Tesserodoniella, Vaz-De-Mello & Halffter, 2006

Vaz-De-Mello, Fernando Z. & Halffter, Gonzalo, 2006, A new dung beetle genus with two new species from Chile (Coleoptera: Scarabaeidae: Scarabaeinae), Zootaxa 1193 (1), pp. 59-68 : 60-62

Tesserodoniella gen. nov.

( Figs. 1–10 )

Type species Tesserodoniella elguetai sp. nov.

Etymology

Tesserodon , a similar genus, and – iella, small, refers to the proximity of this genus to the Australian genus Tesserodon Hope and to its small size relative to other Chilean Scarabaeinae. The name of this genus is feminine in gender.

Diagnosis

The new genus is distinguished from all other New World Scarabaeinae by the following combination of characters: Eyes small, feebly visible dorsally when head is retracted ( Figs. 1, 6 ); anterior trochantofemoral pit (as defined by Génier & Kohlmann 2003) present; elytra with wide pseudepipleuron externally to seventh discal stria; mesosternal disc with a transverse depression; abdomen with ventrites articulated, sixth abdominal ventrite as long as ventrites 3–5 together; pygidium with a basal transverse sulcus.

Description

Body: oval and short, size small (5.1–6.1 mm). Dorsal surface microgranulate; head and pronotum covered by irregular, dense, conspicuous punctures. Head: as long as wide, without visible dorsal carinae or sutures. Clypeus with two teeth separated by short Ushaped emargination, and external lobe beside each tooth. Dorsal eye surface reduced, triangular, or elongated. Head without occipital bead. Clypeal ventral process cariniform, bordering clypeal emargination. Mentum anteriorly concave. Labial palpus with first segment subcylindrical, widened medially; second segment almost spherical, slightly longer than first; third segment short, cylindrical, narrower than others. Prothorax: subrectangular or rhomboidal. Anterior angles acute. Laterally with ventrally directed carina in posterior two­thirds; carina externally directed in anterior third, originating at strong angle in lateral border, subparallel in posterior two­thirds, convergent in anterior third. Posterior margin straight. Hypomeron with acute transverse carina, extending from external side of procoxal cavity to anterior third of lateral pronotal carina. Hypomeral surface concave anterior to transverse carina, flat to feebly convex posterior to transverse carina, with longitudinal keel parallel to external margin. Elytra: Disc convex, with seven double striae; striae with small umbilicate punctures separated by five or more diameters. Humerus without conspicuous calli. Pseudoepipleuron with two inconspicuous striae; one dividing pseudoepipleuron in almost equivalent halves, conspicuous only medially; second stria juxtaposed to epipleural carina, conspicuously impressed from basal fifth to pseudoepipleural apex. Epipleuron wide, gradually narrowed to apex, except for strongly widened basal region. Microgranulations on elytral disk and pseudoepipleuron more conspicuous than on remaining body parts. Hind wings reduced. Mesosternum: long, narrowed medially. Surface covered by large, dense, ocellate punctures. Disc with evident, transverse concavity; convex at each side of depression. Mesoepimeron trapezoidal with strong carina parallel to anterior margin. Meso­metasternal suture straight, inconspicuous, effaced, in obtuse angle. Metasternum: covered by large, dense ocellate punctures; punctures larger laterally, denser, deeper, smaller on disc. Anterior lobe narrower at base than apically, apically 4/3 as wide as basal width; with small lateral round depression at base, depressions linked to each other by concave, inconspicuous U­shaped sulcus; sulcus with vertex posteriorly directed. Legs: apico­anterior femoral pit present, rounded. Protibia conspicuously curved internally, externally less curved due to apical expansion; externally with three conspicuous teeth in apical half, median tooth closer to apical tooth. Ventral median longitudinal carina with strong tubercle at tarsal insertion. Spur conical, narrow, as long as tarsal segments 1–3 combined. Protarsus feebly longer than apical tibial width; segments 1–4 subequal, subcylindrical, as long as wide; tarsomere 5 as long as tarsomeres 2–4 together, laterally flattened, distally widened. Claws small, simple, falciform. Mesofemur elongated. Mesotibia triangular with straight sides, evenly widened to apex, as long as mesofemur. Larger mesotibial spur subconical, just shorter than mesotarsomeres 1–2 combined. Mesotarsomeres 1–4 decreasing in size towards claw; tarsomere 5 with claw as long as tarsomeres 3–4 combined. Metafemur evenly and strongly widened at middle, with strong posterior ventral carina; posterior margin prolonged into conspicuous lobe in apical fourth. Metatibia long, narrow, weakly widened apically; externally serrate in apical two thirds; apex strongly widened externally, obliquely truncate. Metatibial spur subconical, as long as tarsomeres 1–2 combined. Metatarsi similar to that of middle legs. Abdomen with ventrites 2–4 of equal length, ventrite 5 one third the length of ventrite 4; ventrite 6 as long as 3–5 combined, not narrowed medially. Pygidium almost twice as wide as long; disc strongly convex with ocellate punctures medially; bordered complete, with strong basal sulcus. Male genitalia with asymmetric parameres, left paramere (in dorsal view) longer and wider at apex.

Sexual dimorphism

Male protibia with strong internal apical tooth directed foreward and downward, external teeth narrower than in females; male metatibiae with larger external serrations; and male abdominal ventrite 5 narrowed medially (width even in females).

Remarks

The new genus is readily distinguishable from other New World canthonine genera. The genus is quite similar to two Australian genera: Tesserodon Hope and Aptenocanthon Matthews. These three genera are all characterized by the presence of the anterior trochantofemoral pit and the position and form of the pseudoepipleuron. Based on our study of dung beetle genera, we predict that these characters are phylogenetically informative and that the three genera form a clade. The three genera may be related, although more distantly, to the South American genera Zonocopris Arrow , Cryptocanthon Balthasar , Paracryptocanthon Howden & Cook , as well as the New Zealand genus Saphobius Broun , because they all share the trochantofemoral pit structure. However, Zonocopris , Cryptocanthon , Paracryptocanthon , and Saphobius all have a somewhat distinct pseudoepipleuron. Tesserodoniella differs from both Australian genera in the form of the prothorax, elytral striae, and in having the first metatarsomere slightly larger than the second.

Figures

FIGURES 1–9. 1–5. Tesserodoniella elguetai n. sp.: 1. head; 2. elytron; 3. hind leg; 4. parameres; 5. protibia; 6–9. Tesserodoniella meridionalis n. sp.: 6. head; 7. elytron; 8. hind leg; 9. parameres.

FIGURE 10. Map of central Chile showing distribution of Tesserodoniella elguetai n. sp. (circles) and T. meridionalis n. sp. (triangles).