Towaipecten katieae Beu, 1995
BEU, A. G. 1995. Pliocene Limestones and their scallops. Lithostratigraphy, pectinid biostratigraphy, and paleogeography of eastern North Island late Neogene limestone. Institute of Geological & Nuclear Sciences Monograph 10. Institute of Geological and Nuclear Sciences, Ltd., Lower Hutt, New Zealand, 243 p. [p. 50, figs. 21a, 22a-c]
1995 Towaipecten katieae Beu, 1995
A. G. Beu, 1995, figure 21.
A. G. Beu, 1995, figure 22.
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«DESCRIPTION: Shell 93-130 mm high, most adult specimens 110-120 mm high, length approximately equal o height (h/l ranges from 0.93 to 1.04), weakly inflated, left valve more inflated than right. Sculpture of very low, wide radial costae, 28 to 36 primary costae on material seen (mean 31, frequency maximum 29 costae); RV costae uniform, smooth and strap-like, with a single secondary costa almost filling each interspace, all moderately prominent over umbonal half of disc but fading out progressively over ventral half so ventral margin of large specimens bears only weak commarginal growth ridges; LV costae relatively high and rounded over umbonal quarter to third of disc, lower and progressively wider over remainder of disc, remaining obvious to ventral margin, with one (or, on a few costae, 2-4) shallow subdividing grooves, and a single low, wide secondary costa filling each interspace over umbonal half of disc (commencing 20-30 mm from umbo), widening and becoming weakly subdivided over ventral half of disc to produce an appearance, near ventral margin of large shells, of very many very low, wide, similar strap-like costae. No radial plicae observed on any specimens.
Radial interspaces and ventral areas of auricles bear numerous low, thin, sharp, moderately widely spaced, simple, arcuate commarginal lamellae. Auricles small, with weakly sinuous anterior and posterior margins as described for genus, shallow but obvious byssal sinus remaining on right anterior ear of large adults. Radial costae reflected on interior by weak, rounded, poorly defined internal costae, developing into prominent, sharp rib carinae over outermost 15 mm of large specimens. Margins smooth, straight in plane of commissure, i.e. not crenulated by radial costae or internal rib carinae. Hinge with wide, shallow resilifer and weak, narrow resilial teeth; remainder of interior not seen. DIMENSIONS: See Appendix B. TYPE MATERIAL: GS/14852, U23/f188, U23/047267, banks of small tributary of Maharakeke Stream 50 m west of junction of Waiou Road and Marakeke Road, 1 km north of Hatuma Quarry, east of Takapau; Te Onepu Limestone, with Phialopecten thomsoni (holotype, TM7670, and seven paratypes); GS11513, U24/f6209, U24/770831, shellbed on side of small valley 100 m southeast of Towai Road, 400 m west ofcrest of central Puketoi Range; Te Onepu Limestone, with Phialopecten thomsoni (2 pantypes); GS14795, T25/f135, T25/609689, Makuri quarry, north side of Makuri-Owahanga Road at southern entrance to Makuri Gorge, east of Pahiatua; Te Onepu Limestone, with P. thomsoni (17 paratypes). OTHER MATERTAL EXAMINED: (a) Te Onepu Limestone: GS14806, T25/f131, T25/611667, hilltop south of Pori Road at large depression in southern Puketoi Range (2 poor, incomplete); GS14668, U23/f165, U23/048267, track cutting in bank of tributary of Maharakeke Sneam 50 m south of type locality (3, incomplete); GS4455, U24/f6457, U24/777833, crest of Puketoi Range north of Towai Road (one poor; lithology as for GS11513, above); GS2440, V22/f8489, V22/141422, quarry, Argyll Road, Otane (several fragments). (b) Seconds Ridge Conglonarate: GS12421, U21/f5, U21/972802, seconds ridge, 3 km north of Ruahine Hut on northem Ruahine Range crest (3 poor; with one fragment of T. mariae, moderately common P. thomsoni, rare Z. delicatula); GS1485, U21/f8500, U21/972802, Waghorn's (1927) collection from above locality (2 poor, with P. thomsoni). (c) Kaumatua Formation: GS12481, U21/f9, U21/933667, shellbeds in grey sandstone 100 m upstream from Mangleton Road, Jumped-up Stream, Ohara Depression (2 poor, incomplete, with P. thomsoni). REMARKS: Towaipecten katieae n.sp. closely resembles T. mariae, but reaches a slightly larger size, has more prominent radial costae on the umbonal half of the left valve and, above all, lacks the prominent plicae that are present on all specimens of T. mariae. The sculptural and size differences ate slight, apart from the presence or absence of plicae, and there can be little doubt that T. katieae was the direct ancestor of T. mariae. AGE: Towaipecten katieae is almost entirely limited to Mangapanian rocks; specimens from Seconds Ridge Conglomerate are construed as basal Nukumaruan. ETYMOLOGY: The new species is named for my daughter Katie, who helped collect the type specimens from both Maharakeke Stream and Towai Road.» ALAN GLENN BEU, 1995
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