Nowadays, the requiem sharks comprise one of the most diverse and widespread families of selachians, i.e., Carcharhinidae. Among the carcharhinids, the genus Carcharhinus has the largest number of living species, namely, at least 35. Known from fossils as old as the Cretaceous, the requiem sharks did not significantly radiate before the Eocene (when Carcharhinus also appeared), and their diversification mainly occurred in Neogene times. Here, we describe a new species of requiem shark, Carcharhinus dicelmai sp. nov., based on fossil teeth from Lower Miocene (18.4–18.1 Ma) strata of the Chilcatay Formation of the East Pisco Basin (southern Peru). Upper teeth of C. dicelmai sp. nov. are typically provided with a slender, smooth-edged cusp; a marked coronal twist; and a distal heel that bears 1–5 coarse, angularly lobate serrae that become more prominent toward the base of the cusp. The dentition of C. dicelmai sp. nov. appears less akin to that of most other carcharhines to the cutting-clutching type, and seemingly testifies to the development of more predominantly clutching adaptations. A carcharhinid tooth from the Burdigalian to lower Langhian Cantaure Formation of Venezuela is reassigned to C. dicelmai sp. nov., suggesting a trans-Panamanian distribution for this extinct shark species.
The spectrally-resolved characterization of the atmospheric emission has a fundamental role in the study of the Earth radiation balance, and only a measurement performed in a wide spectral range enables us to separate the contributions to the radiative balance due to the different altitudes, constituents and physical phases. The REFIR-PAD (Radiation Explorer in the Far InfraRed -Prototype for Application and Development) Fourier transform spectroradiometer can perform a characterization of the broadband radiative signature of clouds and aerosols, with the only limitation of the need of low levels of water vapour like those that are obtainable in high altitude stations during winter. The capabilities of this kind of measurement have been assessed in a series of test campaign performed in Tuscany during the winter of 2006/2007 when atmospheric emission spectra have been acquired in various transparency conditions and the evidence of transparency in the far-infrared region below 600 cm −1 has been demonstrated. REFIR-PAD operates in the spectral range extending from 100 to 1400 cm −1 with a resolution of 0.5 cm −1 , using room-temperature detectors and optics and a compact, misalignmentcompensated design. The instrument, developed at IFAC-CNR, Florence, has been successfully deployed in several campaigns, both in the ground based zenith-looking geometry and in the nadir-looking balloon borne configuration. The operating spectral range of the REFIR-PAD spectroradiometer encompasses great part of the atmospheric emission spectrum, from the relatively unexplored far-infrared region below 400 cm −1 , dominated by water vapour rotational band, to the atmospheric transparency window, where a number of atmospheric instruments are already operating and can provide intercomparison data.
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