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Early Jurassic Trochotomidae (Vetigastropoda, Pleurotomarioidea) from the Neuquén Basin, Argentina

Published online by Cambridge University Press:  04 June 2015

S. Mariel Ferrari
Affiliation:
Museo Paleontológico Egidio Feruglio, Av. Fontana 140, U9100GYO, Trelew, Chubut, Argentina 〈mferrari@mef.org.ar〉Consejo Nacional de Investigaciones Científicas y Técnicas, Rivadavia 1917, Buenos Aires, Argentina
Susana E. Damborenea
Affiliation:
Departamento Paleontología Invertebrados, Museo de Ciencias Naturales, Univ. Nac. La Plata, Paseo del Bosque s/n, A1900FWA La Plata, Argentina 〈sdambore@fcnym.unlp.edu.ar〉, 〈mmanceni@fcnym.unlp.edu.ar〉; 〈patagonianoyster@gmail.com〉Consejo Nacional de Investigaciones Científicas y Técnicas, Rivadavia 1917, Buenos Aires, Argentina
Miguel O. Manceñido
Affiliation:
Departamento Paleontología Invertebrados, Museo de Ciencias Naturales, Univ. Nac. La Plata, Paseo del Bosque s/n, A1900FWA La Plata, Argentina 〈sdambore@fcnym.unlp.edu.ar〉, 〈mmanceni@fcnym.unlp.edu.ar〉; 〈patagonianoyster@gmail.com〉Consejo Nacional de Investigaciones Científicas y Técnicas, Rivadavia 1917, Buenos Aires, Argentina
Miguel Griffin
Affiliation:
Departamento Paleontología Invertebrados, Museo de Ciencias Naturales, Univ. Nac. La Plata, Paseo del Bosque s/n, A1900FWA La Plata, Argentina 〈sdambore@fcnym.unlp.edu.ar〉, 〈mmanceni@fcnym.unlp.edu.ar〉; 〈patagonianoyster@gmail.com〉Consejo Nacional de Investigaciones Científicas y Técnicas, Rivadavia 1917, Buenos Aires, Argentina

Abstract

Trochotomidae is a small but distinctive extinct family of pleurotomarioidean gastropods characterized by trochiform shells with an elliptical trema. Two new species of trochotomids are described from Pliensbachian deposits in the Neuquén Basin, Argentina. The new genus-group name Placotoma is proposed to replace the pre-occupied name Discotoma Haber non Mulsant. The record of Trochotoma (Trochotoma) protonotialis new species and Trochotoma (Placotoma) neuquensis new species in the early Jurassic of Argentina extends the paleobiogeographical distribution of the genus (and the family) to the Southern Hemisphere. The new taxa reported here represent a component of the pleurotomarioidean adaptive radiation that took place in the Tethyan region during the earliest Jurassic. They are related to local patch coral reefs of shallow, open-marine paleoenvironments, agreeing with the known habitat of most species of this family. The group was well represented in the Tethyan region during the Mesozoic, especially during the Jurassic, and the new species represent its southernmost occurrence.

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Articles
Copyright
Copyright © 2015, The Paleontological Society 
Figure 0

Table 1List of nominal species once referred to Trochotomidae, with an indication of their updated generic affinities. Those discussed in this paper (including supplementary data) are in bold type. Taxa doubtfully related to this family are indicated with question marks.

Figure 1

Figure 1Location map and simplified logged sections at Santa Isabel (A), Carrán Curá (B) and Cerro Roth (C) in southern Neuquén Province, Argentina. Beds with Trochotoma indicated with an arrow. Paleogeography after Legarreta and Uliana (2000), sections adapted from Damborenea et al. (1975) and Damborenea (1987).

Figure 2

Figure 2(1–7) Trochotoma (Trochotoma) protonotialis n. sp. (1) MLP 26172, holotype, (1a) lateral view; (1b) apical view. (2) MLP 12168, paratype. (2a) lateral view; (2b) apical view; (2c) basal view. (3) MCF-PIPH 554. (3a, b, c) lateral views; (3d) apertural view; (3e, f) basal and umbilical views; (3g) apical view. (4) MCF-PIPH 553, lateral view. (5) MCF-PIPH 684, lateral view. (6) MCF-PIPH 555. (6a) lateral view; (6b, c) lateral and apical views. (7) MLP 12167. (7a, b) lateral views; (7c) apical view. (8, 9) Trochotoma (Placotoma) neuquensis n. sp. (8) MLP 26171, holotype. (8a) lateral view; (8b) apical view. (9) MLP 26173, paratype. (9a) lateral view; (9b) apical view. Scale bar represents 5 mm.

Figure 3

Figure 3Diagram showing the variations of height/width ratio in Trochotoma protonotialis n. sp. Note that R2 indicates a good correlation between these parameters.

Figure 4

Table 2Measurements of Trochotoma (T.) protonotialis n. sp.

Figure 5

Figure 4Paleobioegeographical distribution of Trochotoma s.l. species. Base map depicting early Jurassic paleogeography compiled from various sources.

Figure 6

Figure 5Reproduction of original illustrations of some species comparable to T. protonotialis n. sp. (1, 2) Trochotoma (T.) calix (Phillips). (1) from Phillips 1829, pl. 11, fig. 30; (2) from Hudleston 1885, pl. 4, figs. 6, 6a–b. (3) Trochotoma (T.) magnifica Cossmann, from Cossmann 1885, pl. 8, figs. 15, 16. (4) Trochotoma (T.) carinata Lycett, from Lycett 1857, pl. 4, fig. 5. (5, 6) Trochotoma (T.) affinis Eudes-Deslongchamps. (5) from Eudes-Deslongchamps 1843, pl. 8, fig. 8–10; (6) from Eudes-Deslongchamps 1868, pl. 8, fig. 6a, b. (7) Trochotoma (T.) bicarinata (d’Orbigny), from d’Orbigny 1853, pl. 340, fig. 9, 10. (8, 9) Trochotoma (T.) gradus Eudes-Deslongchamps; (8) from Eudes-Deslongchamps 1843, pl. 8, fig. 4–7; (9) from Eudes-Deslongchamps 1868, pl. 4, figs. 2a, b. (10) Trochotoma (T.) obtusa Morris and Lycett, from Morris and Lycett 1851, pl. 10, fig. 15b. (11) Trochotoma (T.) rathieriana (d’Orbigny), from d’Orbigny 1853, pl. 342, figs. 7, 8. (12) Trochotoma (T.) tabulata Morris and Lycett, from Morris and Lycett 1851, pl. 10, fig. 17a. (13) Trochotoma (T.) schlumbergeri Eudes-Deslongchamps, from Eudes-Deslongchamps 1868, pl. 8, fig. 5a, b. (14) Trochotoma (T.) orientalis (Kiparisova), from Kiparisova 1952, pl. 6, figs. 1a, c Scale bars=5 mm.

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