Saotomia Borovec & Anderson, 2021

Borovec, Roman & Anderson, Robert, 2021, Saotomia tuberculata, a new genus and species of Peritelini (Coleoptera Curculionidae; Entiminae) from São Tomé, West Africa, Zootaxa 4966 (5), pp. 571-577 : 572-576

Saotomia Borovec & Anderson , gen. n.

( Figs. 1–10 )

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Type species. Saotomia tuberculata Borovec & Anderson , spec. n., by present designation. Gender. Feminine.

Diagnosis. Small-sized Peritelini , 3.0– 3.3 mm; body densely covered by appressed scales; epifrons occupying almost the entire width of rostrum in dorsal view, rostrum at base as wide as space between anterior margins of eyes, continuous with the head in lateral profile; fronto-epistomal area large, glabrous, distinctly declined ventrally; antennal sockets lateral, dorsally barely visible, scrobe in profile with dorsal margin directed to middle of eye and ventral margin directed downwards deeply below eye; pronotum small in size in comparison to elytra; elytra lacking humeral calli, with numerous longitudinal tubercles prominent in lateral profile; metatibiae lacking corbels; onychium with a single claw; ventrite 1 in middle distinctly longer than 2, 2 shorter than 3+4; all sutures between ventrites straight; penis with temones almost twice as body of penis; tegmen lacking parameres; female sternite VIII with plate narrowly umbrella-shaped with posterior margin membranous; gonocoxites well sclerotised, with very short, laterally prominent subapical styli.

Description. Size small, 3.0– 3.3 mm. Body integument dark brownish, antennae and tarsi paler, rusty brownish. Dorsal and ventral side of body densely covered by appressed scales, only fronto-epistomal area glabrous, antennal funicles with clubs and tarsi setose. Ventral part of pronotum and mesoventrite, with corresponding parts of pro- and mesocoxae, more densely covered by yellowish appressed scales. Dorsal side of body with inconspicuous short erect piliform setae.

Head ( Figs 3, 4 ) wide and short, slightly enlarged posteriad, vertex perfectly flat, wide; ventrally lacking scales, unpunctured, smooth. Eyes medium-sized, subdorsal, prominent from outline of head; laterally subcircular, not reaching dorsal border of head. Rostrum short, slightly wider than long, short basal part tapered anteriad with concave sides, then subparallel-sided; dorsal border short and flat, in apical half conspicuously declined in profile, ventral border almost flat, with distinct transverse ridge at base. Epifrons short and very wide, occupying almost the entire width of rostrum in dorsal view, very short base tapered anteriad, almost the entire remaining length with parallel sides, flat, with only median longitudinal groove indicated in some specimens, at base as wide as space between anterior margins of eyes, continuous with the head, anteriorly slightly rounded. Fronto-epistomal area conspicuous, large, glabrous, unpunctured, smooth, reddish brown, distinctly declined ventrally, separated posteriorly from epifrons by sharp boundary between scaled and glabrous space, with two to three prominent pairs of fine short setae. Epistome small, of the same color as frons, posteriorly V-shaped, carinate, indistinctly separated from the frons. Antennal sockets placed laterally, dorsally visible only as very small fossae at place of antennal insertion between epifrons and frons; scrobe in profile subtriangular, moderately large, with dorsal margin directed to middle of eye and ventral margin directed downwards deeply below eye, separated from eye and ventral border of rostrum by slender squamose stripe. Mandibles small, projecting anteriorly, lacking scales, with three laterally placed setae. Subgena squamose only in basal and lateral parts. Prementum with two long and fine setae.

Antennae slender; scape reaching anterior margin of pronotum in repose, distinctly longer than funicle; funicle with 7 articles, each article apex, articles 1 and 2 conical, articles 3–7 slightly wider than long; club broadly oval.

Pronotum ( Fig. 1 ) short in comparison to length of elytra, subrhomboidal, widest slightly behind midlength, sides laterally pointed, posterior margin V-shaped, medially roundly projected posteriad. Anterior margin laterally straight without ocular lobes or vibrissae, obliquely directed posteroventrally. Procoxal cavities contiguous, round, moderately large, placed at midlength of prosternum, occupying majority of space of short ventral part of prosternum.

Scutellar shield dorsally not visible.

Elytra ( Fig. 1 ) elongate-oval, widest at about midlength, constricted in basal part, with base as wide as base of pronotum and obliquely subtruncate distally, lacking humeral calli; base angularly V-shaped; odd-numbered interstriae slightly wider than even-numbered ones, with slight longitudinal tubercles, larger on odd interstriae and on posterior declivity, distinctly prominent in lateral profile; slope of declivity vertical, overhanging apices of elytra in dorsal view. Elytra 10-striate; striae punctate, punctures hidden under vestiture, striae sinuous between tubercles. Hindwings absent. Mesocoxae semiglobular, mesosternal process about as wide as ¼ of mesocoxal width. Metacoxae slightly transverse, metaventral process obtuse, wider than transverse diameter of metacoxa. Tergite VII and VIII in both sexes moderately well sclerotised, tergite VIII in males bowl-shaped, apically rounded, in females subtriangular.

Legs moderately slender. Femora swollen, lacking teeth, only metafemora with unobtrusive, microscopic tooth on distal area of underside. Trochanters with one long seta. Protibiae long and slender, straight, narrowest before apex; apex obliquely subtruncate, inner part armed with very short brownish sparse spines, outer part fringed with short yellowish bristles, with discernible brownish mucro, lacking spur; inner side inconspicuously denticulate, with 5–6 hardly visible small brownish grains with long seta; middle and hind leg similarly shaped, indistinctly denticulate. Metatibiae with apical surface small, oval, glabrous, with long mucro and fringed internally by short, sparse, yellowish spines, and externally by dense yellowish bristles, lacking corbel. Tarsi slender, with tarsomere 1 slightly shorter than 2+3, tarsomere 3 bilobed, distinctly wider than tarsomere 1 or 2; tarsomere 5 (onychium) long, bearing a single, long claw.

Abdominal ventrites ( Fig. 5 ) 1.2–1.3× longer than wide, elongate with almost straight sides; ventrite 1 in middle 2.6–2.8× as long as ventrite 2, length behind metacoxa only slightly longer than ventrite 2; ventrite 2 0.7× as long as ventrites 3 and 4 combined; ventrite 3 as long as ventrite 4; ventrite 5 in males shorter, apically obtusely truncate, in females longer, apically rounded. All sutures straight, sutures between ventrites 1–3 fine and narrow, between ventrites 3–5 deep and wide.

Male terminalia. Penis moderately short, well sclerotised, temones 1.8–1.9× longer than body of penis; endophallus long, with complex of distinct endophallites. Tegmen with complete ring lacking parameres, manubrium twice as long as diameter of ring. Spiculum gastrale short, moderately robust, anteriorly hook-shaped curved and enlarged to flat plate, posteriorly with fused short basal arms; hemisternites short, curved ( Fig. 7 ).

Female terminalia. Sternite VIII ( Fig. 10 ) with plate narrowly umbrella-shaped, longer than wide, anterior margin fringed by fine, sparse, long setae, posterior margin membranous; apodeme about 2.5× longer than plate, widest at midlength, terminating at midlength of plate. Gonocoxites (e.g., Fig. 8 ) long and slender, well-sclerotised, evenly tapered and pointed apically, with short, laterally prominent subapical styli, each stylus with apical tuft of fine setae. Spermatheca with rounded corpus and well-developed ramus and collum ( Fig. 9 ).

Sexual dimorphism. The sexes are externally indistinguishable except for slight differences in shape of ventrite 5.

Etymology. The genus is named Saotomia after the island of São Tomé where the only known species is found. Gender is feminine.

Biology. There is no information available about how the specimens were collected.

Taxonomic position. The present situation regarding the tribal division of Entiminae is far from one of well defined, monophyletic groups. Often, tribal names applied to Palaearctic taxa are also applied to superficially similar Afrotropical taxa. Thus, although we consider the newly described genus in the tribe Peritelini , so called Afrotropical Peritelini are very different from the nominal genus Peritelus Germar, 1824 and all other 27 genera of Palaearctic Peritelini (we are not including the 4 genera described or known from Socotra Islands and Saudi Arabia, they are related to Afrotropical taxa). However, solving this problem is not the focus of the present paper and such must be done based on examination of morphological and molecular data of extensive material, a study that is currently in progress.

Genera listed in Afrotropical Peritelini can be defined by an ‘otiorhynchinae’ type of antennal socket, trisetose mandibles, pronotum lacking ocular lobes and vibrissae, elytra lacking laterally prominent humeral calli (shoulders), metatibiae lacking corbels and claws fused. The Afrotropical Peritelini mainly include genera of medium to moderately large size (6 mm in Systates Gerstaecker, 1871 to 24 mm in Seneciobius Aurivillius, 1921 ), collected mainly from woody vegetation, with only a much smaller number of genera and species of small size (2.5 mm in Opseobarypeithes Hustache, 1939 to 5.3 mm in Afrotroglorrhynchus Hustache, 1939 ), with a mostly terricolous way of life. These latter taxa are known mainly from eastern Africa, high elevation mountains of Kenya and the Democratic Republic of Congo and Rwanda. The only exception from West Africa is Saotomia , most similar to the periteline genera Dysommatus Marshal, 1933 , known from the Democratic Republic of Congo and Rwanda, and Fernandius Marshall, 1954 known from Equatorial Guinea. Saotomia shares with them a small body size, moderately slender antennae and legs, glabrous declinate frons, epistome subtriangular at extreme apex of rostrum and also the same structure of the abdominal ventrites with an obtuse wide metaventral process, ventrite 1 distinctly longer than 2, 2 shorter than 3+4 and all sutures between the ventrites straight. Saotomia can be easily distinguished from Dysommatus and Fernandius by a very wide epifrons, occupying the majority of the width of the rostrum (in Dysommatus and Fernandius the epifrons is narrower than half of width of rostrum), rostrum continuous with head (separated by distinct transverse sulcus), antennal sockets barely visible in dorsal view (fully visible), dorsal border of antennal socket directed to middle of eye in profile (to or above dorsal margin of eye), antennal scapes reaching anterior border of pronotum (midlength of pronotum), pronotum without granules or punctures (with distinct granules or large punctures), base of pronotum angularly V-shaped (straight) and also by a single tarsal claw (two equally long and connected claws). Using the incomplete key to genera of Afrotropical Peritelini published by Hustache (1939), Saotomia belongs with the genera Oreorrhinus Marshall, 1935 , Seneciobius Aurivillius, 1921 and Xestorhinus Aurivillius, 1926 , known from Kenya, Uganda and Tanzania based on its antennal sockets not visible in dorsal view. From these three genera, Saotomia is easily distinguished by its small size (the three other genera have body size of 6–15 mm), epifrons almost as wide as respective part of rostrum (conspicuously narrower), frons smooth, glabrous, separated posteriorly from epifrons by sharp border between glabrous and densely squamose parts (punctate as in epifrons, not separated from epifrons posteriorly) and also by a single tarsal claw (two equally long and connected claws).

A single claw in Entiminae is an unusual character state, but known from the Afrotropical region in three genera, Gyponychus Pascoe, 1870 and Synaptoplus Gerstrecker, 1871 ( Cneorhinini Lacordaire 1863 ) and Heisonyx Marshall, 1947 ( Embrithini Marshall, 1942 ). These four genera (including the newly described genus) belong to different tribes and it is apparent, this character state has likely been independently derived in the three lineages. Saotomia is, for example, easily distinguished from the three above stated genera by lacking metatibial corbels, while Cneorhinini and Embrithini have well developed, mostly densely squamose corbels.

By its short pronotum in comparison to elytral length and also in the constricted base of the elytra, Saotomia is also similar to the cneorhinine genus Omotrachelus Kolbe, 1883 , known from Cameroon, Congo, Gabon, Ivory Coast and Democratic Republic of Congo. From this genus it is easily distinguishable by lacking metatibial corbel ( Omotrachelus has metatibial corbel developed), antennal sockets directed towards eye (directed below eye), well defined and visible posterior margin of pronotum (posterior part of pronotum is covered by elytral collar) and also by single tarsal claw (two equally long connate claws).

Note that in the comparison with the genus Dysommatus , we are using a group of species related to the type species Dysommatus rufulus Marshall, 1933 , as some of the species described under this genus belong to the genera Tapinomorphus Hartmann, 1904 and Tylauchen Marshall, 1955, an issue that will be resolved in a forthcoming paper.

Figures

FIGURES 1–4. Saotomia tuberculata. 1. Dorsal habitus. 2. Lateral habitus. 3. Head and rostrum, dorsal view. 4. Head and rostrum, lateral view.

FIGURES 5–10. Saotomia tuberculata. 5. Abdomen, ventral view, male; scale bar = 1 mm. 6. Penis, dorsal view, male; scale bar = 0.5 mm. 7. Sternite IX, ventral view, male; scale bar = 0.5 mm. 8. Gonocoxites, dorsal view, female; scale bar = 0.5 mm. 9. Spermatheca, female; scale bar = 0.5 mm. 10. Sternite VIII, female; scale bar = 1 mm.