Squatinella Bory de St. Vincent 1924
Creators: name: Luo, Yongting
name: Segers, Hendrik
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Rotifera
Eurotatoria
Ploima
Lepadellidae
Squatinella

description: Genus Squatinella Bory de St. Vincent, 1924
Our material contains two distinct taxa of Squatinella, both belonging to the S. longispinata-leydigii group as recognized by Koste (1978). The taxonomy of the members of this group is complex and confused due to the rarity of the species and the sometimes contradictory reports. Based on an examination of original sources and the present and other material seen by us, we follow Myers’ (1942), Pourriot’s (1971) and Koste & Shiel’s (1989) conclusion that the group contains at least two well-definable species-level taxa, diagnosed as follows (see Table 3), albeit with changes in synonymy:
- Squatinella longispinata (Tatem, 1867) (synonyms: S. leydigii (Zacharias, 1886), S. uniseta (Collins), S. unisetatus (Hudson & Gosse), S. tripus (Hudson)) is here considered to be a relatively small species, with three foot pseudosegments and bearing a minute spine dorsally and terminally on the last foot pseudosegment. Its dorsal lorica spine narrows gradually into a sharp terminal point. Note that neither the (rather superficial) original description of S. longispinata by Tatem (1867) nor that of S. leydigii by Zacharias (1886) mention a foot spine, which may have been overlooked in these early reports. The relevance of the short spines flanking the dorsal spine, as reported for S. longispinata by Pejler (1962) requires further evaluation.
- Squatinella variegata (Levander, 1894) (note that Koste’s (1978: T. 58 fig. 2a) reproduction of the foot of S. variegata differs in some minute but important aspects from Levander’s (1894) original figure), a relatively robust species with two short foot pseudosegments and a third terminal element. Based on the peculiar morphology of the terminal foot pseudosegment, we believe that, in S. variegata, the third foot pseudosegment and toes are fused into a single element, while the vestiges of the toes are indicated by a short terminal fissure. This we conclude from the position of the dorsal sensory groove, which is situated basally and dorsally on the third foot pseudosegment in Lepadellidae, and is situated in the same position on the terminal element of the foot in S. variegata and related taxa (see below, Figure 1b). There is no additional toe spine and the dorsal spine is more or less parallel sided along much of its length, and ends in a blunt tip.
Relatively large specimens reported by Pourriot (1971) as having a dorsal spine of more than 1.5 times the body length (“f. longiseta ” after Pourriot 1971), may yet be another taxon, in view of the report of them having a different foot structure with two clearly separated toes (Koste, 1978). The two taxa in our material differ in a number of significant aspects from either S. longispinata or S. variegata, prompting us to describe them as new species, as follows.
description: Published as part of Luo, Yongting & Segers, Hendrik, 2020, Eight new Lepadellidae (Rotifera, Monogononta) from the Congo bring to level endemism in Africa's rotifers, pp. 371-387 in Zootaxa 4731 (3) on pages 378-380, DOI: 10.11646/zootaxa.4731.3.6, http://zenodo.org/record/3653632