Dinosaur fauna niche partitioning based on calcium isotopes from Jurassic Morrison Formation
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Ben Creisler
Jun 20, 2025, 11:04:31 AMJun 20
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Ben Creisler
A new paper:
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Liam Norris, Rowan C. Martindale, Aaron Satkoski, John C. Lassiter & Henry Fricke (2025)
Calcium isotopes reveal niche partitioning within the dinosaur fauna of the Carnegie Quarry, Morrison Formation
Palaeogeography, Palaeoclimatology, Palaeoecology 113103
doi: https://doi.org/10.1016/j.palaeo.2025.113103
https://www.sciencedirect.com/science/article/abs/pii/S0031018225003888
Highlights
We present a new calcium isotope dataset from the Late Jurassic Morrison Formation.
δ44/40Ca from teeth indicate niche partitioning in herbivorous dinosaurs.
δ44/40Ca confirm that bone was not a significant part of the diet of Allosaurus.
Our data challenge assumptions about controls on calcium isotopes in herbivores.
Plant tissue types ingested are the most significant driver of herbivore δ44/40Ca.
Abstract
A longstanding question in paleontology is the ecosystem structure of dinosaur communities, particularly in the Upper Jurassic Morrison Formation, which preserves numerous sauropod taxa. Here we provide evidence of niche partitioning from stable calcium (Ca) isotopes preserved in tooth enamel from five taxa found in the Carnegie Quarry at Dinosaur National Monument [Allosaurus (n = 5), Camarasaurus (n = 4), Camptosaurus (n = 2), Diplodocus (n = 5), Eutretauranosuchus (n = 1)] to reconstruct trophic structure of Morrison Formation ecosystems. Based on the herbivore Ca isotope data, Camarasaurus and Camptosaurus fed upon different resources, whereas Diplodocus utilized resources similar to both the larger and smaller herbivores. Comparing δ44/40Ca from our dataset with previously published data on δ44/40Ca from dinosaur tooth enamel indicates that plant components eaten, not height in the canopy, is likely the most significant driver of skeletal δ44/40Ca in herbivorous dinosaurs. The most common large carnivore in the Morrison Fm., Allosaurus, was an opportunistic carnivore that ate whatever prey it could find, including all three sampled herbivores. δ44/40Ca indicates that Allosaurus likely did not eat significant amounts of bone, confirming it as a carnivore specializing in tearing flesh. Across trophic levels, niche partitioning was an important part of ecosystem function in the Morrison Fm. and allowed many species of large dinosaur to coexist for millions of years.
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Liam Norris, Rowan C. Martindale, Aaron Satkoski, John C. Lassiter & Henry Fricke (2025)
Calcium isotopes reveal niche partitioning within the dinosaur fauna of the Carnegie Quarry, Morrison Formation
Palaeogeography, Palaeoclimatology, Palaeoecology 113103
doi: https://doi.org/10.1016/j.palaeo.2025.113103
https://www.sciencedirect.com/science/article/abs/pii/S0031018225003888
Highlights
We present a new calcium isotope dataset from the Late Jurassic Morrison Formation.
δ44/40Ca from teeth indicate niche partitioning in herbivorous dinosaurs.
δ44/40Ca confirm that bone was not a significant part of the diet of Allosaurus.
Our data challenge assumptions about controls on calcium isotopes in herbivores.
Plant tissue types ingested are the most significant driver of herbivore δ44/40Ca.
Abstract
A longstanding question in paleontology is the ecosystem structure of dinosaur communities, particularly in the Upper Jurassic Morrison Formation, which preserves numerous sauropod taxa. Here we provide evidence of niche partitioning from stable calcium (Ca) isotopes preserved in tooth enamel from five taxa found in the Carnegie Quarry at Dinosaur National Monument [Allosaurus (n = 5), Camarasaurus (n = 4), Camptosaurus (n = 2), Diplodocus (n = 5), Eutretauranosuchus (n = 1)] to reconstruct trophic structure of Morrison Formation ecosystems. Based on the herbivore Ca isotope data, Camarasaurus and Camptosaurus fed upon different resources, whereas Diplodocus utilized resources similar to both the larger and smaller herbivores. Comparing δ44/40Ca from our dataset with previously published data on δ44/40Ca from dinosaur tooth enamel indicates that plant components eaten, not height in the canopy, is likely the most significant driver of skeletal δ44/40Ca in herbivorous dinosaurs. The most common large carnivore in the Morrison Fm., Allosaurus, was an opportunistic carnivore that ate whatever prey it could find, including all three sampled herbivores. δ44/40Ca indicates that Allosaurus likely did not eat significant amounts of bone, confirming it as a carnivore specializing in tearing flesh. Across trophic levels, niche partitioning was an important part of ecosystem function in the Morrison Fm. and allowed many species of large dinosaur to coexist for millions of years.
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