Plectromerus grimaldii Nearns & Branham

Nearns, Eugenio H. & Branham, Marc A., 2005, A new species of Plectromerus Haldeman (Coleoptera: Cerambycidae) from Dominican amber with notes on the fossil Plectromerus tertiarius Vitali, Zootaxa 1088, pp. 17-24 : 19-23

publication ID	https://doi.org/ 10.5281/zenodo.273338
DOI	https://doi.org/10.5281/zenodo.6265266
persistent identifier	https://treatment.plazi.org/id/BC186E20-9E51-0A7F-FED5-FE31FB422466
treatment provided by	Plazi
scientific name	Plectromerus grimaldii Nearns & Branham
status	sp. nov.

Treatment

Plectromerus grimaldii Nearns & Branham View in CoL , new species

Figs. 1a View FIGURE 1. a , 2a–d View FIGURE 2. a – d , 3 View FIGURE 3. a b, 3d

Description. FEMALE. Length 7.1 mm, width 1.8 mm (measured across humeri). Habitus as in Figure 1a View FIGURE 1. a . General form small, narrow, subcylindrical. Elytra with two indistinctly defined and very faint, transverse ferruginous fasciae on each elytron, one at basal third and another just behind middle. Head with front nearly flat, transverse, with a median, shallow line from between eyes to just beyond vertex, slightly concave between antennal tubercles, which are somewhat raised and widely separated. Much of head surface is obscured by an opaque film, exposed areas with surface opaque, alveolatepunctate. Eyes coarsely faceted, prominent, transverse, subreniform ( Fig. 2b View FIGURE 2. a – d ). Antennae elevensegmented, slightly longer than body, impunctate; scape bowed, third antennomere subequal to scape, almost twice as long as fourth, fifth antennomere longest, about 2.6 times longer than fourth, antennomeres 611 becoming progressively shorter, sixth through eighth slightly longer than third, eleventh slightly longer than fourth, basal antennomeres subcylindrical, from fifth slightly flattened, apices of antennomeres 6–10 produced externally, antennomeres 7–9 slightly bowed ( Fig. 3 View FIGURE 3. a b, 3d). Antennomeres 2–6 ciliate beneath with coarse, moderately long, suberect, hairs. Pronotum subcylindrical, about 1.5 times as long as wide, widest at middle, slightly broader at apex than base, sides broadly inflated, arcuately constricted at basal third, and a slight inflation just before apex; basal margin slightly arcuate; disk convex. Surface opaque, alveolatepunctate. Scutellum small, rounded, almost as long as broad, impunctate. Elytra about 2.7 times as long as width at humeri, about 2.5 times as long as pronotal length, about 1.3 times broader basally than pronotum at widest (at middle); sides nearly parallel, slightly sinuate around middle, evenly rounded to apex which is subtruncate; epipleural margin moderately sinuate. Elytral disk slightly concave medially, subsuturally, creating a faint costa on each elytron. Surface shining; punctation dense, coarse, punctures becoming finer towards apex and sides, almost obsolete on apical third; glabrous. Underside with prosternum shining; narrowest area of prosternal process between coxae about 0.25 times as wide as coxal cavity, and about 0.5 times the width of apex of process which is cordate (emarginated at middle of apex). Mesosternum surface shining, sparsely and finely punctate ( Fig. 2b View FIGURE 2. a – d ). Metasternum surface shining, sparsely and finely punctate, with a few suberect hairs; first visible abdominal ventrite longest, about 2.5 times longer than second, about as long as next three visible abdominal ventrites combined, fifth visible abdominal ventrite evenly, broadly rounded, slightly longer than fourth. Legs very finely punctate, with femora clavate, meso and metafemora arcuate, underside of each femoral club with a small triangular tooth with posterior edge smooth; metafemora about 1.2 times longer than metatibiae; tibiae slightly flattened, expanded apically, base of tibiae slightly arcuate ( Fig. 2c View FIGURE 2. a – d ).

Etymology. We are pleased to name this species for Dr. David Grimaldi (AMNH) for his contributions to the study of insects in amber and for making the specimen of this species available for study.

Type. Holotype, female, in the collection of the AMNH, No. DR16535. Included in a piece of Dominican amber (OligoMiocene) from the Dominican Republic. Amber yellowbrownish, moderately clear; cut and polished to a flat, oval shape, measuring 18.5 X 15 X 8 mm. Specimen is in good condition except damage to left antenna: antennomere 7 is incomplete, antennomeres 8–11 are missing.

Discussion. Although gender cannot be determined conclusively, we believe the holotype of P. grimaldii to be female based on the evenly, broadly rounded fifth visible abdominal ventrite and the lack of an irregular patch of coarse punctures in front of each prosternal coxa (a male characteristic seen in many extant species of Plectromerus ).

From other congeners, P. grimaldii can be distinguished by the following combination of characters: the shape and punctation of pronotum (widest at middle, alveolatepunctate), the elytral punctation (dense, coarse), the glabrous pronotum and elytra, and the small, nonserrate metafemoral tooth ( Fig. 2c View FIGURE 2. a – d ). Plectromerus punctatus (Fisher) and P. exis Zayas also have small metafemoral teeth which are not serrate, however these species can be distinguished by having the third antennomere longest (fifth longest in P. grimaldii ) and different pronotal dimensions: in P. punctatus the pronotum is almost as wide as long, in P. exis the pronotum has a distinct tubercle in the center and the length is about 1.8 times the width (1.5 times as long as wide in P. grimaldii ).

Notes on Plectromerus tertiarius Vitali holotype: ventral habitus as in Fig. 1 View FIGURE 1. a b (dorsal habitus completely obscured), length approximately 7 mm (exact measurement not possible since abdomen is bent up through open elytra), included in a piece of Dominican amber (Lower Miocene) from the Dominican Republic. Amber yellowbrownish, partially obscured by numerous, small bubbles; cut and polished in a nearoval shape, measuring 42 X 22 X 15 mm. Specimen is damaged as follows: metathoracic legs are missing except coxae and trochanters; left antenna is damaged, missing part of antennomere 8, completely missing antennomeres 9–11. One important character in particular, the prosternal process between coxae, is not visible due to position of pro and mesothoracic legs. Elytral punctation can be inferred from ventral view due to open elytra which are semitranslucent. Vitali (2004) states that the holotype is a male, however, we see nothing to support this. In our opinion, the broadly rounded fifth abdominal segment is more indicative of a female Plectromerus (irregular patches of coarse punctures in front of each prosternal coxa are also not visible but the view is partially obscured). Vitali (2004) also states that the first abdominal ventrite is 3 times longer than other visible ventrites, however, our measurements show it to be about 2 times longer.

Plectromerus grimaldii superficially resembles P. tertiarius in pronotal shape and elytral punctation. They differ, however, with respect to elytral apices (subtruncate in P. grimaldii , evenly rounded in P. tertiarius ) and visible abdominal ventrite relationships (first ventrite as long as next 3 visible abdominal ventrites combined in P. grimaldii , first ventrite slightly longer than next 2 visible abdominal ventrites combined in P. tertiarius ). In addition, significant differences can be seen in antennomere morphology. These differences exceed the variation in antennal morphology seen in extant species and across gender in Plectromerus . In P. grimaldii , the fifth antennomere is about 1.9 times longer than the tenth (about 1.6 times longer in P. tertiarius ), fifth antennomere about 1.5 times longer than seventh (about 1.1 times longer in P. tertiarius ). In P. tertiarius , the seventh antennomere is slightly longer than the sixth (subequal in P. grimaldii ) and the eleventh antennomere is slightly longer than the tenth (subequal in P. grimaldii ). In addition, antennomeres 5–10 are distinctly produced externally in P. tertiarius , whereas in P. grimaldii , antennomeres 6–10 are only moderately produced externally ( Fig. 3 View FIGURE 3. a b–d).