Mikrischyrum Cadena-Castañeda & Tavares, 2021

Cadena-Castañeda, Oscar J., Rodríguez, Nixon Oscar Parra, Res, Gustavo Costa Tava-, Rodríguez, Diana Marcela Trujillo & Arias, Ronald Fernando Quintana, 2021, Studies on Neotropical Pseudophyllinae: The status of the genus Brachyauchenus Brunner von Wattenwyl, 1895 and its species (Orthoptera: Tettigoniidae: Pseudophyllinae: Platyphyllini), Zootaxa 5027 (4), pp. 546-562 : 556-558

Mikrischyrum Cadena-Castañeda & Tavares n. gen.

http://lsid:zoobank.org:act: A3B1F47E-8008-4B0E-AC62-4C9B558D947E http://lsid.speciesfile.org/urn:lsid: Orthoptera .speciesfile.org:TaxonName:515121

Type species. Mikrischyrum minutus ( Nickle, 2006)

Diagnosis. Body small-sized (12.5–21 mm.) and robust, predominantly brown coloration, usually with some conspicuous spots on the pronotal disc and apex of the femora and tibiae ( Fig. 7 ). Pronotum granulated, lower margin of lateral lobes not projecting laterally; meso- and metazonal sulci not connecting on the lateral lobes and generally divided on the pronotal disc ( Fig. 7B ). Wings developed, slightly covering the abdomen or reaching the eighth abdominal segment ( Fig. 7A ); vein Rs originating near the apex of the tegmina. Legs short and compressed, not striated on the outside nor inside (except the chevrons of the hind femur). All femora unarmed dorsally and only the hind tibia bearing dorsal spines. Fore coxae with short, apically-rounded coxal spine, mid and hind coxae unarmed, femora with brown or yellowish-brown mid-sized ventral spines. Prosternum armed with two apicallypointed pyramidal spines; lateral margins of mesosternum weakly inflated, margins of metasternum unmodified. Tenth tergite and epiproct unmodified. Cerci short, stout, conical, apically rounded with a small pre-apical inward spine. Styli not exceeding half the length of the subgenital plate. Females unknown.

Taxa included. Mikrischyrum minutus ( Nickle, 2006) n. comb. (Type species) and M. festae ( Griffini, 1896) n. comb.

Etymology. The name is formed by the combination of two Greek words: mikró (μικρό) = little, and ischyrós (ισχυρός) = robust. The name refers to the apparency of the species included in this new genus. The gender of the name is being established as neuter.

Distribution. Panama (Darien), Peruvian Amazon, and possibly the Ecuadorian Andes.

Comparison. Mikrischyrum n. gen. is similar to Baliophyllum Beier, 1962 and to Drepanoxiphus Brunner von Wattenwyl, 1895 (this last genus needs an urgent revision), differing by its small size and robustness, as well as having short and stout legs in contrast to the slender and moderately elongated legs of the species of the other genera.

The new genus differs from Baliophyllum in lacking the translucent patches between the brown stripes of the hind wings as seen in Baliophyllum maculipenne Beier, 1962 . This species has spots on the pronotal disc that vary among the series. For example, the type specimen lacks spots on the pronotal disc, but in other specimens photographed from La Selva, Heredia Province, Costa Rica, only the posterior margin of the pronotal disc is outlined in yellowish color. Other specimens from the same locality have the entire pronotal disc of yellowish color (see images of the Orthoptera Species File). This coloration in the pronotal disc is present in both species of the new genus.

Mikrischyrum n. gen. differs from Drepanoxiphus , by the brownish coloration of the species of the new genus; the tegmina are ovoid and broad (almost as long as wide), covering all abdominal tergites but not greatly surpassing the abdominal apex; the Rs vein originates near the apex of the tegmina. In contrast, Drepanoxiphus species are generally greenish (some species lose their color after being preserved in alcohol, appearing to be brownish or yellowish), and some species may be brown; the tegmina are lanceolate (longer than wide) and in the known species they widely exceed the apex of the abdomen, vein Rs originates near the middle of the tegmen.

Comments. This new genus is erected to include two small and delicate species, that do not fit the diagnostic characters proposed here for Brachyauchenus . Braun (2002) tentatively allocated a species not yet described in Drepanoxiphus from the Andes of southern Ecuador, questioning its preliminary position and suggesting that it could also be allocated into a new genus since the subgenital plate of the female was triangular and not widely divided at the apex, as commonly occurs in Drepanoxiphus species. Later the same author placed the Ecuadorian species (yet to be described) in Brachyauchenus ( Braun, 2008) , perhaps due to the similarity with M. festae n. comb., differentiating superficially by spots on the pronotum, one on the anterior margin of the pronotal disc and two at each end of the posterior border for the undescribed species, and M. festae n. comb. only by the two spots on the posterior edge of the pronotal disc.

Few specimens were collected of the species within of this new genus, with no additional records since its original description, most likely due to the arboreal habitus of the species, found in low understorey canopy foliage, 4 to 10 m above ground level and never collected in lower forest strata ( Nickle, 2006). Due to the lack of specimens, we could not examine genital characters or the stridulatory apparatus.

Following, we provide the key to separate Mikrischyrum n. gen. known species. The coloration of the pronotum was not included, since it can be variable, and due to the few specimens collected, it is not a reliable character to differentiate the species. This usually occurs in several Platyphyllini species, as mentioned above in this contribution for Baliophyllum . This chromatic variability is also observed in Brachyplatyphylloides riosi Cadena-Castañeda & Braun, 2011 (a detailed discussion on the coloration of the pronotum is provided in ( Cadena-Castañeda & Braun, 2011)), and in an undescribed species of Triencentrus , with specimens without spots in the pronotum, partially pigmented in different proportions or the pronotal disc completely pigmented (Cadena-Castañeda in prep.).

Figures

FIGURE 7. Mikrischyrum festae Griffini, 1896 n. comb. Male habitus A. Lateral and B. Dorsal view. (Photos: © Orthoptera Species File reproduced with permission).