Pherodactylus rectanguli (Xu, Fang & Wang, 2020 ) Cadena-Castañeda & Liu & Yu & Hu & Wu & He, 2023

Cadena-Castañeda, Oscar J., Liu, Yi-Jiao, Yu, Zhe-Yuan, Hu, Tian-Hao, Wu, Shi-Yang & He, Zhu-Qing, 2023, Are the recently described fossil Mole Crickets of Myanmar amber real gryllotalpids? (Orthoptera: Gryllotalpidae & Gryllidae), Zootaxa 5311 (1), pp. 48-64 : 52-59

† Pherodactylus rectanguli (Xu, Fang & Wang, 2020) n. comb.

Figs. 1–6

= † Chunxiania fania Xu, Wang & Fang, 2022 n. syn.

= † Tresdigitus gracilis Jiang, Xu, Jarzembowski & Xiao, 2022 n. syn.

General description. Male (based on specimens ECNU-AM-0019 and ECUN-AM-0010, Figs. 1–3 ). Smallsized (8.07 mm.). Predominantly yellowish coloration with grayish and black spots. Cephalic capsule with dorsal surface (from vertex to fastigium) and upper area of frons with dark brown to black stripes; area surrounding ocelli, mandibles, lower margin of genae, and frons ocher; ocelli yellow; eyes greyish. Frons with a yellow inverted “Y”,

* for the data may be doubtful due to different measurement method.

starting from vertex, dividing at fastigium, and branching to the inner margin of each lateral ocellus. Pronotal disc greyish brown, with black corner rims and delimiting pronotal disc from lateral lobes; pronotal disk with two distinct large dark “eyespots”. Lateral lobes of pronotum with upper half grayish brown and lower half yellowish. All legs are yellowish with black or grayish spots, irregularly scattered, most noticeable on femora. Tegminae translucent, with veins outlined in light yellow. Abdomen yellowish covered by various black or grayish spots. Body covered with short or mid-sized fine hairs. Head as wide as pronotum, rounded and smooth; almost as wide as high in frontal view, with epistomal suture little concave. Vertex rounded. Eyes ovoid, not protruding. Lateral ocelli circular, central ocellus absent. Eyes and antennal pits located very low on face, close to epistomal suture, almost at the same level. Fastigium wide, almost four times as wide as scape. Maxillary palpi with the 4 th and 5 th longer, apical segment of labial palpi flattened. Thorax. Pronotum longer than wide, covered by several and mid-sized hairs; anterior margin concave and broader than posterior margin, with long bristles; lateral lobules rectangular, wider than high and with a rounded lateral edge, ventral margin almost straight. Wings. Tegmina short and ovoid, reaching to the second abdominal tergite. Mirror in oval shape, longer than wide, with a curved dividing vein; harp with three dividing veins; apical field reduced; lateral field two longitudinal veins from base to apex, and ten transversal veins born from the second longitudinal vein to costal margin. Hind wings no visible. Legs. Coxa and trochanter not elongated. Foreleg robust with long setae, large and oval tympana in both sides, on middle of fore tibiae; three movable dactyls on apical part of fore tibiae, first tarsomere almost as long as fore tibiae, other two tarsomere short. Mid leg slender, coxa robust, with a process partly covering trochanter; femur slightly slenderer than fore femur; tibia slightly inflated, shorter than femur, armed at apex with three inner spurs and two outer spurs. Hind leg elongated, femur strong, tibia with several small spines on dorsal side at apex. Three internal apical spurs long, and two external apical spurs short. The first and third tarsomere long and the second one short. Abdomen cylindrical; tergites with few short hairs; epiproctus subtriangular, apex rounded; subgenital plate short, wider than long, apex rounded; cerci almost as long as the two-thirds of hind tibia, covered by abundant medium-sized hairs.

Female (emended description; based on specimens ECNU-AM-0002 and ECUN-AM-0024, Figs. 4 , 5 ). Similar to the males in shape and size, differing by the following characters: the color tones are darker than the males, but keep the same pattern. Tegmina absent. Abdomen with hairs and several long bristles on dorsal side. Epiproct triangular, with rounded posterior margin. Ovipositor almost straight, apex of valves sharp, pointed, and lanceolate in dorsal view. Subgenital plate trapezoidal, apex moderately protruding.

Male nymph (based on specimen ECNU-AM-0045, Fig. 6 ). Similar to the adult males, but no developed wings, with a more fragile and slender appearance. It differs from the adults, because the tympana are smaller in diameter than the other adult specimens examined. The small tympana in immature specimens can happen. This structure increases its size in adults.

Measurements (mm).

Adult male ECNU-AM-0019 ( Fig. 1 , 2 ): BL: 8.07; HL: 1.07; PL: 1.57; PW: 1.43; FWL: 2.18; FFL: 1.61; FTL: 1.04; MFL: 1.41; MTL: 1.09; HFL: 3.15; HTL: 1.82; AL: 5.14; CL: 2.26.

Adult male ECNU-AM-0010 ( Fig. 3 ): PL: 1.47; PW: 1.33; FWL: 2.05; FFL: 0.98; FTL: 1.06; Body broken, uncertain for else.

Adult female ECNU-AM-0002 ( Fig. 4 ): BL: 8.20; HL: 1.21; PL: 1.69 PW: 1.71 FFL: 1.56; FTL: 0.97; MFL: 1.91; MTL: not visible; HFL: 3.63; HTL: 2.54; AL: 4.63, OL: 1.82.

Adult female ECNU-AM-0024 ( Fig. 5 ): BL: 5.24; HL: 1.06; PL: 1.60; PW: uncertain; FFL: 1.45; FTL: 0.95; MTL: 1.42, femur and tarsus incomplete; HFL: 3.34, HTL: 2.56; AL: 3.82, CL: 2.39, OL: 1.72.

Nymph ECNU-AM-0045 ( Fig. 6 ): BL: 5.22; HL: 0.87; PL: 1.33, PW: uncertain; FFL: 1.40; FTL: 0.83; MFL: 0.97, MTL: 0.82; HFL: 2.49; HTL: 1.71; AL: 3.25; CL: 1.67.

Remarks. Synonymy and new combination at the species level are justified as follows:

1) † P. micromorphus Poinar et al. 2020 is a subadult female specimen, which looks different in the shape of the pronotum in contrast to the holotype of † P. rectanguli n. comb. (a subadult male). However, when the photos of specimens are taken from different angles, an optical effect will be caused, which confuses us to consider them as different shapes. This can be happened in the additional specimens of † P. rectanguli n. comb. studied here. The fore tibia does not vary in both specimens. Only in the holotype of P. rectangulari n. comb., a bending of the ventral edge is observed, but this can happen due to dehydration during fossilization. However, we prefer to keep this species as valid, since the subadult female holotype specimen of † P. micromorphus had a wing pad, which is different from the adult females of † P. rectangulari n. comb.

2) † C. fania n. syn. is an adult male specimen. In the images of the original description, its diagnostic characters coincide with † P. rectanguli n. comb. in terms of the shape of fore tibia, apical spurs organization and shape, and location of the spurs of hind tibia. The hind tibiae are thin and moderately elongated, and the shape of pronotum and its spots coincide in these specimens. Unfortunately, the venation of † C. fania n. syn. is not observed due to preservation.Although the subgenital plate of † C. fania n. syn. dehydrated in fossilization process and coiled dorsally, it still could be observed in a triangular shape, which is similar to those of field crickets in a semicircle shape.

3) † Tresdigitus gracilis n. syn. is a nymph of indefinite sex (possibly female in penultimate or ultimate instar), not as developed as the two “species” previously synonymized. In the key presented in the original description by Jiang et al., 2022, the arrangement of head and the shape of pronotum are some of the characters proposed by the authors to distinguish the species from † P. rectanguli n. comb. The disposition of the head can vary in the way that insects die, and thus remains when fossilized. In contrast to † P. rectanguli n. comb., its head is in a normal position, locating mouthparts down (hypognathous/ hypognathous mandible). Other characters that stand out in † T. gracilis n. syn. is the moderately expanded fore tibia, and the small tympanum. However, it is common for crickets that they are different in these characters in their early stages. Through molting and growth, the tympanum becomes larger, and the tibiae attains the shape final in the last stages of insect development ( Table 2 ; Ball and Cowan, 1978).

In this study, we provide well-preserved males, females, and nymphal specimens, in which most of the morphological characters can be studied. It is applicable to verify the similarities and differences with the other recently described fossil taxa of “Mole Crickets” with those specimens. In terms of coloration, it was feasible to show that the coloration of † P. micromorphus is similar to those of the two males studied here. † P. rectanguli n. comb. has the same color pattern, but its image was darker in the original description (possibly due to a lack of brightness or light from the photographic record). For † C. fania n. syn., the same issue happened as mentioned above.

All the specimens in the different stages of development have similar coloration, with two distinct large dark “eyespots” of similar shape; lower half of the anterior lobe of the yellow pronotum; shape and location of apical spurs of fore tibia; hind tibia serrulate with small spines; apex with conspicuous slender spines. The number of dorsal spines on legs is not reliable classification characters due to its intraspecific variation, which may be different from one leg to the other leg on one specimen ( Cadena-Castañeda et al. 2022b).

We consider † Pherodactylus micromorphus and † P. rectanguli n. comb. as valid genus and species. Both genera were described in 2020, and the original description of † P. micromorphus is available on March of 2020, while † Tresdigitus rectanguli is published on August of 2020. It is worth noting that Poinar et al. (2020) proposed a more reasonable taxonomic placement of its genus and species than the other authors, consisting with our results discussed and analyzed here.

† Burmagryllotalpa longa is proposed to move under Gryllidae : Gryllinae : Sclerogryllini : Pherodactylina n. subtr. Although this species shares some morphologies with † Pherodactylus species, † B. longa completely lacks tympanum, and its pronotum is dorsally curved without spots on pronotal disc that characterize † Pherodactylus species. Thus, we consider † B. longa as valid.

Figures

FIGURE 1. Habitus of †Tresdigitus rectanguli n. comb., specimen ECNU-AM-0019. A, photograph, ventral view. B, photograph, dorsal view. Scale bars = 1 mm.

FIGURE 2. Forewing morphology of †Pherodactylus rectanguli n. comb., specimen ECNU-AM-0019, adult male and Sclerogryllus punctatus. A, photograph of left forewing. B, drawing of left forewing. C. right forewing of S. punctatus. Scale bar = 0.5 mm.

FIGURE 3. Habitus of †Pherodactylus rectanguli n. comb., specimen ECNU-AM-0010, adult male. A, photograph, dorsal view. B, photograph, ventral view. Scale bars = 1 mm.

FIGURE 4. Habitus of †Pherodactylus rectanguli n. comb., specimen ECNU-AM-0002, adult female. A, photograph, ventral view. B, photograph, dorsal view. Scale bars = 1 mm.

FIGURE 5. Habitus of †Pherodactylus rectanguli n. comb., specimen ECNU-AM-0024, adult female. A, photograph of right side. B, photograph of left side. Scale bars = 1 mm.

FIGURE 6. Habitus of †Pherodactylus rectanguli n. comb., specimen ECNU-AM-0045, juvenile male. A, photograph of right side. B, photograph of left side. Scale bars = 1 mm.