Spiriferina arakiwa Macfarlan 2023, new species
Creators: name: Macfarlan, Donald Alexander Bankier
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Brachiopoda
Rhynchonellata
Spiriferinidae
Spiriferina
Spiriferina arakiwa

description: Spiriferina arakiwa new species
Fig. 7: 1–13, Fig. 8A.
2009 Spiriferina n. sp. B; MacFarlan et al. p. 266.
Holotype. OU 15292, a double-valved internal mould and partial external, from H46/f056, McF H25, Jewitt Road, southern Hokonui Hills. Collected by J.D. Campbell and the author, 9 March 1982. The specimen is distorted.
Derivation of name. Ara-a-kiwa (the whales’ way) is the Māori name for Foveaux Strait between the south coast of the South Island and Stewart Island or Rakiura. The new species is present in several localities along the southern limb of the Southland Syncline close to the strait. The name arakiwa is proposed as a noun.
Material. A total of 21 specimens were catalogued from seven collections, of which 15 yielded valid measurements.
Kawhia Syncline. Taharoa: R 16/f6811 (AU154).
Southland Syncline. Otapiri Valley: Conical Hill E45/f8960 (JDC 1837), E45/f0061 (McF C9).
Heale Ridge: E45/f0085 (McF E49). Jewitt Road, S. Hokonui Hills: E46/f0056 (McF H25). Crighton Road, Waimahaka: F47/f0013 (JDC 3796). Waikawa Valley: G47/f6523 (GS 7061).
Description. Medium sized spiriferinide, wider than long (most specimens with ventral valve 10–24 mm long, 10–32mm wide). Hingeline long, straight with rounded cardinal extremities, rounded flanks and anterior margin. Maximum width in posterior part of valves. Dorsal valve moderately convex, ventral valve more inflated with wide area and distinct sharply rounded apex. Ventral interarea flat, broadly triangular. Narrow, well-developed angular fold in dorsal valve, corresponding v-shaped sulcus in ventral valve. Flanks of each valve with 4 to 5 strong costae with rounded crests and troughs. Anterior commissure deflected by narrow uniplication. Shell coarsely punctate.
Concentric ornament of foliaceous growth lamellae on both valves, stronger and more closely spaced near the anterior margin. Some specimens show the bases of widely spaced spines, which are more closely spaced near the anterior margin (Fig. 7.13, Fig. 8A). Other specimens do not show spines, possibly as a result of wear. Spines are poorly shown on the holotype, but a few show small matrix plugs indicating that they are hollow and tubular.
Internal Characters Dorsal valve with broad, thin concave hinge plates and small, close-set sockets (Fig. 7.11b). Cardinal process small, not prominent. Ventral valve with short, narrow median septum and short dental plates which are thick and rounded posteriorly. Delthyrium triangular, open.
Dimensions. Dimensions of the holotype and representative specimens, and statistics for all specimens with valid measurements are shown in Table 1.
Range and distribution. Ururoan (Pliensbachian—Early Toarcian). The distribution is unusual, with three of the six localities on the southern limb of the Southland Syncline.
Remarks. The new species resembles the type species of Spiriferina (S. walcotti), from the Hettangian and Sinemurian of Europe (Ager 1994), in having strong costae and a narrow v-shaped fold, but S. walcotti is more rounded in outline with a proportionally shorter hingeline and less well-developed interarea. It is possibly closer to the European S. muensteri, which has blunter costae, and a beak which projects more strongly posteriorly and not as high an area. The larger size distinguishes it from the much smaller, very strongly costate S. sophiaealbae Fig. 10A).
OU 47225 from the Otapiri Gorge (E45/f0061) is small, with a high ventrally-projecting apex, but is distorted (Fig. 7.12a,b). It may represent a different species. Other specimens in the same collection are more typical of S. arakiwa (Fig. 7.7). Callospiriferina radiata is present in the same collection.
description: Published as part of Macfarlan, Donald Alexander Bankier, 2023, Latest Triassic and Early Jurassic Spiriferinida (Brachiopoda) of Zealandia (New Zealand and New Caledonia), pp. 1-58 in Zootaxa 5277 (1) on pages 9-11, DOI: 10.11646/zootaxa.5277.1.1, http://zenodo.org/record/7891491