Metopomystrum muriciense Silva & Skejo

Silva, Daniela Santos Martins, Skejo, Josip, Pereira, Marcelo Ribeiro, Domenico, Fernando Campos De & Sperber, Carlos Frankl, 2017, Comments on the recent changes in taxonomy of pygmy unicorns, with description of a new species of Metopomystrum from Brazil (Insecta, Tetrigidae, Cleostratini, Miriatrini), ZooKeys 702, pp. 1-18 : 2-4

Metopomystrum muriciense Silva & Skejo sp. n. Figures 1, 2, 3

Specimen.

Holotype 1♂, in alcohol. Original label: "Brasil, Alagoas, Murici, Estação Serra do Ouro (9°14.54'S, 35°50.2'W), 21-23/i/2013. C. Sperber e equipe leg." “[licença Sisbio n° 37717]" (MNRJ). Conservation status: left antenna broken.

Type locality.

Brazil: Alagoas state, municipality of Murici, Estação Serra do Ouro, the holotype was caught in forest leaf litter [coordinates 9°14.54'S, 35°50.2'W].

Etymology.

The species name refers to the municipality of Murici.

Diagnosis.

This species can be distinguished from other species of Metopomystrum by the following set of characters: (i) long and acute fastigium, directed forwards, slightly upwards in its apex, (ii) forehead, genae and posthumeral spots in the pronotum yellowish, (iii) tegmina, alae and tegminal sinus absent, (iv) lateral lobes of the pronotum directed slightly sidewards, with rounded apex and yellowish band, (v) sternomentum necklace-shaped, brown with yellowish spots.

Comparative notes.

The species can easily be separated from winged Colombian species ( M. lilianae and M. pehlkei ) by the horn morphology, fastigium having a rounded anterior margin in those species, while it is acute in M. muriciense Silva & Skejo, sp. n., and it is directed upwards in those species, while forwards in M. muriciense Silva & Skejo, sp. n. Metopomystrum lilianae and M. pehlkei are winged species, with visible tegmina, narrower than the maximum width of the mid femora, and tegminal sinus, hence narrow infrascapular area which is wide and evident in apterous M. muriciense Silva & Skejo, sp. n. From the apterous Colombian species M. amazoniensis , the new species can be separated by the straight horn, not directed upwards as in M. amazoniensis . However, the two species only share morphology of the anterior margin, laterally vertex being narrower in M. muriciense Silva & Skejo, sp. n. than in M. amazoniensis . The occipital area in M. muriciense Silva & Skejo, sp. n. is much longer than in Colombian species of the genus. The species is morphologically most similar to M. apterum , also from Brazil, with which it shares numerous morphological features, differing however in horn (projection of the fastigium of the vertex) direction-forwards and slightly upwards in M. muriciense Silva & Skejo, sp. n., while slightly downwards in M. apterum . In M. muriciense Silva & Skejo, sp. n. the vertex is narrower and more acute than in M. apterum .

Holotype description.

Head. In lateral view (Figs 2C, 3A): occipital area elongated and granulated, head and compound eye insert exerted above the pronotal disc; vertex is not visible; fastigium of vertex and frontal carina forming long triangular horn with acute apex that is as long as the compound eye measured from its most frontal point to the apex; frontal carina not projecting; antennal groove situated slightly below the compound eye, almost at the level of its lower margin; palpi compressed, segments enlarging towards apex. In frontal view (Fig. 2A): frontal costa above the bifurcation long; frontal costa bifurcation placed between the compound eyes; scutellum very narrow; scapus two times as wide as scutellum; antennae filiform with 15 antennomeres, segments elongated, cylindrical with smooth margins, paired lateral ocelli situated between the compound eyes, slightly below the frontal costa bifurcation; median ocellus placed in the end of facial carinae, in the place where frontal costa shallowly continues towards the clypeal triangle, of which carinae are also weak and not prominent, in the widest part; head slightly wider than the width between the lateral margins of the compound eyes. In dorsal view (Fig. 2B): vertex between the eyes as wide as a compound eye’s horizontal diameter; fastigium of the vertex triangular, with acute apex; median carina of the vertex inconspicuous; fastigium lowest in the part of median carina, forming depression; occipital area 2 × shorter than a compound eye’s vertical diameter and granulated. Coloration (Figs 2 A–C, 3A): fastigium of the vertex and vertex between the compound eyes dark brown; lateral area between frontal costa and lateral carinae of the vertex dark brown as well; median part of occipital area yellowish, with dark ornamentation; behind the eyes dark brown band with weaker pale brown and yellowish band inside; frons, clypeal triangle and gena pale yellowish; palpi pale; first four antennomeres almost white.

Pronotum. Brachypronotal (because of lack of wings it can be also regarded nanopronotal, organs of flight not visible), reaching abdominal apex. In lateral view (Figs 2C, 3 A–B): median carina slightly undulated; prozonal carina visible, short, extralateral carina inconspicuous, visible as a few fine tubercles; ventral sinus absent, covered with infrascapular area; sulci between prozonal and humero-apical carina deep; paranota smooth, with few pits and tubercles, triangularly shaped (in typical way for non- Batrachideinae tetrigids); lateral lobe directed sidewards and truncated in apex; humero-apical carina connected to external lateral carina, which is parallel to median carina; infrascapular area wide, almost as wide as mid femur, with numerous shallow depressions (places where the chitinous layer is thinner, well visible by changing light under stereomicroscope); width of the infrascapular area decreasing towards apex; infrascapular area connected to narrow lateral area; internal lateral carina parallel to external lateral carina; apex of the pronotum directed upwards. In frontal view (Fig. 2A): shoulders not projected, lateral pronotal lobes directed downwards and sidewards. In dorsal view (Figs 2B, 3C): dorsum rich in fine granules, tubercles and small pits (shallow depressions in chitinous layer, look like holes, light permeable); anterior margin of the pronotum truncated, slightly inverted, prozonal carinae short, visible; angle between humero-apical and external lateral carinae obtusely rounded; median carina not strongly elevated, continuous; interhumeral carina indistinct; small posthumeral spots present; pronotum suddenly narrowed in the apex, its apex acute; lateral lobes with weak triangular ventrolateral projection with bluntly truncated apex, directed outwards and backwards. Coloration: dorsum brown, holes and granules being pale when enlightened; distal part of the disc, around apex, with numerous pale spots; ventral third of paranota with pale yellowish band; two posthumeral yellowish spots present, left rounded, while right triangular, smaller than observed in other Tetrigidae species.

Wings. Flightless species, tegmina and wing not visible, reduced and covered by infrascapular area of pronotum, not functional. (Note: to check if wings are present pronotum needs to be broken. We did not want to break the pronotum since there is only one specimen, the holotype). Sternomentum (Fig. 2C) [= modified prothoracic sternum]. Sternomentum collar-like, necklace shaped, well visible in lateral and ventral view, brown in color, ornamented with numerous yellowish spots of the same shape as pits on pronotal surface.

Legs (Figs 2 A–B, 3 A–D). Fore legs: fore femur approximately rounded in cross-section; dorsal margin carinated, dorsal carina made of fine tubercles, slightly undulated; ventral carina made of fine tubercles too, almost straight; fore femur widened in medial part, narrowed towards proximal and distal connection; distal part of the dorsal margin bearing a blunt tooth; fore tibia robust, slightly longer than fore femur; distal third of the inner margin equipped with four pairs of spines; proximal tarsal segment short, with three rounded pulvilli on its ventral surface; distal tarsal segment longer than the proximal, at its apex with two claws. Mid legs: femur with distinctly carinated dorsal and ventral margins; dorsal and ventral carinae of the mid femur visible in lateral view, not very prominent; dorsal and ventral margins finely tuberculated, slightly undulated to almost straight; mid tibia slightly shorter than the mid femur, robust, with small spines on its inner margin; proximal tarsal segment short, with angular pulvilli on ventral surface; distal segment four times as long as proximal, at its apex with claws. Hind legs: dorsal and ventral margins of hind femora finely granulated, without lappets or projections; genicular and antigenicular teeth small; clearly visible hind femur elongated and reaching slightly below the pronotal apex when extended; external surface finely granulate, with seven transverse ridges in its external surface (or more if short are counted towards the knee); dorso-external and ventro-external carinae of the hind femur without tubercles or projections, smooth, dorsal margin in dorsal view straight; ventral margin and inner ventral margin of the hind femora straight; tibial sulcus (= the depression on the ventral side of the hind femora in which the tibiae are put when the grasshopper is walking) half as wide as hind femora in ventral view; hind tibiae robust, shorter than hind femora with dorsal surface concave, ventral convex, dorsal surface with two rows of spines from its middle to the connection tarsus; inner margin with nine visible spines, outer with seven, on connection of tibia and tarsus there are 6 spines, three on each side; proximal segment of the hind tarsus with acute pulvilli; mid segment short; distal segment as long as proximal, having two claws in its apex. Coloration: fore femur yellowish, with small amount of darker areas in its dorsal part; fore tibia of the same colour as fore femur, with two dark rings, the distal one being broader and darker; proximal segment of fore tarsus dark; one half of the distal segment pale, the other part dark; claws yellowish with dark apex. Mid femur yellowish, with dorsal and distal part being dark and having four dark patches in external surface; mid tibia yellowish, with two dark rings, the distal one being broader and darker; proximal segment of the mid tarsus pale brown; distal segment with two thirds yellowish, apical third dark, claws yellowish with dark apex; ventral external area of the hind femur very dark; median external area lighter brown; dorsal area somewhat darker than median, but lighter than ventral; hind knee yellowish; hind tibia yellowish with brownish patches, not forming dark rings; proximal and mid segment of hind tarsi yellowish, apical part of the distal segment darker, rest of it yellowish; claws light with dark apex.

Abdomen (Figs 3A, 3 D–F). Subgenital plate bilobate, with deep triangular incision; each lobe triangular with blunt apex; in lateral view subgenital plate with apex directed upwards; cerci short, robust, their basal part swollen and hirsute. Coloration: visible parts of dorsal sternites dark brown, similar to pronotum; upper lateral parts of the sternites light yellowish, from the middle to the connection with sternites orna mented with dark brown and yellowish patches; epiproct and cerci yellowish; subgenital plate light brown; sternites light brown and each of them ornamented with a pair of thin pale lines, having darker margins outside.

Female.

Unknown.

Measuremens (all in mm).

Body length from the tip of the fastigium projection to the end of the abdomen 10.8; fastigium length 1.03; vertical eye diameter 0.96; horizontal eye diameter 0.67; vertex width 0.41; pronotum length 8.12; pronotum lateral lobes maximal width 1.86; infrascapular area length 5.54; fore femur length 1.61; fore femur width 0.62; fore tibia length 1.63; mid femur length 1.99; mid femur width 0.59; mid tibia length 1.48; hind femur length 5.11; hind femur maximal width 1.67; hind tibia length 4.08; proximal hind tarsal segment length 0.51; mid hind tarsal segment length 0.04; distal hind tarsal segment length 0.50.