Gerontoformica maraudera, Barden and Grimaldi

Phillip Barden & David A. Grimaldi, 2016, Adaptive Radiation in Socially Advanced Stem-Group Ants from the Cretaceous, Current Biology 26, pp. 515-521 : 538-539

Gerontoformica maraudera, Barden and Grimaldi , New Species, Fig. S2D,E

Diagnosis (worker): Readily distinguishable from other Gerontoformica species by elongate mandibles incapable of full adduction against clypeus; frontal lobe with pointed and projected anterolateral margin; sparse, thick setae coating head and body; five maxillary palpomeres; reduced metanotum; distinct band-like constriction between first and second gaster segments. Total length 8.67.

ZooBank LSID. urn:lsid:zoobank.org:act:64ED00D2-0 562-49A4-9E55-1E17F9C83CCF

Description (worker): all measurements in millimeters (mm).

Head: Sparsely setose, setae up to 0.36 length; head 1.21 length from posterior margin of head to anterior margin of clypeus in frontal view; 1.06 wide excluding eyes. Ocelli present. Occipital foramen broadly rounded. Vertex of head flattened, its posterolateral margins broadly rounded. Eyes situated high on head, 65% the distance above anterior margin of clypeus to posterior margin of head. Eyes bulging, 0.43 long, 0.24 deep. Cuticle between antennae raised into frontal lobe, frontal carina originate at inner margin of eye, diagonally leading to anterior margin of frontal lobe, terminating as a slight pointed expansion. Antenna total length 6.07: scape 0.66, pedicel 0.19, funicular segment I 0.89, II 0.63, III 0.63, IV 0.60, V 0.61, VI 0.54, VII 0.56, VIII 0.54, IX 0.51, X 0.56. Clypeus appearing reduced, anterior and lateral margins obscured by desiccation; anterolateral margin with small pointed projection; anterior margin with characteristic stout, setae-like denticles (0.03 long), difficult to enumerate,>15. Mandibles elongate, 1.00 long, exceeding width of clypeus preventing flush retraction as in other Gerontoformica ; apex with two denticles, apical tooth slightly larger; external margins slightly setose. Labium broad, possessing at least six interwoven rows of small, pointed denticles; anterior margin with fine, tapered setae. Labial palps with two palpomeres (damaged and not possible to measure accurately); maxillary palp with five palpomeres: I 0.13, II 0.23, III 0.33, IV 0.44, V unclear.

Mesosoma: Weber’s length 2.90. Dorsal lengths: Pronotum 1.07, mesonotum 0.70, propodeum 1.44. Dorsal sclerites with sparse setae throughout. Pronotum broadly rounded with high collar; depression situated just anterior to collar. Propleuron reduced, slightly visible in lateral view. Mesonotum expanded dorsally; thoracic gemmae appear to be present. Metanotum apparently lost or highly reduced. Pronotum elongate, gradually rounded; metapleural gland opening gaping, facing posteriorly. Forelegs lost beyond the forecoxae; one midleg preserved; hind legs lost beyond femur. Procoxa with tapered setae along anterior edge, 0.69 long. Mesocoxa 0.53 long; mesotrochanter 0.36 long; mesofemur 1.69 long, trochantellus present; mesotibia highly setose, measurement obscured by fracturing and distortion, mesotibial spur not visible; tarsal segments highly setose, pretarsal claw with subapical tooth. Metacoxae 0.74 long; metatrochanter 0.37 long; metafemur 2.46 long.

Metasoma: Petiole not tergosternally fused, with broad anterior face, nodiform; approximately 1.06 total length. Node broadly rounded with setae along dorsal face; maximum height 0.67, decreasing to 0.57 at gaster attachment (sternal projection comprising 50% of this height). Underside of petiole and sternite of gaster segment I (abdominal segment III) possessing narrow projection that appears to be attached to both sclerites, projection with perpendicular anterior and ventral margins, anteroventral margin with sharp hook. Helcium distinct, rugose segment expanding to reach petiole. Gaster rugose throughout, with sparse elongate setae. Distinct band-like constriction between gaster segments I and II. Sting exuded slightly.

Type: Holotype JCZ Bu1846. Wingless female (presumed worker). Preserved in a 11 x 7 x 5 mm piece of transparent yellow amber previously shaped into bead. Myanmar: Kachin State dated to the Albian-Cenomanian boundary (ca. 99 Ma) [S10]. Housed at the American Museum of Natural History.

Etymology: As in “marauder,” in reference to the fierce appearance and dramatic mandibles.