Biostratigraphic, evolutionary, and paleoenvironmental significance of the southernmost lepidocyclinids of the Pacific coast of South America (East Pisco Basin, southern Peru)

Distribution and paleoenvironmental framework of middle Miocene marine vertebrates along the western side of the lower Ica Valley (East Pisco Basin, Peru)

“…The EPB is a 180-km-long, northwest-to-southeast trending sedimentary basin whose sediments are now exposed along a narrow coastal plain between the towns of Pisco and Nazca, being located just landward of where the Peru-Chile trench is impinged on by the aseismic Nazca Ridge (Figure 1a), a region of buoyant, topographically high oceanic crust (Hampel et al, 2004;Hsu, 1992;Macharé & Ortlieb, 1992;Pilger, 1981). The basin fill includes, from oldest to youngest, the Eocene Caballas, Paracas and Otuma formations, the lower Miocene Chilcatay Formation, and the middle-upper Miocene Pisco Formation (Coletti et al, 2018(Coletti et al, , 2019DeVries, 1998DeVries, , 2007DeVries & Jud, 2018;DeVries et al, 2017;Di Celma et al, 2017;Dunbar et al, 1990). These units are heterogeneous in composition and bounded by regionally extensive unconformities, commonly demarcated by lags of igneous pebble-to boulder-sized clasts, which account for periods of subaerial exposure and represent major breaks of the sedimentary record of the EPB (DeVries, 1998).…”

A rhinopristiform sawfish (genus Pristis) from the middle Eocene (Lutetian) of southern Peru and its regional implications

“…This hypothesis was based on i) the occurrence of some taxa of foraminifera (e.g., the genera Bolivina ORBIGNY, 1839, Nonion MONTFORT, 1808, and Uvigerina ORBIGNY, 1826) and nannoplankton [e.g., Coccolithus pelagicus (WALLICH, 1877)] that are currently associated with cool waters, and ii) the frequent observation of loose scales of clupeoid fishes (i.e., anchovies and sardines), which correlates with relatively cool water environments in the Quaternary record of the Humboldt Current System off the Peruvian coast (UHEN et al, 2011, and references therein). However, a recent re-examination of the actualistic data about the micro-and nannofossil taxa from the Yumaque deposits revealed a somewhat weak correlation with cool waters (COLETTI et al, 2019), whereas the small-sized fish scales that are omnipresent in the same beds cannot be positively identified as belonging to any member of Clupeoidea (personal observation by A.C.), a group of teleosts whose first unambiguous occurrence in the fossil record of the East Pisco Basin occurs in the upper Miocene strata of the Pisco Formation (COLLARETA et al, 2015;LAMBERT et al, 2015). Furthermore, considerations on the record of large benthic foraminifera from the Los Choros member, which includes abundant lepidocyclinids, as well as nummulitids and members of the extant genus Amphistegina ORBIGNY, 1826, provided a different interpretation of the Paracas depositional setting as a tropical palaeoenvironment (MO- RALES-REYNA et al, 2010COLETTI et al, 2019).…”

“…However, a recent re-examination of the actualistic data about the micro-and nannofossil taxa from the Yumaque deposits revealed a somewhat weak correlation with cool waters (COLETTI et al, 2019), whereas the small-sized fish scales that are omnipresent in the same beds cannot be positively identified as belonging to any member of Clupeoidea (personal observation by A.C.), a group of teleosts whose first unambiguous occurrence in the fossil record of the East Pisco Basin occurs in the upper Miocene strata of the Pisco Formation (COLLARETA et al, 2015;LAMBERT et al, 2015). Furthermore, considerations on the record of large benthic foraminifera from the Los Choros member, which includes abundant lepidocyclinids, as well as nummulitids and members of the extant genus Amphistegina ORBIGNY, 1826, provided a different interpretation of the Paracas depositional setting as a tropical palaeoenvironment (MO- RALES-REYNA et al, 2010COLETTI et al, 2019). As mentioned above, pristids are currently known as tropical/subtropical fishes (e.g., COMPA-GNO & LAST, 1999;WUERINGER et al, 2009;CAPPET-TA, 2012;DULVY et al, 2014); therefore, the present record of Pristis sp.…”

“…1.B). Similar to the transgressive sequences that comprise the geologically younger Chilcatay and Pisco formations (e.g., DI CELMA et al, 2017COLETTI et al, 2018;DEVRIES & JUD, 2018), the Paracas Formation is comprised of a coarse-grained lower portion (i.e., the Los Choros Member, consisting of conglomerates and mixed siliciclastic-bioclastic sandstones characterised by abundant tests of large benthic foraminifera) that is overlain by a package of finer sediments (i.e., the Yumaque Member, consisting of silty sandstones and siltstones that feature a rich planktic assemblage) (RIVERA, 1957;TSUCHI et al, 1988;DUNBAR et al, 1990;DEVRIES, 1998DEVRIES, , 2017DEVRIES et al, 2006;LEÓN et al, 2008;UHEN et al, 2011;COLETTI et al, 2019) (Fig. 1.B).…”

“…In the same area, ca. 6 km WSW of the collection site, the depositional age of the lower Yumaque beds has been recently reconstructed as close to 42.37 Ma (i.e., Lutetian Stage) by means of calcareous nannoplankton biostratigraphy (COLETTI et al, 2019;Fig. 1.C).…”