaeta a5. Abd I–V terga with 20+20 ordinary chaetae, with 1 +1 wrc (wrc 7 ordinary), 1 +1 globular sensilla s2 (Fig. 2A). Sensilla s3 absent. LEGS CHAETOTAXY. Typical of the genus (Table 2), consisting of ordinary chaetae of variable size (Fig. 3C– E). CLAWS. Claw III bulkier than claw I and II. Claws subequal in unguis length (with a trend as unguis I> unguis II> unguis III). Unguis basal and posterior auxiliary lamellae well developed (Fig. 3C–E). Unguiculus 0.5–0.6 as long as unguis. ABD. IV STERNUM AND FURCA. Abd. IV sternum with 2 +2 neosminthuroid chaetae and 2 + 2 chaetae. Manubrium with 2+2 posterior chaetae and 1+ 1 pegs with convex tip articulated with a corresponding concavity of the dens (Fig. 3G). Proximal subsegment of dens with a posterior chaeta (Fig. 3G); distal subsegment posteriorly with two basal spines and one chaeta at the middle. Anterior side of dens with five apical spines, spines without elongated apex (Fig. 3G). Dens ordinary, as in Fig. 3G. Mucro smooth, without teeth (Fig. 3G). ABD. VI: ordinary with nine dorsal chaetae; each anal valve with a chaeta. Mature females with 8+ 8 ventral chaetae each anal valve with a chaeta av and several granular crests; mature females with 6+6 to 8+ 8 ventral chaetae. Genital plate: female with 2+2 chaetae. Male unknown. TENACULUM AND VENTRAL TUBE. Tenaculum with 3+3 hook-like teeth (Fig. 3F). Ventral tube bulky with two apical pairs of chaetae. Distribution and ecology So far known only from the type locality, where it co-exists with M. minimus. Molecular data One topotype specimen sequenced (sample code 46-Q23-086), BOLD process id CSCOL002-25.