Abstract
Abstract. Occurrences of suspected sauropod geo-gastroliths and "exoliths" (exotic clasts) are compared with authentic finds of stomach stones in the sauropods Diplodocus, Cedarosaurus, and Camarasaurus. Sedimentological and taphonomical evidence from classic sauropod dinosaur localities in the Late Jurassic Morrison Formation (Cleveland-Lloyd Dinosaur Quarry, Dry Mesa Dinosaur Quarry, Carnegie Quarry/Dinosaur National Monument, Howe Quarry, Como Bluff, and Bone Cabin Quarry) reveals very few sauropod finds with unambiguous gastroliths. The scarcity of clasts in the fine-grained sediments of most of the localities suggests that only a small number of sauropods possessed gastroliths. The occurrence of a hypothetical avian-style gastric mill in sauropods is not supported by taphonomical evidence. Exoliths that are abundant in the Early Cretaceous of the western USA are nearly absent in Late Jurassic sediments. Without an association with fossil bone, there is no convincing evidence that such clasts represent former gastroliths. It is more plausible that most exoliths have been transported in hyperclastic flows or that surface-collected stones are weathering relicts of former conglomerate layers.
Highlights
One of the most interesting topics of herbivorous dinosaur paleobiology is the digestion and nutrition of sauropods, the largest terrestrial vertebrates of all time (Sander et al, 2011)
Fieldwork and first-hand observations were conducted at many classic sites in the North American Late Jurassic Morrison Formation, including the Carnegie Quarry in the Dinosaur National Monument, Cleveland-Lloyd Dinosaur Quarry, Como Bluff and Bone Cabin Quarry, Dry Mesa Dinosaur Quarry, Howe Quarry, and Howe Stephens Quarry (Fig. 1)
Fieldwork focused on comparative study of available sedimentary rocks, sauropod finds at these localities, their taphonomy, and prospecting for exotic stones in and around the quarries
Summary
One of the most interesting topics of herbivorous dinosaur paleobiology is the digestion and nutrition of sauropods, the largest terrestrial vertebrates of all time (Sander et al, 2011). Given the abundance of articulated sauropod remains worldwide, the paucity of associated gastroliths is striking and raises the question of whether their absence can be explained by taphonomical processes alone. This resulted in opposing viewpoints regarding sauropod gastroliths: one group of authors mostly ignores finds (e.g., Calvo, 1994; Lucas, 2000), and another group firmly believes in the presence of gastroliths and a taphonomical bias (e.g., Christiansen, 1996). In the absence of evidence of gastrolith-aided trituration of foodstuffs in sauropods (Wings and Sander, 2007), the authenticity of sauropod gastroliths can be debated in general
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