Natatolana, Bruce, 1981

Keable, Stephen J., 2006, Taxonomic Revision of Natatolana (Crustacea: Isopoda: Cirolanidae), Records of the Australian Museum 58 (2), pp. 133-244 : 141-142

of Natatolana in the characters noted below ( Keable, 1999).

Other putative synapomorphies that may define Natatolana as a monophyletic group include: the smooth medial surface of the mandibular molar lacking slender setae (see Keable, 1996b; Keable, 1999); the short antennule in which the flagellum is shorter than, or subequal in length to the peduncle with articles broader than longer; and the narrow frontal lamina lacking a posteroventral projection. Comparison of these additional synapomorphies to characters occurring in other genera suggest, however, that they are not unique and further analysis is necessary before their phylogenetic significance can be fully evaluated.

The composition, relationships and phylogenetic significance of the four existing informal groups (the N. albicaudata , N. pellucida , N. valida and N. woodjonesi groups— Bruce, 1986; Wägele & Bruce, 1989) within Natatolana are unclear because characters used in defining them may not be shared by all members of the group and/ or may be shared by species excluded from the group. For example, ambiguous characters used in defining these groups include:

entire or complete coxal furrows—these occur in species placed in both the N. albicaudata and N. pellucida groups;

pereopod 2 lacking robust setae on the palm of the propodus—this is a condition that occurs in all species included in both the N. pellucida and N. woodjonesi groups;

pereopod 7 basis narrow with margins straight—this state occurs in the N. pellucida group and is indistinguishable from the state described for the N. valida group (pereopod 7 basis narrow, broadening distally, margins nearly straight).

Furthermore, conflicting statements have been made regarding the composition of the informal groups within Natatolana and some of the characters used in formulating them. For example, N. rossi and N. hirtipes have been included in the N. valida group, which is characterized by having “coxal plates with furrows feeble or absent”, despite N. rossi and N. hirtipes being differentiated from N. matong on the grounds that they have “distinct” or “conspicuous” coxal furrows ( Bruce, 1986, p. 97). Also, many species do not readily fall into these groups ( Bruce, 1986; Bruce & Olesen, 1995; this study).

A robust phylogenetic analysis of Natatolana is, therefore, required to determine the utility of these groups. A relevant character that has not been highlighted previously is the development of long, modified, robust setae on the posterior margins of the merus of pereopods 1–3 and on the distal margin of the carpus of pereopods 4–6 (Plate 1). These specialized setae are only known to occur on males of the species Bruce (1986) placed in the N. pellucida group ( N. pellucida , N. corpulenta , N. galathea , N. laewilla , N. longispina ) and N. debrae n.sp., N. sinuosa n.sp. and N. zebra n.sp. This and other characters included in the species diagnoses presented here, however, were used in a phylogenetic analysis by Keable (1996) that was inconclusive (being both ambiguous and partially resolved) regarding species relationships within Natatolana . The main conclusions of this analysis were that morphological characters are difficult to use because of problems in defining enough character state transitions to resolve relationships. This was viewed as being possibly the result of a strong adaptation to the benthic/scavenging niche, resulting in a conservative morphology, and/or particular speciation processes. Consequently, study of functional morphology of species of Natatolana to further resolve morphological character states and use of molecular techniques to clarify patterns of speciation within the genus were suggested to aid progress in determining species relationships.

Material examined during this study indicates the need to place Natatolana lurur Bruce, 1986 and N. wullunya Bruce, 1986 in synonymy with N. arcicauda Holdich, Harrison & Bruce, 1981 , and N. nammuldi Bruce, 1986 , respectively. Therefore, 59 previously described species are recognized and, with the addition of 13 species described here, the total number of species now in the genus is 72.