Propeamussium zitteli (Hutton, 1873)
HUTTON, F. W. 1873b. Catalogue of the Tertiary Mollusca and Echinodermata of New Zealand, in the collection of the Colonial Museum. Wellington, Government Printer, for Colonial Museum and Geological Survey Dept. xvi + 48 p. [p. 32].
1873 Pecten zitteli Hutton, 1873
Pecten sp.; K. A. Ziettel, 1865, Fossile Mollusken und Echinodermen aus Neu-Seeland, plate 9, figures 1b, 3.
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«118. P. zittelli, Pecten (belonging to the group P. pleuronectes), Zittel, Voy. Novara, Palae., p. 53. Sub-orbicular, compressed, smooth, with eleven internal ribs, which do not reach to the margin of the valves, the two upper ones very short; ears equal, obtuse, smooth. Height, .85 ; length, .8.
Localities.— Poverty Bay (L) ; Whangape Lake, Waikato; coast between Raglan and Port Waikato; Papakura (Hochstetter); Cape Kidnappers; Cobden.» FREDERICK WOLLASTON HUTTON, 1873
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«Type material. Pecten zitteli Hutton lectotype (of Boreham 1965, p. 35, pl. 5, fig. 7) GNS TM2845, Hutton’s (1873b) specimen from Whangape Lake, Waikato (Whaingaroan, Oligocene). Zittel’s (1865, pl. 9, fig. 3) illustrated specimen of ‘Pecten sp.’, from locality 2, Hunua Range near Papakura, was one of the specimens included in Pecten [now Propeamussium] zitteli by Hutton (1873b, p. 32), so it is a paralectotype of P. zitteli. This specimen is still in NHMW, according to Flügel (1959, p. 838), with registration number NHMW 1959/335/45, although I did not see it. Replicas (TM4255, 4256) of Zittel’s illustrated specimens are held in GNS. The identity of Amussium papakurense Clarke, 1905 needs to be clarified from better material, and presumably a neotype, before its synonymy with P. zitteli is certain; the location of Clarke’s type material is not known to me.
Remarks. Boreham (1965, p. 35, pl. 5, fig. 7) described and illustrated the lectotype of Propeamussium zitteli (Hutton, 1873b). Beu (1970b) and Beu & Maxwell (1990, p. 243-244) commented on the difficulties of identifying these small, thinshelled species, most of which are represented by fragile, incomplete material, in many cases merely internal moulds. The sculpture on the left valve differs more between species than that on the right (Maxwell 1988, p. 45), and it is essential to describe well preserved left valves to establish species unequivocally. P. zitteli is one of a poorly known group of Propeamussium species occurring throughout New Zealand in Eocene to late Miocene bathyal mudstone, as well as in the living fauna. Clarification of this and the following species requires further research beyond the scope of this paper.»
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. 26]
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«LECTOTYPE (TM 2845), a cast in fine mudstone of a double-valved individual. The internal impression of the right valve is superimposed on the external impression of the left.
TYPE LOCALITY: Whangape Lake, Waikato. Age, Whaingaroan (Lower Oligocene).
ORIGINAL DESCRIPTION: "Sub-orbicular, compressed, smooth, with eleven internal ribs, which do not reach to the margin of the valves, the two upper ones very short; ears equal, obtuse, smooth. Height, .85; length, .8."
REDESCRIPTION (based on the lectotype): Shell small, very thin, subcircular in outline, slightly higher than wide. Ears of left valve small, equal, their dorsal margins short, with rounded obtuse angles at the extremities; ears of right valve not preserved. Exterior of left valve sculptured by fine, regularly spaced, concentric grooves; exterior of right valve not preserved. Interior of right valve having about eight or more strong spaced ribs, not extending to the ventral shell margin; interior of left valve not preserved.
DIMENSIONS: height, 21 mm; length, 20 mm.
REMARKS: Marwick (1928, p. 452) located Pecten zitteli Hutton in Parvamussium Sacco, type Pecten duodecim-Iamellatus Bronn, described as having subequal ears, internal radial ribs, and external sculpture of fine concentric grooves on both valves (see Grant and Gale, 1931, p. 235; Woodring, 1925, p. 74). The lectotype of P. zitteli certainly has subequal ears, internal radial ribs, and distinct concentric grooves on the exterior (at least on the right valve). Hutton originally described his species as smooth, but he could have been referring to a different specimen or species from another of the localities he listed. Small, thin shells with equal or subequal ears, internal ribs, and both valves smooth or finely concentrically striated, which occur in rocks of suitable (deep water) facies through the Tertiary of New Zealand, have usually been placed in Parvamussium zitteli Hutton. The limits of variation within the species, or even with the group, are difficult to assess: the shells are fragile, often only internal casts are preserved, and seldom are right and left valves found associated. A Recent species has been described from the New Zealand archibenthal zone, namely P. maorium Dell (1956, p. 20, fig. 30, 31), which differs from P. zitteli in having markedly unequal ears, with moderately deep byssal sinus in the right anterior ear, and slightly discrepant sculpture on opposite valves.»
BOREHAM, A. U. E. 1965. A revision of F. W. Hutton's pelecypod species described in the Catalogue of Tertiary Mollusca and Echinodermata. New Zealand Geological Survey Paleontological Bulletin, 37: 1-125, pls. 1-20. [p. 35, 36]
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Parvamussium zitteli (Hutton); A. U. E. Boreham, 1965, A revision of F. W. Hutton's pelecypod species described in the Catalogue of Tertiary Mollusca and Echinodermata, plate 5, figure 7, Lectotype, left and right valves (TM 2845).
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