Journal of Paleontology, 92(3), 2018, p. 373–387 Copyright © 2018, The Paleontological Society 0022-3360/18/0088-0906 doi: 10.1017/jpa.2017.89


The oldest turritelline gastropods: from the Oxfordian (Upper Jurassic) of Kutch, India


Shiladri S. Das,1 Sandip Saha,1 Subhendu Bardhan,2 Sumanta Mallick,3 and Warren D. Allmon4


1Geological Studies Unit, Indian Statistical Institute, 203, Barrackpore Trunk Road, Kolkata-700108, India ⟨shiladri@gmail.com⟩ ⟨sandipsaha.ju@gmail.com⟩ 2Department of Geological Sciences, Jadavpur University, Kolkata-7000032, India ⟨sbardhan12@gmail.com⟩ 3Department of Geology, Triveni Devi Bhalotia College, Raniganj-713347, India ⟨sumanta.geol87@gmail.com⟩ 4Paleontological Research Institution, and Department of Earth and Atmospheric Sciences, Cornell University, 1259 Trumansburg Road, Ithaca, New York,14850 USA ⟨wda1@cornell.edu⟩


Abstract.—Turritellid gastropods are important components of many Cretaceous–Recent fossil marine faunas world- wide. Their shell is morphologically simple, making homoplasy widespread and phylogenetic analysis difficult, but fossil and living species can be recognized based on shell characters. For many decades, it has been the consensus that the oldest definite representatives of Turritellidae are from the Lower Cretaceous, and that pre-Cretaceous forms are homeomorphs. Some morphological characters of the present turritelline species resemble those of mathildoids, but many diagnostic characters clearly separate these two groups. We here describe and/or redescribe—based on examination of more than 2600 near complete specimens—four species from the Upper Jurassic Dhosa Oolite Member of the Chari Formation in Kutch, western India, and demonstrate that they are members of Turritellidae, subfamily Turritellinae, on the basis of diagnostic characters including apical sculptural ontogeny (obtained from SEM study), spiral sculpture, and growth line patterns. The four species are in order of abundance, Turritella jadavpuriensis Mitra and Ghosh, 1979; Turritella amitava new species; Turritella jhuraensis Mitra and Ghosh, 1979, and Turritella dhosaensis new species. The turritelline assemblages occur only on the northeastern flank of the Jhura dome (23°24’47.57”N, 69°36’09.26”E). Age of the Dhosa Oolite has recently been confirmed based on multiple ammonite species. All these points indicate that these fossils are the oldest record of the family Turritellidae—by almost 30 million years—in the world.


Introduction


The gastropod family Turritellidae is widely regarded as a monophyletic group within basal caenogastropods commonly known as “cerithioids” (Cerithioidea, sensu Strong et al., 2011; Cerithimorpha, sensu Golikov and Starobogatov, 1975; also see Lydeard et al., 2002; Ponder et al., 2008). Turritellids can be extremely abundant in assemblages in which they occur, from Lower Cretaceous to Recent (Allmon, 2007), including several fossil assemblages in India (Malarkodi et al., 2009; Mallick et al., 2013; Bardhan et al., 2014). The group has also been the subject of numerous studies of predation intensity in the fossil and Recent records (e.g., Allmon et al., 1990; Mallick et al., 2013, 2014; Paul et al., 2013). The recent consensus has been that the oldest definite


representatives of the subfamily Turritellinae (and perhaps the family Turritellidae, as well) are from the Lower Cretaceous (Valanginian Stage) of Poland (Turritella polonica Schröder, 1995; see Bandel, 1993; Tracey et al., 1993; Schröder, 1995; Kaim, 2004; Allmon, 2011) (ca. 133.9–139.4 Myr; Gradstein et al., 2012), and the group is moderately diverse and abundant by later in the Early Cretaceous (Ellisor, 1918; Abbass, 1962; Allmon and Cohen, 2008). Turritellidae was, however, long


reported to have originated in the late Paleozoic (e.g., Knight et al., 1960, p. I316; Sepkoski, 1982, p. 28), and the genus Turritella sensu lato has occasionally been cited (although never with much detailed analysis) from the Jurassic and even Triassic (e.g., Hudleston, 1892, p. 227–235; Dacque, 1905; Edwards, 1980; Fürsich, 1984; Meier and Meiers, 1988; Tekin, 1999; Bandel, 2006). Many 19th and early-20th century workers considered any high-spired gastropod lacking a selenizone and with a U-shaped apertural sinus as “Turritella,” but many of the early Mesozoic examples so assigned have since been placed in other groups, especially Mathildoidea (Bandel, 1991, 1995; Hikuroda and Kaim, 2007; Gründel and Nützel, 2013). Within Turritellidae, details of shell form, including apical


angle, whorl profile, and especially spiral sculpture, usually allow relatively unambiguous recognition of species in fossils, and the group has long provided important guide fossils in Cretaceous and Cenozoic biostratigraphy (e.g., Woodring, 1930, 1931; Gardner, 1935; Stenzel, 1940; Wheeler, 1958; Kauffman, 1977; Sohl, 1977; Saul, 1983; Squires, 1988). These characters, however, are also clearly homeomorphic across the family (Merriam, 1941; Marwick, 1957; Kotaka, 1978; MacNeil and Dockery, 1984; Allmon, 1994, 1996). Thus, while detailed morphological examination (e.g., with SEM of protoconch and


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