Adaeulum sp., copyright Charles Haddad.

Belongs within: Triaenonychidae.

The adaeines: South Africa’s cryptic micro-giants
Published 7 February 2017

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).

Systematics of Adaeinae
<==Adaeinae [Adaeidae, Adaeini]
    |--Larifuga Loman 1898DB21, S92
    |    |--*L. weberi Loman 1898S92
    |    |--L. avus Staręga 1989S92
    |    |--L. calcarata Lawrence 1931S92
    |    |--L. capensis Lawrence 1931S92
    |    |--L. dentifer Lawrence 1931S92
    |    |--L. granulosa Lawrence 1931S92
    |    |--L. mantonae Lawrence 1934 [=L. mantoni]S92
    |    |--L. montana Lawrence 1931S92
    |    |--L. oneraria Kauri 1961S92
    |    `--L. rugosa (Guérin-Méneville 1837)KMS14 [=Phalangium rugosumS92]
    `--+--+--Larifugella Staręga 1992DB21, KMS14
       |  |    |--*L. afra Lawrence 1933KMS14
       |  |    |--L. longipalpis Lawrence 1934S92
       |  |    |--L. natalensis (Lawrence 1931) [=Adaeulum natalense]S92
       |  |    |--L. valida Lawrence 1963S92
       |  |    `--L. zuluana Lawrence 1937S92
       |  `--Adaeum Karsch 1880BS20, S92 [incl. Metadaeum Roewer 1923R23]
       |       |--*A. asperatum Karsch 1880S92
       |       |--A. capense (Roewer 1915)KMS14 [=Metadaeum capenseS92; incl. A. brincki Kauri 1961S92]
       |       |--A. granulosum Lawrence 1931S92
       |       |--A. hewitti Roewer 1931S92
       |       |--A. latens Loman 1898S92
       |       |--A. obtectum Loman 1898S92
       |       |--A. spatulatum Lawrence 1931S92
       |       `--A. squamatum Lawrence 1931S92
       `--Adaeulum Roewer 1915DB21, BS20
            |  i. s.: A. brevidentatum Lawrence 1934S92
            |         A. coronatum Kauri 1961S92
            |         A. monticola Lawrence 1939 [=A. monticolum]S92
            |         A. warreni Lawrence 1933S92
            |--A. humifer Lawrence 1963BS20, S92
            `--+--A. moruliferum Lawrence 1938BS20, S92
               `--+--A. robustum Lawrence 1937BS20, S92
                  `--+--+--*A. areolatum (Pocock 1902)S92, BS20, S92 [=Adaeum areolatumS92]
                     |  `--A. godfreyi Lawrence 1931BS20, S92 [incl. A. coxidens Lawrence 1931S92]
                     `--+--A. bicolor Lawrence 1931BS20, S92
                        `--A. supervidens Lawrence 1933BS20, S92
Adaeinae incertae sedis:
  Montadaeum Lawrence 1931S92
    `--*M. purcelli Lawrence 1931S92
  Cryptadaeum Lawrence 1931S92
    `--*C. capense Lawrence 1931S92
  Micradaeum Lawrence 1931S92
    `--*M. rugosum Lawrence 1931S92
  Heteradaeum Lawrence 1963S92
    `--*H. exiguum Lawrence 1963L63
  Paradaeum Lawrence 1931BS20, S92
    `--*P. rattrayi Lawrence 1931S92

*Type species of generic name indicated


[BS20] Baker, C. M., K. Sheridan, S. Derkarabetian, A. Pérez-González, S. Vélez & G. Giribet. 2020. Molecular phylogeny and biogeography of the temperate Gondwanan family Triaenonychidae (Opiliones: Laniatores) reveals pre-Gondwanan regionalisation, common vicariance, and rare dispersal. Invertebrate Systematics 34: 637–660.

[DB21] Derkarabetian, S., C. M. Baker, M. Hedin, C. E. Prieto & G. Giribet. 2021. Phylogenomic re-evaluation of Triaenonychoidea (Opiliones: Laniatores), and systematics of Triaenonychidae, including new families, genera and species. Invertebrate Systematics 35: 133–157.

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

[KMS14] Kury, A. B., A. C. Mendes & D. R. Souza. 2014. World checklist of Opiliones species (Arachnida). Part 1: Laniatores—Travunioidea and Triaenonychoidea. Biodiversity Data Journal 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.

[L63] Lawrence, R. F. 1963. The Opiliones of the Transvaal. Annals of the Transvaal Museum 24 (4): 275–304.

[R23] Roewer, C.-F. 1923. Die Weberknechte der Erde: Systematische Bearbeitung der bisher bekannnten Opiliones. Gustav Fischer: Jena.

[S92] Staręga, W. 1992. An annotated check-list of Afrotropical harvestmen, excluding the Phalangiidae (Opiliones). Annals of the Natal Museum 33 (2): 271–336.

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