Palaeopronyssiformia Wiesner, Will, and Schmidt, 2017

Wiesner, Jürgen, Will, Kipling & Schmidt, Joachim, 2017, Two new genera and species of tiger beetles from Baltic amber (Coleoptera: Carabidae: Cicindelinae), Insecta Mundi 2017 (577), pp. 1-14 : 2-4

Palaeopronyssiformia Wiesner, Will, and Schmidt , new genus

Type species. Palaeopronyssiformia groehni Wiesner, Will, and Schmidt , new species.

Description. Body length: 11.4 mm in the type specimen.

Head. Markedly broad due to large, hemispherical protruded eyes ( Fig. 2 ). Mandibles with two teeth of the incisor region ( Fig. 8 ). Labrum 1.5 times wider than long, with six setae near apical margin and five teeth in middle of apical margin; the central tooth is distinctly shorter than the lateral teeth, the internal latero-apical teeth are longest ( Fig. 7 ). Antennae filiform, probably extending posterior behind elytral shoulders. Maxillary palpus with three visible palpomeres (the basal one is invisible). Apical palpomere presumably two times longer than the following palpomere, third palpomere stouter than the apical two, all sparsely setose. Labial palpus with two slender palpomeres, the basal one densely covered with long setae, 2.5 times longer than apical palpomere ( Fig. 9–11 ). Frons, vertex and orbital plates densely covered with rather deep furrows ( Fig. 2 , 6 .) Two supraorbital setae each side ( Fig. 2 , 6 ); setae on clypeus could not be found. Vertex steeply slanted towards front,

Pronotum. Moderately small and slender, only slightly longer than broad, with maximum width slightly before middle, and with apical margin distinctly broader than basal margin ( Fig. 12 ). Anterior margin distinctly convex in middle; lateral margin unbordered throughout, slightly sinusoidal with middle part convex, anterior lateral angles distinctly protruded laterally, and intermediate parts (levels of anterior and posterior transverse furrows) concave. Basal margin probably nearly straight with laterobasal angles slightly obtuse, rounded at tip, not protruded laterally. Disc in anterior ¾ with moderately engraved dense transverse furrows both sides of median line ( Fig. 2 , 12 ). Anterior and posterior transverse grooves broad and moderately deep, with intermediate part distinctly globose.

Elytra. Elongated-ovate, with maximum width slightly before the apical third, not fused. Shoulders broad, obtuse angulate with humerus rounded; lateral margin slightly but distinctly concave before middle. Chaetotaxy and patterns of micro- and macrosculpture could not be imaged.

Legs. Slender, of usual cicindelid shape, last tarsomeres with two small claws apically ( Fig. 3 ).

Etymology. The name is composed of the prefix Palaeo (Greek palaios = ancient) and the name of the genus Pronyssiformia , whose female labrum it resembles.

Diagnosis. As the ventral and lateral sides of the fossil are not visible (see Preservation status of the type specimen below), the incorporation into the phylogeny of the subfamily Cicindelinae is hypothetical. The glabrous head with six labral and four suborbital setae and the obviously glabrous pronotum are indicators for the membership of subtribe Iresina Rivalier, 1971 . Within this subtribe, the shape of the labrum most resembles the female of Pronyssiformia excoffieri (Fairmaire, 1897) , a monotypic genus from China, from which it differs by the large eyes, the presence of two suborbital setae instead of one posterior only and the furrows on head and pronotum.

Remarks. Rivalier (1971: 137) distinguished the subtribe Prothymina Horn, 1910 by the number of labial setae. The presence of only four setae made it distinctly different from the subtribe Iresina Rivalier, 1971 , which exhibited six or more labial setae. Bouchard et al. (2011: 103) proposed the older name Dromicina Thomson, 1859 as replacement name for Prothymina . Genus Pronyssiformia Horn, 1929 was included by Horn in the subtribe Prothymina , which had been omitted by Rivalier (1971). And in fact, this genus would not fit with Rivalier’s key (1971: 137), as it has 6 labral setae and would therefore key out as a member of subtribe Iresina , where it should be placed near Distipsidera Westwood, 1837 .

Palaeopronyssiformia groehni Wiesner, Will, and Schmidt , new species

( Fig. 1–12 )

Holotype. Female in Baltic amber; size of amber piece approximately 44 x 24 x 7 mm, irregularly cut, with GPIH collection number 4924, coll. Gröhn no. 8155 , Holotype Palaeopronyssiformia groehni , des. Wiesner , Will , and Schmidt , 2017. Deposited in Geologisch-Palaeontologisches Institut of University Hamburg ( GPIH, now CeNak, Centrum für Naturkunde, collection of Carsten Gröhn), Hamburg, Germany ( Fig. 5 ) .

Preservation status. A clear piece of amber, crossed by several fracture lines. A large flow line runs through almost the entire amber piece and adjoins the embedded Cicindelinae fossil laterally and dorsally, and therefore, the lateral aspect of the fossil cannot be viewed using light microscopy, and structures on dorsal surface of elytra are not visible ( Fig. 1 ). In addition, the entire ventral surface is densely covered by milky coating ( Fig. 4 ). The right protarsi, the left mesotarsi, and the right metatarsi reach to the surface of the amber piece and are thus lost; the apical part of the left hindleg is broken away and preserved in the same piece of amber 20 mm at the side of the beetle ( Fig. 3 ). Probably as a result of microbial processes during embedding of the beetle in the resin most parts of its body give insufficient contrasts in the micro-CT analyses, which is particularly apparent on the ventral surface of the prothorax and the abdomen. However, most details of diagnostic importance of the external morphology of the head and pronotum as well as the outline of the elytra were reconstructed based on both, light and X-ray microscopic analyses.

Syninclusions. A small Diptera dorsal of the Cicindelinae fossil ( Fig. 1 ), stellate hairs and other tiny plant remains, several dirt particles.

Description. See diagnosis and description chapters of the monotypic genus above.

Body length. 11.4 mm.

Color. Difficult to identify due to the possibility of preservation artifacts. Dorsal surface of head and pronotum seemingly rufescent-brown, with some metallic luster. Color of elytra and ventral surface of body unrecognizable.

Head. 1.4 times wider than pronotum. Frons with eight deeply engraved long and additional 4–5 shorter transverse furrows, vertex with 2–3 transverse furrows, orbital plates with 7–8 long and deeply engraved longitudinally furrows; latter continuing towards disc with additionally diagonally furrows which are directed to the center of disc ( Fig. 2 , 6 ).

Pronotum. Presumably 1.05 times longer than wide, with basal margin approximately 0.8 times as broad as apical margin (note that the pronotal basal margin is hardly recognizable in the fossil).

Elytra. 1.7 times longer than wide.

Etymology. N amed after Carsten Gröhn, Glinde, Germany, discoverer of this remarkable Baltic amber fossil.

Differential diagnosis. Presently, Tetracha cf. carolina is the only Eocene Cicindelinae species identified to species level. Palaeopronyssiformia groehni new genus, new species, differs from T. carolina by the shape of labrum and pronotum. The labrum of T. carolina has four setae only and four short marginal teeth, the pronotum has its maximum width nearly behind the head, the anterior corners of pronotum are more advanced than the anterior margin of prosternum. For comparison with Palaeoiresina cassolai new genus, new species, see description of the latter, below.

Figures

Figure 1. Palaeopronyssiformia groehni, new genus, new species, light microscopic image of the holotype, dorsal aspect.

Figure 2. Palaeopronyssiformia groehni, new genus, new species, holotype, light microscopic image of head and pronotum, dorsal aspect; the arrows point to the insertions of the supraorbital setae.

Figures 3–5. Palaeopronyssiformia groehni, new genus, new species, light microscopic image of the holotype. 3) Terminal part of left hind leg broken away from the specimen (preserved near the left corner of the amber piece as shown in fig. 5), and several stellate hairs (syninclusions) mainly near bottom of this photo. 4) Ventral aspect of body; latter is fully covered by milky coating. 5) General view with contours of the amber piece.

Figures 6–11. Palaeopronyssiformia groehni, new genus, new species, volume rendering of the holotype. 6) Head, frontal aspect; the black arrows point to the insertions of the supraorbital setae and the labral setae. 7) Anterior part of head with labrum; the reconstructed contour line of labrum is shown below (the white circles represent the pores of the six labral setae). 8) Frontal section through head with mandibles; the reconstructed contour line of the apical portion of mandibles is shown below. 9) Head, ventral aspect. 10) Anterior part of head showing palps; note that the terminal labial palpomeres are not shown due to limited scanning sector. 11) Labial palpomeres; note that based on this scanning results most setae show too low contrast and can thus not be imaged. Abbreviations: ant: antenna; ce: compound eye; ct: central tooth of labrum; hc: head capsule; hyp: hypopharynx; la-e: external latero-apical tooth of labrum; la-i: internal latero-apical tooth of labrum; lbp: labial palps; ll: lateral lobe of labrum; mdb-l: left mandible; mdb-r: right mandible; mo: molar; mxp: maxillary palps; ti: teeth of the incisor region.

Figures 12–13. Simplified reconstructions of the general habitus of the holotypes. The probable respective outlines of those parts of the body which could not be visualized are marked as dotted lines. 12) Palaeopronyssiformia groehni, new genus, new species. 13) Palaeoiresina cassolai, new genus, new species.