MEXICO: Holotype female, depository unknown (Sissom 2000).

M. granosus is most similar to M. segmentatus by sharing pedipalp chela fingers margin straight lacking proximal notch and median lobe; nineteen trichobothria on patella retrolateral and seven on ventral surface. It can be separated from M. segmentatus by having entirely densely granular surfaces on the femur, patella, tibia dorsal surfaces, prolateral leg surfaces, carapace, and tergites (Figures 1, 2), instead of having scattered fine granulation. M. granosus is distinguished from M. gertschi, M. grubbsi, and M. segmentatus by having the marginal and median lamella indistinguishable in females and vestigial in males, instead of having median lamella furrow in both sexes deep, completely separating marginal from median lamella. Males of M. granosus have pedipalp chela fingers margin straight, but the male pedipalp fingers margin of M. gertschi and M. grubbsi are emarginated, bearing a proximal notch and median lobe that creates a gap when fingers close. M. granosus has three trichobothria in series et, em, and six in v, whereas M. gertschi has four, five and eight in et, em and v respectively; and M. grubbsi has four in em.

The following redescription supplements Soleglad’s (1976) description and is based on 10 adult males, 3 adult females, 2 subadult females, 1 subadult male, 8 juvenile females and 4 juvenile males. Character variation is reported for the sexes as noted.

Color and infuscation: Base color yellowish to orange. Carapace: tergites, prolateral surface of legs, sternum, genital operculum, pectinal basal piece, fused lamella, metasoma, and telson, with dense, marbled infuscation (Figures 3–6). Chelicerae: manus base color yellowish with reticulated longitudinal infuscation, fingers moderately infuscate proximally. Pedipalps: base color orange with fuscous markings, all carinae densely infuscate. All trichobothrial bases with a bright yellowish areola. Legs: retrolateral surface yellowish. Spiracles light beige. Pectinal teeth whitish to light beige. Sternite III median and submedian surface densely infuscate, sternite IV–VII median carina infuscate, other surface immaculate. Telson vesicle ventral surface with three broad bands of infuscation flanking two submedian bands of yellowish base color, all surface infuscate dorsally. Aculeus base faintly infuscate, reddish distally.

Chelicerae: Manus dorsal surface smooth, lustrous, with three macrosetae distally, decreasing in size from median to lateral surface. Movable finger, retrolateral margin with subdistal and medial denticles triangular, subequal; distal and basal denticle slightly larger; prolateral margin with three smaller, triangular, subequal denticles, situated in distal half of the finger; retrolateral distal finger size half of prolateral distal finger. Fixed finger margin with three denticles, proximal two adjacent and distal separate; distal denticle elongate and sharp (Figure 7); ventral surface of manus, fixed and movable finger with an interspaced tuff of setae with curved tips. Serrula absent.

Carapace: Length equal to 0.9 times the posterior width. Surface shagreened, with enlarge scattered granules covering entire surfaces (Figure 8). Distal margin with two pairs of macrosetae; emarginated, bilobed, with a shallow median notch, with extreme lateral sides curving placing lateral ocelli in a laterofrontal position. Two pairs of lateral ocelli of equal size, lateral ocular carinae strong, costate-granular. Median ocular tubercle raised, situated in anterior half of carapace. Superciliary carinae strongly (♀) or weakly (♂) granular, lower than median ocelli. Anteromedian sulcus deep and broad, with scattered granules; posteromedian, proximal half with a granular carina and distal half with a deep and broad depression; anterolateral, deep and narrow; posterior transverse shallow.

Coxosternal region: Sternum pentagonal, subequilateral, length equal to 0.8 times the width, with five to ten pairs of microsetae. Median sulcus of sternum with anterior and posterior margins broadened, moderately deep (♂), or very deep (♀). Coxa IV two and half times longer than coxa II. Coxae I–IV surfaces with scattered granules and margins densely granular; coxa II, prolateral subproximal margin with three oblique slit-like structures, adjacent to a moderate (♀) or low (♂) granular protuberance; coxae II–IV, prolateral carinae strongly granular (Figures 20, 21).

Pedipalps, Femur prolateral, dorsal and retrolateral intercarinal surfaces shagreened (Figure 9), ventral surface with a cluster of fine granules medially. Dorsal prolateral, dorsal retrolateral, ventral prolateral and dorsal prolateral carinae complete, irregularly granular; retrolateral dorsosubmedian complete, weak proximally, becoming strongly granular distally; retrolateral ventral and ventral median carinae vestigial, reduced to few granules proximally; ventral retrosubmedian partial, with a scattered enlarged granules on proximal half; prolateral ventral vestigial, one or two median granules; prolateral ventrosubmedian partial, with enlarged granules on proximal fifth. Patella width 1.5 times greater than femur width. Dorsal intercarinal surfaces shagreened, prolateral, retrolateral, and dorsal sparsely finely granular. Dorsal prolateral, dorsal retrolateral, ventral prolateral, ventral retrosubmedian, and retrolateral median complete, granular; retrolateral dorsosubmedian absent; prolateral process reduced, expressed as a spiniform enlarged tubercle, prolateral median carina vestigial, expressed by one or two median granules (Figures 10–13). Chela length 1.9 times greater than femur and patella, width 1.6 times greater than patella and 1.1 than femur. Dorsal intercarinal surfaces shagreened, a dense field of minute and coarse granules subdistally, other surfaces with scattered minute and coarse granules. Dorsal retrolateral carina complete, strongly granular, extending to proximal four-fifths of the fixed finger, becoming weaker and smooth distally; dorsal retrosubmedian accessory vestigial, irregularly granular, restricted to trichobothrium Dt; dorsal median and dorsal retrosubmedian with an enlarged proximal tubercle, complete, irregular, granular forming two rows proximally, converging into a single row distally; prolateral dorsal, dorsal prosubmedian and dorsal prolateral, fused, irregular, with five to seven scattered granules proximally, minute and coarse granules medially, and coarse granules extending to fixed finger to the extent of trichobothrium dsb; retrolateral dorsal partial, minute granules on median two quarters; retrolateral dorsosubmedian vestigial, restricted to distal short row of coarse granules between trichobothria Et₄ and Et₅; retrolateral median complete, strongly granular, ending at the level of trichobothria Et₃ and Et₄; retrolateral subventral accessory and retrolateral subventral vestigial, restricted to a distal short row of coarse granules converging to trichobothrium Et₂, commonly merging to ventral retrolateral carinae; retrolateral ventral partial, irregular, with minute granules restricted by trichobothria Esb and Est; ventral retrolateral complete, strongly granular, in some specimens forming a ring of granules around trichobothrium V₄; ventral median partial, strongly granular proximally, becoming weak medially and merging with a field of granules distally, ventral retrolateral and ventral median forming an acute angle proximally, becoming parallel medially to distally; ventral prolateral and prolateral ventral complete, merging to a low tubercle proximally, multiple rows of granules curving to prolateral condyle distally; prolateral ventral accessory partial, restricted to midpoint of the manus as a multiple row of minute and coarse granules, prolateral median partial, irregular, coarse granules row restricted to proximal half (Figures 14–17). Pedipalp fixed and movable fingers: notches, lobes, and gap when fingers closed absent; dentate margin sublinear, compound, with multiple rows of prolateral, median and retrolateral denticles; prolateral, prolateral accessory, retrolateral and median denticles aligned in an oblique row angling retrolaterally in position III–VI. Fixed finger median row comprising six or seven denticle subrows with, commonly two, occasionally one denticle in position I, four to six in position II–VII; flanked by a two- or three-denticle retrolateral accessory median subrow, absent in position I; median subrows divided by six or seven retrolateral denticles, indistinguishable from median subrows’ denticles in position VII/VIII–X; median accessory subrows divided by five or six subpaired retrolateral accessory denticles, absent on I and undistinguishable from median accessory denticles subrows on VII/VIII–X; flanked by six or seven prolateral denticles and a subpaired prolateral accessory denticles in position III–VI, absent on I and II, vestigial to absent on VII–X. Movable finger median denticle row comprising six or seven median denticle subrows, zero to one in position I, three to seven in positions II–IX, zero on X; flanked by a two- or three-denticle median accessory denticles subrows, absent in position I; median subrows divided by seven to eight retrolateral denticles, indistinguishable in position IX and X, and median accessory subrows divided by six to seven subparied retrolateral accessory denticles, absent in position I, undistinguishable in position VII–X; flanked by nine prolateral denticles, position III–X subparied by prolateral accessory denticles, lower and less defined in positions VIII–X (Figures 18, 19).

Trichobothrial pattern Type C, neobothriotaxic. Femur trichobothria d, e, and i positioned proximally, equidistant; d on dorsal surface, e on ventral prolateral carina, i ventral to dorsal prolateral carina (Figure 9). Patella trichobothria d₁ and d₂ on dorsal surface proximal and medial respectively; i on prolateral distal half, ventral to dorsal prolateral carina; eb₁–eb₄, and eb₅–eb₆ dorsal to retrolateral median carina; esb₁, em₁, est₁, et₁, et₂ and eb₅–eb₇, esb₂, em₃, est₃, et₃ dorsal and ventral to retrolateral median carina respectively, esb₂, petite, em₂ on retrolateral median carina, v₁–v₆ proximal to ventral retrosubmedian carina (Figures 10–13). Variation in trichobothrial counts as follow: series v, 2 specimens, 5 left/5 right; 14, 6/6; 1, 6/5; 1, 7/7; et, 16, 3/3; 1, 3/2; est, 13, 4/4; 2, 3/4; 1, 3/3; em, 15, 3/3; 1, 3/2; esb, 15, 2/2; 1, 2/1. Chela trichobothrium Db on retrolateral surface between dorsal retrolateral and retrolateral dorsal carinae; Dt on dorsal surface at distal end of dorsal retrosubmedian accessory carina; series db–dt on dorsal and db on retrolateral surface, between denticle positions VIII and IX; series eb–et on retrolateral surface, eb between position VIII and IX; esb between positions VI and VII; est between positions V and VI, et at position IV; Eb₁–Eb₃ on retrolateral surface, between retrolateral median and ventral retrolateral carinae; Esb petite, proximal to Eb₁; Et₁ on dorsal surface close to retrolateral condyle, Et₂–Et₅ on retrolateral surface, Eb₂–Eb₄ on distal margin of manus, Eb₄ not petite, Eb₅ on base of movable finger; V₁–V₃ on dorsal surface, equidistant, V₄ on ventral retrolateral carina; ib and it on distal margin of fixed finger (Figures 14–17).

Legs: Basitarsi, prolateral ventral and retrolateral ventral spinule rows partial, distal half with two or three sparse spinules on legs I–III, absent on leg IV; retrolateral and retrolateral dorsal rows absent on I–IV; macrosetal counts on legs I–IV, respectively: dorsal 2:2:2:2, retrolateral dorsal, 2:2:3:3; retrolateral ventral, 5:5:5:5; prolateral ventral, 4:4:4:4, all macrosetae not pigmented, translucent and shaped as tines; dorsal and retrolateral dorsal macrosetae arranged in two separate parallel rows on legs I–IV. Telotarsi I–IV, each with single irregular ventromedian row of scattered spinules and one ventrodistal spinule, flanked by prolateral and retrolateral rows of six macrosetae. Ungues short and curved.

Genital operculum: Wider than long, with four (♂) or six (♀) pairs of short and translucent macrosetae; sclerites free longitudinally, anterior margin fused on distal two thirds (♂) or fused longitudinally by a loose pleura folding into a valve covering the genital opening (♀). Genital papillae present, protruding posteriorly (♂) or absent (♀) (Figures 20, 21).

Hemispermatophore: Distal lamina 1.1 times the length of trunk; tapering distally, basal constriction well-developed (Figures 26–28). Capsule’s dorsal and ventral troughs strongly sclerotized, merging into a complete, thick, transverse plate, dividing lamina and trunk (Figure 28). Marginal terminus of dorsal and ventral troughs with a spiculate processes with 25 and 24 irregular spines [in part Sissom’s (1994) accessory lobes], respectively. Hemi-mating plug gelatinous. Sperm duct formed by a spicule-coated membrane (sensu Jacob et al. 2004) connected to the spiculate processes of the dorsal and ventral troughs and to the crown-like process (sensu Jacob et al. 2004). Trunk broad proximally, tapering distally; crown-like process relatively long, with row of six to eight irregular spinules on the margin; truncal flexure and dorsal axial carinae well-developed (Figures 26–28).

Pectines: Basal piece with three or five pairs of macrosetae, proximal surface granular, V-shaped (♂) or isosceles trapezoidal (♀). Marginal and median lamellae nearly fused into one piece with a fine, shallow furrow (♂), or completely fused, indistinguishable furrow (♀). Fulcra absent. Pectinal teeth: three to four (♂) or one to four (♀). Pectines relatively short, fused lamella aligned with midpoint of coxa IV (Figures 20, 21).

Tergites: I–VI, intercarinal surfaces shagreened, densely covered with minute and coarse granules, posterior margin with rows of irregular granules (Figures 1 and 2); dorsal median and dorsal lateral carinae partial, costate-granular, restricted to proximal half (♂) or vestigial (♀). VII, intercarinal surfaces shagreened; dorsal median carina partial, restricted to anterior half of segment, costate-granular; dorsal sublateral carinae vestigial, comprising few serrate granules restricted to anterior half of segment; dorsal lateral and lateral median carinae converging anteriorly, serrate, posterior granules enlarged.

Sternites: Sternite III, surface around pectines shagreened; sternites IV–VI, surfaces smooth to weakly granular medially, shagreened laterally; spiracles minute, ovoid, 2.0 times longer than wide; sternite V, ventral surface distinct hyaline glandular area posteromedially, densely cover with micropores (♂) or absent (♀) (Figure 20). Sternite VII, intercarinal surfaces shagreened, without hyaline glandular area posteromedially; carinae obsolete, except ventral median, variable from a row of weak granules to coarse granules medially; ventrolateral with a row of coarse granules medially.

Metasoma: Length 0.9 times greater than mesosomal length (Table 1); segment I, 0.6; II, 0.7; III, 0.8; IV, 1.2; and V, 2.1 length greater than width; segment V width 0.9 times greater than telson width. Segments I–V, dorsal intercarinal surfaces scattered, finely granular, lateral and ventral shagreened. Dorsal lateral carinae complete, strongly serrate; lateral median carinae complete, serrate on I–III, weakly lobate posteriorly on IV, partial, reduced to anterior half, irregular scattered granules on V. Lateral inframedian carinae complete, with scattered, coarse granules on I, partial, granular, restricted to posterior half on II and III, vestigial and restricted to a posterior marginal tubercle on IV, absent on V. Ventral lateral carinae complete, serrate. Ventral submedian carinae vestigial, restricted to a marginal paired tubercle posteriorly on I–IV, absent on V. Ventral median carina complete, strongly serrate on I–V (Figures 23–25). Macrosetal counts on carinae of segments I–V, respectively: dorsal lateral, 4:4:4:5:7; lateral median, 4:4:5:5:3; lateral inframedian, 4:2:2:1:0; ventral lateral, 3:3:3:3:2; ventral sublateral, 0:0:0:0:1; ventral submedian, 3:3:3:3:4.

Telson: Vesicle globose, length 1.4 times greater than width (Table 1); dorsal surface with finely punctuated and scattered minute granules (♂) or smooth (♀); ventral surface scattered with minute and coarse granules, carinae obsolete, with four or five pairs of short translucent macrosetae, annular ring moderately developed (Figure 22). Aculeus, fairly elongated, laterobasal microserration and subaculear tubercle absent, venom delivery openings slit-like, paired.

Megacormus granosus has been reported in the vicinities of the National Park Pico de Orizaba, on the slopes of the Trans-Mexican Volcanic Belt facing the Gulf of Mexico, and between Orizaba and Huatusco, Veracruz.

All adult males were collected by pitfall traps, suggesting high motility within the leaf litter. They were particularly abundant in the May 2012 expedition. This behavior in males and the period of the year may be related to the mating season of the species. All adult females and immatures of both sexes were collected exclusively using Berlese funnels, suggesting these are comparatively less mobile. A total of 72 Berleses and 180 pitfalls were used to sample two hectares, of which 18 (25%) and 11 (5%), caught 18 and 9 specimens respectively. These yields are consistent with low population density of this species; adult males are particularly rare. The habitat of, and behavior exhibited by, this species as well as its cryptic morphology (color resembling substrate; relative small size) are congruent with a humiculous ecomorphotype (Prendini 2001).

The catalog of the scorpions of the world (Fet et al. 2000) indicates that the location of M. granosus type material is either unknown or lost. It is important to investigate the whereabouts of Gervais’ unique specimen to verify the holotype, or failing this, to designate a neotype. Workable keys to the species of Megacormus are provided in Sissom (1994). The genus Megacormus is under revision by O.F. Francke (per. comm.).