Large-Field Electron Imaging and X-ray Elemental Mapping Unveil the Morphology, Structure, and Fractal Features of a Cretaceous Fossil at the Centimeter Scale

New Dendrobranchiata fossil preserved in the Brazilian Cretaceous (Aptian/Albian) from the Araripe Basin, Piauí State

The fossil shrimp Somalis piauiensis n. gen. n. sp. is a new fossil record of Penaeoidea from the Araripe Basin. The purpose of this study is to describe a new decapod crustacean from the Romualdo Formation of the Santana Group and compare it with other fossil Dendrobranchiata described from this basin. The new fossil is characterized by a carapace with antennal and branchiostegal spines. Long rostrum, with thirteen evident dorsal spines yielding a serrate appearance. The laminar scaphocerite is large with a weakly rounded lateral margin and is longer than the rostrum. The fossil specimen is the first occurrence of shrimp in the Piauí territory.

Physicochemical investigation of shrimp fossils from the Romualdo and Ipubi formations (Araripe Basin)

The Ipubi and Romualdo Formations are Cretaceous units of the Araripe Basin (Santana Group). The first and most ancient was deposited in a lake environment, and some fossils were preserved in shales deposited under blackish conditions. The second was deposited in a marine environment, preserving a rich paleontological content in calcareous concretions. Considering that these two environments preserved their fossils under different processes, in this work we investigated the chemical composition of two fossilized specimens, one from each of the studied stratigraphic units, and compared them using vibrational spectroscopy techniques (Raman and IR), X-ray diffraction and large-field energy-dispersive X-ray spectroscopy (EDS) mappings. Calcite was observed as the dominant phase and carbon was observed in the fossils as a byproduct of the decomposition. The preservation of hydroxide calcium phosphate (Ca₁₀(PO₄)₆(OH)₂, hydroxyapatite) was observed in both fossils. In addition, it was observed that there was a smaller amount of pyrite (pyritization) in the Romualdo Formation sample than in the Ipubi one. Large-field EDS measurements showed the major presence of the chemical elements calcium, oxygen, iron, aluminum and fluoride in the Ipubi fossil, indicating a greater influence of inorganic processes in its fossilization. Our results also suggest that the Romualdo Formation fossilization process involved the substitution of the hydroxyl group by fluorine, providing durability to the fossils.

Characterization of Arsenic in dried baby shrimp (Acetes sp.) using synchrotron-based X-Ray Spectrometry and LC coupled to ICP-MS/MS

The arsenic content of dried baby shrimp (Acetes sp.) was investigated as part of an independent field study of human exposure to toxic metals/metalloids among the ethnic Chinese community located in Upstate New York. The dried baby shrimp were analyzed in a home environment using a portable X-ray Fluorescence (XRF) instrument based on monochromatic excitation. Study participants had obtained their dried baby shrimp either from a local Chinese market or prepared them at home. The shrimp are typically between 10-20 mm in size and are consumed whole, without separating the tail from the head. Elevated levels of As were detected using portable XRF, ranging between 5-30 μg/g. Shrimp samples were taken to the Cornell High Energy Synchrotron Source (CHESS) for Synchrotron Radiation μXRF (SR-μXRF) elemental mapping using a 384-pixel Maia detector system. The Maia detector provided high resolution trace element images for As, Ca, and Br, (among others) and showed localized accumulation of As within the shrimp's cephalothorax (head), and various abdominal segments. As quantification by SR-μXRF was performed using a Lobster hepatopancreas reference material pellet (NRC-CNRC TORT-2), with results in good agreement with both portable XRF and ICP-MS. Additional As characterization using μX-ray Absorption Near Edge Spectroscopy (μXANES) with the Maia XRF detector at CHESS identified arsenobetaine and/or arsenocholine as the possible As species present. Further arsenic speciation analysis by LC-ICP-MS/MS confirmed that the majority of As (>95%) is present as the largely non-toxic arsenobetaine species with trace amounts of arsenocholine, methylated As and inorganic As species detected.