Cacomorphocerus Schaufuss, 1891

Kazantsev, Sergey V. & Perkovsky, Evgeny E., 2020, The first Cacomorphocerus species (Coleoptera, Cantharidae) from Rovno amber a second species of the genus with 11 - segmented antennae, Zootaxa 4751 (2), pp. 395-400 : 396-400

Genus Cacomorphocerus Schaufuss, 1891

Type species: Cacomorphocerus cerambyx Schaufuss, 1891

= Hoffeinsensia Kuska et Kania, 2010 type species: Hoffeinsensia jantarica Kuska et Kania, 2010 : Kazantsev, 2013

Remarks. Cacomorphocerus Schaufuss, 1891 lists nine species, including the one described below; all known species have been until now described from Baltic amber.

Cacomorphocerus meridionalis sp. n. (Figs. 1–5)

Description. Adult male. Dark brown to black. Head transverse. Eye small, eye diameter ca. 2 times shorter than interocular distance. Ultimate maxillary palpomere prominent, elongate and securiform, ca. 3.5 times longer than penultimate palpomere, seemingly glabrous in distal half. Antennae attaining to elytral two thirds, scapus only slightly wider than pedicel, antennomeres 3–8 conspicuously widened, with antennomere 7 almost saucer-shaped, antennomeres 9–11 filiform; antennomere 3 ca. 1.4 times longer than antennomere 2 and ca. 1.1 times shorter than antennomere 4; length ratio of antennomeres 2.5:1:1.5:1.7:1.8:1.6:1.1:1.8:2.4:3:4.2 (Figs 1–5).

Pronotum slightly elongate, ca. 1.1 times longer than wide, rectangular, with parallel, almost straight, emarginate before hind angles sides, slightly convex anterior and medially sinuate posterior margins, with a pair of obscure sickle-shaped posterior swellings. Scutellum elongate, triangular, rounded at apex (Fig. 4).

Elytra relatively wide, ca. 2.4 times longer than wide, parallel-sided, roughly punctuate, with scarce moderately long decumbent pubescence (Fig. 1).

Ultimate ventrite elongate, relatively broad; penultimate ventrite transverse, semi-circularly concave distally (Fig. 2).

Legs long, slender; femurs subequal in length to tibiae, femurs and tibiae narrow, straight; tarsomeres widened; hind tarsus with tarsomere 1 ca. 1.9 times longer than tarsomere 2; all claws simple (Fig. 3).

Length: 7.4 mm. Width (at elytral humeri): 1.7 mm.

Female. Unknown.

Type material. Holotype, male, SIZK No. K-541.

Type locality and horizon. Klesov (Pugach quarry), Rovno amber, the Late Eocene .

Syninclusions. One Chironomidae (Diptera) .

Etymology. The name of the new species is derived from the Latin for ‘southern’, alluding to the location of the Klesov, Rovno amber locality with respect to Baltic amber proper deposits.

Diagnosis. Cacomorphocerus meridionalis sp. n. may be distinguished from C. endecacerus , also with 11 antennomeres, by the conspicuously wider antennomeres 5, 6 and especially 8 (Figs. 1–5).

Discussion

The tribe Cacomorphocerini was erected to accommodate two genera distinguished by twelve or sixteen antennomeres with the 3 rd to 9 th or 10 th antennomere dilated and/or saucer-shaped ( Fanti & Kupryjanowicz 2018). Cacomorphocerus has 12 antennomeres and Sucinocantharis Kusìka & Kania, 2010 has 16 antennomeres. Later, the genera Eridanula Fanti & Damgaard, 2018 and Noergaardia Fanti & Damgaard, 2018, possessing, respectively, 17 and 19 antennomeres, with 3 rd to 9 th antennomeres saucer-shaped or irregular, were also referred to the tribe ( Fanti & Damgaard 2018), and Cacomorphocerus , the type genus of the tribe, was found to include species with 11-segmented antennae ( Poinar & Fanti 2019), so the tribe Cacormorphocerini came to be characterised by 11 to 19 antennomeres with the 3 rd to 8 th /10 th dilated or saucer-shaped. Recently, the tribe Cacomorphocerini was complemented with the genus Sucinorhagonycha Kusìka, 1996 , which has filiform or slightly dentate 12-segmented antennae ( Fanti & Pankowski 2019).

Now, if we follow the logic of the above-mentioned, it would be only reasonable to attribute to Cacomorphocerini such extant taxa of soldier beetles as Lycocerus Gorham, 1889 , Fissocantharis Pic, 1921 or Walteriella Kazantsev, 2001 , with both filiform and conspicuously widened middle antennomeres of their 11-segmented antennae, or such apparently closely related groups as Cantharis Linnaeus, 1758 and Themus Motschulsky, 1858 , with filiform antennae, and Cyrebion Fairmaire, 1891 , with widened middle antennomeres. The inclusion of the type genus of Cantharini , of which Cantharis is the type genus, into Cacomorphocerini will render the latter synonymous. It is also worth mentioning that antennal forms somewhat similar to those in Cacomorphocerini , i.e., with dilated and strongly modified middle antennomeres, are come across in other cantharid subfamilies, for instance, in Silinae and Dismorphocerinae (e.g., Brancucci 1980).)

The current higher classification of the Cantharidae , however, is based not on antennal structures, but in greater part on the inner head structures, wing venation and the structure of ultimate abdominal segments and male and female genitalia (e.g., Brancucci 1980), while none of these characters have been ever studied in amber soldier beetles for obvious reasons. No matter if Cacomorphocerini proves to be a good taxon or a synonym of Cantharini , it seems necessary to substantiate any further action by sound reasoning that would take into account results of the study of the mentioned structures, which may be possible someday through the access to synchrotron X-ray microtomogra-

phy. As we are currently not able to do so, we choose to abstain from any taxonomical action regarding the status of Cacomorphocerini pending the emergence of such results.

Acknowledgements

It is our pleasant duty to express gratitude to Dr. Ekaterina Martynova for kindly taking photographs of the specimen and Anatoly Vlaskin for cutting and polishing the piece (both SIZK).

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