Dispiriferina sp. cf. D. chilensis ( Forbes, 1846 )

Macfarlan, Donald Alexander Bankier, 2023, Latest Triassic and Early Jurassic Spiriferinida (Brachiopoda) of Zealandia (New Zealand and New Caledonia), Zootaxa 5277 (1), pp. 1-58 : 30

Dispiriferina sp. cf. D. chilensis ( Forbes, 1846)

Fig. 18 : 7, 8.

Material. Two ventral valve internals, C2061 and C2062, from Ben Bolt: E45/f9446 ( JDC 737).

Description. Medium sized spiriferinide, slightly wider than long, (dorsal valve 20–21 mm long, 22.7 and 25.9 mm wide). with hingeline about two-thirds of valve width. Maximum width posterior of half valve length. Lateral and anterior margins convex. Flanks moderately convex, with shallow, poorly defined sulcus. C2062 ( Fig. 18.7 ) has about eight moderately strong rounded costae on each flank, and a shallow, poorly defined sulcus with five more bluntly rounded costae. Part of the right flank is damaged. C2061 ( Fig. 18.8 ) is of similar size and shape but has a better-defined concave sulcus with about three barely discernible costae.

Area low, triangular, with rounded apex, open delthyrium. Median septum narrow, about 0.3 of valve length, dental plates thicker but short. Posterior part of valve with thickened muscle field.

Dimensions. Dimensions of both specimens are shown in Table 7.

Range and Distribution. Mid-Aratauran of Ben Bolt, Otapiri Valley .

Remarks. These two specimens are the only Zealandian Jurassic spiriferinides seen to date with costae developed in the fold and sulcus.

Forbes (1846) described Spirifer chilensis from material collected on the Beagle Expedition (1831–1836) from the Jurassic of Chile and sent to him by Charles Darwin. The species was redescribed by Manceñido (1981) as Spiriferina chilensis from the Lower Jurassic of Neuquén Province, Argentina. It is listed by Aberhan (1993) from the Sinemurian of Chile, where it is the essential element of the Spiriferina chilensis association.

Manceñido (1981) suggested that “a case could be made for the retention of Siblík’s Dispiriferina as a subgenus of Spiriferina (s.l.) in which S. chilensis could probably be accommodated” (p. 652). This proposal is accepted here, with Dispiriferina treated as a genus as in Siblík (1965) and subsequent authors.

The New Zealand specimens are generally similar to D. chilensis but are smaller and less inflated than the specimens figured by Forbes (1846) and Manceñido (1981).

Figures

FIGURE 18. Callospiriferina radiata. (x3). 1 OU 47167 (E45/f9860) dorsal valve, latex of interior. 2 OU 46818 (E45/f9860) dorsal valve, latex of interior. 3 C4258 (E45/f9860 dorsal valve, latex of interior. 4 C3048 (E45/f9860) dorsal valve, latex of interior. 5 BR 3287 (E45/f9860) internal mould of ventral valve, latex of interior. 6 OU 46872 (E45/f0085) (a) internal mould of dorsal valve, (b) part of valve enlarged to 20x to show impressions of punctae. Dispiriferina sp. cf. D. chilensis (x3). 7 C2062 (E45/f9116) internal mould of ventral valve. 8 C2061 (E45/f9116) internal mould of ventral valve.