Tibetothyris hamishi MACFARLAN 2023, n. sp.
Creators: name: MACFARLAN, DONALD ALEXANDER BANKIER
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Brachiopoda
Rhynchonellata
Terebratulida
Dielasmatidae
Tibetothyris
Tibetothyris hamishi

description: Tibetothyris hamishi n. sp.
Fig. 7 1–9, 8A–B.
2019: Aulacothyris sp. A MacFarlan p. 574, fig. 13 a-d. (NZGS BR 3207 only).
Holotype. OU 47309, a shelly specimen with an external mould of the dorsal valve and beak, from F45/f329, JDC 4216, west of Dolamore Park, Hokonui Hills. Collected by J.D. Campbell and S. R. Owen, 21/10/1992. Shell material altered to clay or zeolite.
Derivation of name. This species is named for Dr Hamish Campbell of GNS Science.
Material. The data series consists of fifteen specimens, thirteen of which yielded valid measurements.
New Caledonia. île Ducos: NC/f050 (GS 12763), NC/f0087 (AU 7168)
Kawhia Syncline. Coast south of Arataura Pt: R 15/f8837 (AU 69), R 15/f8838 (AU 70). North Marokopa Coast: R 16/f6898 (GS 10009), R 16/f8645 (? GS 10006). Marokopa: R 16/f0337 (AU 12074). Pomarangai Rd E of Moeatoa: R 16/f8877A (AU 8987).
Southland Syncline. Otapiri – Taylors Stream: E45/f0279 (JDC 4059), E45/f9622 (JDC 1296). Dolamore Park: F45/f0329 (JDC 4216). Waimumu Valley: F45/f8523 (GS 5188).
Description. Small to medium sized terebratulide with elongate elliptical outline. The dorsal valve is moderately convex posteriorly and flatter anteriorly, with a shallow, rounded sulcus developing close to the beak and extending anteriorly.
The ventral valve is strongly convex posteriorly. The anterior part has concave flanks, and a strongly convex central part. The anterior commissure is shallowly sulcate. The shell surface is smooth or has a few strong, stepped concentrics anteriorly. Punctae are coarse and closely spaced.
The beak is large and triangular with a bluntly rounded tip. The foramen is large, circular, mesothyrid, and is surrounded by a short pedicle collar (Fig. 7.1a, 7.3a, 8B). The beak ridges are strong, bluntly rounded. Deltidial plates are poorly shown and are small and widely disjunct (fig. 7.1a, 7.3a).
On the dorsal valve the hingeplate has a broad, shallow U-shaped septalium supported by a wide, shallow median septum with fine longitudinal grooves which appear to be muscle attachments (Fig 7.8a, 8A, B), and a small cardinal process (Fig. 8B). The posterior tip of the dorsal valve reaches the anterior of foramen. The dental plates are short, widely separated and divergent (Fig. 7.8a, b, 8B).
Dimensions. Dimensions of the holotype and representative specimens, and statistics for all measurable specimens are shown in Table 2. A length vs width graph is shown in Fig. 9A.
Range and Distribution. Otapirian of New Caledonia, Kawhia Syncline and Southland. Nearly all the material is late Otapirian, but the specimen from NC/f0087 (île Ducos, New Caledonia) is early Otapirian.
Remarks. The shape is distinctive. Specimens from the Oretian and Otamitan of Southland are of similar shape and size but lack the strongly convex central part and concave flanks of the new species. From the limited material examined, they appear to belong to a separate but related species.
BR 3207 (R16/f6898, GS 10009) was figured in MacFarlan (2019, fig 13:13a-d) as Aulacothyris sp. A. It is badly distorted, but re-examination shows that it is much better placed in the new species.
This species is larger than T. johnstoni, less inflated, and lacks the strong folding on the ventral valve. The dental plates are short and widely separated, resembling those of T. johnstoni rather than T. depressa.
description: Published as part of MACFARLAN, DONALD ALEXANDER BANKIER, 2023, Otapirian (Rhaetian) Terebratulida (Brachiopoda) of Zealandia, pp. 1-34 in Zootaxa 5374 (1) on pages 9-12, DOI: 10.11646/zootaxa.5374.1.1, http://zenodo.org/record/10148159