Rovnoscydmus, Jałoszyński, Paweł & Perkovsky, Evgeny, 2016

Jałoszyński, Paweł & Perkovsky, Evgeny, 2016, Diversity of Scydmaeninae (Coleoptera: Staphylinidae) in Upper Eocene Rovno amber, Zootaxa 4157 (1), pp. 1-85 : 36-38

publication ID	https://doi.org/ 10.11646/zootaxa.4157.1.1
publication LSID	lsid:zoobank.org:pub:6BF4514A-892F-499F-BC1E-B7920C7A00B0
DOI	https://doi.org/10.5281/zenodo.5681761
persistent identifier	https://treatment.plazi.org/id/03A187A9-291A-FFD4-FF03-C63F9E01FC3C
treatment provided by	Plazi
scientific name	Rovnoscydmus
status	gen. nov.

Treatment

† Rovnoscydmus View in CoL gen. n.

Type species: Rovnoscydmus frontalis (here designated).

Diagnosis. A genus of Glandulariini with loosely assembled antennae gradually thickening distally or with very indistinctly demarcated club composed of antennomeres IX–XI; basisternal part of prosternum about as long as coxal part and not demarcated posteriorly by carina; notosternal sutures complete; hypomeral ridges present; prosternal intercoxal region lacking process or carina; mesoventrite lacking median carina between mesocoxae but indistinctly carinate in front of mesocoxae; metaventral intercoxal process narrow and notched at middle; lateral margins of metacoxae distant from lateral margins of metaventrite; pronotum lacking lateral edges or carinae, with short median transverse antebasal groove, lacking pits; each elytron with one small and asetose basal fovea; prothorax and possibly also tempora with thick bristles (not visible in some specimens).

Description. Body (108–164) elongate, relatively slender and strongly convex, with distinctly marked constriction between head and pronotum and between pronotum and elytra, BL 0.64–1.10 mm.

Head capsule ( Figs 112–114 View FIGURES 112 – 114 , 118–119 View FIGURES 118 – 119 , 123–124 View FIGURES 123 – 125 , 129 View FIGURES 126 – 129 , 134 View FIGURES 130 – 134 , 137–138 View FIGURES 135 – 138 , 142–144 View FIGURES 139 – 144 , 148–150 View FIGURES 145 – 150 , 153–154 View FIGURES 151 – 154 , 159 View FIGURES 155 – 160 , 163– 164 View FIGURES 161 – 164 ) with anterior part (in front of occipital constriction) subtrapezoidal and short, eyes located anteriorly, large, strongly convex and coarsely faceted; tempora ( Figs 112 View FIGURES 112 – 114 , 124 View FIGURES 123 – 125 , 138 View FIGURES 135 – 138 , 149 View FIGURES 145 – 150 ; tm) about as long as eyes or slightly longer or shorter; occipital constriction ( Figs 112 View FIGURES 112 – 114 , 159 View FIGURES 155 – 160 ; occ) about as broad as frons between eyes or slightly narrower; frons ( Figs 112 View FIGURES 112 – 114 , 118 View FIGURES 118 – 119 , 123 View FIGURES 123 – 125 , 149 View FIGURES 145 – 150 , 159 View FIGURES 155 – 160 ; fr) subtrapezoidal, posteriorly confluent with strongly transverse vertex ( Figs 112 View FIGURES 112 – 114 , 118 View FIGURES 118 – 119 , 123 View FIGURES 123 – 125 , 149 View FIGURES 145 – 150 , 159 View FIGURES 155 – 160 ; vt); clypeus ( Fig. 113 View FIGURES 112 – 114 ) not demarcated from frons by groove. Tempora in most specimens lack thick bristles, but in K-7350 ( Fig. 149 View FIGURES 145 – 150 ) several short bristles can be seen.

Antennae ( Figs 112–114 View FIGURES 112 – 114 , 118–119 View FIGURES 118 – 119 , 123–124 View FIGURES 123 – 125 , 133–134 View FIGURES 130 – 134 , 137–138 View FIGURES 135 – 138 , 142–143 View FIGURES 139 – 144 , 148–150 View FIGURES 145 – 150 , 153–154 View FIGURES 151 – 154 , 159 View FIGURES 155 – 160 , 163–164 View FIGURES 161 – 164 ) relatively long, loosely assembled, gradually thickened distally or with very indistinctly demarcated club composed of antennomeres IX–XI.

Pronotum ( Figs 112 View FIGURES 112 – 114 , 118 View FIGURES 118 – 119 , 123 View FIGURES 123 – 125 , 128 View FIGURES 126 – 129 , 133 View FIGURES 130 – 134 , 138 View FIGURES 135 – 138 , 142 View FIGURES 139 – 144 , 148–150 View FIGURES 145 – 150 , 153 View FIGURES 151 – 154 , 163–164 View FIGURES 161 – 164 ) in dorsal view oval with weakly arcuate or nearly straight anterior and posterior margins, sides strongly rounded, anterior and posterior pronotal corners weakly marked, obtuse-angled and blunt; pronotum broadest in anterior half or near middle; pronotal base with short transverse antebasal groove ( Fig. 112 View FIGURES 112 – 114 ; abp) slightly deepened at each end. Sides of pronotum lacking edges or carinae; in some specimens ( Figs 123 View FIGURES 123 – 125 , 128–129 View FIGURES 126 – 129 , 143 View FIGURES 139 – 144 , 148 View FIGURES 145 – 150 , 153 View FIGURES 151 – 154 ) variously developed thick bristles can be seen on lateral pronotal margins and/or prothoracic hypomera.

Prosternum with basisternal part ( Figs 114 View FIGURES 112 – 114 , 119 View FIGURES 118 – 119 , 124–125 View FIGURES 123 – 125 , 129 View FIGURES 126 – 129 , 134 View FIGURES 130 – 134 , 143 View FIGURES 139 – 144 , 154 View FIGURES 151 – 154 ; bst) long, as long or nearly as long as coxal part, notosternal sutures ( Figs 114 View FIGURES 112 – 114 , 119 View FIGURES 118 – 119 , 129 View FIGURES 126 – 129 , 143 View FIGURES 139 – 144 ; nss) complete; interprocoxal region lacking carina or process; prothoracic hypomera ( Figs 114 View FIGURES 112 – 114 , 119 View FIGURES 118 – 119 , 124 View FIGURES 123 – 125 , 129 View FIGURES 126 – 129 ; hy) with hypomeral ridges ( Figs 114 View FIGURES 112 – 114 , 129 View FIGURES 126 – 129 , 138 View FIGURES 135 – 138 , 143 View FIGURES 139 – 144 ; hyr; but visible only in some specimens, probably because of very small size and a film of air coating the prothorax). It is unknown whether the procoxal sockets are closed or open.

Mesoscutellum ( Figs 112 View FIGURES 112 – 114 , 118 View FIGURES 118 – 119 , 123 View FIGURES 123 – 125 , 128 View FIGURES 126 – 129 , 133 View FIGURES 130 – 134 , 138 View FIGURES 135 – 138 , 142 View FIGURES 139 – 144 , 149 View FIGURES 145 – 150 , 153 View FIGURES 151 – 154 ) well-visible between elytral bases, small, subtriangular.

Mesoventrite ( Figs 114 View FIGURES 112 – 114 , 119 View FIGURES 118 – 119 ; v2; 125, 160) best exposed in specimens K-347 ( Fig. 119 View FIGURES 118 – 119 ), K-25702 ( Fig. 125 View FIGURES 123 – 125 ) and K-8972 ( Fig. 160 View FIGURES 155 – 160 ), lacking mesoventral intercoxal process between mesocoxae, in front of mesocoxal cavities with pair of impressions functioning as procoxal rests ( Figs 119 View FIGURES 118 – 119 , 125 View FIGURES 123 – 125 , 160 View FIGURES 155 – 160 ; pcr) separated at middle by carinate but weakly elevated projection of anterior ridge, in specimens K-25702 ( Fig. 125 View FIGURES 123 – 125 ) and K-8972 ( Fig. 160 View FIGURES 155 – 160 ) setae surrounding each lateral impression are well visible.

Metaventrite ( Figs 114 View FIGURES 112 – 114 , 119 View FIGURES 118 – 119 , 125 View FIGURES 123 – 125 , 129 View FIGURES 126 – 129 , 134 View FIGURES 130 – 134 , 137 View FIGURES 135 – 138 , 143 View FIGURES 139 – 144 , 160 View FIGURES 155 – 160 ; v3) subquadrate or subrectangular and slightly shorter than broad, with slightly rounded sides, posterior margin deeply bisinuate in front of metacoxae but weakly convex laterally, each metacoxa separated from lateral margin of metaventrite by 1/4–1/5 width of ventrite; metaventral intercoxal process ( Figs 114 View FIGURES 112 – 114 , 119 View FIGURES 118 – 119 , 125 View FIGURES 123 – 125 , 129 View FIGURES 126 – 129 , 137 View FIGURES 135 – 138 , 143 View FIGURES 139 – 144 , 160 View FIGURES 155 – 160 ; mtvp) narrowly but distinctly separating metacoxae, with distinct median notch. Anterior margin of metaventrite with dense 'wooly' setae forming bisinuate fringe behind posterior margins of mesocoxal cavities (well-visible only in specimens K-25702 ( Fig. 125 View FIGURES 123 – 125 ) and K- 8972 ( Fig. 160 View FIGURES 155 – 160 )).

Elytra ( Figs 112 View FIGURES 112 – 114 , 118 View FIGURES 118 – 119 , 123 View FIGURES 123 – 125 , 128 View FIGURES 126 – 129 , 133 View FIGURES 130 – 134 , 138 View FIGURES 135 – 138 , 142 View FIGURES 139 – 144 , 148–149 View FIGURES 145 – 150 , 153 View FIGURES 151 – 154 , 158 View FIGURES 155 – 160 , 163–164 View FIGURES 161 – 164 ) elongate and oval, each with one small but distinct and asetose basal elytral fovea ( Figs 112 View FIGURES 112 – 114 , 118 View FIGURES 118 – 119 , 123 View FIGURES 123 – 125 , 128 View FIGURES 126 – 129 , 133 View FIGURES 130 – 134 , 138 View FIGURES 135 – 138 , 142 View FIGURES 139 – 144 , 149 View FIGURES 145 – 150 ; bef), humeral calli well-marked.

Hind wings in some specimens (e.g., Figs 115 View FIGURES 115 – 117 , 118 View FIGURES 118 – 119 ) protruding from under elytra, long.

Legs ( Figs 112, 114 View FIGURES 112 – 114 , 118–119 View FIGURES 118 – 119 , 123–125 View FIGURES 123 – 125 , 128–129 View FIGURES 126 – 129 , 133–134 View FIGURES 130 – 134 , 137–138 View FIGURES 135 – 138 , 142–144 View FIGURES 139 – 144 , 148–149 View FIGURES 145 – 150 , 153–154 View FIGURES 151 – 154 , 160 View FIGURES 155 – 160 , 163– 164 View FIGURES 161 – 164 ) moderately long, slender; pro- and mesocoxae suboval, metacoxae strongly transverse; all trochanters small and subtriangular; femora moderately and gradually clavate; tibiae slender, straight or nearly straight; tarsi moderately long and slender, tarsomeres slightly flattened.

Abdomen with six visible sternites ( Figs 114 View FIGURES 112 – 114 , 119 View FIGURES 118 – 119 , 125 View FIGURES 123 – 125 , 137 View FIGURES 135 – 138 , 143 View FIGURES 139 – 144 , 160 View FIGURES 155 – 160 ; st3–8) subequal in length or with sternite III longer than IV and sternite VIII longest (depends on the position of abdomen and post mortem shrinkage of abdominal segments). Tip of pygidium exposed in some specimens (e.g., Fig. 118 View FIGURES 118 – 119 ; pg).

Distribution and composition. Rovnoscydmus includes two nominal species and nine specimens representing an unspecified number of undescribed species from the Eocene of Europe ( Fig. 38 View FIGURES 35 – 38 ), area currently within northwestern Ukraine.

Etymology. The name Rovnoscydmus is derived from the locality name Rovno and the stem - scydmus commonly used in generic names of Scydmaeninae . Gender masculine.

Remarks. This is another genus of Glandulariini with the metacoxae broadly separated from the lateral metaventral margins, similarly as in Glaesoconnus , Amimoscydmus Leptocharis , Parapseudoconnus (Neuraphomimus) , some species of Sciacharis and Scydmaenozila. Rovnoscydmus differs from all the extant genera with similar metacoxae in the same way as Glaesoconnus , i.e., in having the mesocoxae contiguous, not separated by carinate and elevated mesoventral intercoxal process. Differences between Rovnoscydmus and Glaesoconnus are numerous and include: the antennae slender and loosely assembled in Rovnoscydmus (short and compact in Glaesoconnus ); the prothoracic hypomera with hypomeral ridges in Rovnoscydmus (because of very small body this structure is visible only in some studied specimens; Glaesoconnus lacks hypomeral ridges); the pronotal base bearing short median transverse groove in Rovnoscydmus (four pits in Glaesoconnus ); and each elytron with one basal fovea in Rovnoscydmus (two distinct foveae in Glaesoconnus ).

Rovnoscydmus View in CoL resembles Stenichnus View in CoL to a lesser extent than Glaesoconnus View in CoL ; it is rather more similar, at least in its general body form, to Microscydmus Saulcy & Croissandeau, 1893 View in CoL . Morphological structures of the latter genus were illustrated in detail in Jałoszyński (2014d). Rovnoscydmus View in CoL and Microscydmus View in CoL share similarly slender and very small body (BL about 1 mm and less) and several morphological details, but clearly differ in the elytral bases (in Microscydmus View in CoL with a large and deep basal impression, missing in Rovnoscydmus View in CoL ), the length of the basisternal part of prosternum (much shorter than coxal part in Microscydmus View in CoL vs. about as long as coxal part in Rovnoscydmus View in CoL ), the intermesocoxal region (bearing carinate mesoventral process in Microscydmus View in CoL vs. lacking process in Rovnoscydmus View in CoL ), the metacoxae (laterally adjacent to metanepisternum and lateral metaventral margin in Microscydmus View in CoL vs. distant from sides of metaventrite in Rovnoscydmus View in CoL ), and in the pronotal base (with two pairs of antebasal foveae, of which the inner pair is usually connected by groove in Microscydmus View in CoL vs. transverse groove or impression with slightly deepened ends in Rovnoscydmus View in CoL ).

There are also several other extant genera of Glandulariini superficially similar to Rovnoscydmus View in CoL in the general body form and small size, as the Neotropical Heteroscydmus Franz, 1980 View in CoL and Amimoscydmus View in CoL , or Afrotropical Oreoeudesis Franz, 1985 View in CoL . These genera were revised and their morphological structures illustrated in Jałoszyński (2013a, 2015g). All of them have a robust, carinate and elevated mesoventral intercoxal process, a structure missing in Rovnoscydmus View in CoL .

Among specimens identified as belonging in Rovnoscydmus , some characters are not present, or rather not visible, in all inclusions. The hypomeral ridges can be seen (at least as faint lines) in specimens K-9579, K-26348, K-8970 and K-8968, but not in K-347, K-25702, UA-1556, K-7350, K-3037, K-8972 and K-3322; the lateral pronotal bristles are discernible in specimens K-25702, K-26348, K-8968, K-7350, K-3037 and K-8972 but not in K-9579, K347, UA-1556, K-8970 and K-3322. It seems, however, that the very small and slender body makes these structures difficult to observe, and the silver film of air covering the prothorax obscures some details. All these specimens are interpreted as congeneric, but only two of them can be identified as two distinctly different species, on the basis of a unique modification of the frons (K-9579.) and exceptionally small body, much smaller than all remaining specimens (K-347). It is unclear whether some of the remaining specimens, similar in size to K- 9579, are conspecific with the latter specimen or not, or how many species they represent. For this reason, they are treated below not as sp. 1, sp. 2 and so on, but rather as specimen 1, specimen 2 and so on. Their morphological structures were compiled in the generic diagnosis, so it is important to describe them in as much detail as possible. Further study (based on additional specimens or using high-resolution imaging methods, e.g., the synchrotron tomography) is necessary to verify the hypothesis that these specimens all belong in one genus. Characters seen under light microscopes, although leading to such preliminary conclusions as presented here, do not provide a deciding answer. It is noteworthy that specimens K-8968, K-8970, K-8971 and K-8972 (described below as specimen 4, 5, 8 and? Rovnoscydmus specimen 9) were found in one piece of amber. This suggests that they all not only belong to the same genus, but also may be conspecific. However, it was not possible to find convincing morphological evidence to support or reject such a hypothesis.