Metavononoides: Retreating from the Coast

I've commented before on the taxonomic issues bedevilling the study of South American harvestmen, particularly members of the diverse family Cosmetidae. Recent years have seen researchers make gradual but steady progress towards untangling these multifarious snarls by more firmly establishing the identities of this family's many genera.

Metavononoides guttulosus photographed by P. H. Martins, from Kury & Medrano (2018).

The genus Metavononoides was established by Roewer in 1928 for two species from south-eastern Brazil. As with other Roewerian genera, its definition was not exactly robust, being based on a combination of tarsal segment count together with the presence of a pair of large spines on the dorsal scutum. The genus was later re-defined by Kury (2003) who used it for a group of species found in the Brazilian Atlantic Forest region around Rio de Janeiro. Members of this group shared a number of distinctive features including the presence of a distinctive U-shaped marking (later dubbed a 'lyre mask' or 'lyra')on the scutum. A number of species previously placed in other genera were transferred to Metavononoides, and the next few years saw the description of a couple more species in the genus. And then Paecilaema happened.

The genus Paecilaema was first established by C. L. Koch in 1839 but a poor description of its type species P. u-flavum lead to confusion about its identity. Over time, Paecilaema became associated with a large number of species over a range stretching from Mexico to Brazil (as an aside, it doesn't help matters that Paecilaema has been one of those names that taxonomists have found themselves chronically uncertain how to spell). When Kury & Medrano (2018) recently set out to determine the exact identity of Paecilaema by determining that of its type, they fixed P. u-flavum as a species that was common around Rio de Janeiro and that corresponded to one of the species included by Kury (2003) in Metavononoides. As a result, many of the species shifted by Kury (2003) into Metavononoides were shifted once again into Paecilaema. Many of the species assigned to Paecilaema from outside the Atlantic Forest Region remain unrevised but will almost certainly prove to require re-classification.

Metavononoides barbacenensis photographed by P. H. Martins, from Kury & Medrano (2018).

Metavononoides was not outright synonymised with Paecilaema, though. Among the group of species possessing the aforementioned lyra on the scutum, Kury & Medrano (2018) identified two distinct subgroups. In one, corresponding to Paecilaema, the lyra is made up of two components. Part of the lyra is composed of light coloration on the plane of the scutum itself while another part is raised granules. In some species, these granules are particularly concentrated along the margins of the lyra (you can see an example on this on Flickr, photographed by Mario Jorge Martins; though labelled Metavononoides, this individual is now identifiable as Paecilaema u-flavum). In the second subgroup, corresponding to Metavononoides, the differentiated coloration on the plane of the scutum is absent and the lyra is composed solely of raised granules. Not only are the two genera morphologically distinct, they are also more or less geographically distinct. Whereas Paecilaema is found in the moist broadleaf forests closer to the coast, Metavononoides is now restricted to species largely found in the grasslands and shrublands further inland, corresponding to the Cerrado region. Though more depauperate of species than it was before, the identity of Metavononoides is certainly firmer.

REFERENCES

Kury, A. B. 2003. Annotated catalogue of the Laniatores of the New World (Arachida, Opiliones). Revista Ibérica de Aracnología, special monographic volume 1: 1–337.

Kury, A. B., & M. Medrano. 2018. A whiter shade of pale: anchoring the name Paecilaema C. L. Koch, 1839 onto a neotype (Opiliones, Cosmetidae). Zootaxa 4521 (2): 191–219.

Roewer, C. F. 1928. Weitere Weberknechte II. II. Ergänzung der: "Weberknechte der Erde", 1923. Abhandlungen der Naturwissenschaftlichen Verein zu Bremen 26 (3): 527–632, 1 pl.

The Adaeines: South Africa's Cryptic Micro-Giants

Adaeulum sp., copyright Charles Haddad.

The Triaenonychidae are the family of Gondwanan harvestmen. While there are other families of harvestmen with a Gondwanan distribution (such as my own favoured family, the Neopilionidae), none of them are nearly as widespread and diverse as the triaenonychids. Despite their diversity, however, our understanding of triaenonychid relationships remains uncertain, and the family's classification poorly defined.

Within their range in Africa, Australasia and South America, triaenonychids can easily be distinguished from most other families of short-legged harvestmen by the structure of the claws on the hind two pairs of legs. Whereas members of other families bear a pair of simple claws on these legs, triaenonychids have a single claw with side branches on each leg. Branched claws are also found in the New Zealand genus Synthetonychia, which occupies its own distinct family, but that genus is easily recognised by its unusual body shape without a distinct eyemound. The Gondwanan Triaenonychidae were divided by Roewer into three subfamilies (Triaenonychinae, Triaenobuninae and Adaeinae) based on the shape of the sternum (the plate running along the underside of the body between the leg coxae). The significance of this feature was later questioned by Forster (1954) who recognised two subfamilies Triaenonychinae and Soerensenellinae on the basis of claw morphology (soerensenellines having longer side branches on the claws than triaenonychines) and reduced Roewer's subfamilies to tribes of Triaenonychinae. No large-scale analysis of triaenonychid phylogeny has been done so far, so it remains unestablished whether we should prefer one classification or the other (or possibly neither).

Typical triaenonychine (left) and adaeine (right) sternal shapes, from Forster (1954).

The Adaeinae or Adaeini may be one of the better defined of Roewer's original subgroups and recent authors have expressed the opinion that this may indeed turn out to be a natural clade. Whereas members of the Triaenonychinae sensu stricto and Triaenobuninae have a sternum that has a spearhead-shaped expansion at the front end and a broadened base at the back, members of the Adaeinae have a sternum that is a triangular or wedge shape without a posterior expansion. The adaeines are likely to be endemic to southern Africa; Kury et al. (2014) did list a single Australian species, Dingupa glauerti, in the Adaeinae but I would hazard a guess that future study proves this species to be misplaced (as has been found with other Australasian 'adaeines').

About forty species of adaeines are currently recognised, all from South Africa, but it is entirely likely that more remain to be described. The hard, granular body surface of adaeines inevitably picks up a covering of dirt and grit, making them exceedingly difficult to spot when not moving. Nevertheless, adaeines can be quite large as harvestmen go, with some being up to a centimetre in body length. Conversely, Micradaeum rugosum, a species found in the vicinity of Cape Town, is only about three-and-a-half millimetres in body length (Lawrence 1929). As with other species of Triaenonychidae, the large, raptorial pedipalps are larger and more robust in male adaeines than in females, and often have more pronounced spines. In some species of the genus Larifuga, nowever, spines or denticles may be more prominent on the female's pedipalps than on the male's, though the male's pedipalps are still larger and stronger overall (Lawrence 1937).

REFERENCES

Forster, R. R. 1954. The New Zealand harvestmen (sub-order Laniatores). Canterbury Museum Bulletin 2: 1–329.

Kury, A., A. Mendes & D. Souza. 2014. World checklist of Opiliones species (Arachnida). Part 1: Laniatores—Travunioidea and Triaenonychoidea. Biodiversity Data Journal 2: e4094. doi: 10.3897/BDJ.2.e4094

Lawrence, R. F. 1929. The harvest-spiders (Opiliones) of South Africa. Annals of the South African Museum 29 (2): 341–508.

Lawrence, R. F. 1937. The external sexual characters of South African harvest-spiders. Transactions of the Royal Society of South Africa 24 (4): 331–337, pls 14–15.

Metereca: Crossing the Divide

The crowdfunding campaign for my research on New Zealand harvestmen is still active. So far we're about 25% of the way towards the goal! Please click on the link above, and do your part to support your favourite arachnologist.

Dorsal view and pedipalp of Metereca papillata, from Roewer (1935).

There can be little doubt that the continent with the least studied harvestmen fauna relative to its likely diversity is Africa. Africa is home to a wide range of harvestmen lineages, some of which are found nowhere else on earth, but many remain unrevised. Among these poorly known elements are numerous members of the family Assamiidae. Among these are the members of the genus Metereca, which I drew as the semi-random subject for this post.

The Assamiidae are a family of short-legged harvestmen found in tropical regions of the Old World: Africa, Asia and Australia. I've spoken enough in the past about the shadow of Carl-Friedrich Roewer that hangs heavy over harvestmen systematics. Recent years have seen a large amount of research being conducted on the harvestmen of the Neotropics, resulting in a vast improvement in our taxonomic understanding for that part of the world. The harvestmen of the Old World, unfortunately, are yet to attract the same attention. Assamiids were last extensively reviewed by Roewer in 1935. He divided them between 17 subfamilies but in the usual Roewerian way these were mostly based on fairly superficial features (numbers of subsegments in the leg tarsi, whether the palp femur has long spines or only short denticles, etc.) that may not be that significant. Staręga (1992) published a checklist of African harvestmen in which he synonymised assamiid 'genera' that Roewer had placed in separate subfamilies, thus implicitly synonymising the subfamilies they were tied to.

Metereca is a genus of about fifteen known species of assamiid found across Africa. Roewer (1935) placed it in his subfamily Erecinae, supposed features of which included simple claws and the absense of a pseudonychium (a 'false claw' between the two real claws) on the third and fourth tarsi, two subsegments in the first telotarsus, small denticles on the pedipalp femur, concealed spiracles, and no median spine on the front margin of the carapace. However, the Erecinae as defined in this way included genera from all three of the Old World continents. Considering that other harvestmen groups have turned out to have a strong correlation between geography and phylogeny, I'd be willing to put money on Roewer's Erecinae not being monophyletic.

That same doubt applies to Metereca (though I'm not sure I'd put money on it this time), which is one of the larger erecine genera currently recognised. Supposed features of Metereca include a lack of dorsal spines on the body, and a four-segmented first tarsus and two-segmented second telotarsus. Species have been assigned to this genus from widely separated parts of the continent: the Congo, Tanzania, Mozambique. But not only is this a genus defined primarily by the absence of features (always a bit suspect), but other groups of harvestmen have tended to show a division between western and eastern Africa. It would be worth someone's time in the future, I think, to confirm whether Metereca really does cross the divide that others don't.

REFERENCES

Roewer, C. F. 1935. Alte und neue Assamiidae. Weitere Weberknechte VIII. (8. Ergänzung der "Weberknechte der Erde" 1923). Veröffentlichungen aus dem Deutschen Kolonial- und Uebersee-Museum in Bremen 1 (1): 1–168, pls 1–9.

Staręga, W. 1992. An annotated catalogue of Afrotropical harvestmen, excluding the Phalangiidae (Opiliones). Annals of the Natal Museum 33 (2): 271–336.

Metabiantes

Metabiantes leighi, from Schönhofer (2008).

The handsome fellow in the photo above represents a species of the genus Metabiantes, currently the largest recognised African genus of harvestmen in the family Biantidae. Metabiantes species are currently recognised from the greater part of sub-Saharan Africa, with species known from as far north as Kenya on the east coast and the Ivory Coast in the west (Staręga 1992). The bulk of study on this genus, however, has focused on the South African species. Kauri (1961) divided the southern African species between two groups based on genital morphology. Schönhofer (2008) recorded that the widespread Transvaal species M. leighi inhabits leaf litter in evergreen forests. It seems to inhabit slightly drier microhabitats than other harvestmen in the area.

Compared to many other harvestmen, Metabiantes species do not show a high degree of sexual dimorphism. The males' chelicerae tend to be a bit larger, and consequently the front of the carapace tends to be a bit broader (Schönhofer 2008). In some species, the metatarsus of the males' second leg bears a series of teeth (Lawrence 1937). While I haven't found any explicit investigation of the role that such modifications play, the fact that the second legs in harvestmen fill a sensory function (being used much like the antennae in insects) provides a likely suggestion.

REFERENCES

Kauri, H. 1961. Opiliones. In: Hanström, B., P. Brinck & G. Rudebeck. South African Animal Life: Results of the Lund University Expedition in 1950–1951 vol. 8 pp. 9–197. Almqvist & Wiksell: Uppsala.

Lawrence, R. F. 1937. The external sexual characters of South African harvest-spiders. Transactions of the Royal Society of South Africa 24 (4): 331–337.

Schönhofer, A. L. 2008. On harvestmen from the Soutpansberg, South Africa, with description of a new species of Monomontia (Arachnida: Opiliones). African Invertebrates 49 (2): 109–126.

Staręga, W. 1992. An annotated check-list of Afrotropical harvestmen, excluding the Phalangiidae (Opiliones). Annals of the Natal Museum 33 (2): 271–336.

The Problem with Sacesphorus

Probably not the subject of today's post: an unidentified assamiid from Thailand, from here.

One of the most frustrating things about many older taxonomic resources can be the shortage of illustrations. Up until the early part of the twentieth century, at least, it was something of a rarity for a publication to include extensive figures of their subject(s). So when I was presented for my semi-random subject of the week with the Burmese assamiid Sacesphorus maculatus, described by T. Thorell in 1889, I was not entirely surprised to discover that this Asian harvestman has never actually been illustrated.

At present, Sacesphorus maculatus is the only recognised species in its genus, known only from the Bago region in southern Burma. Unfortunately, that in itself doesn't necessarily indicate much. The Assamiidae are perhaps the most diverse group of Laniatores (short-legged harvestmen) in the tropics of the Old World, but they are also some of the least studied. The last extensive revision of the family was by our old friend Carl-Friedrich Roewer in 1935, and like many of Roewer's classifications its accuracy is suspect. Roewer divided the assamiids between seventeen subfamilies, but the characters separating most of these subfamilies are fairly superficial and probably do not reflect actual relationships (Staręga implicitly synonymised some of the African subfamilies in 1992 when he synonymised genera from different 'subfamilies' together). Roewer placed Sacesphorus in the Erecinae, which he characterised by features such as the absence of a pseudonychium (a claw-like process between the two true claws at the end of each leg), smooth leg claws, a two-segmented telotarsus on the front legs, and the absence of a median spine along the front edge of the carapace. All of these are fairly generalised characters, and some (such as tarsal segment number) are probably more variable than Roewer realised. Many short-legged harvestmen possess a pseudonychium as nymphs but lose it as they grow into adulthood, and the distribution of this feature in the assamiids may require more investigation.

Similar issues attend the identification of assamiid genera. Thorell (1889) originally distinguished Sacesphorus from the genus Pygoplus, also found in Burma and eastern India, by the presence in the former of a small spine in the middle of the eyemound. Roewer recognised a number of 'erecine' genera in Burma and eastern India, largely on the basis of tarsal segment numbers and armature of the dorsum. The relationship between all these genera deserves a second look. Many other groups of harvestmen have been successfully raised from the Roewerian quagmire in recent years; the assamiids are still waiting.

REFERENCES

Roewer, C.-F. 1935. Alte und neue Assamiidae. Weitere Weberknechte VIII. (8. Ergänzung der “Weberknechte der Erde” 1923). Veröffentlichungen aus dem Deutschen Kolonial- und Uebersee-Museum in Bremen 1: 1–168.

Staręga, W. 1992. An annotated check-list of Afrotropical harvestmen, excluding the Phalangiidae (Opiliones). Annals of the Natal Museum 33 (2): 271–336.

Thorell, T. 1889. Viaggio di Leonardo Fea in Birmania e regioni vicine. XXI.—Aracnidi Artrogastri Birmani raccolti da L. Fea nel 1885–1887. Annali del Museo Civico di Storia Naturale di Genova, Serie 2a 7: 521–729.

Biantidae: The Importance of Titillators

An unidentified member of Biantinae, photographed in Singapore by WJ.

Long-time readers of this site will be familiar with my rants about the influence of early 20th-century arachnologist Carl-Friedrich Roewer on Opiliones taxonomy (just enter 'Roewer' into the search box near top right on this page). One of Roewer's larger errors (but an understandable one in context) involved the species he included in the family Phalangodidae. As Roewer had it, this was an almost cosmopolitan family, with representatives on all continents. However, as research has progressed, it has become clear that Roewer's Phalangodidae was a polyphyletic assemblage of a number of different lineages of relatively generic-looking Laniatores (short-legged harvestmen). Firm distinction of some of these lineages (now recognised as separate families) often requires examination of the male genitalia, something Roewer never did.

Specimen of Lacurbs, from A. B. Kury.

The Biantidae are one of these families of ex-phalangodids. They are a pantropical family, with representatives in South America, Africa and Asia. Biantids have eyes well-separated on the carapace instead of on a common central eye-mound, and they bear a strong external resemblance to another family of Laniatores that I've covered before, the South American Stygnidae. Distinguishing biantids from stygnids depends on two features: the presence of a process of the tarsi of the third and fourth legs in Stygnidae, and the presence of a ventral sclerotised plate on the penis of the Stygnidae versus no plate and dorsal processes called titillators (named for an obvious possible function) on the penis of Biantidae. However, despite the strong external similarity, stygnids and biantids are not closely related: a recent molecular phylogenetic analysis of Laniatores places them in separate superfamilies, with stygnids in the Gonyleptoidea and biantids in the Samooidea (Sharma & Giribet 2011).

Representative biantid penes, from Kury & Pérez González (2007). Left: Caribbiantes (Stenostygninae), dorsolateral view; right: Biantes sherpa (Biantinae), lateral and dorsal views. Ti = titillators; Co = conductors.

Biantidae are divided between four subfamilies (Kury & Pérez González 2007). The African genera Lacurbs and Zairebiantes are more divergent than the other two subfamilies: Lacurbs has the scutum (dorsal shield) of the opisthosoma (the rear part of the body) widest in the middle and narrowing towards the front and back, while other biantids are more or less straight-sided, and has the tibiae and metatarsi of the hind legs armed and swollen. Zairebiantes has its eyes placed closer together and further forward than other biantids, and Pinto-da-Rocha (1995) suggested that its classification as a biantid may require re-evaluation. The other two subfamilies, the South American Stenostygninae and the African and Asian Biantinae, contain the great majority of biantids and share the presence of dense scopulae (pads of hairs) on the third and fourth tarsi. Apart from their distribution, the latter two subfamilies are distinguished by genital morphology: in Stenostygninae, the titillators are rigid and sit forward to cover the capsula interna of the penis, while in Biantinae they are soft and fold back and out so that they don't cover the capsula interna.

REFERENCES

Kury, A. B., & Pérez González, A. 2007. Biantidae Thorell, 1889. In Harvestmen: The Biology of Opiliones (R. Pinto-da-Rocha, G. Machado & G. Giribet, eds) pp. 176-179. Harvard University Press: Cambridge (Massachusetts).

Pinto-da-Rocha, R. 1995. Redescription of Stenostygnus pusio Simon and synonymy of Caribbiantinae with Stenostygninae (Opiliones: Laniatores, Biantidae). Journal of Arachnology 23 (3): 194-198.

Sharma, P. P., & G. Giribet. 2011. The evolutionary and biogeographic history of the armoured harvestmen—Laniatores phylogeny based on ten molecular markers, with the description of two new families of Opiliones (Arachnida). Invertebrate Systematics 25: 106-142.

Taxon of the Week: Metarhaucus

Metarhaucus lojanus, from Roewer (1912).

This was a bit of an unfair ID challenge, I'll admit. The most distinctive feature of the Cosmetidae, the harvestman family to which this animal belongs, is their laterally flattened pedipalps, not shown in the picture above. Without that, you would have had to combine vaguer features such as the overall shape of the body, the lack of spines on the eyemound (most related families have at least small spines) and how the divisions between the regions of the dorsal shield are less sharply incised than in other families.

Metarhaucus is a genus of eleven species of cosmetid, mostly found in Colombia, Ecuador and Peru (a single species has been described from Costa Rica; Kury, 2003). The genus has not been revised since the days of Roewer so it suffers the usual problems with Roewer's usage of genera based on characters that may turn out to be unreliable with further study. Roewer's (1912) defining characters for Metarhaucus were the presence of six pseudosegments in tarsus I, more than six pseudosegments in tarsus III, third and fourth legs much thicker than the front two pairs and the presence of a median pair of tubercles on the second and fourth areas of the dorsal shield. The South American Cosmetidae are currently under review by researchers in Brazil; time will tell whether Metarhaucus survives their scrutiny.

REFERENCES

Kury, A. B. 2003. Annotated catalogue of the Laniatores of the New World (Arachida, Opiliones). Revista Ibérica de Aracnología, special monographic volume 1: 1-337.

Roewer, C. F. 1912. Die Familie der Cosmetiden der Opiliones - Laniatores. Archiv für Naturgeschichte, Abteilung A 10: 1-122, pl. 1-2.

Gonyleptids are Just So Cool

I was recently sent the following photos by Gabriel Whiting asking if I was able to supply an ID:





He had photographed this animal at Itatiaia in the province of Rio de Janeiro in Brazil. The photos don't give a direct indication of its size but Gabriel told me that it was quite big (at least for a bug) and you can see a couple of other insects in the wider photo for comparison.

It's obviously a harvestman of the South American family Gonyleptidae. A photo of a similar individual in Kury & Pinto-da-Rocha (2007) led me to identify Gabriel's mystery opilionid as Acutisoma unicolor (a paper currently in press will apparently shift its genus allocation to Goniosoma). According to Kury (2003), Itatiaia happens to be the type and (so far) only recorded locality for this species and information specifically relating to this species seems to be thin on the ground.

Casting the net wider, Acutisoma unicolor belongs to the subfamily Goniosomatinae which is endemic to the Brazilian coastal region (Kury & Pinto-da-Rocha, 2007). As large, readily visible animals, goniosomatines have been subject to a reasonable amount of study, particularly in regard to reproduction. Males of at least some goniosomatines may maintain territories in which they may guard harems of up to five females. Fights over territory may be long and fierce with the main appendages used being the long filiform legs II and the powerfully armed legs IV (Machado & Macías-Ordóñez, 2007). Most goniosomatines observed to date lay their batches on eggs in gaps between rocks or on the walls of caves. The eggs are generally looked after by the females though males have been recorded watching over eggs laid in their territory whose mother has temporarily gone elsewhere (Buzatto & Machado, 2009). Newly hatched juveniles may also remain clustered around the female.

REFERENCES

Buzatto, B., & G. Machado. 2009. Amphisexual care in Acutisoma proximum (Arachnida, Opiliones), a neotropical harvestman with exclusive maternal care. Insectes Sociaux 56 (1): 106-108.

Kury, A. B. 2003. Annotated catalogue of the Laniatores of the New World (Arachida, Opiliones). Revista Ibérica de Aracnología, special monographic volume 1: 1-337.

Kury, A. B., & R. Pinto-da-Rocha. 2007. Gonyleptidae Sundevall, 1833. In Harvestmen: The Biology of Opiliones (R. Pinto-da-Rocha, G. Machado & G. Giribet, eds) pp. 196-203. Harvard University Press: Cambridge (Massachusetts) and London.

Machado, G., & R. Macías-Ordóñez. 2007. Reproduction. In Harvestmen: The Biology of Opiliones (R. Pinto-da-Rocha, G. Machado & G. Giribet, eds) pp. 414-454. Harvard University Press: Cambridge (Massachusetts) and London.

Taxon of the Week: Collonychium

Dorsal view of an unidentified Collonychium species. Photo by Abel & Ana.

Just a brief Taxon of the Week entry today because unfortunately I don't have a lot of info available on this taxon. The name Collonychium was recently revived from taxonomic limbo by Kury (2003) for two species of gonyleptid harvestmen found in south-east Brazil. Collonychium bicuspidatum is found in the provinces of Rio de Janeiro, São Paulo and Paraná while C. perlatum is found in Espírito Santo and Minas Gerais. Collonychium bicuspidatum had previously been included in the genus Paragonyleptes, of which it is the type species, before Kury (2003) recognised the type specimen of Collonychium bicuspidatum as a juvenile female of Paragonyleptes bicuspidatus (despite having the same species names, these two were originally described as separate species). A number of other southern Brazilian harvestman species had been assigned to Paragonyleptes, mostly by the famed creator of artificial classifications Carl-Friedrich Roewer and Cândido Firmino de Mello-Leitão (who, if anything, out-Roewered Roewer). These species were mostly listed by Kury (2003) as Gonyleptinae incertae sedis so they may or may not be Collonychium species.



I'm not entirely sure what's happening in this photo, again by Abel & Ana. Gonyleptids such as Collonychium have very powerful posterior-directed hindlegs, often with large spines pointing inwards on the retrolateral side (they're not as prominent in this individual, but in other species they may be very scary indeed). I think the individual in the photo above may be executing a handstand in order to bring the hindlegs into a better position to scissor with them at its intimidator (in this case, the photographer).

REFERENCE

Kury, A. B. 2003. Annotated catalogue of the Laniatores of the New World (Arachnida, Opiliones). Revista Ibérica de Aracnología, volumen especial monográfico 1: 1-337.

Saintly Harvestmen (Taxon of the Week: Equitius)

Features of Equitius formidabilis. Basically, a lot of spikes. From Hunt (1985).

The Australian harvestman genus Equitius was first named by the French arachnologist Eugene Simon in 1880. Now there was nothing particularly odd about that - for many years in the late 1800s, Simon was not so much an arachnologist as the arachnologist, achieving a reputation none of his contemporaries could match, and possibly none of his successors either (apparently, the Muséum National d'Histoire Naturelle still has his chair and desk on display). Simon used classical names for many of his genera, and Equitius was such a genus - there are numerous personages in Roman history by the name of Equitius, including an early Catholic saint. In this case, unfortunately, Simon seems to have dropped the ball somewhat in terms of getting the word out, because in 1903, the British researcher Pocock described a very similar species as belonging to a new genus, Monoxyomma. Then the baton was taken up by arachnology's favourite bête noire, Roewer, who in 1915 and 1931 added further genera, distinguished (as usual for Roewer) by the most superficial of features*, to the list. It wasn't until 1985 that the Australian Glenn Hunt combined all these genera into a single one, Equitius, found in southern Queensland and New South Wales.

*Hunt (1985) was later to refer to specimens for which the Roewerian system would have identified oneside as Equitius, and the other as Monoxyomma.

Equitius is a member of the Triaenonychidae, a family of Laniatores or short-legged harvestmen. Laniatores generally tend to be rather spiky, heavily-armoured creatures, but some triaenonychids have a tendency to be particularly baroque, with high spines ornamenting the eyemound and abdomen, and large spiny pedipalps in the males. The greatest diversity of triaenonychids has been described from Australasia (though southern Africa is fast catching up), and in my experience triaenonychids are the easiest harvestmen to find in New Zealand. That is, assuming that you can see them - they can readily be found by lifting logs and stones in moist areas, but the usual triaenonychid response when disturbed is to ball up their legs and freeze, at which point they become very difficult to spot against the background. Even if you do spot them, they still have the defense of the distinctive harvestman odour, which has on at least one occasion nearly (I stress nearly) fooled me into thinking that an individual I'd found was both dead and in a reasonably advanced state of decay.


An individual of a North American triaenonychid species, Fumontana deprehendor. Fumontana is something of a biogeographic enigma - despite its Appalachian distribution, it appears to be more closely related to Southern Hemisphere triaenonychids than to other North American species (which are quite possibly not correctly assigned to Triaenonychidae). Photo from the Marshal Hedin Lab.

One intriguing feature of a number of triaenonychid genera is the occurrence of male dimorphism, with one male form failing to develop the enlarged pedipalps and other secondary sexual characteristics of the other male form. In many similar cases in other animals, such male dimorphism is related to trade-offs between attractiveness to females and overall vitality, but it has not been demonstrated if that is the case with triaenonychids. Glenn Hunt studied the development of effeminate males in Equitius doriae for his PhD thesis, but unfortunately only the abstract was ever published (Hunt, 1981). Hunt found that effeminate males became dormant over winter an instar earlier than normal males, suggesting that dimorphism in this genus may be as much a matter of environmental factors as anything else.

REFERENCES

Hunt, G. S. 1981. Male dimorphism and geographic variation in the genus Equitius Simon (Arachnida, Opiliones). Dissertation Abstracts International B 41: 4375.

Hunt, G. S. 1985. Taxonomy and distribution of Equitius in eastern Australia (Opiliones: Laniatores: Triaenonychidae). Records of the Australian Museum 36: 107-125.

Taxon of the Week: Stygnoplus

Cluster of an unidentified Stygnidae species. Photo from here.

South America is the current centre of described harvestmen diversity, with the bulk of this diversity represented by Laniatores - the shorter-legged, heavily armoured and often quite spiky suborder of Opiliones. Of the twenty-six families of Laniatores recognised in Pinto-da-Rocha & Giribet (2007), sixteen are found in the Neotropics (excluding the Podoctidae, whose sole "Neotropical" representative, Ibantila cubana from Cuba, was described from a specimen collected in a botanical garden and probably represents an introduction from parts unknown). The majority of research on South American harvestmen has focused on the largest family, the Gonyleptidae, but the remaining families are all waiting their turn.

The genus Stygnoplus belongs to one of these families, the Stygnidae. A number of features support the Stygnidae as a monophyletic group, perhaps the most apparent being their disassociated eyemound. Unlike most other harvestmen that have the two eyes located on a central eyemound, stygnids have the eyes placed some distance apart without a central mound - still fairly close in the subfamily Nomoclastinae, further apart in the subfamilies Stygninae and Heterostygninae (to the latter of which Stygnoplus belongs). About eighty species of Stygnidae have been described to date, but the existence of a number of undescribed species is known (Kury & Pinto-da-Rocha, 2002). Like most South American Opiliones, the stygnids have mostly only been studied from a taxonomic point of view, with very little known about their natural history. However, the Stygnidae are ahead of the game in that, unlike most other South American Opiliones (or, for that matter, Opiliones in general), they have been the subject of an actual phylogenetic analysis (Pinto-da-Rocha, 1997).


Another unidentified stygnid. Photo by artour_a.

The known centre of diversity for the Heterostygninae (including Stygnoplus) is the Lesser Antilles, though Stygnoplus was recorded from the mainland of South America by Villarreal-Manzanilla & Rodríguez (2004). (The type species, Stygnoplus forcipatus, had originally been described from the mainland, though with the completely uninformative and decidedly untrustworthy locality citation of "Colombia".)



In the absence of any other images of Stygnoplus online, here's Villarreal-Manzanilla & Rodríguez's (2004) figures of the Venezuelan species Stygnoplus lomion. Feel free to print them off, cut them out and see if you can assemble your own model of a South American arachnid. The appendages shown in the lower part of the plate are the pedipalps - stygnids, like many Laniatores, have absolutely terrifying raptorial pedipalps. If you look closely at the second photo on this post, you'll see that in this family the femora (the first large segment) of the pedipalps are quite long, giving these animals a quite impressive reach, perfectly designed to strike terror into the hearts (or other significant circulatory organs) of small invertebrates everywhere.

REFERENCES

Kury, A. B., & R. Pinto-da-Rocha. 2002. Opiliones. in Amazonian Arachnida and Myriapoda (J. Adis, ed.) pp. 345-362. Pensoft: Sofia.

Pinto-da-Rocha, R. 1997. Systematic review of the neotropical family Stygnidae (Opiliones, Laniatores, Gonyleptoidea). Arquivos de Zoologia 33(4): 163-342.

Pinto-da-Rocha, R., & G. Giribet. 2007. Taxonomy. In Harvestmen: The Biology of Opiliones (R. Pinto-da-Rocha, G. Machado & G. Giribet, eds.) pp. 88-246. Harvard University Press: Cambridge (Massachusetts).

Villarreal-Manzanilla, O., & C. J. Rodríguez. 2004. Descripción de una nueva especie y dos nuevos registros del género Stygnoplus (Opiliones, Stygnidae) para Venezuela. Revista Ibérica de Aracnología 10: 179-184.

Taxon of the Week: Cynortula, Cynortula

Vonones ornatus, one of the few species of Cosmetidae found in the southern United States. Photo by Lynnette Schimming from Bug Guide.

The systematics of South American harvestmen have long been one of the taxonomic world's God-awful messes, with the painstaking work of Pinto-da-Rocha, Kury and associates only recently managing to go some way towards drawing it from the mire. The blame for this morass can be placed almost entirely with a single person - Carl-Friedrich Roewer, who described about a third of the world's total of harvestmen species, some 2,260 taxa. He was able to attain this prodigious output by employing a highly artificial mode of classification. Individual specimens were assigned to species and species assigned to higher taxa on the basis of quite superficial characters such as the number of sub-segments in the legs or the number of spines on the abdomen. Character systems such as genitalia that are now regarded as highly significant were not considered*. Many of the features used by Roewer have since turned out to be variable within individuals of a single species, and sometimes within a single individual - in the case of number of tarsal segments, more than one author (such as Hickman, 1939) has described specimens that have differing numbers of segments on the left side from the right, which would require that each side belong to a different genus, if not subfamily!

*To be fair, Roewer could probably be forgiven for his neglect of genitalic characters. While genitalia had been used by some authors in taxonomy by the early 1900s, the practice was not yet widespread and its importance not widely recognised.

It has to be said that the names he gave his excessive outpourings of taxa were not exactly inspired either. Many of them were derived by sticking some suffix or prefix onto a pre-existing name. For instance, from the original name Cynorta, he gave us Cynortula, Cynortoides, Eucynorta, Cynortella, Cynortellana, Cynortellina, Eucynortula, and I'll stop now before my head explodes. Trust me, there's a lot more. To quote Kury (2003), "The dreadful, uninspired and sometimes cumbersome names created by Roewer and Mello-Leitão and followers, and which are deformations of place names, people's names and (the worst!) pre-existing generic names, are best left alone."

The above-listed genera belong to the family Cosmetidae, one of the largest harvestman families in the Neotropics. While still officially divided into two subfamilies, these are divided solely by whether the claws on legs III and IV are smooth or pectinate and this distinction is not expected to stand up to proper phylogenetic analysis should one ever be conducted (Kury & Pinto-da-Rocha, 2007). While the work of Kury and associates has vastly improved matters with the Gonyleptidae, the other major Neotropical family of short-legged harvestmen*, the Cosmetidae remain almost untouched by modern researchers**.

*Harvestmen fall into three groups, the mite-like, long-legged and short-legged harvestmen. I covered mite-like harvestmen once before. Long-legged harvestmen are the daddy-long-legs type harvestmen. Short-legged harvestmen are generally more heavily armoured, and while they do tend to have shorter legs than long-legged harvestmen, they probably have what would be fairly long legs for any other group of animal. The first episode of Life in the Undergrowth included footage of egg-guarding behaviour in a short-legged harvestman.

**Fortunately, I have reasons, such as the publication of Kury et al. (2007), to hope this may change over the coming years.



The genus Cynortula Roewer, 1912, as it currently stands, contains 32 species from throughout tropical Central and South America, from Mexico and the Bahamas to Bolivia and Brazil (the illustration above, from Goodnight & Goodnight, 1947, shows Cynortula granulata from Trinidad). Lord only knows what will happen to this genus in the future, however. Roewer (1923) seems to have supplied the last description of the genus, and described it as "Schlanke Tiere mit langen, dünnen Beine. 1. und 3. Area mit je 1 mittlerer Tuberkel-Paar; 2., 4. und 5. Area und 1.-3. frei Tergit unbewehrt. 2. Chelicere-Glied auch beim ♂ klein und normal gebaut oder seltener beim ♂ viel dicker als beim ♀ unten oben das 1. Chelicere-Glied weit überragend. Beine: die basal Glied des 3. und 4. Bein auch beim ♂ von gleichem Habitus und gleicher Stärke wie die des 1. und. 2. Bein; Endabschnitt des 2. Tarsus 3-gliedrig; 1. Tarsus 6-gliedrig; 2.-4. Tarsus jeweils mehr als 6-gliedrig, variabel. Sekundäre Geschlechtsmerkmale des ♂ bisweilen am 4. Bein."* This roughly translates (if I translate it correctly through the gibberish of BabelFish) as "Slim animals with long, thin legs. 1st and 3rd areas always with 1 central pair of tubercles; 2nd, 4th and 5th areas and 1st-3rd free tergites unarmed. 2nd cheliceral segment of ♂ small and normally built or more rarely with ♂ much larger than ♀. Legs: basal segments of 3rd and 4th legs the same as 1st and 2nd legs; Final section of 2nd tarsus 3-segemented; 1st tarsus 6-segmented; 2nd-4th tarsus in each case more than 6-segmented, variable. Secondary sexual characteristics sometimes present in 4th leg of ♂." For those not familiar with variation in harvestmen, that's not a very impressive list of distinguishing features. In fact, in Roewer's key to the Cosmetidae, only one character is used to key Cynortula out from similar genera - whether the dorsal ornamentation is a tubercle (Cynortula) or a spine (other genera). Not convincing.

*If there are any German speakers reading this, I apologise profusely for the errors that I have no doubt are all through that. As a result of its publication not too long after the Great War, with materials in short supply in Germany, Roewer (1923) was condensed as much as possible for publication and hence is entirely composed in a series of arcane abbreviations. Any grammatical errors are therefore probably the result of my attempts to restore the description to a readable form.

REFERENCES

Goodnight, C. J., & M. L. Goodnight. 1947. Studies of the phalangid fauna of Trinidad. American Museum Novitates 1351: 1-13.

Hickman, V. V. 1939. Opiliones and Araneae. British, Australian and New Zealand Antarctic Research Expedition Reports Series B 4: 157-188.

Kury, A. B. 2003. Annotated catalogue of the Laniatores of the New World (Arachida, Opiliones). Revista Ibérica de Aracnología, special monographic volume 1: 1-337.

Kury, A. B., & R. Pinto-da-Rocha. 2007. Cosmetidae. In Harvestmen: The Biology of Opiliones (R. Pinto-da-Rocha, G. Machado & G. Giribet, eds.) pp. 182-185. Harvard University Press: Cambridge (Massachusetts).

Kury, A. B., O. Villarreal-Manzanilla & C. Sampaio. 2007. Redescription of the type species of Cynorta (Arachnida, Opiliones, Cosmetidae). Journal of Arachnology 35 (2): 325-333.

Roewer, C. F. 1923. Die Weberknechte der Erde: Systematisches Bearbeitung der bisher bekannten Opiliones. Gustav Fischer: Jena.