Talochlamys williamsoni (Zittel, 1865)
ZITTEL, K. A. 1865. Fossile Mollusken und Echinodermen aus Neu-Seeland. In F. von Hochstetter, M. Hörnes & F.R. von Hauer (Eds.), Paläontologie von Neu-Seeland. Reise der Österreichischen Fregatte Novara, Geologischer Theil, 1 (2): 15-68, pls. 6-15. [p. 50, pl. 9, fig. 11a-11c]
1864 Pecten williamsoni Zittel, 1865
K. A. Zittel, 1865, plate 9.
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«Char. Testa subrotundata, altior quam longa, aequivalvis, paullo convexa, regulariter radiatim costata. Costae viginti quinque ad triginta, medianae inornatae, laterales sparsim squamosae. Auriculae inaequales, costis squamosis ornatae.
Höhe 20 — 40 Millim., Länge 17 —35 Millim. Die Schale dieser häufig vorkommenden Art ist gerundet, höher als lang und von regelmässiger Form. Die Oberfläche mit etwa 20—25 geraden Radialrippen bedeckt, von denen der grössere Theil abgerundet und unverziert ist; zuweilen, vornehmlich bei jungen Exemplaren, zeigen jedoch die Seitenrippen vereinzelte, ziemlich entfernt stehende dachziegelfÖrmige Schuppen. Die Zwischenfurchen sind wenig breiter, als die Rippen und von starker concentrischer Zuwachsstreifung bedeckt, die auch über die Rippen fortsetzt. Die Ohren sind sehr ungleich und tragen fünf schuppige Rippen. Name nach Herrn J. Williamson, Superintendent der Provinz Auckland. Vorkommen: Aotea-Hafen (häufig).» KARL ALFRED VON ZITTEL, 1865
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«Type material. Pecten williamsoni four syntypes NHMW 1959/335/44/14; three plaster replicas GNS TM4208-4210. The specimen illustrated here, NHMW 1959/335/44/1 (Fig. 15A; that illustrated by Zittel 1865, pl. 9, fig. 11b) is here designated the lectotype of Pecten williamsoni Zittel, as it is possible that the remaining syntypes are not conspecific; from locality 4, Orotangi Sandstone member of Whaingaroa Formation (Whaingaroan, Oligocene), Puketoa Point, Aotea Harbour (Boreham 1965, p. 22). More specimens from this locality are present in GS6719 (R15/f6011). The species was named after John Williamson, Superintendent of Auckland Province during Hochstetter’s visit (Zittel 1865, p. 51).
Dimensions. Lectotype: H 36.5, L 33.0 mm; paralectotype, Zittel’s (1865, pl. 9, fig. 11a), interior illustrated: H 28.2, L 25.2 mm; small unfigured right valve paralectotype: H 9.2, L 8.5 mm.
Remarks. The lectotype of Pecten williamsoni has fairly regular, even radial costae with few subdivisions or intercalated secondary costae, apart from narrow secondary costellae appearing in the centres of the primary interspaces around the ventral margin. The interior of the right valve paralectotype illustrated by Zittel (1865, pl. 9, fig. 11a) reveals no internal rib carinae. Its hinge has prominent resilial and dorsal teeth only, with deep intermediate pits. The lectotype has 27 radial costae, counting the two narrow costae on each end of the disc. Its surface bears low commarginal ridges, raised into lamellae over the radial costae in some places, c. 0.6–0.7 mm apart near the ventral margin, curving slightly towards the venter in the radial interspaces. The right valve paralectotype in Zittel’s (1865, pl. 9, fig. 11c) figure is much less inflated than the lectotype left valve, and its radial costae are a little narrower and more widely spaced than on the lectotype. It bears 29 radial costae, including three and a very weak fourth intercalated between the primary costae on the anterior end of the disc c. 10 mm from the umbo, two intercalated on the posterior end c. 7 mm from the umbo, one primary costa in the centre of the disc subdivided into two c. 4 mm from the umbo, and another secondary costa intercalated alongside the subdivided one c. 4 mm from the umbo. These characters demonstrate that T. williamsoni is best referred to Talochlamys. The fine ‘herringbone pattern’ microsculpture characteristic of Mimachlamys (Waller 1991) is not visible on any of these specimens, but their surfaces are a little abraded. However, the subdivision and intercalation of radial costae (characteristic of Chlamydini; Waller 1991) and the lack of internal rib carinae demonstrate that P. williamsoni is better located in Talochlamys than in tribe Mimachlamydini. T. williamsoni appears to be closely related phylogenetically to the Australian species group of T. keiloriana (Crespin, 1926) (Beu & Darragh 2001, p. 108, figs 32H, I, 36A-H, 37A-H), that is, it seems to belong in Talochlamys (sensu stricto). The small right valve paralectotype has complete auricles; the long, pointed anterior auricle projects beyond the edge of the strongly opisthocline disc, whereas the posterior auricle is very short, with a concave posterior margin. Boreham (1965, pp. 21-22) pointed out that the Duntroonian (late Oligocene) species from Southland, Otago and Canterbury, T. chathamensis (Hutton, 1873b), has fewer (20-23, mean 22) radial costae but is otherwise similar to T. williamsoni (24-27 radial ribs, mean 26).
Two further specimens labelled as Pecten williamsoni are present in NHMW, but are not type material as they were not mentioned by Zittel. NHMW 1865/XXXVII/94 is a small left valve interior in grey sandstone, with the same locality data as the lectotype (H 19.4, L 17.6 mm). NHMW 1865/XXXVII/95 is a very incomplete specimen, seen largely as a cross-section, consisting of orange-brown shell material in a fawn matrix, and is evidently from a different locality from the other material; it lacks a locality label and its identity is uncertain. Suter (in Bartrum 1919, p. 105) identified juvenile specimens from Kaawa Creek, coast south of Waikato Heads, Southwest Auckland (Opoitian, early Pliocene), as Chlamys williamsoni, but Laws (1936, p. 50) dismissed this identification ‘until better material is available’. This Whaingaroan (Oligocene) species does not occur at Kaawa Creek, and Bartrum’s (1919) record would have been based on one of the younger Talochlamys species such as T. zelandiae (Gray, 1843).» BEU, A. G., S. NOLDEN & T. A. DARRAGH. 2012. Revision of New Zealand Cenozoic fossil Mollusca described by Zittel (1865) based on Hochstetter’s collections from the Novara Expedition. Memoirs of the Association of Australasian Palaeontologists, 43: 1-69, figs. 1-21. [p. 38]
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Talochlamys williamsoni (Zittel, 1865); A. G. Beu, S. Nolden & T. A. Darragh, 2012, Revision of New Zealand Cenozoic fossil Mollusca described by Zittel (1865) based on Hochstetter’s collections from the Novara Expedition, figure 15A.
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