380


Journal of Paleontology 92(3):373–387


convex whorl. Apical ornamentation, he said, is characterized by “unicarinate” spiral ornamentation, but he did not specify the primary spirals (i.e., the apical ontogenetic formula). In T. jadavpuriensis, however, all three primary spirals appear simultaneously (formula A1B1C1d2). Zaria angulata (Sowerby, 1840) from the Miocene


sediments of Kutch (Vredenburg, 1928; Harzhauser et al., 2009, p. 343, fig. 3A–D; Kulkarni et al., 2010, p. 314, fig. 2g) is similar to the slender variant of T. jadavpuriensis. Both have a similar imbricate whorl profile, basally bicarinate shell and relatively less-strong keel in comparison with the inflated variant of the present species. Growth line patterns, however, differ in these two species: Z. angulata is characterized by opisthocline growth lines, while T. jadavpuriensis has proso- cline growth lines. Moreover, T. jadavpuriensis is larger than Z. angulata and has a more acute apical angle compared to Z. angulata. Unfortunately, the nature of apical ornamentation is not known for Z. angulata.


Turritella jhuraensis Mitra and Ghosh, 1979 Figures 9.1–9.3, 10.1–10.3


Type.—Neotype: specimen no. ISI/g/Jur/T 31.


Occurrence.—This species is known only from the Oxfordian horizons ~ 1km south-east of the village of Jhura near a pond, Kutch (23°24’47.57”N, 69°36’09.26”E).


Figure 8. Sketch of growth line patterns in Turritella jadavpuriensis Mitra and Ghosh, 1979. Note wide intraspecific variability of growth line traces. For full description of the patterns see text. (1–4) Abapertural views (maximum diameters: (1) 16.1mm, (2) 14.5mm, (3) 15.1mm, (4) 15.3mm) with broken aperture.


sculpture, and siphonotomatous aperture clearly differentiate it from T. jadavpuriensis. Turritella jadavpuriensis might be compared with


Turritella woodsi Lisson, 1925 from the Oligocene to Miocene of southern Peru (DeVries, 2007, p. 341, fig. 6.8–6.14) in having keeled ornamentation. However, the position of the keel differs in these two species. In T. jadavpuriensis, the keel is anteriorly (abapically) placed while in T. woodsi the keel is located posteriorly (adapically). Moreover, the Peruvian species attains very large size (up to 110mm) and has more whorls. Turritella jadavpuriensis is also distinguished from T. woodsi in growth line pattern: growth line formula 3-3-M-A/C-P in T. jadavpuriensis versus 5/4-1/2-D-B-P/OR in the Peruvian species.


Eames (1952) identified Turritella imbricataria Lamarck,


1804 from the Eocene of Pakistan, based on a single fragmentary specimen whose apical part was, however, well preserved, and he placed it within the genus (or subgenus) Haustator. This species resembles T. jadavpuriensis in being basally (abapically) carinate. Eames (1952) provided a detailed description of the apical ornamentation (which was very rare in those days). According to him, the Pakistani T. imbricataria is characterized by a smooth, rounded protoconch with one


Description.—Shell small to medium in size with five to eight whorls. Maximum observed whorl diameter 8.5mm; maximum observed height 28.2mm. Apical angle 22–26°; apical angle and pleural angle not equal; pleural angle slightly smaller. Suture moderately to deeply incised. Protoconch and early tel- eoconch whorls unknown. Earliest known whorl ~ 0.6mm in diameter; A, B, and C spirals prominent, but C spiral stronger and B spiral weak. Space between A and B spirals wider than space between B and C. In later whorls (~4.3mm diameter), D spiral developed between C spiral and suture, its strength remaining much weaker than other three spirals (Fig. 9). Primary spiral C remains strong throughout ontogeny. Spiral C rounded in profile on early whorls, but becomes sharp, keel-like in adult whorls. One secondary spiral betweenAandBspirals in later whorls (whorl diameter = 6.4mm) (Fig. 9). Shell basally carinate; carina thin and sharp at peripheral (outer) margin. Between inner carina and outer carina, a feeble thread devel- oped. Whorl profile convex to frustrate. Lateral growth lines not well preserved, but probably straight and slightly prosocline (Fig. 9). Aperture subrounded, higher than wide. Columellar lip distinct and outer lip very thin.


Materials.—Four syntypes originally selected by Mitra and Ghosh (1979) and deposited in the Repository Section, Geological Survey of India (G.S.I), Kolkata were lost. One neotype (specimen no. ISI/g/Jur/T 31) and nine paraneotypes (specimen nos. ISI/g/Jur/T 32-40) have been assigned here.


Remarks.—Turritella jhuraensis lacks the highly angulated C spiral, which forms a very sharp, blade-like ridge in T. jadavpuriensis.In T. jadavpuriensis, the distances between


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