Chiquiticus Reyes-Hernández & Solodovnikov, 2024, gen. nov.
Creators: name: Reyes-Hernández, José L.
name: Solodovnikov, Alexey
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Staphylinidae
Chiquiticus

description: GenusChiquiticusgen. nov.
Figs 1, 2, 3, 4 A – C
Type species.
Heterothops pusio J. L. LeConte, 1863, here designated.
Included species.
Chiquiticus arizonicus (Smetana, 1971), comb. nov. ex. Heterothops [holotype and 2 paratypes from CNC examined]; Chiquiticus campbelli (Smetana, 1971), comb. nov. ex. Heterothops [holotype, and 7 paratypes from CNC examined]; † Chiquiticus cornelli (Chatzimanolis & Engel, 2013), comb. nov. ex. Heterothops [photos of the holotype and one paratype from AMNH examined]; Chiquiticus gemellus (Smetana, 1971), comb. nov. ex. Heterothops [holotype from MCZ and 2 paratypes from CNC 2 examined]; † Chiquiticus infernalis (Chatzimanolis & Engel, 2013), comb. nov. ex. Heterothops [moved to Chiquiticus based on the data in the publication]; Chiquiticus occidentis (Casey, 1886), comb. nov. ex. Heterothops [holotype of Heterothops mediocris Fall, 1907, from MCZ examined, H. mediocris is a junior synonym of H. occidentis according to Smetana (1971) and non-type material identified by A. Smetana in CNC]; Chiquiticus pusio (LeConte, J. L., 1863), comb. nov. ex. Heterothops [1 presumed syntype or at least historical specimen examined, (MCZ) conspecific with the type material according to Smetana (1971) and non-type material identified by A. Smetana in CNC]; Chiquiticus rambouseki (Blackwelder, 1943), comb. nov. ex. Heterothops [1 syntype from NHM examined].
Diagnosis.
Small Staphylininae mainly around 2.5–3.5 mm long (Fig. 1 A, B) with subconical head with ventral basal ridge but without postgenal ridge (Fig. 1 C); without supra-antennal punctures (Fig. 4 A); pronotum transverse (PW / PL ≥ 1.1), with its maximum width in posterior half, with paired punctures on dorsal series widely separated from each other (Fig. 4 B); mesanapleural sutures transverse not reaching or fusing with external part of prepectus (Fig. 1 F); males with black combs on first mesotarsomeres, but without black combs on mesotrochanters; tergites VII and VIII without broader, foliose setae in addition to usual acuminate, simple setae; tergite X not fused to lateral tergal sclerites in males.
Description.
Body small (TL = 2.3–3.9 mm). Head (Fig. 1 C): frontoclypeal (epistomal) “ suture ” complete; head about as wide as long (HW / HL> 0.9 but <1.1); neck from moderately (NW / HW> 0.75 but <0.90) to distinctly wide (NW / HW ≥ 0.90); dorsal macrosetae: anterolateral clypeal punctures present; frontoclypeal punctures present; supra-antennal punctures absent; parocular punctures present as one on each side or absent; basal punctures present, single; posterior frontal punctures located posterior to temporal punctures; gular sutures separated, gula with distinct transverse basal impression; ventral basal ridge (VBR) present, postgenal ridge absent; postmandibular ridge (PMR) extended diagonally towards gula; infraorbital ridge extends to PMR; nuchal ridge absent or rudimentary, at most present as a linear impression but not a ridge; eye from medium large (EYL / HL ratio> 1 / 2 but <3 / 4) to very small (EYL / HL ratio less than 3 / 10); antennomere 1 distinctly shorter than antennomeres 3 and 2 combined; male and female antennomere 11 at least two times longer than antennomere 10; left mandible with proximal, not bifid tooth; maxillary palps: palpomere 4 (apical) subulate, distinctly shorter than palpomere 2, palpomere 3 markedly dilated compared to palpomere 4; labial palps: palpomere 3 (apical) more or less cylindrical, distinctly narrower and longer than palpomere 2, parallel-sided and needle-shaped, palpomere 2 markedly dilated at apex.
Thorax (Fig. 1 E, F): prothorax with slightly transverse pronotum (PW / PL ≥ 1.1) with one pair of setiferous punctures in dorsal series widely separated from each other, the distance between them being about equal to the distance between them and the lateral margin; sublateral setiferous punctures present or absent; sternacostal (transverse carina) ridge medially not protruding; antesternal membrane with distinct semisclerotized plate (Fig. 1 E); pronotum and prosternum not fused in procoxal cavity, pronotosternal suture complete in cavity; pronotal hypomeron not setose, without postcoxal hypomeral process; upper probasisternum with or without pair of macrosetae. Mesothorax: mesoscutellum without posterior scutellar carina, without sub-basal ridge; elytron without humeral spines or spine-like setae, with evenly setiferous punctation on disc and epipleuron; mesanapleural sutures (Fig. 1 F) transverse not reaching or fusing with external part of prepectus, medially fused or nearly touching each other; apex of mesobasisternal intercoxal process varies from sharply pointed to obtuse angle, without V-shaped projection medially; mesocoxal cavities contiguous; pericoxal ridge absent. Metathorax with wings present, with veins CuA and MP 4 fused in one vein; metakatepisternal processes divided. Legs: protarsomeres expanded in both sexes; apical tarsomere of all legs with one empodial seta distinctly shorter than tarsal claws; protibial row of laterodorsal spines always present in females but maybe absent in males in some species; ventral tibial spur resting at base of apical excavation connected to tibial margin by thin membranous region; first segment of mesotarsi in males with black comb lateroventrally, without pale adhesive setae; mesotrochanters in both sexes without black comb.
Abdomen: tergites III – V with only anterior transverse basal carina; tergites III – VI with a large posteromarginal macroseta on each side (Fig. 1 D); tergites VII and VIII without broader, foliose setae in addition to the usual acuminate, simple setae; anterior transverse basal carina of tergite VII not continuing to paratergites; lateral tergal sclerites IX cylindrical; male sternite VIII with medial apical emargination; male sternum IX symmetrical. Aedeagus with rounded apex.
Distribution.
Nearctic region, Central America, the Caribbean. Introduced into Central Europe: C. pusio in Germany (Schülke and Renner 2020) and another species related to C. pusio collected in Austria with a car net.
Ecology.
The North American species occur in various types of debris like leaf litter and similar substrates, with some species also occurring facultatively in mammal burrows or nests (Neotoma Say & Ord, 1825), especially in drier regions (Smetana 1971; Adam Brunke pers. comm.). In Europe, where they are introduced, they have been collected using car nets.
Comparison.
Chiquiticus gen. nov. can be distinguished from all other genera of Staphylininae in broad sense (Newton 2022) by the combination of characters mentioned in the diagnosis. From species close to the type of Heterothops, it is distinguished by the paired setiferous macropunctures of the dorsal series being distinctly separated from each other, by a black comb on first mesotarsomere of males, and by presence of only one posteromarginal macrosetae on each side of tergites III – VI. In species close to the type of Heterothops, the paired setiferous macropunctures of the dorsal series are close together, the distance between them being distinctly less than the distance between dorsal row and respective lateral margin of pronotum. Also, in the true Heterothops, males do not have a black comb on the first mesotarsomere and their pattern of posteromarginal large macrosetae on tergites III – VI is 1, 1, 2 and 2 per side. For more details on the differentiation between Chiquiticus gen. nov. and Heterothops species from Central Europe, see Schülke and Renner (2020). Presence of a frontoclypeal “ suture ” is a rare trait in Staphylininae, which in Chiquiticus gen. nov. is always visible. In Staphylininae this character is found in few basal lineages, like Arrowinus Bernhauer, 1935, several genera of Amblyopinina including Loncovilius Germain, 1903 (Reyes-Hernández et al. 2024), and in the relatives to Chiquiticus, Amazonothops (Jenkins Shaw et al. 2020), and Ctenandropus. Additionally, Chiquiticus gen. nov. displays an antesternal plate, currently known as a unique character of groups such as Arrowinus and several tribes united in Xatholininae sensu Żyła and Solodovnikov (2020). However, this plate sometimes is also found in Amblyopinina among Staphylinini, for example in species that are close to the types of the currently non-monophyletic genera Heterothops and Cheilocolpus (Reyes-Hernández et al. 2024). Furthermore, Chiquiticus exhibits unique characters shared only with the related genera Ctenandropus and Amazonothops, such as the presence of transverse mesanapleural sutures distinctly separated from the external portion of the prepectus (Fig. 1 F and fig. 3 E in Jenkins Shaw et al. (2020) misinterpreted as “ transvere ridge (TR) ”) and distinctly elongated protergal glands (fig. 3 F in Jenkins Shaw et al. (2020)). Chiquiticus is distinguished from Ctenandropus by the subconical head with ventral basal ridge; the transverse pronotum (PW / PL ≥ 1.1) with its maximum width in the posterior half; usually by presence of intercoxal carina separating the upper probasisternum and lower probasisternum; and by tergites III – V lacking a posterior transverse carina. In Ctenandropus, the head is subquadrate, without postgenal ridge or ventral basal ridge; the pronotum is as long as wide (PW / PL> 0.9 but <1.1), with its maximum width in the anterior half; without intercoxal carina separating the upper probasisternum and lower probasisternum; and tergites III – V have a posterior transverse carina. Chiquiticus is distinguished from Amazonothops by the absence of a black comb on the mesotrochanters of males and foliaceous setae on the tergites in both sexes, by distinctly short empodial setae, by the tergite X not fused to internal face of lateral sclerites and by paramere with rounded apex and short lateroapical setae.
Etymology.
The name is derived from the Latinization of the word “Chiquitico”, which is a term used in some Hispanophone countries to refer to very small things. The gender is masculine.
New combinations notes.
The extinct species † C. infernalis from Dominican Amber is here restudied based on the original descriptions only. Many details important for the taxonomic placement of this species (e. g. pronotum and mesanapleural sutures) are not visible in the photos of this fossil there and probably they would be available only with the mCT examination. However, such visible features as habitus including small body size, as well as antennal bases located close to each other, very elongated last antennomere that is almost as long as the two preceding ones, oval and setose preapical maxillary palpomere that is clearly wider than the apical one, and wide neck allowed us to conclude that † C. infernalis is an extinct member of the new genus Chiquiticus. For † C. cornelli, in addition to the original description, we were able to examine better photos of the holotype and paratype kindly made available at our request (Fig. 3). In these images, in addition to the characters previously described for † C. infernalis, the connection of the anterior tentorial arms (Fig. 3 B) and the widely separated paired punctures in the dorsal series (Fig. 3 C) are visible. It should be noted that both fossil species are known only from females. Also, two specimens of the extant C. rambouseki (Blackwelder, 1943) that we examined were females and not in the best condition; however, the combination of their visible characters allows the species to be placed in Chiquiticus.
Biogeographic note.
As far as currently known, the Nearctic is the region with the greatest species diversity of Chiquiticus. However, the Chiquiticus fossils found in mid-Miocene Dominican amber (Chatzimanolis and Engel 2013) could suggest that Nearctic speciation took place after the genus dispersed there from the southern hemisphere where its closely related genera Amazonothops and Ctenandropus are also found (Reyes-Hernández et al. in prep.). Such dispersal may have occurred via the GAARlandia land bridge (Iturralde-Vinent 2006; Masonick et al. 2017; Iturralde-Vinent and MacPhee 2023).
description: Published as part of Reyes-Hernández, José L. & Solodovnikov, Alexey, 2024, Two new rove beetle genera in Staphylininae that reduce " Heterothops " and " Quedius " taxonomic wastebaskets (Coleoptera, Staphylinidae), pp. 81-98 in ZooKeys 1218 on pages 81-98, DOI: 10.3897/zookeys.1218.135558