Goniosoma calcar, copyright Glauco Machado.

Belongs within: Goniosomatinae.

Goniosoma is a genus of goniosomatine harvestmen in which the legs are relatively short, with relatively weak armature on femur IV in the male (DaSilva & Gnaspini 2009).

Gonyleptids are just so cool
Published 27 January 2010

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 Goniosoma unicolor. 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, Goniosoma 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.

Systematics of Goniosoma

Characters (from DaSilva & Gnaspini 2009): Eye-mound low and generally with one pair of medium-sized or very large spines (exception: tubercle like a medium-sized granule in G. macracanthum). Coxa IV with one pointed prolateral apical apophysis with 1 small sub-basal posterior process, oblique or nearly longitudinal and slightly curved downward; retrolateral apical apophysis large, of same size or larger than trochanter, or, at least, like a spine. Femur short, curved inward (from with a strong curvature to almost straight) and very granulated; flat granules, mainly on retrolateral row (row2); dorsal rows, on apical region, very granulated and disorganised and/or with a nearly longitudinal comb of granules (very close to each other); dorsal–prolateral apical apophysis large and curved backward. Tarsal process short, medium-sized or long (from minute to larger than tarsal claws); if large in male, female has medium-sized tarsal process. Tarsal claws simple. Penis longer than wider; apical group of setae with four setae on a single longitudinal row (exception: one additional ventral seta, but very small, in G. vatrax); basal group with three setae on longitudinal, L-like or oblique row, and one additional very small, ventral seta; all setae pointed. Glans without or with ventral process; with apical lamina or thin (without lamina); stylus with a dorsal apical ‘beak’.

<==Goniosoma Perty 1833DG09 (see below for synonymy)
    |  i. s.: G. lepidum Gervais 1844 (n. d.)DG09
    |         G. monacanthum Gervais 1844 (n. d.)DG09
    |         G. obscurum Perty 1833 (n. d.)DG09
    |         G. versicolor Perty 1833 (n. d.)DG09 [=Progoniosoma versicolorK03]
    |--G. carum (Mello-Leitão 1936) [=*Xulapona cara, Lyogoniosoma carum]DG09
    `--+--+--*G. varium Perty 1833DG09 (see below for synonymy)
       |  `--+--G. capixaba DaSilva & Gnaspini 2009DG09
       |     `--+--G. roridum Perty 1833 [=Progoniosoma roridum]DG09
       |        `--G. venustum Koch 1839 [incl. G. geniculatum Mello-Leitão 1931]DG09
       `--+--G. vatrax Koch 1848 (see below for synonymy)DG09
          `--+--G. macracanthum (Mello-Leitão 1922) [=Progoniosoma macracanthum, *Lyogoniosoma macracanthum]DG09
             `--+--+--G. dentipes Koch 1839 (see below for synonymy)DG09
                |  `--G. ensifer (Mello-Leitão 1940)DG09 [=Progoniosoma ensiferDG09, Acutisoma ensiferKP-R07]
                `--+--G. apoain DaSilva & Gnaspini 2009DG09
                   `--+--G. calcar (Roewer 1913) [=Progoniosoma calcar]DG09
                      `--G. unicolor (Mello-Leitão 1932) [=Glyptogoniosoma unicolor, Acutisoma unicolor]DG09

Goniosoma Perty 1833DG09 [incl. Glyptogoniosoma Mello-Leitão 1932DG09, Glypotgoniosoma (l. c.)K03, Goniosomella Mello-Leitão 1936DG09, Lyogoniosoma Mello-Leitão 1926DG09, Liogonissoma (l. c.)K03, Metalyogoniosoma Soares & Soares 1946DG09, Progoniosoma Roewer 1913DG09, Progonissoma (l. c.)K03, Xulapona Mello-Leitão 1936DG09]

Goniosoma dentipes Koch 1839 [=*Progoniosoma dentipes; incl. P. cruciferum Mello-Leitão 1923, Acutisoma cruciferum, *Glyptogoniosoma cruciferum, Goniosoma grossum Koch 1839, Progoniosoma grossum, Glyptogoniosoma perditum Mello-Leitão 1936, Acutisoma perditum, Progoniosoma tijuca Roewer 1930, Goniosoma tijuca]DG09

*Goniosoma varium Perty 1833DG09 [=Gonyleptes spinipes Gray in Griffith 1833 non Perty 1833R23; incl. Acutisomella cryptoleuca Mello-Leitão 1940DG09, Acutisomella intermedia Mello-Leitão 1937DG09, Acutisoma intermediumDG09, Goniosoma junceum Perty 1833DG09, Goni. patruele Perty 1833DG09, Progoniosoma patrueleDG09, *Metalyogoniosoma unum Soares & Soares 1946DG09, Goniosoma xanthophthalmum Mello-Leitão 1931DG09, Goni. xanthophathalmum (l. c.)K03, Goni. xatnhophthalmumDG09]

Goniosoma vatrax Koch 1848 [incl. Progoniosoma minense Mello-Leitão 1932, Goniosoma minense, *Goniosomella perlata Mello-Leitão 1936, Lyogoniosoma perlatus (l. c.), L. perlatum]DG09

*Type species of generic name indicated


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.

[DG09] DaSilva, M. B., & P. Gnaspini. 2009. A systematic revision of Goniosomatinae (Arachnida: Opiliones: Gonyleptidae), with a cladistic analysis and biogeographical notes. Invertebrate Systematics 23: 530–624.

[K03] 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.

[KP-R07] Kury, A. B., & R. Pinto-da-Rocha. 2007. Gonyleptidae Sundevall, 1833. In: Pinto-da-Rocha, R., G. Machado & G. Giribet (eds) Harvestmen: The Biology of Opiliones pp. 196–203. Harvard University Press: Cambridge (Massachusetts).

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

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

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