Comparison of Terebrasabella spp.

The characters that distinguish the two species described here are as follows:

Thoracic uncini form: Terebrasabella hutchingsae sp. nov., has two forms of acicular uncini (“palmate” and heterodont-crested uncini) both of which are different to the single type present in Terebrasabella fitzhughi sp. nov., (homodont-crested uncini). Terebrasabella heterouncinata possesses only heterodontcrested acicular uncini.

Abdominal uncini form: T. hutchingsae sp. nov., has acicular uncini that are a smaller version of the longhandled “palmate” uncini of chaetiger 1, whereas those of T. fitzhughi sp. nov., are homodont-crested with a series of many fine teeth. T. heterouncinata possesses long-handled heterodont-crested acicular uncini.

Ventral peristomial lappets: anteriorly elongate on specimens of T. fitzhughi sp. nov., and relatively shorter and distally-rounded on T. hutchingsae sp. nov. T. heterouncinata has small, triangular, distallyrounded ventral collar lappets.

The number of rasp-shaped avicular uncini per row: on chaetiger 7, is greater in T. hutchingsae sp. nov., (~50) than in T. fitzhughi sp. nov., (<24). T. heterouncinata has fewer uncini in chaetiger 7 (~23 per row), but more uncini in chaetiger 8 (~19 per row) than either of the other 2 species (both <15).

The faecal tracks of T. hutchingsae sp. nov., and T.fitzhughi sp. nov., bifurcate in the 8th chaetiger, not the in the 10th chaetiger as in T. heterouncinata .

The main characters that distinguish all three species of Terebrasabella are the different types of uncini. These are summarised in Table 1.

Uncini number and type in thorax and abdomen of:

Chaetiger Terebrasabella heterouncinata Terebrasabella hutchingsae sp. Terebrasabella fitzhughi

nov. sp. nov.