Nanometa clade

Introduction

The ‘‘Nanometa clade’’ is an Australian lineage that includes the genus Nanometa, some species currently classified as Orsinome and an undescribed genus. Very little is known about the biology and diversity of this group.

Characteristics

Spiders from the ‘‘Nanometa clade’’ have numerous unique characteristics that make them easy to distinguish from other tetragnathids. ‘‘Nanometa clade’’ members have ramified median tracheae (with a branching pattern very different from that of the tetragnathine genus Glenognatha). Females have cheliceral denticles between the anterior and posterior rows of cheliceral teeth. Males have stridulatory ridges on the book-lung plates and small denticles on the fourth coxae's mesal surface.

Discussion of Phylogenetic Relationships

Forster and Forster (1999) placed the genus Nanometa and the species Orsinome lagenifera in a separate family, Nanometidae, but they did not provide a explicit justification for their proposed new family. All phylogenetic analyses that have included Nanometa found it deeply nested within Tetragnathidae, which would of course render this latter family paraphyletic (Álvarez-Padilla, 2007; Álvarez-Padilla et al., 2009; Dimitrov and Hormiga, 2009). Nanometa and Orsinome sarasini are treated as a lineage under the informal name ‘‘Nanometa clade’’. The genus Orsinome is not monophyletic and the species Orsinome sarasini is not congeneric with the leucaugine Orsinome vethi (the type species). At present time it is not possible to ascertain how many of the species included in Orsinome are actually members of the ‘‘Nanometa clade.’’ The tree presented here is taken from Álvarez-Padilla et al. (2009).

References

Álvarez-Padilla F., Dimitrov D., Giribet G., Hormiga G. 2009. Phylogenetic relationships of the spider family Tetragnathidae (Araneae, Araneoidea) based on morphological and DNA sequence data. Cladistics (In press).

Álvarez-Padilla F. 2007. Systematics of the spider genus Metabus O. P.-Cambridge, 1899 (Araneoidea: Tetragnathidae) with additions to the tetragnathid fauna of Chile and comments on the phylogeny of Tetragnathidae. Zool. J. Linn. Soc. 150: 285–335.

Dimitrov D., Hormiga G. 2009. Revision and cladistic analysis of the orbweaving spider genus Cyrtognatha Keyserling, 1881 (Araneae, Tetragnathidae). Bulletin of the American Museum of Natural History 317: 1-139.

Forster R.R., Forster L. 1999. Spiders of New Zealand and their Worldwide Kin. University of Otago Press, Dunedin, NZ.