Waidelotinae, Bukejs, Alekseev & Pollock, 2019

Bukejs, Andris, Alekseev, Vitalii I. & Pollock, Darren A., 2019, Waidelotinae, a new subfamily of Pyrochroidae (Coleoptera: Tenebrionoidea) from Baltic amber of the Sambian peninsula and the interpretation of Sambian amber stratigraphy, age and location, Zootaxa 4664 (2), pp. 261-273 : 262-264

Subfamily Waidelotinae subfam. nov.

urn:lsid:zoobank.org:act:F0102E1F-BFED-4809-8C42-E91C8117522E

Type genus: Waidelotus gen. nov., by present designation

Differential diagnosis. Waidelotinae subfam. nov. differs from the other five subfamilies of Pyrochroidae by the following combination of features: (1) penultimate tarsomere of all tarsi deeply bilobed, antepenultimate tarsomere of pro- and mesothoracic tarsi slightly bilobed, antepenultimate tarsomere of each metathoracic tarsus slightly widened apically; (2) pronotum laterally margined in basal half; (3) eyes emarginate; (4) pretarsal claws appendiculate; (5) prosternal intercoxal process incompletely separating prothoracic coxae; (6) pronotum with fine posterior submarginal groove; (7) head without distinct constriction behind eyes; (8) posterior pronotal pits absent; and (9) elytral pubescence homogeneous.

Waidelotinae subfam. nov. shares several characters with the extant subfamilies Pilipalpinae , Pedilinae and Tydessinae but cannot be placed in any of them as they are presently defined. The full suite of characters exhibited by this adult specimen renders it distinct from any of the extant subfamilies. Therefore, we propose a new subfamily for inclusion of the single Eocene genus. The reasons for such decision are outlined below.

Pilipalpinae and the new subfamily share the following characters: terminal maxillary palpomere cultriform, head without distinct constriction behind eyes, pretarsal claws appendiculate. Meanwhile, Waidelotinae subfam. nov. differs from Pilipalpinae in havingthe penultimate tarsomere of each metathoracic tarsus not lobed (bilobed in Pilipalpinae ), elytral pubescence short and homogenous (mostly dimorphic in Pilipalpinae ), pronotum laterally margined in basal half (entirely smooth in Pilipalpinae ), and emarginated compound eyes (eyes entire in Pilipalpinae ).

Pedilinae and the new subfamily share following characters: eyes emarginate, pretarsal claws appendiculate, intercoxal prosternal process incompletely separating prothoracic coxae. Waidelotinae subfam. nov. differs from Pedilinae in having its antepenultimate tarsomere of each metathoracic tarsus not lobed (bilobed in Pedilinae ), pronotum with fine posterior submarginal groove (deep in Pedilinae ), pronotum laterally margined in basal half (not margined in Pedilinae ), and head without distinct constriction behind eyes (head with constriction in Pedilinae ).

Waidelotinae subfam. nov. shares with Tydessinae following characters: pronotum laterally margined in basal half, pretarsal claws appendiculate, elytral pubescence homogenous. The newly proposed subfamily differs from Tydessinae in possessing afine posterior submarginal pronotal groove (absent in Tydessinae ), mesothoracic coxae conical, head without distinct constriction behind eyes (constricted in Tydessinae ), posterior pronotal pits absent (present in Tydessinae ), and intercoxal prosternal process incompletely separating prothoracic coxae (in contrast to completely separated prothoracic coxae in Tydessinae ).

Waidelotinae subfam. nov. is distinguished from Pyrochroinae in the appendiculate pretarsal claws, antepenultimate tarsomere of each pro- and mesothoracic tarsus slightly bilobed, pronotum laterally margined in basal half, pronotum with fine posterior submarginal groove, and posterior pronotal margin without narrow, raised bead.

The new subfamily differs from Agnathinae by its emarginate eyes, exposed antennal insertions, filiform antennae, cultriform terminal maxillary palpomere (securiform and slightly expanded in Agnathinae ), pronotum with fine posterior submarginal groove, prothoracic coxal cavities open posteriorly, trochantins exposed, penultimate and antepenultimate tarsomeres of each pro- and mesothoracic tarsus slightly bilobed.

Additionally, Waidelotus gen. nov. can be distinguished from the fossil genus Palaeopyrochroa Abdullah, 1965 (described from Baltic amber) as follows: (1) elytra with homogenous short, semierect setae (in contrast to dimorphic in Palaeopyrochroa ); (2) filiform antennae (serrate in female of Palaeopyrochroa , and probably pectinate or flabellate in male ( Pollock 1995)); (3) pronotum with fine posterior submarginal groove (pronotum with deep posterior submarginal groove in Palaeopyrochroa ); (4) pronotum laterally margined in basal half ( Palaeopyrochroa lacking lateral pronotal margins); (5) penultimate tarsomeres and antepenultimate tarsomeres of each pro- and mesothoracic tarsus slightly bilobed (only penultimate tarsomeres bilobed in Palaeopyrochroa ) (6) pronotal punctation small and elytral punctation finer (pronotal punctation fine and elytral punctation coarser in Palaeopyrochroa ), and (7) smaller body size (4.7 mm in contrast to 6 mm in Palaeopyrochroa ).

Description. Body medium-sized, elongate, subparallel-sided, flattened dorsally and slightly convex ventrally; covered with homogeneous setae; punctation dense, small to fine. Head prognathous, without distinct constriction behind eyes; eyes large, prominent, emarginate, widely separated; clypeus transverse, convex; frontoclypeal suture distinct; labrum free, transverse; mandibles with bifid apex; maxillary palpi 4-segmented, with terminal palpomere cultriform; antennae 11-segmented, filiform, moderately long, terminal antennomere short. Antennal insertions exposed. Pronotum transverse, with maximum width in posterior one-fourth, slightly narrower than basal width of elytra, without posterior pits or antebasal sulci; pronotum laterally margined in basal half; posterior margin slightly trisinuate, with fine submarginal groove; posterior angles orthogonal. Scutellar shield trapezoidal, moderately large. Elytra elongate, subparallel-sided, widest in posterior one-third; humeri prominent. Epipleura narrow, extending about to posterior margin of abdominal ventrite 3. Prosternum with anterior margin not produced anteriorly; prosternal process narrow, incompletely separating prothoracic coxae. Prothoracic coxal cavities open posteriorly. Trochantins exposed. Mesothoracic ventrite with longitudinal sharp carina medio-posteriorly, and posterior margin with narrow process, separated from mesothoracic episterna by complete suture. Metathoracic ventrite wide and long; discrimen well developed in posterior 1/2. Legs long and slender. Prothoracic coxae large, conical, projecting. Trochanters heteromeroid. Tibiae long, slender, almost straight, with two small, simple apical spurs of equal length. Penultimate tarsomere of all tarsi deeply bilobed; antepenultimate tarsomere of each prothoracic tarsus slightly bilobed, antepenultimate tarsomere of each mesothoracic tarsus slightly bilobed ventrally, antepenultimate tarsomere of each metathoracic tarsus slightly widened apically. Pretarsal claws symmetrical, appendiculate, with small denticle basally. Abdomen with five visible, freely articulated ventrites.

Composition. The new subfamily is proposed for a single genus consisting of one extinct Eocene species.