Armatalona Sinev, 2004

Damme, Kay Van & Dumont, Henri J., 2009, Notes on chydorid endemism in continental Africa: Matralona gen. n., a monotypic Alonine from the Fouta Djalon Plateau (Guinea, West Africa) (Crustacea: Cladocera: Anomopoda), Zootaxa 2051, pp. 26-40 : 35-36

Similarity with Armatalona Sinev, 2004

Matralona gen. n. is not alone in its intermediate position. Within the subfamily, the Austral(as)ian Armatalona Sinev, 2004 shows resemblance. The genus contains two species previously classified in Alona Baird, 1843 , removed by Sinev (2004). Armatalona is close to Matralona gen. n. but differs in several characters ( Table 2 ). For example, Armatalona has strongly modified setae on the second antennae, an autapomorphy for the genus according to Sinev (2004). In our opinion, both are valid genera, though Matralona gen. n. could in extremis be regarded as a marginal Armatalona . The habitus of Armatalona and Matralona gen. n. differs, latter having a narrower anterior head shield, leaving the labrum exposed ( Fig. 5 ). In Armatalona , the head shield extends laterally and protects antennules and labrum ( Fig. 5 ). On limbs, Armatalona retains important ancestral features: long anterior setae on the first limb and three setae in the IDL ( Sinev 2004), reduced in Matralona gen. n. These characters are present in species complexes of the Hexalona- branch ( Table 2 ), closer to true Alona (quadrangularis- complex). They may represent a relatively ancestral morphology.

Affinities between Matralona gen. n. and Armatalona include characters of phylogenetic importance ( Table 2 ; Van Damme & Dumont 2008b). Others may result from convergence: the two genera share a small body size, limb reductions (like P3) and a similar postabdomen. These characters may be subject to strong variation. A peculiar similarity is the forward folding of the second antennae ( Figure 5 ). Still, a combination of characters separates Armatalona and Matralona gen. n. from the rest of the subfamily. If a result of common ancestry, this small lineage had little success in comparison to the widespread and common Coronatella - and Hexalona branches: today only a few species survive. Alternatively, similarities with Armatalona may be homoplastic, which is not uncommon in Chydoridae .

The characters of “ Alona ” simoneae , listed above, suggest 1. ancient origin and 2. strong isolation. We assign this species to a monotypic genus, Matralona gen.n. If derived from common ancestry, populations leading to Armatalona and Matralona gen. n. are likely disjunct since long and both represent relicts of their lineage. Matralona gen. n. is an example of divergence in limb morphology between Aloninae with similar external characters: at first sight, habitus is similar to that of other small alonines. We discuss affinities with several two-pored Aloninae in the next section.

Figures

FIGURE 5. The two-pored Matralona gen. n. and Armatalona Sinev, 2004. Both genera show similarities in external and limb morphology and may derive from a close common ancestor (or another result of homoplasy?). Both genera have the general appearance of small-sized Aloninae and previously belonged to Alona Baird, 1843. Top. Matralona simoneae (Dumont, 1981), Fouta Djalon, Guinea. Labral keel is completely exposed when compared to Armatalona. Below. Armatalona macrocopa (Sars, 1894), Australia. The spine-like antennal setae above the head are typical for the genus (Sinev 2004).