Borehamia Beu, 1978
BEU, A. G. 1978. Taxonomy and biostratigraphy of large New Zealand Pliocene Pectinidae (Phialopecten and Mesopeplum). New Zealand Journal of Geology and Geophysics, 21: 243-269, figs. 1-30. [p. 259]
« Mesopeplum Iredale, 1929
[...] Subgenus Borehamia n. subgen.
TYPE SPECIES: Pecten crawfordi Pliocene, New Zealand.
A group of New Zealand fossil species apparently related to Mesopeplum differs from species listed above in Mesopeplum (Mesopeplum) in reaching a much greater size, at least in later members of lineages (up to 125 mm in M. crawfordi), in having much weaker radial folds (almost lost in M. hilli), in having the right valve much more inflated than the left, in having small, almost square, equilateral ears lacking the byssal notch and sinus, and in having radial ribs that are more raised, more widely spaced, and more nearly square in section than those of Mesopeplum (sensu stricto). The lack of the byssal sinus and notch and the marked difference in convexity between the two valves indicate that its mode of life was lying on the sea bed with no byssal attachment in adulthood, and swimming frequently. The new subgenus Borehamia is proposed for this group of species.
Superficially similar overseas pectinid generic groups such as Flexipecten, Nodipecten, and Swiftopecten were all considered by Hertlein (1969, p. N355) to be related to Chlamys, and have either equally convex valves or the left valve more inflated than the right. No overseas Pectinidae I am aware of exhibit the combination of features of Mesopeplum (Borehamia), which seems to be an endemic New Zealand group. Species included in the new subgenus are listed here, and the Pliocene ones discussed more fully below: Mesopeplum (Borehamia) crawfordi (Hutton, 1873), Waipipian, Wairarapa, "Maunga-Pakeha Taipo" (Opoitian?; Waipipian of Wanganui, Hawkes BayWairarapa, North Canterbury; Nukumaruan of Wanganui).
M. (B.) aff. crawfordi (Hutton) of Boreham (1961, p. 655, fig. 1, p. 667), Waiauan (middle or upper Miocene), North Canterbury. M. (B.) hilli (Hutton, 1873), ?Nukumaruan, Napier (Opoitian to Mangapanian, Wanganui and Hawkes Bay). M. (B.) aff. hilli (Hutton) discussed below, Altonian (Lower Miocene) of North Canterbury. M. (B.) toaense (Marwick, 1928), Kapitean (Upper Miocene and basal Pliocene), Chatham Islands (Kapitean, Chatham Islands and Wairarapa). The new subgenus is named after Anne U. E. Boreham (Mrs G. H. Scott), formerly of N. Z. Geological Survey, in honour of her valuable contributions to New Zealand stratigraphy and molluscan taxonomy, and particularly to Hawkes Bay Plio-Pleistocene stratigraphy and the taxonomy of Pectinidae.»
ALAN GLENN BEU, 1978
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Mesopeplum (Borehamia ) crawfordi (Hutton); A. G. Beu, 1978, Taxonomy and biostratigraphy of large New Zealand Pliocene Pectinidae (Phialopecten and Mesopeplum), figure 3.
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