Serranillus Barr, 1995: 246

Harden, Curt W. & Caterino, Michael S., 2024, Systematics and biogeography of Appalachian Anillini, and a taxonomic review of the species of South Carolina (Coleoptera, Carabidae, Trechinae, Anillini), ZooKeys 1209, pp. 69-197 : 69-197

Serranillus Barr, 1995: 246

Adult diagnosis.

Males of Serranillus are easily distinguished from Anillinus by the “ serrate ” modification of the last abdominal ventrite, which bears three protruding blunt lobes (Figs 15 B , 18 B , 19 B ), and by the greatly reduced and inconspicuous right paramere which lacks setae (Figs 15 D , 19 D ). The last abdominal ventrite of male Serranillus also has large lateral extensions internally, visible when the abdomen is removed and cleared (Fig. 20 C ). The dorsal body surfaces of Serranillus are typically more setose than members of Anillinus , particularly the elytra ( Sokolov et al. 2004), but members of some Anillinus species are similarly setose ( Sokolov 2021). The pair of median setae on the mentum are on the mentum tooth itself in all specimens of Serranillus examined by us (Fig. 11 A ), while in Anillinus they are typically basad the tooth (Fig. 11 B ). Both mandibles in Serranillus possess a retinacular tooth near the base (Fig. 11 C ), while in Anillinus only the right mandible has a tooth (Fig. 11 D ). In addition to the reduced size of the right paramere, the right basal lobe of the median lobe of the aedeagus in Serranillus is reduced to a thin strip. The internal sac of the aedeagus in all species also contains a coiled sclerite on the left side, which is absent in Anillinus . The female spermathecae of Serranillus species are relatively small and have a stem that is nearly straight before the curved apex (Fig. 21 S, T ). The spermathecae are similar in shape to those of A. albrittonorum and A jancae , but the stem in those species is more slender and curved outward from the base (Fig. 21 N ).

Larval diagnosis.

Differing from the single known late-instar Anillinus larva by mandibles with terebrae lacking serrations (Fig. 14 B ) and stipes of maxilla with setae of group gMX unevenly placed (Fig. 14 D ).

Diversity.

Four previously described species, one species described as new below, and at least 10 undescribed species (Suppl. material 3).

Distribution.

Few occurrence records have been previously published for Serranillus . The type locality of Serranillus dunavani (Jeannel) is Sassafras Mountain, near Rocky Bottom in Pickens Co, South Carolina, and the species has also been reported from Great Smoky Mountains National Park ( Sokolov and Carlton 2008, 2010). Barr (1995) described Serranillus jeanneli from Coweeta Hydrologic Laboratory in Macon County, North Carolina, and stated the range extended from the Great Balsam Mountains in western North Carolina to northern Georgia, but gave no further details. He also mentioned in passing the existence of additional species in Cloudland Canyon (Dade County, GA) and the Piedmont of North Carolina and South Carolina. The Cloudland Canyon species is currently interpreted as Serranillus magnus (Zaballos & Mateu, 1997) , described from material mislabeled as from Brazil ( Sokolov and Carlton 2012). Sokolov and Carlton (2008) described Serranillus septentrionis from southwestern Virginia and cite a record of S. jeanneli from White County, Georgia. Museum records and personal collecting provide a more complete view of the range of the genus (Fig. 1 A ). Collectively, the genus occupies most of the southern Appalachians from NC to northwest GA, with disjunct occurrences in southwestern VA, the Black and Bald Mountains of NC and TN, central and western Alabama, and the Cumberland Plateau of northern Tennessee. A pair of female Serranillus in the CMNH collection bearing Connecticut locality labels is mislabeled according to the collector (S. Peck, pers. comm., July 2019).

Figures

Figure 1. Distribution maps of eastern Nearctic Anillini A Serranillus B Anillinus. White dots: all known occurrences. Black dots: locations of new DNA sequence vouchers from this study. Data from Harden (2024).

Figure 11. SEM micrographs of mouthparts of Appalachian Anillini genera A mentum of Serranillus dunavani (Jeannel) B mentum of Anillinus choestoea C mandibles of S. dunavani, dorsal aspect D mandibles of A. choestoea, dorsal aspect. Scale bars: 0.1 mm.

Figure 14. Details of late-instar larvae of Appalachian Anillini A head of Anillinus jancae sp. nov., dorsal aspect, left antenna and right mandible omitted B left mandible of Serranillus dunavani (Jeannel), dorsal aspect C right maxilla of A. jancae, dorsal aspect D right maxilla of S. dunavani, dorsal aspect E urogomphi of A. jancae, dorsal aspect. Scale bar: 0.1 mm.

Figure 15. Serranillus dunavani (Jeannel) A habitus B last abdominal ventrite, ventral aspect C left paramere, left lateral aspect D right paramere, right lateral aspect E median lobe, right dorsolateral aspect. Scale bars: 1 mm (A); 0.1 mm (B – E).

Figure 18. Serranillus jeanneli Barr. A dorsal habitus, abdomen removed for DNA extraction B last abdominal ventrite, ventral aspect C left paramere, left lateral aspect D median lobe (with right paramere attached, black arrow), right dorsolateral aspect. Scale bars: 1 mm (A); 0.1 mm (B – D).

Figure 19. Serranillus monadnock holotype A dorsal habitus B abdominal ventrites, ventral aspect (black arrow = posterior margin of medial area with stretched microsculpture) C left paramere D right paramere E median lobe. Scale bars: 1 mm (A); 0.1 mm (B, C, D, E).

Figure 20. Morphological features of Serranillus A Serranillus sp. “ South Carolina, Coon Branch ” dorsal habitus B head of Serranillus monadnock, dorsal aspect (black arrows = ocular tubercles) C dorsal aspect of abdominal ventrites of Serranillus septentrionis (black arrows = lateral extensions of last abdominal tergite). Scale bars: 1 mm (A); 0.1 mm (C).

Figure 21. Spermathecae of Anillini species A, B Anillinus chandleri C Anillinus castaneus D Anillinus murrayae E Anillinus simplex F Anillinus dentatus G Anillinus sp. “ South Carolina, Coon Branch ” H Anillinus micamicus I Anillinus mica J Anillinus choestoea K Anillinus seneca L Anillinus montrex M Anillinus arenicollis N Anillinus jancae O Anillinus cf. nantahala P Anillinus cherokee Q Anillinus loweae R Anillinus merritti S Serranillus dunavani T Serranillus jeanneli. Scale bar: 0.1 mm.