Ataenius thomasi Schnepp and Ashman, 2020

Schnepp, Kyle E. & Ashman, Krystal L., 2020, A new species of Ataenius Harold (Coleoptera: Scarabaeidae: Aphodiinae) from the southeastern United States, with a lectotype designation, Insecta Mundi 2020 (841), pp. 1-7 : 2-7

Ataenius thomasi Schnepp and Ashman , new species

Figures 7–12 , 14 .

Type material. Holotype ( Fig. 7–9, 11 ): “ Fla. Alachua Co. / NE Gainesville / 28 Mar. 1977 / L. R. Davis, Jr. // [on red] HOLOTYPE / Ataenius thomasi / Schnepp & Ashman, 2020” ( FSCA).

Paratypes: “ Fla. Alachua Co. / NE Gainesville / 28 Mar. 1977 / L. R. Davis, Jr.” (2 FSCA) ( Fig. 12 ) ; “FLOR- IDA: Alachua Co., / Gainesville / [handwritten] 25-III-1977 / L. R. Davis, Jr.” (1 FSCA) ; “FLA. Baker County / St. Mary’s R. at / Fla. Hgw. 23 #484 / xii.30.47 FNYoung” (1 FSCA) ; “ Orange Grove / Miss 7-10-34 / R. H. Beamer ” (4 SEMC) ; “ Billy’s Island / Okefenokee Swamp / June 1912. Ga. // Cornell U. / Lot. [handwritten] 440 / Sub. [handwritten] 37 // Cornell U. / Lot. 539 / Sub. [handwritten] 459 // OLCartwright / Collection / 1961” (1 USNM) .

In addition, all paratype specimens have the following bottom label: “[on yellow] PARATYPE / Ataenius thomasi / Schnepp & / Ashman 2020”.

Diagnosis. Ataenius thomasi is distinguishable from other North American Ataenius by the combination of: shortened body form; clypeus and frons lacking fine, transverse wrinkles; meso- and metatibiae with apical accessory spine strongly reduced or absent; clypeus lacking teeth; base of head with band of punctures coarser than those on clypeus; scutellar shield lacking punctures or depressions; pronotum apparently lacking marginal setae (possibly abraded in all specimens examined); elytra with striae impressed and distinctly punctate, intervals weakly convex and glossy, with minute punctures; anterolateral margins of pronotum deflexed, scarcely visible in dorsal view.

Description. Holotype: Sex unknown. Body short, elongate oval, 4.2 mm long, width at elytral humeri 1.7 mm, width at middle of elytra 1.9 mm; dorsum glossy black; legs and venter dark rufous. Head: Clypeus broadly rounded on each side of shallow median emargination, sides straight to sharply rounded, right-angled gena; surface finely, evenly punctate, punctures separated by about their diameter, surface between punctures smooth; occipital area with crossband of coarser punctures than frons, separated by 1–2 times their diameter. Pronotum: About one-fourth wider than long, 1.2 mm long at middle, 1.5 mm wide at base and apex; sides broadly arcuate, anterior angles obtuse, posterior angles broadly rounded; anterolateral margins deflexed, scarcely visible in dorsal view; sides and base margined, finely crenate around posterior angles; surface with mix of evenly spaced fine punctures and irregularly placed, moderately coarse punctures separated by 1–2 times their diameter, becoming denser laterally and finer apically on disk. Scutellar shield short, triangular, impunctate. Elytron: Short and convex, 2.4 mm long, together almost one-half longer than wide, sides arcuate, humeral angle strongly dentate; striae strong, distinctly punctate; intervals weakly convex, smooth and glossy but with scattered minute punctures. Venter: Mesoventrite weakly carinate posteriorly between coxae. Metaventrite glossy, middle line strong and deep, approximately the length of the first two abdominal ventrites combined; discal area finely punctate, lateral one-sixth becoming scabrous at sides; metaventrite with triangle anterior to metacoxae moderate, not sharply defined. Abdominal ventrites glossy, finely punctate throughout, punctures becoming coarser laterally where they are separated by 2–4 times their diameter; ventrites finely fluted along anterior margins, the fluting increasingly longer on each ventrite posteriorly. Legs: Profemur with posterior face smooth, glossy, finely punctate, punctures separated by 3–4 times their diameter. Meso- and metafemur glossy, finely punctate, punctures separated by 3–5 times their diameter; posterior marginal line strong, extending from tibia halfway to the trochanter. Meso- and metatibiae with minute accessory spine, appearing as a slight projection at apex of tibia; lower spurs fine and slender, approximately as long as first tarsomere; first metatarsomere slightly longer than following three tarsomeres combined.

Variation (n = 9). Body length of paratypes 3.8–4.2 mm; width at elytral humeri 1.5–1.7 mm; coarse punctures on the pronotal disc sparser in some specimens.

Distribution. Ataenius thomasi appears to be restricted to the Southeast Coastal Plain ( Fig. 14 ).

Etymology. Named in honor of the late Michael C. Thomas, coleopterist, mentor, and friend.

Remarks. Intrageneric groupings in Ataenius are not based on comprehensive phylogenetic analyses of the genus and are poorly defined. These assemblages often have members that do not fit easily into any particular species group and could be placed in monotypic “groups”, as well as species that share similar combinations of external character states but may belong to different species groups ( Stebnicka and Lago 2005). These issues make it extremely difficult to place new species into established groups. Based on general body form, A. thomasi is similar to A. brevis , sharing with it many of the characters that would place it in the strigatus group, but is distinguishable from that species by its smooth, punctate head, reduced or absent meso- and metatibial apical accessory spine, deflexed anterolateral margins of the pronotum, and male genitalia. Shared character states that would suggest placement in the aequalis-platensis group (Stebnicka 2005) are the meso- and metatibiae with accessory spine reduced or lacking, the surface of the head lacking wrinkles, and to a lesser degree the form of the male genitalia. The parameres of A. brevis are evenly narrowed (in lateral view) from the base to near the apex with the apex slightly deflexed while A. thomasi are abruptly narrowed basally then parallel sided (in lateral view) to the broadly rounded apex. Future phylogenetic analyses are required to confidently place A. thomasi , as well as confirm or reclassify current species groups.

From the available label data, it appears neither A. brevis nor A. thomasi are attracted to lights.

Though the new species is not placed into a group, the following amended key for the Ataenius strigatus group is modified from Stebnicka and Lago (2005) to include A. thomasi .

4(1). Elytra short, oval with convex margins, length less than 2 times as long as pronotum; humeral denticles strong, acutely pointed. USA.......................................................... 4a

— Elytra elongate, nearly parallel-sided, length 2.1 times as long as pronotum or longer, humeral denticles fine to moderate, usually obtuse........................................................ 5

4a(4). Meso- and metatibiae with apical accessory spine conspicuous ( Fig. 5 ); punctures of abdominal ventrites coarse ( Fig. 2 ); clypeus and frons with transverse sculpturing, appearing finely wrinkled ( Fig. 3 ); anterolateral margins of pronotum slightly explanate, clearly visible in dorsal view ( Fig. 1 )................................................................................ A. brevis Fall

— Meso- and metatibiae with apical accessory spine absent or reduced ( Fig. 11 ); punctures of abdominal ventrites fine ( Fig. 8 ); clypeus and frons lacking transverse sculpturing, smooth and punctate ( Fig. 9 ); anterolateral margins of pronotum deflexed, scarcely visible in dorsal view ( Fig. 7 )............................................................ A. thomasi Schnepp and Ashman , n. sp.

Figures

Figures 7–12. Ataenius thomasi Schnepp and Ashman. 7) Dorsal view of holotype. 8) Ventral view of holotype. 9) Frontal view of holotype. 10) Holotype labels. 11) Ventral view of metatibia of holotype, arrow indicates reduced accessory spine. 12) Male genitalia of paratype.

Figures 13–14. Distribution of Ataenius brevis and Ataenius thomasi in the southeastern United States. 13) Ataenius brevis Fall. 14) Ataenius thomasi, new species.

Figures 1–6. Ataenius brevis Fall. 1) Dorsal view of lectotype. 2) Ventral view of lectotype. 3) Frontal view of lectotype.4) Lectotype labels. 5) Ventral view of metatibia of lectotype, arrow indicates outlined accessory spine. 6) Male genitalia, specimen from Citico, Tennessee.