Search Results (3)

The evolution of baleen whales (Mysticeti) comprises two main phases, namely, (i) a Paleogene phase, which saw the diversification of stem lineages, and (ii) a Neogene phase, dominated by modern-looking, toothless, baleen-bearing forms in the monophyletic group Chaeomysticeti. These two phases are separated by a global turnover event coinciding with a gap—or “dark age”—in the mysticete fossil record. This dark age occurred between 23 and ~18 Ma and is apparently detected worldwide, except in Zealandia. Here, we report on a new mysticete fossil from the Lower Miocene (Burdigalian: ~19.2 Ma) strata of the Chilcatay Formation cropping out at the newly discovered locality of Cerro Tiza (East Pisco Basin, Peru), which represents a limited but precious testament from the last phase of the baleen whale dark age. Two previously mentioned, slightly geologically younger fossils from the same formation are also reappraised herein, revealing the occurrence of at least another baleen whale taxon in the upper Chilcatay strata—one that belongs in the mysticete crown group. Although the Early Miocene remains a problematic time interval for the fossil record of baleen whales, our new results encourage the search for mysticete fossils in the Lower Miocene strata of the East Pisco Basin, whose basin fill preserves a cornucopia of extraordinarily informative marine vertebrate fossils of the Cenozoic age, as well as in coeval deposits worldwide. Full article

We present a technique for the detection of vertebrate skeletons buried at shallow depths through the use of a ground-penetrating radar (GPR). The technique is based on the acquisition of high-resolution data by medium-to-high frequency GPR antennas and the analysis of the radar profiles by a new forward modelling method that is applied on a set of representative traces. This approach allows us to obtain synthetic traces that can be used to build detailed reflectivity diagrams that plot spikes with a distinct amplitude and polarity for each reflector in the ground. The method was tested in a controlled experiment performed at the top of Cerro Los Quesos, one of the most fossiliferous localities in the Ica Desert of Peru. We acquired GPR data at the location of a partially buried fossil skeleton of a large whale and analyzed the reflections associated with the bones using the new technique, determining the possible signature of vertebrae, ribs, the cranium (including the rostrum), and mandibles. Our results show that the technique is effective in the mapping of buried structures, particularly in the detection of tiny features, even below the classical (Ricker and Rayleigh) estimates of the vertical resolution of the antenna in civil engineering and forensic applications. Full article

Molecular information has been gathered from fossilized dental enamel, the best-preserved tissue of vertebrates. However, the association of morphological features with the possible mineral and organic information of this tissue is still poorly understood in the context of the emerging area of paleoproteomics. This study aims to compare the morphological features and chemical composition of dental enamel of extinct and extant terrestrial vertebrates of Crocodylia: Purussaurus sp. (extinct) and Melanosuchus niger (extant), and Rodentia: Neoepiblema sp. (extinct) and Hydrochoerus hydrochaeris (extant). To obtain structural and chemical data, superficial and internal enamel were analyzed by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (SEM-EDS). Organic, mineral, and water content were obtained using polarizing microscopy and microradiography on ground sections of four teeth, resulting in a higher organic volume than previously expected (up to 49%). It is observed that both modern and fossil tooth enamel exhibit the same major constituents: 36.7% Ca, 17.2% P, and 41% O, characteristic of hydroxyapatite. Additionally, 27 other elements were measured from superficial enamel by inductively coupled mass spectrometry (ICP-MS). Zinc was the most abundant microelement detected, followed by Pb, Fe, Mg, and Al. Morphological features observed include enamel rods in the rodent teeth, while incremental lines and semiprismatic enamel were observed in the alligator species. The fossil enamel was in an excellent state for microscopic analyses. Results show that all major dental enamel’s physical, chemical, and morphological features are present both in extant and extinct fossil tooth enamel (>8.5 Ma) in both taxa. Full article