Leptothecata: Sertulariidae

The 16S rRNA sequence of Tridentata borneensis Billard, 1925a from Bali did not match any other sequenced sertulariids, but clustered with other Tridentata species (Fig. 28) in a well-supported clade (BPP = 1, MLBS = 89).

Tridentata loculosa (Busk, 1852) has hydrothecae lacking the prominent, lateral, marginal cusps characteristic of the genus Tridentata, its hydranths are strikingly provided with a ligula, and its gonothecae (although transverselyringed) are closed by a watch-glass-shaped operculum (Migotto 1996: 72), making it somehow distinct from members assigned to that genus so far. Additionally, the 16S rRNA sequence obtained from a Balinese specimen does not cluster with other Tridentata sequences, the latter forming a well-supported monophyletic group (Fig. 28) also including a sequence of T. trigonostoma (Busk, 1852) from Bali, which is identical to a conspecific sequence from Thailand.

Two other sertulariids, namely Idiellana pristis (Lamouroux, 1816) and Diphasia mutulata (Busk, 1852), were also sequenced. The first clusters with a sequence of the same species from Thailand (with an intra-specific genetic distance of 0.4 ± 0.2%), whereas the second, here sequenced for the first time, is sister to all other Diphasia sequences included in the analyses, even though the support values for the genus are low (Fig. 28).