Abyssomelania cramptoni

Kaim, Andrzej, Jenkins, Robert G., Tanabe, Kazushige & Kiel, Steffen, 2014, Mollusks from late Mesozoic seep deposits, chiefly in California, Zootaxa 3861 (5), pp. 401-440: 414-416

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Abyssomelania cramptoni

sp. nov.

Abyssomelania cramptoni   sp. nov.

( Fig. 6 A –E View FIGURE 6. A – E )

2013 “Abyssochrysoid gastropod”; Kiel et al. 2013, p. 32, fig. 15 I –L.

Type locality and strata: Seep limestone from the south end of Waipiro Bay, North Island, New Zealand;. For Campanian (Late Cretaceous). For details see Kiel et al. (2013).

Holotype: GNS TM 8852, four well-preserved adolescent whorls, 28.7 mm high and 12.8 mm wide.

Paratypes: GNS TM 8850, - 51, - 53, well to moderately preserved adolescent shells; GNS TM 8927, juvenile shell.

Additional material: 5 fragmentary specimens from the type locality.

Diagnosis. Tall gastropods (reaching 30 mm in length) with smooth lateral flanks of the adolescent/adult shell and spirally ornamented base. The growth lines opisthocline with angulation in the upper part of the lateral flank. The largest diameter of the whorls in the lower part of the lateral flank.

Description. Tall shell with largest whorl diameter slightly above abapical suture. Protoconch unknown. Juvenile teleoconch ornamented by opisthocline axial ribs and delicate striae. Axial ribs fading out in adolescent shell, adult shell surface smooth apart from opisthocline growth lines and abyssomelanid riblets appearing at the terminal (?) teleoconch whorl. Shell base ornamented by ten spiral ribs intersected by growth lines without knobs. Suture weakly incised. Aperture poorly preserved, D-shaped.

Remarks. This species was preliminarily identified as “Abyssochrysoid gastropod” by Kiel et al. (2013) pending formal description. Together with A. campbellae   n. sp. described below it forms a distinctive genus that inhabited ancient hydrocarbon seeps. Abyssomelania cramptoni   is much smaller than A. campbellae   and has weaker and more numerous spiral ribs on the base. The greatest diameter of the whorl is higher above the abapical suture giving more bulgy appearance than in A. campbellae   . The growth lines of A. cramptoni   are angulated in the upper part of the lateral flank while in A. campbellae   the growth lines are angulated in the middle of the lateral flank.

Etymology. For James S. Crampton, who made the field work in New Zealand possible.