Technomyrmex svojtkai, Perrichot & Engel, 2022

Perrichot, Vincent, Boudinot, Brendon E., Engel, Michael S., Fls, Xu, Chunpeng, Bojarski, Błażej & Szwedo, Jacek, 2022, Ants (Hymenoptera: Formicidae) from Miocene Ethiopian amber: filling gaps in the geological record of African terrestrial biota, Zoological Journal of the Linnean Society 196, pp. 775-791 : 780-782

TECHNOMYRMEX SVOJTKAI PERRICHOT & ENGEL

SP. NOV.

( FIGS 1–3 ; SUPPORTING INFORMATION, FIGS S1 , S 2 )

Z o o b a n k r e g i s t r a t i o n: u r n: l s i d: z o o b a n k. org:act: 565B4980-A80E-450B-A09B-603264A91F50.

Type material: Holotype NHMW-N6976, a complete worker; in Early Miocene (16–23 Mya) amber from the North Shewa Zone, Amhara region, Ethiopia; housed in the Department of Mineralogy and Petrography, Naturhistorisches Museum Wien (NHMW, Austria). Paratypes MAIG 6020, two workers missing portions of legs; in Early Miocene (16–23 Mya) amber from the South Wollo Zone, Amhara region, Ethiopia; housed in the Museum of Amber Inclusions of the University of Gdansk (MAIG, Poland).

Other material: MAIG 6020, one worker missing the head, portions of legs and gaster, but similar to the associated paratypes in its size and preserved structures, particularly the subcylindrical petiole, the shape and position of metathoracic and propodeal spiracles, thus considered here as conspecific; housed in the Museum of Amber Inclusions of the University of Gdansk (MAIG, Poland).

Etymology: The specific epithet honours Mr Matthias Svojtka (University of Vienna) who discovered the fossil representing the holotype and generously made it available for study.

Diagnosis: The species is uniquely identified within Technomyrmex by the following combination of worker characters: (1) anterior clypeal margin with a deep V-shaped median incision; (2) inner margins of incision continuously arched, with no marked angle with broadly semicircular anterolateral clypeal margins; (3) dorsum of head with a single pair of stiff setae situated above posterior level of eyes; (4) compound eyes situated around midlength of head (EPI 59), with about 40 ommatidia; (5) palp formula 6,4; (6) mandible with six conspicuous teeth apically on masticatory margin; (7) counting from the apex, first tooth longest, third and fifth teeth subequal in length, smaller than second and fourth, third to sixth teeth each separated by one denticle, sixth tooth followed by a continuous series of smaller teeth gradually decreasing in size along masticatory margin and basal angle, becoming denticles along entire basal margin; (8) the basal angle indistinct, continuously arched between margins; (9) mesosoma devoid of erect setae; (10) propodeal dorsum as long as declivitous face, their junction broadly rounded.

Description: Holotype. Body integument minutely asperous, mostly glabrous except sparse stiff setae on anterior head margin and gaster. Head only slightly longer than wide. Compound eye oval, moderately large and feebly convex, its outer margin barely surpassing the outline of sides in full-face view, with 38–40 ommatidia. Ocelli absent. Frontal carinae well distant, closer to inner margin of eyes than to each other, not surpassing posterior margin of eyes and without frontal lobe, such that antennal sockets entirely exposed although directed laterad. Antenna 12-merous, scape surpassing vertexal margin by more than one-third its length; first and terminal funicular antennomeres subequal in length, nearly twice as long as broad; all other antennomeres cylindrical, only slightly longer than broad. Vertex with an erect seta (likely paired, but upper left side of head altered) longitudinally aligned with frontal carina, in profile situated at midlength between posterior margins of eye and head. Anterior clypeal margin bordered by seven stiff, short setae inclined ventrally; posterior clypeal margin semicircular, even with posterior level of toruli. Mesosoma: in profile, mesonotal dorsal outline feebly convex in its anterior third, flat and sloped in its posterior two thirds. Mesonotum and propodeum forming a distinct angle at metanotal groove. Metathoracic spiracles raised into distinct tubercules, conspicuously breaking outline of mesosoma in lateral view, distinctly anterior to metanotal groove. Dorsal surface of propodeum flat, declivitous surface convex. In profile, propodeal spiracle at junction of lateral and declivitous surfaces, slightly above midheight of sclerite. Dorsal surface of mesosoma apparently without erect setae. Legs: mesotibia and metatibia each with one spur, that of metatibia pectinate. Metasoma: petiole more than twice as long as wide, nearly as wide as high, broadest around its midlength; ventral and dorsal surfaces feebly convex; ventral surface without lobe, with two anterior longitudinal rows of three short setae. Gaster: abdominal tergite III largest, ventral surface of its anterior projection with a groove that accommodates entire petiole. Tergites III–VI with posterior margin bordered by a row of short appressed setae barely surpassing margin. Tergite VII in dorsal view small, trapezoidal.

Paratypes and other specimens: As for the holotype, although incomplete or partially concealed due to preservation, but with posterior margin of head intact, not emarginate (MAIG 6020 paratypes); palpomeres clearly exposed (MAIG 6020 paratype 1), revealing a palp formula 6,4, with maxillary palp relatively long, exceeding hypostomal margin but not reaching occiput, and labial palp short, about one-third length of maxillary palp; mesonotum constricted and elongate (MAIG 6020 additional worker).

Measurements and indices: Abbreviations are explained in Material and methods. Holotype: BL ~ 2.00, HL 0.50, HW 0.49, EL 0.15, FcW 0.18, SL 0.59, WL 0.77, PL 0.30, PW 0.13, PH 0.12, GL 0.80, GW 0.55, CI 98, OI 30, EPI 59, SI 129. Paratypes and additional worker: HL 0.52–0.54, HW 0.46, EL 0.11–0.15, SL 0.52, WL 0.77, PL 0.25–0.35, PW 0.20, SI 110.

Note: Amber piece MAIG 6020 also contains a fourth, partially preserved worker, which displays a similar petiole and can probably be attributed to Technomyrmex . However, only the mesosoma and petiole are preserved, and it differs by a larger size (WL ~ 2.40 vs. 0.77; PL 0.77 vs. 0.25–0.35) and the presence of a dense, short pubescence covering all sclerites; it probably belongs to another species.

Among the dolichoderines, the petiole reduced to a low segment without a node or scale and overhung by the first gastral segment, which is anteriorly grooved, is shared by Technomyrmex and Tapinoma Förster, 1850 . The pygidium exposed in dorsal view, thus with five gastral tergites visible, as is seen on the new fossil, warrants placement in Technomyrmex (whereas the pygidium is reflexed ventrally, exposing only four gastral tergites in dorsal view in Tapinoma ; see, e.g. Bolton, 2007; Fisher & Bolton, 2016).

The new species is readily recognizable by its anterior clypeal margin with a deep V-shaped incision and broadly rounded lateral margins, the almost complete lack of erect setae on the dorsum of head, mesosoma and first gastral tergite (with the exception of a single pair of setae posterior to the frontal carinae), and the propodeal dorsum that is as long as, or even slightly longer than, the declivitous surface. In all other species of Technomyrmex with a deeply incised clypeal margin, the median notch is either U-shaped or semicircular, but never V-shaped. These and other features, such as the elongate mesosoma and metathoracic spiracles raised on tubercles, suggest that Technomyrmex svojtkai may belong to the bicolor group of species as defined by Bolton (2007).

Figures

Figure 1. Technomyrmex svojtkai sp. nov., holotype worker NHMW-N6976.A, photomicrograph in right lateral view, with tip of gaster curled toward the mouthparts. B, 3D model in nearly the same position, imaged by synchrotron microtomography. C–E, 3D model of body with antennae and legs virtually removed: C, anterior (frontal) view; D, left lateral view; E, posterior (dorsal) view. Scale bar: 0.5 mm. Animated versions of this are available in Supporting Information online (Figs S1, S2).

Figure 2. Technomyrmex svojtkai sp. nov. Phase contrast X-ray synchrotron microtomography of holotype worker NHMW-N6976, with indication of measurements as reported in Material and methods. A, lateral view of body with legs and antennae virtually removed, and with petiole and gaster virtually uncurled to approximate the life position.The left lateral side of the head and mesosoma being crushed, the figure shows them from the horizontally flipped right side in standard left profile view. B, reconstruction in dorsal view, without legs and antennae, and with gaster largely concealing the petiole as in approximate life position. C, head in full-face view. D, head without antennae in full-face view. E, mandibles in dorsal view. F, petiole in dorsal view, with articulation with gaster as preserved. F, gaster in ventral view, with articulation with petiole as preserved, showing the first gastral tergite concavity for accommodation of petiole. Abbreviations: AIII–AVII, abdominal segments III to VII. Scale bars: 0.5 mm, except 0.2 mm for E.

Figure 3. Technomyrmex svojtkai sp. nov., photomicrographs of paratype workers and additional, partial worker, specimen MAIG 6020. A, paratype 1, ventral view. B, paratype 2, dorsal view. C, paratype 2, left lateral view, anterior-oblique orientation. D, non-type, partially preserved worker, right lateral view. Scale bars: 0.25 mm.