Review of the genus Paronychiurus (Collembola: Onychiuridae) and description of two new species

A new diagnosis of Paronychiurus Bagnall, 1948 is given. P. ramosus (Folsom, 1917) and P. eous (Christiansen & Bellin­ ger, 1980) comb. nov. are redescribed on the basis of the types and new specimens. Two new species are described: P. probus sp. n., P. hubbardi sp.n.A key to the species in this genus is presented.


INTRODUCTION
The genus Paronychiurus was established by Bagnall (1948) for Onychiurus ramosus Folsom, 1917.This taxon was recognised as a genus or subgenus by Stach (1954), Salmon (1964), Palissa (1964), Babenko et al. (1988), Weiner (1996) and Pomorski (2000), only Gisin (1960) and Christiansen & Bellinger (1980, 1989) regarded it as synonymous with Onychiurus Gervais, 1841.Bagnall listed the following features in his diagnosis of Parony chiurus: "PAO with compound vesicles, anterodorsal pseudocellus of the head situated outside the demarcated basal area of the antenna, head postero-marginal pseudo celli absent, lateral thoracic (or proximal praecoxal) pseu docelli also absent".It is surprising that for many years these distinguishing characters were overlooked.The most important character generally used to distinguish the genus was the complicated vesicles in the PAO.Weiner (1996) in her revision was the first person to use all the characteristics in Bagnall's definition.Largely as a result of Salmon's (1964) misinterpretation of the genus, various species with compound vesicles, belonging to other genera were placed in Paronychiurus, producing some nomenclatorial confusion within the Onychiurinae.For example, Salmon (1964) placed 40 species within this genus and the authors of the Check-list of the Collembola (http://www.geocities.com/~fransjanssens/taxa/onycinae.htm), updated in January 2001, placed 57 species.
Thanks to the kindness of Prof. Kenneth Christiansen I received several specimens of P. ramosus and unidenti fied specimens, classified as "near ramosus' and "near eous".Detailed studies of P. ramosus confirmed the accu racy ofBagnall's generic decision and showed that a clear majority of Onychiurinae species, classified as Parony chiurus, do not belong in this genus.
Among the unidentified specimens were 2 new species of Parnychiurus.I also examined the type specimens of the North American Onychiurus eous Christiansen & Bel linger, 1980, received from the Museum of Comparative Zoology at Harvard University.The investigation of the material mentioned above convinced me the diagnosis of this genus needed revision.
Diagnosis.Body without lateral pseudocelli.Posterior dorsal cephalic pseudocelli absent.Thoracic tergum I and abdominal tergum III without pseudocelli.Cuticular granulation strong with granular areas.Furca reduced to small depression with 2 small, posterior setae, in contact with the border between abdominal sterna III and IV.Anal spines located on distinct papillae.Distal whorl of setae on tibiotarsi symmetrical, with 11 setae.Antennal III sense organ with 4 simple papillae and 4-5 guard setae.Vesicles in PAO compound.Labium with all five papillae, AC type (according to terminology of Fjellberg, 1999).Chaetotaxy on terga consists of two kinds of setae: Blunt rod-like mesosetae and pointed microsetae, "sen sory" setae on head and body poorly differentiated, abdominal tergum VI with 2 medial setae.
Discussion.The genus Paronychiurus is a monophyletic group of the Hymenaphorurini with 3 diagnostic apomorphies: compound vesicles in PAO, furca as described above, and differentiation of the setae into blunt rod-like mesosetae and pointed microsetae.The genus shares with Heteraphorura Bagnall, 1948 andPsyllaphorura Bagnall, 1948 the synaphomorphy of lacking pseudocelli on abdominal terga II-III.In addition, Paro nychiurus like Psyllaphorura has the anterodorsal pseu docellus of the head situated outside the demarcated basal area of the antenna (except in P. eous).The complexity of vesicles in PAO is shared with Heteraphorura.

SPECIES DESCRIPTIONS
Paronychiurus ramosus (Folsom, 1917) (Figs 1-10) Redescription.Colour white.Size without antennae: Males 1.0-1.2mm, females 1.3 mm.Shape of body squat and broad (Figs 1-2).Antennae as long as head or a little shorter.Furca reduced to small depression, in contact with the border between abdominal sterna III and IV, with 2 small posterior setae (Fig. 6).Cuticular granulation Antennal III sense organ with 4 guard setae, 4 low conical papillae, 2 sensory rods and 2 granulated sensory clubs (Fig. 3-4).Antennal segment IV with subapical organ and ms located in the same row of the posterior setae.Microsensillum of antennal segment III lateral and slightly poste rior to the antennal III sense organ (Fig. 3).
Antennal segment IV with subapical organ and ms located in the row of posterior setae.On antennal segment III microsensillum lateral and slightly posterior to the antennal III sense organ (Fig. 12).
Male ventral organ consists of 10-12 thickened setae situated on the posterior edge of abdominal sternum III and 16-18 similar setae on the anterior edge of abdominal sternum IV around the furca remnant (Fig. 17).
Claw without tooth, empodial appendage nearly as long as inner edge of the claw, without basal lamella (Fig. 14).Distal whorl of setae on tibiotarsi symmetrical, with 11 setae.
Anal spines on distinct basal papillae, moderately thick, weakly curved, 0.8-0.9 the length of hind claw.Remarks.The type specimens are strongly crumpled and for this reason the drawings do not show the true shape of this species.Diagnosis.This species is close to P. ramosus, from which it differs in the presence of 5 guard setae in antennal III sense organ (P.ramosus: 4 guard setae).In addition the two species have distinctly different body shapes (Fig. 2 vs. Fig.25).
Description.Colour white.Length without antennae: Males 1.3 mm, females 1.6-1.8mm (holotype 1.8 mm).Shape of body fusiform (Fig. 25).Antennae as long as head or a little shorter.Furca reduced to a small depres sion in contact with the border between the abdominal sterna III and IV, with 2 small posterior setae (Fig. 21).Cuticular granulation on dorsal surface of the body regular with distinct granular areas.Usually 11-12 grains around each pseudocellus.
Antennal segment IV with subapical organ and ms located in the row of posterior setae.Microsensillum of antennal segment III lateral and slightly posteror to the antennal III sense organ.(Fig. 20).
Male ventral organ absent.Claw without inner tooth, empodial appendage without basal lamella, 0.5-0.7 the length of inner edge of the claw (Fig. 22).Distal whorl of setae on tibiotarsi symmetrical, with 11 setae.Etymology.The name of the new species is derived from the Latin "probus" -upright, honourable.I dedicate the new species to Mrs Danuta Przywara and all members of the "Informal Society of Lovers of Springtails" at the Helsinki Foundation for Human Rights in Warsaw.
Paronychiurus hubbardi sp.n.Diagnosis.This species is closely related to P. probus, from which it differs by more numerous groups of setae around the furca remnant.
Description.Colour white.Length without antennae: Males 1.2-1.6 mm, females 1.4-1.6 mm (holotype 1.25 mm).Shape of body fusiform (Fig. 26).Antennae as long as head or a little shorter.Furca reduced to a small depression, in contact with the border between abdominal sterna III and IV, with 2 small posterior setae, enclosed by a group of 28-30 setae on abdominal sternum IV.This group of setae occurs in both sexes (Fig. 30).Cuticular granulation on the dorsal surface of the body regular with distinct granular areas.Usually 11-12 cuticular grains around each pseudocellus.
Antennal segment IV with subapical organ and ms located in the row of posterior setae.Microsensillum of