Anisotermes bourguignoni, Jouault, Engel, Huang & Nel, 2022

Jouault, Corentin, Engel, Michael S., Fls, Legendre, Frédéric, Huang, Diying, Grandcolas, Philippe & Nel, André, 2022, Incrementing and clarifying the diversity and early evolution of termites (Blattodea: Isoptera), Zoological Journal of the Linnean Society 196, pp. 608-629 : 613-617

ANISOTERMES BOURGUIGNONI JOUAULT, ENGEL, HUANG & NEL SP. NOV.

( FIGS 3–5 )

Z o o b a n k r e g i s t r a t i o n: h t t p: / / z o o b a n k. org/ urn:lsid:zoobank.org:act:A406BDD6-D799-4DB8-93D0-4C2E61C71F1A

Holotype: Specimen identifier NIGP177751 (a complete dealate specimen preserved in a rounded amber piece), housed in the collection of the Nanjing Institute of Geology and Palaeontology Chinese Academy of Sciences (NIGPAS), Nanjing, China.

Etymology: The specific epithet honours Dr Thomas Bourguignon for his work on termite evolution. It is to be treated as a noun in the genitive case.

Locality and age: Noije Bum Hill, Hukawng Valley, Kachin State, Myanmar; Late Albian to Early Cenomanian, ‘Mid’-Cretaceous.

Diagnosis: Imago. Head rounded, with anterior corners slightly orthogonal and posterior corners rounded; left mandible with la longer than LM 1, both sharp; right mandible with an apical and two marginal teeth, ra shorter than RM 1, RM 1 and RM 2 separated by a sharp angle; occiput and frons convex; postclypeus trapezoidal; anteclypeus small; ocelli absent; pronotum massive, trapezoidal, wider than head, anterior margin concave surrounding head, posterior margin broadly convex, with dorsal surface flatly arched in profile, sides convex; tarsi pentamerous; tibial spur formula 3-4-4; protibia with two additional spine (fa, fb); mesotibia with six additional spines (ma-mf); metatibia with at least three additional spines (ha-hc); arolium present; forewing with scale large, with humeral margin welldefined and slightly arched, claval suture strongly curved (PCu), basal suture convex; Sc, RA, RP and CuA heavily sclerotized; Sc branched within scale and going outside of scale; R branched within scale; M weaker than other surrounding veins; CuA with three branches in scales; PCu strongly curved; anal veins not discernible within scale.

Description: Imago. Body c. 10 mm long (from tip of labrum to abdomen apex). Head robust, c. 2.20 mm long (measured from under the pronotum to the tip of the labrum) and c. 1.93 mm wide excluding compound eyes, square-shaped in dorsal view, hypognathous, sides slightly convex, anterolateral corner slightly orthogonal, posterolateral corners rounded, Y-shaped ecdysial scar absent; tentorial pit visible (ttp); postclypeus (pc) 0.32 mm long, trapezoidal; labrum c. 0.50 mm long, lobe-shape, narrower basally; mandibles massive, triangular shaped, at least 0.53 mm high; buccal pieces with glossa (gl), paraglossa (gl), stipe (st), mentum (mt), submentum (sm) visible but not clearly describable; five maxillary palpomeres, combined length as preserved c. 1.2 mm; four(?) labial palpomeres present, with three discernible palpomeres, combined length c. 0.75 mm; compound eyes, c. 0.45 mm long, circular, situated laterally near head midlength, and separated from posterior head margin by more than their length; fontanelle not visible and probably absent; antenna moniliform with at least 22 antennomeres. Pronotum c. 1.60 mm long marginal teeth (number corresponding); sm, submentum; st, stipe; ttp, tentorial pit. Scale bars 0.5 mm (A, C, D); 1 mm (B). and c. 2.73 mm wide, overlapping head dorsally, sides slightly upturned.

Legs robust; procoxa c. 1.38 mm long, profemur c. 1.51mm long, protibia c. 1.41mm long, protarsus at least 0.76 mm long; protibia with three spurs f1, f2, f3 and additional spines; mesocoxa c. 1.13 mm long, mesofemur medially swollen c. 1.57 mm long, mesotibia c. 1.72 mm long, mesotarsus c. 0.64 mm long; mesotibia with four observable spurs m1, m2, m3, m4 and additional spines; metacoxa at least 1.10 mm long, metafemur at least 2.24mm long, metatibia at least 1.50 mm long, with three observable spurs h1, h2, h3, h4 and additional spines; all spurs flattened with serration; all tarsi pentamerous; pretarsal arolium present. Forewing scale c. 2.36 mm long and 1.41 mm wide (measured distally), sclerotized, especially in anal area, with sparse setation. Hindwing scale not visible but proximal part of hindwing clearly cut beyond basal suture.

Abdomen at least.6.0mm long with at least11observable segments; abdominal segments widest at midlength. Cerci multimerous c. 0.52 mm long, five to seven cercomeres (sometimes fused so not clearly countable).

Colour: Not preserved.

Remarks: Anisotermes bourguignoni differs from most other Cretaceous ‘lower’ Isoptera in having a plesiomorphic character in scale configuration (e.g. fine reticulation between veins in the scale), tarsi pentamerous (plesiomorphic character), a tibial spur formula of 3-4-4 and an overall massive trapezoidal-shaped pronotum. The wholly pentamerous tarsi and enriched tibial spur formula tend to imply an early diverged position within Isoptera , among groups like Archotermopsidae , Hodotermitidae , Mastotermitidae and their various extinct relatives. Additionally, its general habitus, and particularly its large pronotum, suggests that A. bourguignoni is related to Mastotermitidae or to taxa belonging to the ‘ Meiatermes -grade’. Interestingly, the hindwings of A. bourguignoni were cut slightly distal from the hindwing basal scale suture, while in the forewing the cut follows the basal suture. The hindwing basal scale suture was probably not fragile enough to break alone after the mating swarm, as it normally happens in a majority of extant termites. This suggests that the suture of the hindwing is rudimentary (symplesiomorphy) as in Mastotermes darwiniensis ( Tillyard, 1931) , and that the new specimen could be related to Mastotermitidae . Another character suggesting placement of Anisotermes within Mastotermitidae is the mandibular shape. In fact, Anisotermes and Mastotermes exhibit a similar configuration of teeth on both mandibles, and length variations (RM 1 conspicuously longer than ra vs. equal in length) are usually indicative of different genera from the same family. Additionally, this placement is strengthened by the diagnostic characters of the new species: ocelli absent, procoxal carina present, arolium present and the aforementioned scale characters. The absence of ocelli indicates affinities with Idanotermitinae , but the new fossil differs from the genus Idanotermes Engel, 2008 in at least its different tibial spur formula (i.e. 3-4-4 vs. 3-4-3). The genus Anisotermes is here tentatively considered as a member of the Idanotermitinae ( Jiang et al., 2021: 379); we confirm this placement mainly based on the presence of the anal lobe (characteristics of Mastotermitidae within the Isoptera ) and based on the absence of ocelli. The new species differs from A. xiai by, inter alia, the presence of the pretarsal arolium and more additional spines along the tibiae.

Figures

Figure 3. Anisotermes bourguignoni sp. nov., holotype NIGP177751. Photographs of habitus. A, dorsal view; B, ventral view. Scale bars: 1 mm.

Figure 4. Anisotermes bourguignoni sp. nov., holotype NIGP177751. Detailed photographs. A, head and pronoun in dorsal view; B, head in ventral view; C, high-resolution X-ray microtomography reconstruction of head in ventral view; D, high-resolution X-ray microtomographyreconstruction ofhead inanterolateral view;E, line drawing ofmandibles;F,line drawingof Mastotermesdarwinensis mandibles.gl,glossa;la,leftapical tooth;lb,labrum;lc,lacinia;lci,lacinialincisor;LM1-LM3,leftmarginalteeth(numbercorresponding); Lp, labial palp; mb, mandibles; Mp, maxillary palp; mt, mentum; pc, postclypeus;pgl, paraglossa; ra, right apical tooth; RM1-RM2, right

Figure 5. Anisotermes bourguignoni sp. nov., holotype NIGP177751. Detailed photographs. A, protarus; B, mesotarsus; C, apex of metatibia; D, line drawing of scale venation with names of veins labelled; E, scale; F, cerci in ventral view with arrows pointing to cercomeres; G, cerci in dorsal view; H, interpretative drawing of protibia; I, interpretative drawing of mesotibiae; J, interpretative drawing of metatibiae. CuA, anterior cubitus; MA, media; PCu, postcubitus; RA, anterior radius; RP, posterior radius; Sc, subcosta; for the nomenclature of tibial spines and spurs refers to Krishna et al., 2013. Scale bars: 0.2 mm (A, F, G); 0.5 mm (B, C, D, E, G, H, I, J).