Belongs within: Opiliones.
Contains: Stenostygninae, Hinzuanius, Metabiantes, Biantes, Samoidae, Stygnomma.
The Samooidea are a group of laniatorean harvestmen that commonly possess a scopula and a sexually dimorphic metatarsus III (Sharma & Giribet 2011). Eyes are dissociated and not borne on a central ocularium in the families Biantidae and Stygnommatidae. The basichelicerite is elongated in males of Stygnommatidae but not in Biantidae.
Biantidae: the importance of titillators
Published 4 April 2012
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.
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).
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.
Systematics of Samooidea
<==Samooidea [Biantoidea]
|--Biantidae [Biantoidae, Hinzuanidae]SG14
| |--Zairebiantes Kauri 1985S92 [ZairebiantinaeKPG07]
| | `--*Z. microphthalmus Kauri 1985S92
| |--LacurbsinaeKSP-G15
| | |--Lacurbs Sørensen 1896S92 [LacurbsinaeKPG07]
| | | |--L. nigrimana Roewer 1912 [=L. nigrimanus]S92
| | | `--L. spinosa Sørensen 1896S92
| | |--Eulacurbs Roewer 1949KSP-G15, S92
| | | `--*E. paradoxa Roewer 1949S92
| | |--Metalacurbs Roewer 1915P-GM24
| | | |--*M. simoni Roewer 1915S92, KSP-G15
| | | |--M. cornipes (Roewer 1958) [=Prolacurbs cornines (l. c.)]S92
| | | |--M. foordi Pérez-González & Mamani 2024P-GM24
| | | |--M. oedipus (Roewer 1958) [=Prolacurbs oedipus]S92
| | | `--M. villiersi (Roewer 1953) [=Prolacurbs villiersi]S92
| | `--Prolacurbs Roewer 1949KSP-G15, S92
| | `--*P. singularis Roewer 1949S92
| |--StenostygninaeP-GAB09
| `--BiantinaeKPG07
| |--HinzuaniusL62
| |--MetabiantesKPG07
| |--Eubiantes Roewer 1915L62, S92
| | `--*E. africanus Roewer 1915S92
| |--Acudorsum Loman 1902R23, S92
| | `--*A. albimanum Loman 1902S92
| |--Hoplobiantes Roewer 1915R23
| |--Cryptobiantes Kauri 1961K61
| | `--*C. protector Kauri 1961S92
| |--Fageibiantes Roewer 1949KPG07, S92
| | |--*F. bicornis (Fage 1946) [=Biantes bicornis, Fageibantes (l. c.) bicornis]S92
| | `--F. bispina Lawrence 1959 [=Fageibantes (l. c.) bispina]S92
| |--Biantessus Roewer 1949L63, S92
| | |--*B. nigrotarsus (Lawrence 1933) [=Metabiantes nigrotarsus]S92
| | `--B. vertebralis (Lawrence 1933)S92 [=Metabiantes vertebralisS92, *Biantanius vertebralisL63]
| |--BiantesS89
| |--Monobiantes Lawrence 1962L62
| | `--*M. benoiti Lawrence 1962S92
| |--Biantomma Roewer 1942L62, S92
| | `--*B. nigrospinosum Roewer 1942S92
| |--Clinobiantes Roewer 1927L62, S92
| | `--*C. paradoxus Roewer 1927S92
| |--Biantella Roewer 1927L62, S92
| | `--*B. reticulata Roewer 1927S92
| |--Anaceros Lawrence 1959KSP-G15
| | |--*A. humilis Lawrence 1959S92
| | |--A. anodonta Lawrence 1959S92
| | |--A. canidens Lawrence 1959S92
| | `--A. pauliani Lawrence 1959S92
| |--Hirstienus Roewer 1949KSP-G15, SPG11
| | `--*H. nanus (Hirst 1913) [=Phalangodes nanus]SPG11
| |--Hovanoceros Lawrence 1959KSP-G15, KP-G15
| | `--*H. bison Lawrence 1959KP-G15
| |--Ivobiantes Lawrence 1965KSP-G15, S92
| | `--*I. spinipalpis Lawrence 1965S92
| |--Malgaceros Lawrence 1959KSP-G15, KP-G15
| | `--*M. boviceps Lawrence 1959KP-G15
| |--Probiantes croceus Roewer 1927KSP-G15
| `--Tetebius Roewer 1949KSP-G15, KP-G15
| `--*T. latibunus Roewer 1949KP-G15
`--+--SamoidaeSG14
`--StygnommatidaeSG14
|--StygnommaKP-GP19
`--Stygnomimus Roewer 1927SG11, KP-G15
|--*S. conopygus Roewer 1927 [=Stignomimus conopygus]KP-G15
`--S. malayensis Suzuki 1969 [=Stignomimus malayensis]KP-G15
Nomen nudum: Lacurbs fernandopoensis Prieto 1999SP10
*Type species of generic name indicated
References
[K61] 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.
[KPG07] Kury, A. B., & Pérez González, A. 2007. Biantidae Thorell, 1889. In: Pinto-da-Rocha, R., G. Machado & G. Giribet (eds) Harvestmen: The Biology of Opiliones pp. 176–179. Harvard University Press: Cambridge (Massachusetts).
[KP-G15] Kury, A. B., & A. Pérez-González. 2015. A companion to part 2 of the world checklist of Opiliones species (Arachnida): Laniatores—Samooidea, Zalmoxoidea and Grassatores incertae sedis. Biodiversity Data Journal 3: e6663.
[KP-GP19] Kury, A. B., A. Pérez-González & D. N. Proud. 2019. A new Indo-Malayan family of Grassatores (Arachnida: Opiliones: Laniatores). Invertebrate Systematics 33: 892–906.
[KSP-G15] Kury, A. B., D. R. Souza & A. Pérez-González. 2015. World checklist of Opiliones species (Arachnida). Part 2: Laniatores—Samooidea, Zalmoxoidea and Grassatores incertae sedis. Biodiversity Data Journal 3: e6482.
[L62] Lawrence, R. F. 1962. Resultats scientifiques des missions zoologiques de l’I.R.S.A.C. en Afrique orientale (P. Basilewsky et N. Leleup, 1957). LXXIV. Opiliones. Annales du Musée Royal de l’Afrique Centrale: Sciences Zoologiques 110: 9–89.
[L63] Lawrence, R. F. 1963. The Opiliones of the Transvaal. Annals of the Transvaal Museum 24 (4): 275–304.
[P-GAB09] Pérez-González, A., & A. Alegre Barroso. 2009. On the enigmatic Heterolacurbs ovalis Roewer, 1912 (Opiliones, Laniatores, Biantidae). Zootaxa 2269: 65–67.
[P-GM24] Pérez-González, A., & V. Mamani. 2024. Metalacurbs foordi sp. nov., a new Lacurbsinae (Opiliones, Laniatores, Biantidae) from Ankasa National Park, Ghana. African Invertebrates 65 (2): 199–211.
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.
[R23] Roewer, C.-F. 1923. Die Weberknechte der Erde: Systematische Bearbeitung der bisher bekannnten Opiliones. Gustav Fischer: Jena.
[SP10] Santos, R., & C. E. Prieto. 2010. Los Assamiidae (Opiliones: Assamiidae) de Río Muni (Guinea Ecuatorial), con la descripción de ocho nuevas especies. Revista de Biologia Tropical 58 (1): 203–243.
[SG11] 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.
[SG14] Sharma, P. P., & G. Giribet. 2014. A revised dated phylogeny of the arachnid order Opiliones. Frontiers in Genetics 5 (255): 1–13.
[SPG11] Sharma, P. P., C. E. Prieto & G. Giribet. 2011. A new family of Laniatores (Arachnida: Opiliones) from the Afrotropics. Invertebrate Systematics 25: 143–154.
[S89] Staręga, W. 1989. Harvestmen (Opiliones) from the Mascarene Islands Indian Ocean and resurrection of the family Zalmoxidae. Annals of the Natal Museum 30: 1–8.
[S92] Staręga, W. 1992. An annotated check-list of Afrotropical harvestmen, excluding the Phalangiidae (Opiliones). Annals of the Natal Museum 33 (2): 271–336.