Prionocyphon Redtenbacher 1858
Creators: name: Zwick, Peter
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Scirtidae
Prionocyphon

description: Genus Prionocyphon Redtenbacher, 1858
Type species: Cyphon serricornis Müller, 1821
The generic name („Saw-Cyphon“) alludes to the antennal serration which is more distinct in males than in females. It is very variably expressed among the long-recognized Holarctic species, some males exhibit strong, others weak, indistinct serration. However, the original description of P. serricornis (Müller 1821, my translation) focused on a special quality: „the peculiar build of the basal antennal segment. Namely, this is very large, almost circular, compressed, upper side slightly convex, excavated below; the second segment is very small, rounded, inserted in that excavation on the lower side near the origin of the first under which it rests like under a small plate where it is mostly completely concealed; the third even much smaller, barely visible at high magnification“ (Fig. 40). The enlarged plate-like scape has a sharp medial edge.
It seemed easy to recognize a member of genus Prionocyphon but recent discoveries in Australia and the Neotropics (Watts 2010b; Klausnitzer 2012) revealed traits previously unknown in the genus. Also, several genera were discovered or redescribed that have the same (Mescirtes, Prionoscirtes) or very similar (Prionocara) antennal modifications. Efforts to distinguish the four genera (Ruta 2010; Klausnitzer 2010, 2011a, b, 2012) showed that modified (saltatorial?) hind legs separate Mescirtes, Prionoscirtes, and Prionocara from Prionocyphon. Mescirtes differs additionally from Prionocyphon by its head structure: there is a deep and wide subantennal groove (Zwick 2015d). Information about this detail in the other two genera is missing. Among the genera in question a pore with hair tuft on female sternite 5 is reported only in Prionocyphon. However, similar modifications on sternites occur in, e.g., Microcara (Klausnitzer 2009b), Nothocyphon lanceolatus Zwick, 2015a, and Ora spp. (Libonatti 2014). It is uncertain if the structure is apomorphic.
The derived transformation of the antennal base characterizes a clade comprising Prionocyphon, Mescirtes, Prionoscirtes, and probably also Prionocara. Except for the antennae and the female prehensor the general morphology of Prionocyphon serricornis is not much different from the genus Microcara. Also the male terminalia which include a large U-shaped S8 conform with the basic Microcara - type (Nyholm 1972). Most of the Australian species and the other genera in the clade exhibit more derived character expressions, e.g., the clypeal lobes, the reduced S8 and male genitalia modified in various ways. It appears to me that the historical name Prionocyphon is tied to one of the most archaic representatives of the clade, the three younger names to derived representatives of the group. There is no synapomorphy of Prionocyphon as presently understood. Its taxonomy is in flux, and new concepts are required.
I restrict myself to the alpha-taxonomy of Australian species. I include only those species in Prionocyphon whose subgenal ridge ends freely and is separated from other structures on the lower face of the head by a small gap (the so-called buttonhole; similar to Figs 112−114). However, most species are not very similar to the type species which is suported by sequence data (Cooper et al. 2014: Fig. 1). Selected structures are compared (Table 2), and two are discussed here:
Presumed character states: 0: primitive; 1, 2: increasingly derived;?: no information.
1, Clypeus: 0, no projecting lobes (resembles Fig. 38); 1, vague indications of lobes; 2, prominent lobes (Fig. 39).
2, Male S8: 0, U-shaped; 1, a thin transverse bar (Fig. 48); 2, missing.
3, Abdominal pilosity: 0, homogenous: uniform on ventrites 1–6; 1, heterogenous: ventrites 1–4 with sparse setation and interspersed large sensilla, ventrites 5 and 6 with dense setation, no sensilla (Figs 42–44).
4, Male flagellum: 0, distinctly serrate; 1, indistinctly or only partly serrate; 2, not serrate.
5, Pala: 0, long, well developed (e.g., Figs 51, 59); 1, shortened (Fig. 66, ts); 2, crested (e.g., Figs 72, 73).
6, Trigonium: 0, undivided (e.g., Figs 51, 59); 1, replaced by paired structures (e.g., Figs 71, 75); 2, transformed into elongate tube (Figs 84, 86).
7, Endophallus: 0, no or weak (pale or minute) armature in ejculatory duct; 1, ejaculatory duct with large spines (e.g., Figs 64, 65).
8, Tegmen: 0, separate from penis (Figs 51, 57); 1, capsule-like, connected with penis (e.g., Fig. 73); 2, penis and tegmen converted into a framework of sclerotized rods, a joint or a firm connection between tegmen and penis (e.g., Figs 77, 78, 84).
Like many other marsh beetles male Australian Prionocyphon possess styles. Styles were also observed in two Neotropical species (Klausnitzer 2012), and several Australian species have complex armatures in the wide ejaculatory duct. Both traits seem to distance the Australian species from the type species. Contemporary descriptions and illustrations of P. serricornis (e.g., Klausnitzer 2009b) focus on Northern Hemisphere taxonomy and do not mention these structures. However, they were described and illustrated in morphologically oriented papers. Nyholm (1971, 1972) distinguished „Seitenplättchen“ or „Basalsklerite“ from „Lateralgriffel“ which have similar basolateral positions on the tegmen. Nyholm seems to have distinguished them by shape, but I regard them as homologous. Nyholm (1971, 1972) also described how in P. serricornis the opening of the ductus is on both sides connected to the inner face of the parameres by a very voluminous, partly sclerotized transversely folded ('concertinated') membrane which locally resembles spines. This tough membrane seems to be homologous to endophallic armatures occurring in Australian species and renders separation of the penis and tegmen difficult during dissection of P. serricornis. Fig. 41 shows this concertinated membrane, together with the rudimentary styles of P. serricornis.
Heterogenous abdominal setation is a newly observed character. In most Scirtidae the pilosity on abdominal sternites is uniform, with numerous socketed setae on all segments in comparable density, except reduced above the femora. In heterogenous abdominal pilosity, large socketed setae are sparse on anterior sternites. Between them stand many very small setae with particularly large insertion points, presumably sensilla. There is a dense aggregation of such sensilla on the abdominal intercoxal process and the area immediately behind it, in the middle of S3. Sensilla are numerous on the sides of S3+4, there are fewer on S5, none on S6+7. However, large normal setae on S6 and especially on S7 are much denser than on the anterior sternites (Figs 42−44).
Females of P. latusmandibularis were recognized by their enlarged mandibles, while the presumed female of P. uncatus was taken with males. Other females could not be assigned to particular species, but they were preliminarily assigned to two morphotypes. Whether each morphotype includes one or several species is unknown. All females had normal (not connate) sternites with heterogenous setation. A circular ring in the middle of sternite 5 surrounded a small field with microscopic pores in it, and there were no distinct hairs around it. Sclerites of S8 had closely adjacent or connected front ends. The ovipositors with slender gonocoxites and long tubular stylites were unmodified. No female had large toothed bursal sclerites like the Palaearctic species have (Nyholm 1971; Yoshitomi 2005; Klausnitzer 2009b). A short area of the gonoduct with annular folds or fine internal spinules represented the prehensor. The small spherical bursella had no obvious surface structure and no sclerites in its wall. Two kinds of bursal sclerite were observed:
Morphotype A: a slender curved sclerite leading caudally to a set of seemingly spirally arranged smaller sclerites (Figs 45, 46, 53):
Material studied: 1♀: Acacia Plateau N.S. Wales H.Davidson; 1♀: 36.32S 148.13E NSW Kosciusko NP., 4.1km W Dead Horse Gap 1500m 19 Dec. 1986 - 14 Feb. 1987 766 A.Newton, M.Thayer \ Flight intercept; (window) trap FMHD #86-645 Euc. pauciflora woodland#; 1♀: 41.14S 147,56E TAS 4km SE Weldborough 13Jan.-7Feb.1983 I.Naumann / J.Cardale ex pantrap; 2♀: Australia TAS Mt. Field NP, Lake Dobson Rd. 240m, 30.Jan-5.Feb.1980, wet sclerophyll, A.Newton, M. Thayer (all ANIC).
Morphotype B: a slightly convex transverse field of dense fine spinules (Fig. 47):
Material studied: 1♀: Broken River Rd. Rest Area ca 4km S Eungella QLD 13.1.67 at light J.G.Brooks; 1♀: QLD: 17.458°S 146.021°E Poly Ck, Garradunga, Malaise 5.57m 18694 25 Nov-2 Dec 2009. G.B.Monteith, F.Turco & J.Hasenpusch; 1♀: 17.32S 135.31E GPS QLD: The Millstream 9km NNE Ravenhoe 1045m, 18-21 Jan. 2009 A. Slipinski et al. Light trap; 1♀: QLD: 28.145°S 153.113°E Quainbable Quarry, OF 16 Dec 2008 - 6 Jan 2009, Malaise, G.Monteith; 1♀: Ravenshoe S.F. N. QLD. Tully Falls Rd. 15 6 Nov-12 Dec 1987 A.Walford- Huggins rainf. interc. trap; 1♀: Star Valley Lookout c. 5km W of Paluma QLD 3.vii.67 at light J.G.Brooks; 1 doubtful ♀: 30.22SW 152.44E NSW Dorrigo Nat. Park 13-15 Nov. 1990 T.A.Weir \ Berlesate ANIC1128 rainforest litter (all ANIC).
Watts (2010b) questioned whether all the species that he had assigned to Prionocyphon truly belonged there. A few were indeed misplaced (Watts 2014; Cooper et al. 2014); I leave formal taxonomic steps to C.H.S. Watts who is presently working on them. Despite this, the Australian fauna is exceptionally rich. Australian Prionocyphon radiated remarkably, involving loss of some characters as well as evolution of new ones. It may seem reasonable to subdivide the Australian taxa, or to separate them from “core” Prionocyphon. However, Table 2 shows numerous overlapping character combinations. No matter where a limit between Australian species were drawn, closely related species would be assigned to different groups. I therefore leave all species in Table 2 in the genus Prionocyphon. A new generic diagnosis for the world fauna is a task for the future.
Three informal species groups are recognized. Species descriptions below are grouped by shared characters and follow the sequence of species in Table 2.
description: Published as part of Zwick, Peter, 2016, Australian Marsh Beetles (Coleoptera: Scirtidae). 9. The relations of Australasian Ypsiloncyphon species to their Asian congeners, additions, mainly to Petrocyphon and Prionocyphon, and a key to Australian genera of Scirtinae, pp. 151-198 in Zootaxa 4085 (2) on pages 167-172, DOI: 10.11646/zootaxa.4085.2.1, http://zenodo.org/record/1052535