Tafforeus cainosternus, Perreau, Michel, 2012

Perreau, Michel, 2012, Description of a new genus and two new species of Leiodidae (Coleoptera) from Baltic amber using phase contrast synchrotron X-ray microtomography, Zootaxa 3455, pp. 81-88 : 84-86

Tafforeus cainosternus sp. n.

Type material. Holotype: 3, RUSSIA: amber deposit of Jantarnij, near Kaliningrad (collection of M. Perreau, Paris, n°MP005). Paratypes: Ƥ, same data and same depository as holotype (not scanned by PPC-SRμCT); 3, amber deposit of Jantarnij, near Kaliningrad n°56/2003 ex Friedrich Kernegger collection, will be deposited in Schmalhausen Institute of Zoology, Kiev (not scanned by PPC-SRμCT).

Description. Male (Holotype). Most of the characters are given in the description of the genus, in addition:

Body length 2.3 mm.

Pronotum 1.9 times wider than long, widest close to base. Elytra 1.1 times longer than wide, sides regularly arcuate.

Male protarsus 0.8 times as wide as apex of protibia ( Fig. 12 ). Male mesotarsus 0.75 times as wide as apex of mesotibia ( Fig. 13 ). Male metafemur with tiny tooth in middle of ventral side ( Fig. 14 ).

Aedeagus as long as one-quarter of body length, slender, parameres as long as median lobe and contiguous to it ( Figs. 16–17 ).

Female (paratype) with tarsal formula 5-4-4, without tarsal dilatation.

Distribution. The new species is known only from Baltic amber, from the deposit of Jantarnij, near Kaliningrad, Russia.

Etymology. The name of the new species refers to possible phylogenetic affinities with the genus Cainosternum Notman, 1921 (see discussion below).

Observation. The sample appears intermixed with stellate hairs of evergreen oaks ( Figs. 8–9 ), commonly found in Baltic amber (A. Schmidt, personal communication).

Discussion. Concealed insertions of antennae occur only in two subfamilies of Leiodidae : Leiodinae and Catopocerinae ( Newton 1998) . Tafforeus has six visible abdominal ventrites, a prosternum that is shorter than procoxal cavities, and contiguous metacoxae, as Leiodinae , and not as Catopocerinae which have five visible abdominal ventrites, a prosternum that is longer than procoxal cavities, and metacoxal cavities separated by at least a third of their width ( Newton 1998; Perreau & Růžička 2007). Therefore, Tafforeus takes its place naturally in Leiodinae .

Many morphological characters suggest a phylogenetic placement of Tafforeus in Pseudoliodini rather than in Leiodini or Agathidiini : the closed procoxal cavities and the triangular shape of the prosternal process ( Fig. 10 ) (generally quadrangular in Leiodini (Newton 1998)); the straight apical margin of the labrum (deeply emarginate in Leiodini ); the eighth antennenomere not flattened ( Fig. 11 ) (flattened in Leiodini ); the transversal microreticulation of the pronotum and striolation of the elytra (rare in Leiodini ); the absence of antennal grooves (present in Agathidiini ). However, the combination of 5-5- 4 male and 5-4- 4 female tarsal formula occurs in Agathidiini , and not in Pseusdoliodini (male tarsal formula 5-4-4), except in the monospecific genus Cainosternum Notman, 1921 . This genus has been placed by some authors in Agathidiini for this reason ( Wheeler 1986, 2005), but it is more likely to be placed in Pseudoliodini ( Newton 1998) because of the absence of antennal grooves.

Tafforeus shares the same male and female tarsal formula and the absence of antennal grooves with Cainosternum . Moreover, Tafforeus has a deeply notched mesoventral carina ( Fig. 15 ) as Cainosternum ( Notman 1921; Wheeler 1986), which is not a frequent character state in Leiodidae : apart from Cainosternum , it has only been recorded in the genus Perkovskius Perreau & Růžička, 2007 of the subfamily Camiarinae . Tafforeus differs from Cainosternum in the number of longitudinal rows of punctures on elytra (10 on each in Tafforeus , ca. 20 in Cainosternum ); the pronotum of normal size, approximately as wide as the elytra (small and 0.8 times as wide as the elytra in Cainosternum ) and by the widely rounded apex of the aedeagus (abruptly narrowed before the apex in Cainosternum ).

The unusual combination of characters shared by Tafforeus and Cainosternum : labrum not deeply emarginate; lack of antennal grooves, tarsal formula 5-5- 4 in male and 5-4- 4 in female; mesoventral carina deeply notched, suggests close phylogenetic relationship between these two genera. Compared to Tafforeus and the other genera of Pseudoliodini , Leiodini and Agathidiini , the large number of longitudinal rows of punctures on elytra (ca. 20 on each elytron, twice the common number) and the small size of the pronotum of Cainosternum are likely to be considered as derived characters. However the lack of comprehensive phylogenetic analysis for Leiodinae makes it difficult to interpret character states as plesiomorphies or apomorphies, and the above discussion of relationships among genera should be treated as preliminary hypothesis.

Figures

FIGURES 8 – 17. External and internal morphology of Tafforeus cainosternus sp. n. (holotype) by PPC-SRμCT. 8, habitus dorsal view. 9, habitus lateral view. 10, prosternum and procoxal cavities from behind (pp = triangular prosternal process). 11, antenna. 12, protarsus, dorsal view. 13, mesotarsus, dorsal view. 14, posterior leg (th = ventral tooth). 15, mesoventral carina (msc) and mesocoxal cavity (mcx), lateral view. 16, aedeagus, lateral view. 17, aedeagus, dorsal view.