Cassidinidea Hansen, 1905

Anil, Pathan, Bruce, Niel L., Samson, Rokkarukala & Jayaraj, Kadeparambil Arjunan, 2024, Cassidinidea andamanensis sp. nov., a new species of intertidal Sphaeromatidae (Crustacea: Isopoda) from the Andaman Islands, northern Indian Ocean, Zootaxa 5397 (4), pp. 578-588 : 579-580

Genus Cassidinidea Hansen, 1905

Cassidinidea Hansen, 1905: 113 , 131.– Menzies & Frankenberg, 1966: 44; Schultz, 1969: 115; Kussakin, 1979: 336; Harrison, 1984: 374; Kensley & Schotte, 1989: 207; Harrison & Ellis, 1991: 935. Bruce, 1994:1173; Hendrickx & Espinosa-Perez, 1998: 302; Schotte & Kensley, 2005:1282 ; Khalaji-Pirbalouty & Bruce, 2021: 2.

Cassidisca Richardson, 1905: 272 [nomen nudum – type species not designated].

Dies Barnard, 1951: 701.–de Loyola e Silva, 1960: 52; Carvacho, 1977: 13 [Type species: Dies monodi Barnard, 1951 ; by monotypy; type material and type locality not designated for the species].

Type species: Naesa ovalis Say, 1818 ; designated by Hansen (1905); one syntype held at the Natural History Museum, London ( Bruce 1994).

Remarks: Several characters serve to reliably identify the genus, among others, the long appendix masculina that arises basally from a posteriorly directed lobe, the lateral margins of the head are somewhat flattened and extend laterally, the epistome is visible dorsally, and the pleon has one visible segment, and the penial processes are fused. Cassidina extenda Joshi & Bal, 1962 , an apparently overlooked species, cannot belong to Cassidina Whitelegge, 1902 (see Bruce 1994) as the form of pleon, head, antennula articles 1 and 2 not expanded and flattened, pereopod 1, pleopod are all substantially different. Cassidina extenda does on most of the described characters agrees with Cassidinidea (see Bruce 1994; Hendrickx & Espinoza-Perez 1998; Khalaji-Pirbalouty & Bruce 2021; Schotte & Kensley 2005), and despite some apparent differences (epistome not visible in dorsal view) the species is here placed in the most appropriate combination of Cassidinidea extenda ( Joshi & Bal, 1962) comb. nov.

The species of Cassidinidea present a constant and uniform appearance. Sphaeromatid genera with a dorsoventrally compressed body shape (“flattened”) had been considered variously as a subfamily (e.g. Iversen 1982; Bruce 1994) or a clade ( Wägele 1989) within the Sphaeromatidae . Recently, molecular analysis of Wetzer et al. (2018) clearly showed the non-monophyly of the ‘Cassidininae’, and placed Cassidinidea within the ‘ Dynamene clade’, albeit on relatively slim and somewhat inconsistent evidence. On morphological criteria there is little obvious similarity between Cassidinidea and genera such as Dynamenella Hansen, 1905 other than in the pleopod 1 morphology. It is clear that the relationships between this genus and others in the ‘ Dynamene clade’ are not yet fully understood, nor adequately explained by observable morphology.

Diagnoses to genus may be found in Bruce (1994), Schotte & Kensley (2005); Khalaji-Pirbalouty & Bruce (2021) gave a detailed generic diagnosis and description, and included and annotated list of all known species of Cassidinidea .