Stable isotope evidence for changes in dietary niche partitioning among hadrosaurian and ceratopsian dinosaurs of the Hell Creek Formation, North Dakota

Abstract

Questions related to dinosaur behavior can be difficult to answer conclusively by using morphological studies alone. As a complement to these approaches, carbon and oxygen isotope ratios of tooth enamel can provide insight into habitat and dietary preferences of herbivorous dinosaurs. This approach is based on the isotopic variability in plant material and in surface waters of the past, which is in turn reflected by carbon and oxygen isotope ratios of animals that ingested the organic matter or drank the water. Thus, it has the potential to identify and characterize dietary and habitat preferences for coexisting taxa.In this study, stable isotope ratios from coexisting hadrosaurian and ceratopsian dinosaurs of the Hell Creek Formation of North Dakota are compared for four different stratigraphic levels. Isotopic offsets between tooth enamel and tooth dentine, as well as taxonomic differences in means and in patterns of isotopic data among taxa, indicate that primary paleoecological information is preserved. The existence of taxonomic offsets also provides the first direct evidence for dietary niche partitioning among these herbivorous dinosaur taxa. Of particular interest is the observation that the nature of this partitioning changes over time: for some localities ceratopsian dinosaurs have higher carbon and oxygen isotope ratios than hadrosaurs, indicating a preference for plants living in open settings near the coast, whereas for other localities isotope ratios are lower, indicating a preference for plants in the understory of forests. In most cases the isotope ratios among hadrosaurs are similar and are interpreted to represent a dietary preference for plants of the forest canopy. The inferred differences in ceratopsian behavior are suggested to represent a change in vegetation cover and hence habitat availability in response to sea level change or to the position of river distributaries. Given our current lack of taxonomic resolution, it is not possible to determine if dietary and habitat preferences inferred from stable isotope data are associated with single, or multiple, species of hadrosaurian/ceratopsian dinosaurs.

Palaeoenvironmental drivers of vertebrate community composition in the Belly River Group (Campanian) of Alberta, Canada, with implications for dinosaur biogeography

“…When using palaeoenvironment as a factor, sites were assigned to one of four settings, based on their lithology and predominant fauna: (1) marine, (2) transitional, (3) terrestrial (paralic; lower coastal plain), and (4) terrestrial (alluvial; upper coastal plain). The two terrestrial groupings correspond to the palaeoenvironmental conditions from which the vast majority of dinosaur fossils are known, and represent the two primary environmental regimes discussed in previous studies of dinosaur environmental sensitivity and/or provinciality/endemism [1–7, 9, 19, 20, 22–25, 36, 37, 42–45, 49, 70]. Three non-overlapping grouping were obtained: one for sites with palaeoenvironments reconstructed as marine (Fig.…”

“…We also hypothesize that dinosaurs, particularly those of large body size, will not be sensitive to altitudinal change as recorded in the Belly River Group. This hypothesis is based on the resilience to environmental variation and broad latitudinal distributions seen in many groups of large mammals today [2, 7, 32], though it is at odds with much of the literature on dinosaur environmental associations [1–9, 11, 14, 15, 19–24, 26, 27, 42, 43, 62]. …”

The biota of the Upper Cretaceous site of “Lo Hueco” (Cuenca, Spain)

“…The estimated fractionation value between sauropod enamel and diet (∆ 13 C enamel-diet ) is ~15‰, lower than other fractionation values calculated for sauropods (~16‰; Tütken et al, 2011) and ornithischians (~18‰;Fricke and Pearson, 2008;, and probably points to differences in metabolic and/ or physiological processes or different utilization of plant organic compounds and/or plant parts. Although the Lo Hueco crocodyliform material remains under study and no paleoecological remarks have been attained yet from a morphological perspective, isotopic results indicate that these crocodyliforms may have incorporated food items from brackish sauropods, eusuchian crocodyliforms, and pleurodiran bothremyidid turtles will appear in future studies.…”

Oxygen isotopes of East Asian dinosaurs reveal exceptionally cold Early Cretaceous climates

“…Considering at least partial preservation of the primary isotopic compositions of analyzed apatites, mean δ 18 O mw values of meteoric waters can be estimated at each site using present day relationships established between vertebrate phosphate and water (δ 18 O p − δ 18 O w ). Due to ecological differences between herbivorous (sauropods, ornithopods, ceratopsians, and ankylosaurs) and carnivorous (theropods) dinosaurs, systematic offsets in δ 18 O p values between these dinosaur groups that would reflect differences in diet, water strategies, and foraging micro habitats were expected (7,22,23). However, the δ 18 O p value differences observed between coexisting theropods, sauropods, ornithopods, ceratopsians, and ankylosaurs appear to be randomly distributed from one site to another (Fig.…”