Abyssomelania cramptoni, Kaim, Andrzej, Jenkins, Robert G., Tanabe, Kazushige & Kiel, Steffen, 2014

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

Abyssomelania cramptoni sp. nov.

( Fig. 6A–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 TM8852, four well-preserved adolescent whorls, 28.7 mm high and 12.8 mm wide.

Paratypes: GNS TM8850, -51, -53, well to moderately preserved adolescent shells; GNS TM8927, 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.

Figures

FIGURE 6. A – E. Abyssomelania cramptoni sp. nov. from Campanian (Late Cretaceous) seep carbonates at Waipira III, New Zealand. A. Paratype (GNS TM 8851). B. Paratype (GNS TM 8850), C. Paratype (GNS TM 8853). D. Holotype (GNS TM 8852), the arrow indicates the abyssomelanid riblet. E. Juvenile (GNS TM 8927). F. Hokkaidoconcha occidentalis (Stanton, 1895) from Tithonian (Late Jurassic) seep carbonates at Paskenta, Tehama County, California, USA; GZG. INV. 84981. G – N. Abyssomelania campbellae sp. nov. from Albian (Early Cretaceous) seep carbonates at Cold Fork of Cottonwood Creek, Tehama County, California, USA. G – H. Paratype (GZG. INV. 84983). I-K. Holotype (GZG. INV. 84982). L – M. Paratype (GZG. INV. 84984). N. Paratype (GZG. INV. 84985).