Type Material. Holotype ♂ and one ♀ paratype labeled: “MEXICO: Oaxaca, Santiago Comaltepec, San Bernardino, 16-VIII-2004, 1,715 m asl, bosque de Oreomunnea mexicana; en cópula sobre hojas de Oreomunnea, E. Mora col.”. Paratypes (6 ♂♂, 5 ♀♀) same data as holotype, except: luz fluorescente (1 ♂); 17-IX-2004, luz fluorescente-incandescente (2 ♂♂); 20-VII-2005, luz mercurio (2 ♀♀); 30-IX-2005, luz mercurio (1♂, 2 ♀♀); La Esperanza, VIII-2005, 1,552 m asl, bosque mesófilo de montaña — O. mexicana, luz fluorescente, E. Mora col. (2 ♂♂, 1 ♀).

The holotype and one female paratype are deposited in IEXA. Eleven paratypes are deposited in the following collections: ZMHB (1 ♂), MLUH (1♀), BMNH (1 ♀), CNCI (1 ♂), CNIN (1 ♂), SMCC (1 ♂ 1♀), LLDC (1 ♂ 1♀, and EMAC (1 ♂ 1♀).

Description. Holotype male (Fig. 1). Total length: 11.5 mm; width: 6.1 mm. Body oval-elongate and convex; head, carina of pronotum, elytra, venter, femora and tibiae shiny black; tarsi and antennae shiny reddish brown; depressions of pronotum and base of elytra dull black. Dorsal surface glabrous and venter with scarce, small setae. Clypeus rectangular, wide, apex truncate, anterior angles rounded, length 2/5 cephalic length; surface broadly concave with large, dense and umbilicate punctures; apical fourth with small, simple punctures; sides slightly indented in front of eyes; ocular canthus not prominent. Frontoclypeal suture marked at sides, obliterated at central 2/3. Frons with triangular, central, deep impression, and 2 oblique impressions adjacent to eyes and extending to the vertex; surface with large, dense, and umbilicate punctures. Transverse eye diameter almost 1/7 as wide as head. Antennae 10-segmented, length of club equal to length of antennomeres 2–6 combined. Labrum flat, anterior margin slightly curved; at middle 2.1 times longer than and situated slightly below reflexed underside of clypeus; finely rugose. Mandibles large, bulbous. Mentum almost flat, with anterior declivity marked by a transverse, bisinuate, and setose ridge, and with a small, central tooth.

Pronotum wider than long (1.00:0.55), sides widest at middle and constricted at base; pronotal base lobed at central third; fore angles right, hind angles obtuse; pronotal surface with a transverse, central ridge extending from side to side, and 2 anterior, central, convergent ridges extending from each side of midline of transverse ridge to anterior border; ridges delimiting 4 depressions as follows: two on anterolateral regions, one central, and one on basal third; ridges and depressions with umbilicate, large, dense punctures. Metasternum convex, with deep, narrow longitudinal apical fovea. Elytra longer than wide (1.00:0.40); elytral punctures umbilicate, slightly smaller than those of pronotum; striae scarcely discernible; intervals and costae with dense punctures, almost rugose. Abdomen with a lateral ridge on the first five visible sternites; abdomen ventrally with umbilicate, shallow and dense punctures; propygidium narrowly and distinctly grooved; pygidium wider than long, slightly convex, surface with umbilicate, dense punctures, and a few sparse setae.

Metacoxae laterally angled; femora long and slender; protibiae tridentate, elongate, with basal tooth situated in front of middle, and separated from anterior two teeth; all three pairs of legs with first tarsomere longer than second; tarsi clothed with dense setae, more notably in meso and metatarsi. Claws angularly curved, subapically cleft, and with tooth longer than apex of claw. Genitalia with basal piece longer than parameres; parameres widened at apical third, jointed on inner margin at about basal 3/5; in lateral view, parameres thickened and strongly, apically sinuate (Figs. 2 and 3).

Paratypes (6 ♂♂, 6 ♀♀). Total length: 10.1– 11.4 mm; maximum width: 4.4–6.1 mm. Dorsal and ventral color varies from black to reddish brown or light red. Depressions of pronotum in some specimens are shiny black. Pronotal carina vary slightly in elevation and length. Femora and tibiae are a little stouter in females than in males.

Etymology. The specific epithet is derived from the Latin multi meaning many, and carinata meaning carinate, in relation to the several carinae or ridges present on the pronotal surface.

Remarks. Diplotaxis multicarinata sp. nov. shows the typical characters of the simplex species-group, i.e. the dorsum glabrous, the labrum at least twice as long as the reflexed underside of clypeus, the antennae 10-segmented, the protibiae tridentate with teeth situated in front of middle, and the claws angularly bent and subapically cleft. From the species included in this group, the new species is easily recognized by the combination of two characters: the abdomen laterally ridged and the pronotal surface with rounded ridges (Fig. 1). In addition, the shape of the male genitalia is also distinctive (Figs. 2–3).

Distribution. Diplotaxis multicarinata sp. nov. is only known from the state of Oaxaca in two nearly adjacent localities situated in the municipality of Santiago Comaltepec. This species inhabits cloud forests with Oreomunnea mexicana (Standley) Leroy (Fagales: Juglandaceae) as the dominant tree and located between 1,500–1,750 m of elevation. Forests with O. mexicana as the dominant element are considered a relict and paleoendemic vegetation established in areas that presumably served as Pleistocene refuges of flora and fauna in Mexico (Rzedowski 1991). The nominate subspecies of O. mexicana has a discontinuous distribution in Mexico (Orizaba, Los Tuxtlas, Sierra de Juarez, Chimalapas and Soconusco), Guatemala, and Nicaragua; the other subspecies (O. m. costaricensis Stone) is distributed in Costa Rica and Panamá (Rzedowski & Palacios-Chávez 1977, Challenger 1998).

Biological Notes. A pair of this species was collected in copula on leaves of O. mexicana. The remaining specimens were attracted to lights from July to September.