Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Comparative Study
, 285 (1876)

Calcium Isotopes Offer Clues on Resource Partitioning Among Cretaceous Predatory Dinosaurs

Affiliations
Comparative Study

Calcium Isotopes Offer Clues on Resource Partitioning Among Cretaceous Predatory Dinosaurs

A Hassler et al. Proc Biol Sci.

Abstract

Large predators are overabundant in mid-Cretaceous continental dinosaur assemblages of North Africa. Such unbalanced ecosystem structure involves, among predatory dinosaurs, typical abelisaurid or carcharodontosaurid theropods co-occurring with long-snouted spinosaurids of debated ecology. Here, we report calcium (Ca) isotope values from tooth enamel (expressed as δ44/42Ca) to investigate resource partitioning in mid-Cretaceous assemblages from Niger (Gadoufaoua) and Morocco (Kem Kem Beds). In both assemblages, spinosaurids display a distinct isotopic signature, the most negative in our dataset. This distinct taxonomic clustering in Ca isotope values observed between spinosaurids and other predators provides unambiguous evidence for niche partitioning at the top of the trophic chains: spinosaurids foraged on aquatic environments while abelisaurid and carcharodontosaurid theropods relied almost exclusively on terrestrial resources.

Keywords: Cretaceous terrestrial ecosystems; calcium isotopes; dinosaurs; ecology; palaeodiet; spinosaurs.

Conflict of interest statement

We declare we have no competing interests.

Figures

Figure 1.
Figure 1.
Three isotopes plot: δ43/42Ca as a function of δ44/42Ca (‰, reference standard ICP Ca) for all samples and standards analysed for Ca isotope compositions in this study. Ca isotope compositions fall on a line with a y-axis intercept of 0.009 ± 0.015 (‰, 2 s.e.), indistinguishable from theoretical 0‰ intercept. The slope value of this line is 0.509 ± 0.016 (2 s.e.), indistinguishable from the 0.507 slope predicted by the exponential mass-dependent fractionation law. Error bars at the bottom right are average 2 s.d. for δ43/42Ca and δ44/42Ca. The two most external lines delimit the prediction interval, and the two lines accompanying the middle line correspond to the 95% confidence interval of the regression line. (Online version in colour.)
Figure 2.
Figure 2.
(a) PAAS normalized REE profiles of fossil bioapatite from the Aptian–Albian of Gadoufaoua, Niger. Concentrations are plotted on a logarithmic scale. Plain black line, typical REE profile at Gadoufaoua; yellow line, exotic profile of sample GCA5; purple line, exotic profile of sample GSA7; red line, exotic profile of sample GSP3. (b) PAAS normalized REE profiles of fossil bioapatite from the Cenomanian of Kem Kem Beds, Morocco. Concentrations are plotted on a logarithmic scale. For comparison, the plain black line represents the typical REE profile at Gadoufaoua; yellow line, typical profile of samples from the locality of Jebel Al Qabla; blue line, typical profile of samples from the locality of Bou Laâlou; red line, typical profile of samples from the locality of Takemout.
Figure 3.
Figure 3.
δ44/42Ca data reported from Gadoufaoua (a) and Kem Kem Beds faunas (b). Groups representing at least five specimens are represented through boxplots, for which the middle line represents the median, the box limits correspond to the first and third quartiles, and the whiskers are extended between the maximum and the minimum δ44/42Ca values. The mean 2 s.d. of each measure is represented at the bottom right of each graph. The degree of significance of the difference between the theropod groups are represented with stars (*), with three stars indicating a high significance (Wilcoxon rank-sum test: p-value < 0.001). Taxonomic groups are identified by their number and represent: 1, N. taqueti (n = 2); 2, O. nigeriensis (n = 9); 3, non-spinosaurid theropods from Gadoufaoua (n = 9); 4, S. imperator (n = 8); 5, spinosaurids from Gadoufaoua (n = 8); 6, Lepisosteiformes (n = 3); 7, Pycnodontiformes indet. (n = 5); 8, cf. Araripesuchus (n = 3); 9, Pterosauria indet. (n = 3); 10, non-spinosaurid theropods from Kem Kem Beds (n = 7); 11, Crocodylomorpha indet. (n = 3); 12, spinosaurids from Kem Kem Beds (n = 8); 13, Ne. africanus (n = 1); 14, Stromerichthys sp. (n = 1); 15, Anhangueridae indet. (n = 3).
Figure 4.
Figure 4.
Mixing model of the Ca source for non-spinosaurid theropods (a) S. imperator (b) and spinosaurids (c) from the Gadouafaoua fauna. δ44/42Ca data collected on herbivorous dinosaurs and fishes are represented, respectively, in green and blue squares. In each part of the figure, the faded lower boxplot represents the enamel δ44/42Ca values measured for each apex predator, whereas the dark upper boxplot represents the isotopic signature of their calcium source estimated to be shifted by +0.57‰ from the signature of their enamel (see Diet modelling). Boxplots are yellow for non-spinosaurid theropods (a), violet for S. imperator (b) and red for spinosaurids (c). The line in the boxplot is equal to the median, boxes are limited by their first and third quartile, and whiskers represent the maximum and the minimum values. The estimated diet fraction range of Ca derived from the fish source are indicated in bold above the x-axis and expressed in per cent.

Similar articles

See all similar articles

Cited by 1 PubMed Central articles

Publication types

Substances

LinkOut - more resources

Feedback