Variation and taphonomic implications of composition in modern and fossil malacostracan cuticles (Decapoda: Malacostraca).

The article focuses on the chemical composition and biomineralization of modern and fossil crustacean exoskeletons, emphasizing differences among body parts, taxa, and localities. Using scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), the study analyzed major elements (calcium, magnesium, sodium, phosphorus) in exoskeletons of various crustaceans—including brachyuran and anomuran crabs, stomatopods, isopods, and shrimps—from Bermuda, Georgia (USA), and Lake Tanganyika (Burundi), as well as fossil specimens from Texas and South Dakota. Results show that claw tips are the thickest and most heavily mineralized regions with lower phosphorus and magnesium-to-calcium ratios, except in the land crab Gecarcinus lateralis, which exhibits elevated magnesium levels in denticles. Significant compositional differences exist between taxa (e.g., stomatopods have phosphate-rich cuticles) and between geographic locations, possibly linked to environmental factors like water temperature. Fossil crustaceans display increased phosphorus content due to diagenetic processes, highlighting composition as a key factor influencing crustacean fossil preservation and suggesting multiple independent evolutionary origins of biomineralization within Crustacea.