Metavononoides

Metavononoides barbacenensis, from here.

Belongs within: Cosmetidae.
Contains: Paecilaema.

Metavononoides is a genus of long-legged short-legged harvestmen found in the Atlantic forest of eastern Brazil (Ferreira et al. 2006).

Metavononoides: retreating from the coast
Published 17 May 2019

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.

Systematics of Metavononoides

Characters (from Ferreira et al. 2006): Body length 5–7 mm; U-shaped, lyre-like marking on dorsal scutum; mesotergum depressed; pair of median spines on area III; coxa I with bifid dorsobasal apophysis; legs long (more than 30 mm in smaller species).

<==Metavononoides Roewer 1928FPK06 [=Metavononnoides (l. c.)K03]
    |  i. s.: M. albosigillatus (Mello-Leitão 1941) [=Poecilaemula albosigillata]K03
    |         M. brasiliensis (Mello-Leitão 1923) (see below for synonymy)K03
    |         M. luteopunctatus (Mello-Leitão 1931) [=Poecilaemula luteopunctata]K03
    |         M. lyra (Piza 1944) [=Cynortellana lyra]K03
    |         M. melanacanthus Ferreira, Pedroso & Kury 2005FPK06
    |         M. peculiaris (Roewer 1917) [=Poecilaemula peculiare, Paecilaemula peculiaris, Po. peculiaris]K03
    |         M. preciosus (Roewer 1928)FPK06 (see below for synonymy)
    |         M. renneri Ferreira, Pedroso & Kury 2006FPK06
    |--+--*M. barbacenensis (Mello-Leitão 1923)K03, MKM22, K03 (see below for synonymy)
    |  `--M. guttulosus (Mello-Leitão 1935)MKM22, K03 [=Cynorta guttulosaK03]
    `--+--M. orientalis (Mello-Leitão 1923)MKM22, K03 [=Metavonones orientalisK03]
       `--PaecilaemaMKM22

*Metavononoides barbacenensis (Mello-Leitão 1923)K03, MKM22, K03 [=Metavonones barbacenensisK03; incl. Metavononoides pustulatus Mello-Leitão 1932K03]

Metavononoides brasiliensis (Mello-Leitão 1923) [=Eucynorta brasiliensis, Paecilaemula brasiliensis, Poecilaemula brasiliensis]K03

Metavononoides preciosus (Roewer 1928)FPK06 [=Paecilaemula preciosaK03; incl. Poecilaemula punctilineata Mello-Leitão 1935K03, Metavononoides x-notatus Mello-Leitão 1936K03]

*Type species of generic name indicated

References

[FPK06] Ferreira, C. P., D. R. Pedroso & A. B. Kury. 2006. A new species of Metavononoides from southern Espírito Santo, Brazil (Arachnida: Opiliones: Cosmetidae). Arquivos do Museu Nacional, Rio de Janeiro 64 (3): 231–234.

[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.

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.

[MKM22] Medrano, M., A. B. Kury & A. C. Mendes. 2022. Morphology-based cladistics splinters the century-old dichotomy of the pied harvestmen (Arachnida: Gonyleptoidea: Cosmetidae). Zoological Journal of the Linnean Society 195 (2): 585–672.

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.

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