Introduction

Hagen-Vorhalle is one of the most important Konservat-Lagerstätten of the early Late Carboniferous (Early Pennsylvanian) and has provided remarkable data of supra-regional importance about the evolution of the most ancient Pterygota.

An extraordinary insect fauna was discovered in 1982 and reported in a brief article by Brauckmann and Koch (1982). Over 16, 000 samples were recovered in an excavation campaign in 1990–1997 and by private collectors. Insects are represented by ~310 individuals (mostly in dorsal view with part and counterpart). Hendricks (2005) published a complete list of determinable taxa whereas Brauckmann et al. (2010) presented an actual outline of the insect fauna and their relation to other locations. Most of the material is very well preserved, including basal Neoptera Martynov, 1923 with ~210 specimens in 5 species: Kemperala hagenensis Brauckmann, 1984, Holasicia rasnitsyni Brauckmann, 1984, Kochopteron hoffmannorum Brauckmann, 1984, Heterologopsis ruhrensis Brauckmann & Koch, 1982, and Baryshnyala occulta gen. et sp. n.

Kemperala Brauckmann, 1984 and Holasicia Kukalová, 1958 can be assigned to the family Paoliidae Handlirsch 1906. For diagnosis and included genera see Kukalová (1958), Brauckmann (1984), Brauckmann et al. (1985, 2003, 2010), Prokop and Nel (2007), Ilger and Brauckmann (2008), and Prokop et al. (in press). As shown in the historical compilation by Prokop and Nel (2007), the systematic rank of paoliids and related early Pterygota has been the subject of controversy during the last few decades: Carpenter (1992), for example, traditionally considered them as a family within the “Protorthoptera, ” a clearly polyphyletic “order”. Kukalová-Peck and Brauckmann (1992) assigned the “paoliid line” together with other early Neoptera to the “hemipteroid stem assemblage”. Grimaldi and Engel (2005) placed them as Paoliidae directly in Neoptera without indication of any order. On the other hand, Rohdendorf and Rasnitsyn (1980) and subsequently Rasnitsyn and Quicke (2002) ranked them as Paoliida on ordinal level. Prokop and Nel (2007) did the same, and additionally introduced their Katerinkidae, a closely related new family of the same order. A more general critical discussion of different views of hexapod phylogeny including the Palaeoptera/early Neoptera problem has been provided by (Klass (2007, 2009). In the present contribution we avoid a precise higher systematic assignment, because we do not want to anticipate the final results of the current phylogenetic analyses.

The systematic position of the Kochopteron Brauckmann, 1984 and Heterologopsis Brauckmann & Koch, 1982—which are morphologically similar to the Paoliidae—is unclear and still under controversial discussion. Brauckmann et al. (2003) assigned them to the family ?Cacurgidae Handlirsch, 1911. In contrast, Béthoux and Nel (2002) placed Heterologopsis in the Archaeorthoptera.

Baryshnyala occulta gen. et sp. n. cannot be allocated to any of these groups and is a representative of a new family within the early Neoptera (Baryshnyalidae fam. n.)

Methods

The specimen WMf.N P.21299 is stored in the Hagen-Vorhalle collection of the LWL-Museum für Naturkunde, Westfälisches Landesmuseum mit Planetarium in Münster. It was recovered in an excavation campaign in 1990–1991.

Investigations were done using a Euromex® ZT-45 zoom trinocular with an attached camera tube. Objects were illuminated with a Euromex® EK-1 cold light lamp with polarizing filters to minimize reflections on clay minerals and mica surfaces. Imaging conditions for photo documentation were optimized by varying illumination levels and angles with polarized and non-polarized light. Photographs were taken by using a Canon PowerShot A470 digital point-and-shoot camera with Super Macro function. Digital images were edited using the computer programs IMAGEJ, COREL PHOTO-PAINT and GIMP.

The nomenclature of wing venation follows Kukalová-Peck and Willmann (1990) as well as Kukalová-Peck and Brauckmann (1992). Main vein terminology corresponds to this scheme: ScP– = Subcosta posterior, RA+ = Radius anterior, RP– = Radius posterior, Ma+ = Media anterior, MP– = Media posterior, CuA+ = Cubitus anterior, CuP– = Cubitus posterior, AA+ = Analis anterior, arc = arculus (strong cross-vein between MP– and CuA+), cmf = cubito-median fold (nomenclature follows Nel et al. (2007): convex fold between MP– and CuA+). Attached plus and minus indicate the corrugation of the wing; i.e.: + = above plane of projection, – = below plane of projection.

Systematics Infraclass Neoptera Martynov, 1923 Discussion Small basal Neoptera of the Late Carboniferous

Baryshnyala occulta gen. et sp. n. can be easily separated from all other Neoptera from Hagen-Vorhalle by its very small size (length: ≥9.6 mm, width: 4.2 mm). In comparison to other wings within this group the specimen is about half as long as Heterologopsis ruhrensis (length: ~25 mm, width: ~8 mm). Holasicia rasnitsyni (length: 36 mm, width: 13 mm) and Kochopteron hoffmannorum (length: 41 mm, width: 13 mm) are distinctly larger, and Kemperala hagenensis (length: 61 mm, width: 22 mm) is by far the largest species of basal Neoptera from Hagen-Vorhalle (Fig. 3). Baryshnyala occulta fits very well in this set of proportions: all species show a tendency towards a length/width ration about 3 (l/w = 2.8 in Baryshnyala occulta). Kemperala hagenensis and Kochopteron hoffmannorum seem to vary mostly in the wing length whereas the width is more consistent. In contrast, the wings of Holasicia rasnitsyni vary more in their width and less in length. The variation in Holasicia ruhrensis and Baryshnyala occulta is unknown because they are monotypic.

Further small Late Carboniferous (Pennsylvanian) basal Neoptera from localities in northwestern Germany and thus close to Hagen-Vorhalle are for example (arranged by their stratigraphical age):

Metropatorites kassenbergensis Keller, 1934 (ord. et fam. inc. sed.), Namurian C (Bashkirian: Yeadonian): preserved length: 9 mm, estimated total length: ~22 mm, preserved width: 5 mm, estimated maximal width: ~9 mm.

Micropalentomum minusculum Schmidt, 1962 (Micropalentomidae), late Westphalian A (Bashkirian: Langsettian): length: ~3, 5 mm [sic!], width: ~1 mm.

Eodelopterum priscum Schmidt, 1962 (Miomoptera: Archaemiopteridae), early Westphalian B (late Bashkirian: Duckmantian): length: <5 mm, width: ~2.3 mm.

Heterologellus teichmuellerae Schmidt, 1962 (Protophasmatidae), early Westphalian C (Moskovian: Bolsovian): length: ~18 mm, width: ~7 mm.

Controversala miomopteroides Brauckmann & Herd, 2005 (ord. et fam. inc. sed.), Westphalian D (late Moskovian): preserved length: 19 mm, estimated total length: ~20 mm, width: 8 mm.

Worldwide there are known many other small Neoptera from the Late Carboniferous and Permian. Especially Early Permian Protomeropidae Tillyard, 1926 are very small. For example Westphalomerope maryvonneae Nel et al., 2007 from the early Langsettian (Late Carboniferous: Bashkirian, Westphalian A) of France is twice smaller than Baryshnyala occulta.

Most ancient representative of Holometabola?

The probably earliest evidence for holometabolous insects is a metathoracic wing of Westphalomerope maryvonneae. As the authors correctly pointed out, Holometabola lack a distinct synapomorphy in their wing venation pattern. The allocation to Endopterygota Sharp, 1898 is done by attribution of Westphalomerope maryvonneae to a subgroup of this clade, e.g. the family Protomeropidae. An adapted diagnosis of the family is given by Sukatsheva (1976). The two main characters are (terminology changed to the scheme used in the present paper): (i) a brace (= arculus) between CuA+ and MP–, and (ii) a heavily sclerotizied convex fold in front of CuA+ (= cubito-median fold). Such fold is not restricted to Holometabola but can also be found e.g. in Evenka archaica Rasnitsyn, 1977 which is probably close related to Paoliidae. Furthermore an arculus is also widespread and can be found in Paoliidae and other groups as well.

Both species, Baryshnyala occulta gen. et sp. n. and Westphalomerope maryvonneae, share the following characters within the diagnosis by Kukalová-Peck and Willmann (1990; terminology here adapted): (i) narrow costal area, (ii) very narrow area between ScP– and RA+, (iii) arculus present (typical for Permian Protomeropidae but lacking in Westphalomerope maryvonneae), (iv) well developed and prominent cubito-median fold, sub-parallel to CuA(1)+, (v) branching of Cu close to wing base (this part of the wing is not preserved in Baryshnyala occulta but can be extrapolated from the course of the preserved parts of CuA+ and CuP–), (vi) branched CuA+ (probably plesiomorphic).

Westphalomerope maryvonneae is quite similar to other hindwings in Protomeropidae. Baryshnyala occulta however differs from all Protomeropidae in the following characters: (i) ScP– reaching anterior wing margin and probably distally not fused with RA+, (ii) CuA– not simple but with 3 terminal branches, and—probably most important character—(iii) CuP– branched as rich as CuA+, the first branch (CuP1–) extremely curved backwards. The first character is regarded as an apomorphy of the Protomeropidae by Ivanov and Sukatsheva (2002), whereas Nel et al. (2007) assume it to be a plesiomorphy at the level of Holometabola or even the whole Pterygota. Other plesiomorphic characters of Baryshnyala occulta are the rich branching of ScP– (with 8 anterior branches) and RP– (with 9 terminal branches). The rich branching of CuP– and backward-curving especially of CuP1– is quite unique in Late Carboniferous basal Neoptera.

Therefore we conclude that Baryshnyala occulta is vague related to the Protomeropidae but represents a separate new family of uncertain systematic placement. Both taxa might be stem group representatives of Endopterygota. In this case Baryshnyala occulta would be the most ancient holometabolous insect.

Conclusions

The previously known species of Neoptera from Hagen-Vorhalle are of medium to rather large size. Baryshnyala occulta gen. et sp. n. shows that expanded and carefully directed prospection methods will increase the chance of also finding small insects. A similar conclusion is reached by Zessin et al. (2011).

Very small species and specimens are always in danger of being overlooked during their excavation and subsequent scientific handling. Baryshnyala occulta gen. et sp. n. obviously differs from all other Neoptera and “Palaeoptera” species known from Hagen-Vorhalle by its small size and venation pattern.

Similarities in the venation pattern and the occurrence of a well developed cubito-median fold indicate a systematic position distantly related to the family Protomeropidae but possibly within the Endopterygota. If so, this would date the first occurrence of holometaboly back to the Namurian B (early Bashkirian: Marsdenian).

Baryshnyala occulta shows that the early Neoptera in general can be expected to be much more frequent and diverse than currently known. It is the fifth Neoptera species from this important paleo-ecosystem and enlarges the morphological range of this group. Up to now small Late Carboniferous Pterygota are generally rare, and each new specimen can be essentially important for the knowledge of their early evolution. Further examinations, even in already stored collections, are expected to yield surprising discoveries.