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This species belongs to the Middle American clade of Stenamma (see Branstetter 2012). All conent on this page modified from Branstetter (2013) unless noted otherwise.// Distribution
Northeastern Mexico (Nuevo Leon). Known only from the type locality.
Stenamma tiburon is known only from a single Berlese sample collected from forest at 1650 m elevation.
Worker diagnosis. Integument brown (probably darker in recently collected specimens); small to medium-sized species (see HL, ML, PrW below); head, mesosoma, and gaster mostly smooth and shining, with petiole and postpetiole punctate; promesonotum in profile distinctly asymmetrical, with anterior face gently rounded, dorsal surface flat or only slightly curving, and posterior face short, straight and forming a relatively sharp angle with dorsal surface; median lobe of clypeus bicarinate, projecting, and with a broad and rather deep median emargination at anterior margin; basal margin of mandible straight, without notch or substantial depression; petiolar node distinctly angled posteriad; postpetiole in dorsal view, with distinct mesolateral angles and a longitudinal lobe, giving anterior half of postpetiole a distinct pinched-in appearance; eye of moderate size (EL 0.10–0.12, REL 18–19), oval shaped, with 5–6 ommatidia at greatest diameter; setae on gastral tergites of moderate length and density, suberect to subdecumbent; propodeal spines absent, forming at most an obtuse angle in profile view (PSL 0.06–0.07, PSI 1.0-1.3); frontal lobes narrow (FLD 0.14–0.15, FLI 24–25), not obscuring torular lobes in full-face view (FLD 0.14-0.15, FLI 24-25).
Similar species: Stenamma pelophilum.
Worker description. (4 measured) HL 0.62–0.69 (0.67), HW 0.55–0.63 (0.59), FLD 0.14–0.15 (0.15), PCW 0.03–0.05 (0.05), SL 0.50–0.54 (0.52), EL 0.10–0.12 (0.11), ACL 0.48–0.51 (0.48), ML 0.79–0.86 (0.83), PrW 0.38–0.42 (0.40), PSL 0.06–0.07, SDL 0.05–0.07, PL 0.30–0.32 (0.30), PH 0.19–0.21 (020), PW 0.12– 0.14 (0.13), PPL 0.16–0.18 (0.16), PPH 0.16–0.17 (0.16), PPW 0.20–0.21 (0.20), MFL 0.53–0.59 (0.55), MTL 0.44–0.48 (0.46), CI 88–91 (89), SI 86–92 (88), REL 18–19 (19), FLI 24–25 (25), PSI 1.0–1.3 (1.0), PI 51–57 (51), MFI 103–108 (107), ACI1 67–70 (70), ACI2 93–97 (93).
Small- to medium-sized species; general body color brown to light brown, with extremities becoming yellow-brown (note that all studied specimens are over 40 years old, the color of fresh specimens must be darker); setae golden; mandible with 6 teeth, consisting of 3 distinct apical teeth, a somewhat projecting basal tooth, and 2 inner teeth, which are often worn and indistinct; basal margin of mandible relatively straight, without notch or significant depression; dorsal surface of mandible mostly smooth and shining, with scattered piligerous punctae and a few short basal striae; median lobe of clypeus bicarinate, projecting, and with a broad and rather deep median emargination at anterior margin, apex of lobe with a transverse carina, area between carinae distinctly depressed; carinae on median lobe forming a distinctive triangular shape in anterodorsal view; remaining surface of clypeus mostly smooth and shiny; posterior extension of clypeus between frontal lobes somewhat narrow (PCW 0.03–0.05), with subparallel sides; frontal lobes narrow, not obscuring torular lobes in full-face view; head roughly oval-shaped (CI 88–91), posterior margin flat to slightly concave, never greatly depressed medially; eye of moderate size (EL 0.10–0.12, REL 18–19), oval-shaped, with 5–6 ommatidia at greatest diameter; face nearly completely smooth and shiny, with scattered piligerous punctae and a few longitudinal carinulae around frontal carinae and on genae; scape distinctly shorter than HW (SI 86–92), not quite reaching posterior margin of head when laid back; scape surface mostly smooth and shiny, except for scattered piligerous punctures and faint striae; flagellum with distinct 4-segmented antennal club; mesosoma mostly smooth and shining, except metanotal groove with several longitudinal carinae, metapleuron with faint punctae, and propodeal dorsum and declivity with faint transverse carinulae; promesonotum in profile distinctly asymmetrical, with anterior face gently rounded, dorsal surface flat or only slightly curving, and posterior face short, straight and forming a relatively sharp angle with dorsal surface; metanotal groove distinct, but not very deep; propodeal spines essentially absent (PSL 0.06–0.07, PSI 1.0–1.3), forming at most obtuse angles at transition between dorsal and declivitous faces of propodeum in profile; petiole of moderate length (PL/ HW 0.51–0.57), node of moderate size (PH/PL 0.62–0.67) and distinctly angled posteriad, with anterior face slightly longer and more sloping than posterior face, node dorsum broadly rounded; postpetiole in profile asymmetrical, with long sloping ante-rior face and short nearly vertical posterior face; postpetiole in dorsal view with distinctive mesolateral angles and a longitudinal lobe, giving the anterior half of postpetiole a distinct pinched-in appearance; anterior faces of petiole and postpetiole smooth and shiny, remaining surfaces faintly punctate; most of body with a thin layer of short to medium length standing setae; pilosity on gastral tergites somewhat bilayered, with a layer of longer suberect setae, and a layer of equally dense subdecumbent setae; facial setae short and mostly decumbent; setae on scape subdecumbent to decumbent; setae on legs suberect to appressed, with longer suberect setae on femoral venters and coxae.
Queen description. (1 measured) HL 0.69, HW 0.63, FLD 0.15, PCW 0.05, SL 0.53, EL 0.17, ACL 0.52, ML 0.93, PrW 0.50, PSL 0.09, SDL 0.08, PL 0.34, PH 0.22, PW 0.14, PPL 0.19, PPH 0.19, PPW 0.24, MFL 0.59, MTL 0.49, CI 92, SI 83, REL 27, FLI 24, PSI 1.2, MFI 107, ACI1 68, ACI2 98. Same as worker except for standard queen modifications. See specimen CASENT0622423.
The combination of sculpture, clypeus structure, and postpetiole structure make S. tiburon a very distinctive species that should not be confused with any other MAC species. I include S. pelophilum as a similar species only because both species occur in the same couplet of the key, but these species are very different and can be easily separated by comparing clypeus structure.
It should be noted that this species is known from only nine specimens that were collected in 1969. Thus, the coloration described here is certainly different from what fresh specimens probably look like. Further more, this species has not been included in molecular analyses and it is somewhat uncertain to which species it is most closely related. However, because the postpetiole has a distinct dorsal lobe Branstetter (2013) includes S. tiburon in the lobinodus species group (diagnosis of group given under "comments" section of S. lobinodus) and hypothesizes based on distribution and morphology that is sister to S. lobinodus.
The specific epithet tiburon means shark in Spanish and refers to the triangular, shark-tooth-like shape formed by the longitudinal clypeal carinae and anterior clypeal margin.
Type material. Holotype worker. MÉXICO: Nuevo León, near Monterrey, Mesa de Chipinque, [ca. 25.61°N, 100.36°W], 1650m, 22 Jun 1969 (S. & J. Peck, collection B164) [USNM, pin CASENT0620965, top specimen]. Paratypes: same data as holotype [2w, LACM, CASENT0193030], [1w, MCZ, CASENT0194031], [1dq, 1w, MGBPC, CASENT0622423], [2w, UNAM, CASENT0194031], [1w, USNM, CASENT0620965, bottom specimen].
Branstetter, M. G. 2012. Origin and diversification of the cryptic ant genus Stenamma Westwood (Hymenoptera: Formicidae), inferred from multilocus molecular data, biogeography and natural history. Systematic Entomology 37:478-496. 10.1111/j.1365-3113.2012.00624.x.
Branstetter, M. G. 2013. Revision of the Middle American clade of the ant genus Stenamma Westwood (Hymenoptera, Formicidae, Myrmicinae). ZooKeys 295:1-277. doi: 10.3897/zookeys.295.4905.
Found most commonly in these habitats: 1 times found in forest.
Found most commonly in these microhabitats: 1 times ex sifted leaf litter.
Collected most commonly using these methods: 1 times Berlese.
Elevations: collected at 1650 m
Collect Date Range: collected on 1969-06-22