Amazonopsis, Barr, Cheryl B., 2018

Barr, Cheryl B., 2018, Amazonopsis, an unusual new genus of riffle beetle from South America with two new species (Coleoptera, Elmidae, Elminae), ZooKeys 803, pp. 71-92 : 73

Amazonopsis gen. n. Figs 1, 2, 3, 4, 5, 6, 7, 8, 9, 10

Type species.

Amazonopsis theranyi sp. n.

Other species.

Amazonopsis camachoi sp. n.

Diagnosis.

The flattened and bent pro- and mesotarsal claws of the males (Figs 1, 4, 9) and the pronotal perforations of the females (Fig. 3) are unique among the Elmidae , and both sexes lack pronotal and elytral carinae.

Generic description.

Male. Body stout, elongate-oval, at least 2 × as long as wide; convex dorsally. Surface of dorsum and parts of venter covered by thin, pale gray, microreticulate plastron; thick, glossy plastron present laterally on sterna and adjacent surfaces of coxae, legs (except tarsi), lower margin of hypomeron, abdominal ventrites (except along midline), and entire epipleuron; head (vertex, frons, clypeus) and pronotum with short, broad, flat, pale yellow setae. Tibial cleaning fringes well-developed, formula 2-2-1. Head. Antenna filiform, with 11 antennomeres. Vertex with V-shaped carina opening anteriorly; frons slightly elevated between eyes; eyes large, subcircular in outline. Clypeus rectangular, wider than long. Labrum rectangular, not as wide as clypeus. Mandible with three short, rounded, apical teeth. Maxillary palpus with four palpomeres. Labial palpus with three palpomeres. Pronotum. Subquadrate, slightly wider than long, widest at midlength; without carinae or gibbosities. Disc, including punctures, covered with pale microreticulate plastron. Scutellum subcircular to ovate, flat. Elytron. Elongate, about 3 × as long as wide; without carinae except for swollen, raised base of third interval; humeral angles protuberant. Disc with 10 longitudinal rows of coarse, deep punctures; row 10 near margin with much smaller punctures than rows 1-9. Epipleuron with excavation adjacent to marginal lobe of abdominal ventrite 4. Surface of disc, including punctures, with thin, pale microreticulate plastron, often abraded; cuticle beneath very shiny, reddish-brown. Leg. Femur and tibia covered with thin, shiny layer of dense plastron; tarsus without plastron. Prothoracic leg shortest, metathoracic leg longest. Pro- and mesocoxa globose, metacoxa transverse. Pro- and mesotibia each with anterior and posterior cleaning fringes of long setae; metatibia with a single, posterior fringe. Claws long, without basal teeth; protarsal and mesotarsal inner and outer claws dissimilar; protarsal inner and mesotarsal outer claws enlarged, laterally flattened, bent at base; protarsal outer and mesotarsal inner claws smaller, narrower; metatarsal claws shorter, flattened, but basically unmodified. Venter. Pale microreticulate plastron present on ventral surfaces except at midline; plastron yellow and most evident near lateral thoracic margins and on abdominal ventrites. Prosternum slightly shorter than metaventrite; anterior margin curved posteriad, bounded by pair of small, ventrally directed spines; prosternal process about 2 × as long as wide, margins raised, bluntly rounded at apex. Mesoventrite shortest; deep cavity present to accommodate prosternal process. Metaventrite longest, slightly longer than prosternum; metathoracic discrimen distinct; posteromedial margin with pair of ventrally directed processes. Abdomen with five ventrites; ventrites 1-4 decreasing in length posteriorly, ventrite 5 longer than ventrite 1; ventrites narrower medially and wider laterally; ventrite 4 lateral margin with lobe to link with groove on epipleuron, posterior margin strongly raised and rounded. Genitalia. Trilobate, typical form.

Female. Although the female of A. camachoi is unknown, it is possible, if not likely, that secondary sexual dimorphism is a generic characteristic. Females of A. theranyi exhibit the following differences (Fig. 3): pronotum with two, moderately large, oval perforations of the cuticle on either side of the midline; claws all unmodified; prosternum and metaventrite without paired, ventrally directed spines or processes.

Etymology.

“Amazon”, a Greek word for a legendary race of warrior women, refers to the robust, unique features of the beetles as well as the provenance of the genus; plus “-opsis” from the Greek meaning "look, appearance, likeness." Gender, feminine.

Comparative notes.

In Manzo (2005), Amazonopsis keys to the couplet containing Pagelmis Spangler, 1981 and Stenhelmoides Grouvelle, 1908, because of its extensive dorsal plastron and lack of pronotal and elytral carinae, but matches neither genus. Amazonopsis has a generally uniform distribution of plastron (except for abraded areas), while Pagelmis ( Spangler 1981) and Stenhelmoides ( Grouvelle 1908) exhibit character istic patterns. In addition, the epipleuron-clasping projection on abdominal ventrite 4 in Amazonopsis is lacking in Pagelmis and Stenhelmoides . Amazonopsis is similar to Portelmis Sanderson, 1953, in that both lack elytral carinae, possess a V-shaped ridge behind the eyes, and have a pair of abdominal lobes linking the abdomen to the elytra ( Sanderson 1953). Unlike Amazonopsis , Portelmis has the lateral margin of the fifth, rather than the fourth, abdominal ventrite prolonged to link with the elytral epipleuron; most species have pronotal sublateral carinae; and the tibial cleaning fringes are poorly developed. Xenelmis Hinton, 1936, has a similar body form, but at less than 2 mm long is less than half the size of Amazonopsis . Like Amazonopsis , Xenelmis lacks pronotal carinae, but dissimilarly has two sublateral elytral carinae ( Hinton 1936).