Habitat preference of mosasaurs indicated by rare earth element (REE) content of fossils from the Upper Cretaceous marine deposits of Alabama, New Jersey, and South Dakota (USA)

Abstract

Knowledge of habitat segregation of mosasaurs has been based on lithology and faunal assemblages associated with fossil remains of mosasaurs and stable isotopes (δ13C). These approaches have sometimes provided equivocal or insufficient information and, therefore, the preference of habitat by different mosasaur taxa is still suboptimally constrained. The present study is focused on the analysis of rare earth element (REE) ratios of mosasaur fossils from the Upper Cretaceous formations of western Alabama, USA. Results of the REE analysis are used to infer the relative paleobathymetry associated with the mosasaur specimens and then to determine if certain taxonomic groups showed a preference for a particular water depth. Comparisons are then made with mosasaur specimens reported in the literature from other regions of North America from different depositional environments. Results indicate that Mosasaurus, Platecarpus and Plioplatecarpus may have preferred more restricted habitats based on water depth whereas Tylosaurus and Clidastes favoured a wider range of environments. Results also suggest that Plioplatecarpus lived in a shallower environment than its Platecarpus predecessor. Although the results of this study are encouraging, caution must be exercised before drawing any final conclusions due to the small sample size of most of the taxa analysed.

Endothermic mosasaurs? Possible thermoregulation of Late Cretaceous mosasaurs (Reptilia, Squamata) indicated by stable oxygen isotopes in fossil bioapatite in comparison with coeval marine fish and pelagic seabirds

“…Habitat partitioning could potentially influence the oxygen isotope signature in biophosphates because of differences in the oxygen isotope content of seawater in relation to proximity to shore, which has been observed in present‐day marine mammals (Clementz & Koch ). However, rare earth element data for the three mosasaur genera analysed in this study ( Clidastes , Platecarpus , Tylosaurus ) suggest that they inhabited the same environment despite their difference in adult size (Harrell & Pérez‐Huerta ), limiting the potential variation in δ 18 O of water between taxa.…”

“…Mosasaur material for isotopic analyses (δ 18 O from the phosphate) was extracted mainly from well‐preserved tooth enamel, because the apatite is considered to be resistant to diagenesis (Koch ). For further assessment of the preservation, visual and SEM observations of tooth enamel were conducted and rare earth element (REE) data were evaluated from two previous studies using similar fossils from the same localities (Harrell & Pérez‐Huerta , b ). REE content suggests minimum diagenetic alteration in Mooreville Chalk fossils to the point of using the material to evaluate habitat preference based on light/medium/heavy REE ratios (Harrell & Pérez‐Huerta ).…”

“…For further assessment of the preservation, visual and SEM observations of tooth enamel were conducted and rare earth element (REE) data were evaluated from two previous studies using similar fossils from the same localities (Harrell & Pérez‐Huerta , b ). REE content suggests minimum diagenetic alteration in Mooreville Chalk fossils to the point of using the material to evaluate habitat preference based on light/medium/heavy REE ratios (Harrell & Pérez‐Huerta ). In addition, δ 18 O data from well‐preserved cortical bone were compared to tooth enamel results to determine the possible influence of diagenesis and to evaluate whether δ 18 O‐temperature derived data would reflect body temperatures (Table ).…”

Advanced mosasaurs from the Upper Cretaceous Nakaminato Group in Japan

“…), Caldwell and Konishi (2007) reassigned this specimen to Russellosaurina. Frey et al (2016) Lindgren et al (2007Lindgren et al ( , 2011 suggested that this taxon might have preferred living in the deeper water environment off the continental coast, although most mosasaurs inhabited shallow, epicontinental seas (Bardet & Pereda Suberbiola, 1996;Harrell & Pérez-Huerta, 2015;Kiernan, 2002;Russell, 1988).…”