Chonidris insolita

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Chonidris insolita
Temporal range: Early Cenomanian, Late Cretaceous Burmese amber, Kachin Province, Myanmar
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Haidomyrmecinae
Genus: Chonidris
Species: C. insolita
Binomial name
Chonidris insolita
Perrichot, Wang & Barden, 2020

Chonidris insolita F2d.jpg

Identification

As for the genus, by monotypy.

Distribution

This taxon was described from Burmese amber, Kachin Province, Myanmar (Early Cenomanian, Late Cretaceous).

Biology

Castes

Known from gynes.

Specimens

Fig. 4. Overview and details of alate females (gynes) of Chonidris insolita gen. et sp. nov. Specimen HA04 (A–B), specimen RM2 (C–E), paratype NIGP172003 (F–G), and holotype NIGP171998 (H). Habitus (A, C, F), heads (B, D, H), wings in lateral view. Scale bars: 1 mm (A, C, E, F), 0.25 mm (B, D, G, H).

Originating from amber mines located near Noije Bum Village, Tanai Town, Myitkina District of Kachin State, northern Myanmar. A radiometric dating of zircons from the amber-bearing bed gave a maximum age of 98.79 ± 0.62 Ma (Shi et al., 2012), thus corresponding to the latest Albiane-earliest Cenomanian (mid-Cretaceous), which may not be very different from the age of the amber itself (Smith and Ross, 2018; Yu et al., 2019).

Holotype NIGP171998. Alate gyne. A nicely preserved specimen exposed in right profile and dorsal views, without distortion, but with left side largely obscured by numerous air bubbles, and missing right antennomeres II-XII, tarsomeres II-V and IV-V of right and left hind legs, respectively. In a rounded piece of yellow amber measuring 13 x 8 x 5 mm, with two spiders, two nematocerans (Diptera), and a beetle larva (Coleoptera). NIGPAS, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Science, China.

Paratype NIGP172003. Alate gyne. A specimen exposed in right anterolateral view, without apparent distortion, missing gaster and apices of wings. In a rounded piece of amber measuring 31 x 24 x 6 mm, with a Psocoptera contacting its right hind leg, a tiny parasitic wasp (Hymenoptera) and a beetle (Coleoptera). NIGPAS, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Science, China.

HA04. Alate gyne. A specimen exposed in profile and full facial views, with head and mesosoma distinctly compressed dorsoventrally, right side largely obscured by air bubbles, and missing tarsomeres II-V of right hind leg and apical gastral segments. In a rounded piece of clear yellow amber measuring 21 x 15 x 8 mm. HA, Huangyiren Amber Museum, Taiwan.

RM2. Alate gyne. A specimen exposed in left profile view, with dorsoventral distortion gradually increasing from head to gastral apex, and missing left antennomeres IV-XII. In a rounded piece of amber measuring 26 x 14 x 5 mm, with a myriapod, a true bug, two mites, and numerous debris. RM, Ruipoxuan Museum, Jinan, China.

Nomenclature

The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

  • insolita. †Chonidris insolita Perrichot, Wang & Barden, 2020: 8, figs. 2D-F, 4, 8F (q.) MYANMAR (Burmese amber).

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Description

Queen

holotype NIGP171998, paratype NIGP172003, specimen RM2, mm: HL [1.42] {1.68}; HoL [0.86] {0.658}; EL [0.72]; MDL [1.44] {1.10}; length of antennomeres: I (scape) [1.00] {0.96}, II (pedicel) [0.17] {0.21}, III [1.42] {0.92}; WL (3.66) {3.30}; FWL (5.2) {5.50}; PL (1.33), PH (excluding process) (1.12).

Body length around 10 mm. Cuticle smooth, densely covered by short adpressed setae; additionally with long, thin, erect setae sparsely covering head capsule, mesosoma, legs, and apical portions of gastral segments I-III, setae more densely covering pygidium.

Head about as long as broad, longer than high, circular in frontal view. Vertex and posteroventral surface strongly rounded, anterior surface flat, with short genae (ca. 0.2 x eye length) projecting into cheek-like lobe anteroventrally above mandible insertion. Ocelli distinct, positioned on small, raised, triangular prominence; ocellar diameter as broad as base of first antennomere, interocellar distance about one ocellar diameter. Compound eyes bulging, oval, 0.6 x as broad as long, removed from lateral margins of head capsule. Antennae inserted between compound eyes below their midlength, closely flanking lateral edges of clypeus at base of horn's stalk; base of antenna with basal bulb exposed, inserted within thick annular torulus opening obliquely dorsad; antenna elongate; scape ca. 0.8 x head length, weakly arched, cylindrical; pedicel very short, 0.2 x scape length, about as long as wide, slightly broadened apically; first flagellomere longest antennomere, about 8 x as long as wide (assessed from paratype, where antennae are flattened and elongate but respective ratios are kept); following antennomeres gradually decreasing in length. Posterior and lateral margins of clypeus (epistomal sutures) visible, indicating the horn is the result of an elevated anterior margin. Clypeal horn short (HoI 28-30), expanded at right angle from frons, strongly arched with dorsal surface convex and ventral surface furrowed; lateral margins prolonged basally on frons into raised carinae diverging toward anterior angles of head, just above insertion of mandibles; ventral surface and lateral carinae rimmed by row of short, peg-like denticles, and long, fine, erect setae. Labrum exposed between clypeal carinae, with anterior margin broadly convex and slightly notched medially, posterior margin obscured; dorsal surface coated by long, thin, erect setae. Dorsal margin of mandibles curved dorsally immediately from base, in profile view without distinct elbow, their tips reaching nearby horn's apex, dorsal mandibular margin armed apically as series of sharp, curved teeth; largest apical tooth preceded by two medial teeth of equal length following slight gap; basal portion of mandible (from base to base of medioventral blade) short, simple; distal portion projected medially and ventrally in a large, triangular blade tapering to the tip; the blade with dorsal surface concave, ventral corner rounded, and apical half serrate; tip of mandible with a preapical tooth immediately following the blade and projected posteriorly, and one apical acute tooth curved posteriorly; when mandibles closed, their medial margins parallel and closely approximated, slightly overlapping at ventral corner of blade; accommodated in the triangular clypeal cavity (i.e., concealing the anterior clypeal margin, labrum and ventral surface of horn); maxillary palp with 5 visible segments, labial palp with 3 visible segments.

Mesosoma about twice as long as high. Pronotal colar short, separated from remaining pronotal dorsum by a distinct transverse ridge; pronotum nearly vertical immediately anterior to ridge, feebly convex posterior to ridge (dorsum); posterior pronotal margin with distinct thickening dorsally. Promesonotal suture complete, appears flexible. Mesoscutum shorter than pronotum, mesoscutal dorsal outline faintly convex, with long parapsidal furrows converging posteriorly to reach anterior mesonotal margin. Mesoscutellum prominent; dorsal mesoscutellar surface convex, posterior surface slightly concave, their junction forming a sharp angle. Metanotum medially as high as long, with posterior surface forming distinct angle with propodeal dorsum. Propodeum 1.5 x as high as long, dorsal and declivitous surfaces flat, separated by thin ridge, forming sharp angle; propodeal spiracle slit-like atop rounded nodule, situated around junction of propodeal dorsum and sides. Metapleural gland orifice a small circular concavity. Mesopleuron and metapleuron coated in thin, tapered setae. Legs robust, mesocoxa distinctly shorter than pro-and metacoxae, small trochantellus present on mid- and hind legs; all femora moderately swollen in their basal half; ventral margin of protibia apically with large calcar and two straight, stout setae less than half as long as calcar; mesotibia apically with two long, straight, spurs, one pectinate and one simple; additionally with three short stout setae; metatibia apically with one long, pectinate spur, one long, simple spur, and one short, stout seta; tarsomeres I-IV of all legs with pairs of short, stout setae along entire ventral surface (6 pairs on tI, 3 pairs on tII, 3 pairs on tIII, 2 pairs on tIV), and apically with 2 pairs of simple, stout setae each flanking a spatulate seta (¼ plantar lobe); pretarsal claws strong, with a distinct subapical tooth and pulvilus.

Wing venation as in Dhagnathos except, in fore wing, the pterostigma 3 x as long as broad, cross-vein Rs∙f1 not arched, short stub of 1r-rs tubular, M∙f2 extremely short (1m-cu almost arising at level of Rs∙f2). Hind wing with 11 distal hamuli present, jugal lobe not visible, but lobe may be lost due to damage.

Metasoma. Petiole short-pedunculate, massive, 0.84 x as high as long; in profile, with posterior margin oblique and broadly attached to first gastral tergite (AIII); tergite and sternite of petiole and AIII unfused (suture distinct); petiolar tergite a strongly convex node, with anterior surface approximately twice as long as posterior surface which is nearly vertical in its anterior half, oblique in its posterior half; petiolar sternite with subpetiolar process and lamella (in profile) with a high, transverse tooth pointing ventrally, with anterior face flat, posterior face concave; process followed by a smaller but distinct triangular tooth. First gastral segment bellshaped; tergite with helcium faintly pronounced, with anterior surface behind helcium high, oblique, and dorsal surface strongly convex, short; anteriormost part of first gastral sternite with a distinct mesal process (keel) projecting anteroventrally below helcium. Second gastral segment (AIV) distinctly longer than first, with presclerite largely exposed to form a deep, broad constriction between AIII and AIV. Following segments more or less telescoped, pygidium convex, sting well exserted, distinctly arched dorsally.

Type Material

Holotype. NIGP171998, alate female. Paratype. NIGP172003, alate female. Additional specimens. HA04 and RM2, two alate females. Horizon and locality. Upper Cretaceous, upper Albianelower Cenomanian (ca. 99 Ma); in amber from the Hukawng Valley, Kachin State, Myanmar. Holotype and Paratype: NIGPAS, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Science, China.

Etymology

The specific epithet derives from insolitus (Latin, meaning ‘strange’), and refers to the unusual accommodation of the mandibles within the clypeus.

References