Thecidellina, Thomson, 1915

Simon, Eric, Lüter, Carsten, Logan, Alan & Mottequin, Bernard, 2018, Recent thecideide brachiopods (Thecideida, Thecideoidea) from northern Sulawesi (Indonesia) with discovery of a new Thecidellina species (Thecidellinidae), Zootaxa 4526 (4), pp. 481-515 : 492-493

Comparison with Thecidellina maxilla ( Hedley, 1899)

1899 Thecidea maxilla: Hedley, pp. 508–510, fig. 57.

1920 Thecidellina maxilla: Dall, p. 283.

1927 Thecidellina maxilla: Thomson, p. 140.

1954 Thecidellina maxilla: Cooper, pp. 317–318, pl. 81, figs. 1–10.

1985 Thecidellina maxilla: Zezina, p. 208.

non 1987 Thecidellina maxilla: D’Hondt, p. 41, pl. 4, figs. 1–5.

? 1997 Thecidellina maxilla: Laurin, pp. 453–454, fig. 40A–B.

pp 2007 Thecidellina maxilla: Bitner, p. 498, fig. 3A–E, 3G–H, non fig. 3F.

non 2009 Thecidellina maxilla: Bitner, pp. 17–18, fig. 12A–J.

pp 2014 Thecidellina maxilla: Bitner, p. 259, fig. 11F–I (non fig. 11D–E).

non 2015 Thecidellina maxilla: Bitner, p. 42, fig. 5A–E.

T. maxilla is a large species with horse-shoe shaped dorsal valve with a peripheral ridge smooth to finely granulate. T. mawaliana sp. nov. is a rather small species drop-like shaped with a peripheral ridge ornamented with strong tubercles.

In T. maxilla the brachial bridge is relatively narrower ( Hedley 1899, fig. 57) and the median septum is long, with lateral flanges developed along the inner sides of the brachial cavities ( Hedley 1899, fig. 57, p. 509; Cooper 1954, pl. 81, fig. 10). The brachial cavities are more elongate. The single massive spicules of the intrabrachial ridge which are not completely covering the brachial cavities are rather regular in shape and size.

In T. mawaliana sp. nov. the brachial bridge is wider and the median septum is devoid of lateral flanges. The brachial cavities are oval. The spicules of the brachial cavities, forming complete canopies are thin, irregular in shape and fused together.

The ventral valve floor in T. maxilla is not roughly tuberculate (nearly smooth), the planodeltidium is larger and quite concave dorsally ( Cooper 1954, pl. 81, figs. 5–6). The hemispondylium in T. maxilla is not attached to the valve floor.

Remarks. Non T. maxilla in D’Hondt (1987). In this paper, this species is cited without description but the illustrated specimens are very distinct from the type of T. maxilla. Their median septum is extremely wide and the spicules, differently shaped, form complete canopies on the brachial cavities. This is possibly a new species and this material must be restudied to give accurate taxonomical data.

? T. maxilla in Laurin (1997). This identification remains unclear as no detailed description is provided and the illustrations in this paper are not informative. This material must be revisited to have accurate data for determination.

Non T. maxilla in Bitner (2007, p. 498, fig. 3F). This specimen is probably a representative of T. congregata Cooper, 1954 . Canopying spicules are different from the type of T. maxilla, being single and very massive in the anterior part of the brachial cavities and being extremely small and pointed in the posterior part. In T. maxilla, spicules have a much more regular shape. The right and left sides of the septum have no typical “curled flanges with serrate edges” as in T. maxilla ( Hedley 1899, fig. 57; Cooper 1954, pl. 81, fig. 10).

Non T. maxilla in Bitner (2009, pp. 17–18; fig. 12A–J). These specimens display a peripheral ridge with strong tubercles and a median septum without lateral flanges. In T. maxilla the peripheral ridge is nearly smooth or finely granulated. The space between the brachial bridge and intrabrachial ridge is larger than in T. maxilla. The ventral valve is not emarginate as in the type specimen and has a rough valve floor whereas it is nearly smooth in T. maxilla. The cardinal process and socket ridges are much stronger than in the type population of T. maxilla. These specimens could be representatives of another species derived from the same group as T. maxilla but it needs genetic confirmation.

Non T. maxilla in Bitner (2014, p. 259, fig. 11D–E). These ventral valves have a floor with extremely thick tubercles whereas this surface in the T. maxilla is smooth or finely granulate. The gonad pits are situated more posteriorly and they are much smaller than in T. maxilla or in T. mawaliana sp. nov. Moreover, it has a narrow median groove devoid of tubercles (not a ridge), a character not seen in T. maxilla. They are also not similar to T. mawaliana sp. nov.: in the new species, the valve floor displays much smaller tubercles, the hemispondylium is attached to the bottom of the valve floor for only a short part of its length and the gonad pits are larger.

Non T. maxilla in Bitner (2015, fig. 5A–E). Canopying spicules are different from the type of T. maxilla, being single and very massive in the anterior part of the brachial cavities and being extremely small and pointed in the posterior part. The typical “curled flanges with serrate edges” of the median septum are missing. These specimens are representatives of T. congregata (see hereunder).