Palaeoenvironmental vs. evolutionary control on size variation of coccoliths across the Lower-Middle Jurassic

Western Tethys Early and Middle Jurassic calcareous nannofossil biostratigraphy

“…The reference section for this subzone is Peniche. Although the earliest specimens of L. sigillatus recorded in this study being relatively small (4.34 µm on average for the upper Pliensbachian; Ferreira et al, 2017), its size increases throughout the Toarcian (5.14 µm on average; Ferreira et al, 2017). Stradner (1961) reported specimens of Discolithus sigillatus (basionym of L. sigillatus) as big as 6 to 8 µm from the middle Toarcian Variabilis Zone from SW Germany, but the emended diagnosis of Goy (1981) shows a holotype from the early Toarcian of 5 µm, which is very similar to those observed in this work.…”

“…Biostratigraphy is described with reference to Bown and Cooper (1998) and Mattioli and Erba (1999). Calcareous nannofossil taxonomy follows that of Bown (1987) for muroliths, de Kaenel and Bergen (1993) and Mattioli et al, (2004) for Similiscutum/Biscutum, Mattioli (1996) and Ferreira et al (2017) for Lotharingius, López-Otálvaro et al 2012for Discorhabdus, and Cobianchi et al (1992), Mattioli (1996), Giraud et al (2006) and Tiraboschi and Erba (2010) for Watznaueria. Since this study utilizes Lotharingius and Watznaueria species more frequently than previous biostratigraphic schemes, some taxonomic keys to unambiguously differentiate these two genera are provided.…”

“…However, the taxonomy adopted by some of these authors is someway different to the one followed herein. Actually, biometric studies of Jurassic coccoliths such as those performed on the genera Similiscutum/Biscutum (de Kaenel and Bergen, 1993;Mattioli et al, 2004), Lotharingius (Mattioli, 1996;Fraguas and Young, 2011;Ferreira et al, 2017), Crepidolithus (Suchéras-Marx et al, 2010;Fraguas and Erba, 2010), Discorhabdus (López-Otálvaro et al, 2012) and Watznaueria (Giraud et al, 2006;Tiraboschi and Erba, 2010), resulted in a quantitative and partially revised taxonomy. Such a revision deeply impacts biostratigraphic studies and therefore the chronostratigraphic range of the redefined taxa should be precisely determined.…”

“…Noël (1973) first described Lotharingius barozii from the Toarcian Schistes carton as a Lotharingius with massive buttresses in the axis of its ellipse and asymmetrical radial bars. According to Mattioli (1996;several sections) and the biometric study by Ferreira et al (2017; sections in Portugal and France), this species is characterized by its elliptical shape with a narrow rim, a wide and elliptical central area spanned by an axial cross, and the inner and outer cycles of the distal shield have approximately the same thickness (Mattioli, 1996).…”

Beyond Time and Space—The Aspiring Jurassic Geopark of Figueira da Foz

“…The second one corresponds to the Auxiliary Stratotype Section and Point (ASSP) at the base of the Bathonian at Cabo Mondego (Section 2), 7 km north of the city of Figueira da Foz [19]. The abundant existence of fossil assemblages in these strata is frequent, highlighting the study of micro and macrofaunas of invertebrates [20][21][22] and its evolution during Jurassic times, as well as its paleoenvironmental and paleogeographic implications [23][24][25]. The above mentioned represents a geosite of international relevance [26][27][28][29][30].…”