Thendelecrotona, Nik, Grzegorz Pa Ś, 2007

Nik, Grzegorz Pa Ś, 2007, A new genus and species of the aleocharine tribe Thamiaraeini (Coleoptera, Staphylinidae) from South Africa, Zootaxa 1527, pp. 31-38 : 31-36

Thendelecrotona gen. n.

( Figs. 1–6 )

Type species: Thendelecrotona natalica sp. n.

Diagnosis. Thendelecrotona can be recognized by the combination of the following characters: the head with infraorbital ridge, the maxillary palpus with 4 articles and a moderately defined apical pseudosegment, the labial palpi 2-jointed, the ligula entire (not divided into lobes), the mentum with produced anterior angles, the pronotal hypomera not visible in lateral view, the mesocoxae narrowly separated, the elytral postero-lateral angles strongly sinuate, the tarsal formula 4-5-5.

Description. Body length 2.2–2.4 mm, broad, convex and moderately glossy ( Fig. 1 ).

Head. Circular in outline, temples arcuately narrowed to hind angles; eyes weakly protruding from lateral contours of head; head with infraorbital ridge complete to maxillary insertion. Antennae short, clearly increasing in width apically, extending to base of pronotum.

Mouthparts. Maxilla ( Fig. 2 ) with lacinia longer than galea; galea narrow, rounded apically, subequal in width to lacinia; apex of galea with membranous lobe in apical 1/3; apical and outer margin of lobe covered with several long setae, inner and middle areas of lobe with two longitudinal rows of dense setae ( Fig. 2 ); inner margin of lacinia with spines and long setae; maxillary palpus with 4 articles and a moderately defined apical pseudosegment, article 1 very short, article 2 elongate, slightly widened apically, article 3 distinctly widened apically, longer than article 2, article 4 relatively long, about ½ length of article 3, article 4 with pseudosegment. Labrum ( Fig. 5 ) transverse, widely emarginate apically and with characteristic arrangement of setae. Labium ( Fig. 3 ) with ligula relatively short and broad, about ¾ length of labial palpomere 1; apex of ligula with several pseudopores; prementum with two moderately long medial setae situated one behind the other, insertions of setae almost adjacent; median pseudopore field narrow and more or less linear, lateral pore field with a single setose pore and two asetose pores; labial palpi 2-jointed, article 1 elongate, narrowed towards apex, with 6 long setae, article 2 slightly shorter than article 1, distinctly widened apically; apex with several very short spinules and numerous pseudopores. Mentum strongly transverse ( Fig. 6 ), widest at base, apical margin deeply concave, anterior angles strongly produced, 8 long setae on each side present. Mandibles curved towards apex, right mandible ( Fig. 4 ) with large median tooth at middle of inner margin, strongly serrate in dorsal molar region, “velvety patch” area large, wider than half of mandibular base, composed of combination of anterior row of teeth and basal area of very fine spinules.

Thorax. Pronotum transverse, strongly convex, moderately glossy, widest in the middle, lateral sides arcuate, more strongly narrowed to apex than to base. Hypomera not visible in lateral view. Mesocoxae narrowly separated. Mesoventral process, often referred to as “mesosternal” (see Baehr 1975, Beutel 1986, Belkaceme 1991, Lawrence 1999, Beutel & Haas 2000, Beutel & Lawrence 2005, Friedrich & Beutel 2006) triangular in outline, pointed at apex, extending to about 2/3 of mesocoxae; metaventral process very short, triangular in outline, broadly rounded at apex, extending to 1/3 of mesocoxae. Mesocoxal cavities margined posteriorly by fine bead.

Elytra. Transverse, lateral sides straight, widest at base, postero-lateral angles strongly sinuate.

Abdomen. Acuminate, widest at base, tergites III–IV weakly and shallowly transversely impressed at base, impressions smooth, impunctate, sternites not impressed at base.

Legs elongate, metatarsus long, approximately 3/4 the length of metatibia; basal article of metatarsus long, subequal in length to articles 2 and 3 combined, articles 2–4 relatively short, subequal in length, article 5 elongate, subequal in length to articles 3–4 combined; tarsal formula 4-5-5.

Comparative remarks. Based on the tarsal formula (4-5-5) and the number of segments of the labial palpi, Thendelecrotona is assigned to the tribe Thamiaraeini Fenyes, 1921. Thendelecrotona can be distinguished from the other genera of that tribe by the combination of the following characters: the 4-jointed maxillary palpi with distinct apical pseudosegment (present also in Oxypodinus )( Fig. 2 ), the apical lobe of the galea with two parallel to each other, longitudinal rows of long setae ( Fig. 2 ), and by the mandibles with well defined “velvety patch” area, which is composed of combination of anterior row of teeth and basal area of very fine spinules ( Fig. 4 ).

The new genus most closely resembles species of the genus Mimacrotona Cameron, 1920 , but, besides the characters mentioned above, is distinguished by the tergites III and IV transversely impressed at base (only tergite III is impressed in Mimacrotona ), the entire ligula (divided to the middle in Mimacrotona ) and by the medial setae of prementum situated one behind the other.

Among other genera with transverse pronotum and entire ligula, the new genus most closely resembles Peliusa , Tyloplatyola and Oxypodinus , but is distinguished from them by the medial setae of prementum situated one behind the other. Additionally, Tyloplatyola differs from Thendelecrotona by the mentum with lateroanterior angles not produced, the article 2 of labial palpi not widened apically and the very elongate article 1 of labial palpi. Oxypodinus is distinguished by the very long and not widened apically article 2 of labial palpi, the quadrate mentum and by the parallel-sided ligula. The members of the genus Peliusa differ from the new genus in the build of the labium (short first article of the labial palpi, weakly dilated apically article 2, wide median pseudopore field), the less transverse pronotum and by the elytral postero-lateral angles not sinuate.

Etymology. The name (gender: feminine) is composed of the word Thendele (refers to the type locality) and the generic name Acrotona .

Figures

FIGURE 1. Habitus of Thendelecrotona natalica gen. & sp. n. Scale bar 0.5 mm.

FIGURES 2 – 6. Mouthparts of Thendelecrotona natalica gen. & sp. n. 2 — right maxilla, 3 — labium, 4 — right mandible, 5 — labrum, 6 — mentum. Scale bars 0.1 mm.