Dinosaur Feeding

David B Norman, University of Cambridge, Cambridge, UK

Published online: November 2012

DOI: 10.1002/9780470015902.a0003321.pub2

Full Article on Wiley Online Library

Many dinosaurs can be relatively easily partitioned, on the basis of their tooth morphology and skeletal form, into those that were classically sharp-toothed, agile and fast-moving carnivorous theropods such as Coelophysis, Velociraptor and Tyrannosaurus. Alternatively others had comparatively blunt teeth, were rather heavy-legged and barrel-bodied herbivorous sauropodomorphs, for example, Diplodocus, cerapods, for example, Triceratops and armoured thyreophorans, for example, Sauropelta. However, some dinosaurs, as we shall see (e.g. heterodontosaurs, therizinosaurs, alvarezsaurs and spinosaurs) exhibit anatomies that cannot be so readily categorised; these challenge our understanding of likely feeding behaviours. For these latter creatures a more comparative–deductive approach must be adopted. Detailed investigation of such ‘atypical’ types, as well as the more classic morphologies, suggests that some dinosaurs exploited morpho-functional solutions to the problems posed by feeding that are not seen among present-day animals.

Key Concepts:

Tooth morphology provides direct information about the potential diets of long-extinct animals.
Skeletal morphology provides information about the mechanics and potential lifestyle of long-extinct animals.
Morphology and lifestyle interpretations based on dinosaur skeletons contain information that is relevant to deductions concerning their probable diets.
Jaw mechanics and tooth wear patterns provide objective information about bite forces and the movement of food caught between the teeth.
Carnivores typically eat meat and have predatory habits, but such animals are not exclusively predatory because today many are also known to take carrion opportunistically.
Herbivores typically eat plant material, but some classically herbivorous reptiles (such as land iguanas) are also known to eat eggs, young mammals or chicks, as well as carrion; these considerations also apply to animals such as rodents. So such apparently clear cut human definitions are evidently not as clear in real life.
Finite Element Modelling and Beam Theory have been used to augment information about the range of feeding styles in dinosaurs.
Pleurokinesis is a cranial mechanism that allows classically reptilian herbivores (i.e. ornithopod dinosaurs) to develop a power stroke, during jaw closure, by mobilising the lateral walls of the skull. This enables oral processing (repetitive chewing) of plant material.
Co-evolutionary relationships (between dinosaurs and plants) in the fossil record, notably with respect to the coincident timing of the evolution of angiosperms (flowering plants) and diversification of herbivorous dinosaurs, cannot be proved.

Keywords: herbivores; omnivores; carnivores; piscivores; insectivores; diets; archosaurs; dinosauriforms; Saurischia; theropods; Aves; sauropodomorphs; Ornithischia; cerapods; thyreophorans

	Figure 1. Calibrated phylogeny of the Dinosauria. The dinosaurs split very early (Mid-Late Triassic times) into two distinct lineages: the Saurischia and Ornithischia. The saurischians comprise the predatory theropods (a clade that includes their direct descendants, modern birds (Aves)) and the typically herbivorous sauropodomorphs. By contrast, the ornithischians comprise a wider range of generally herbivorous types: the cerapods: ornithopods, ceratopians and pachycephalosaurs; and the armoured thyreophorans: ankylosaurs and stegosaurs. These are the primary groups that form the basis for discussion in this short essay. Nota bene: The systematic positioning of Eoraptor and Herrerasaurus as basal dinosaurs (attributable to neither Saurischia nor Ornithischia) is a matter of ongoing debate. Lagosuchus and Silesaurus are representative of the ‘near-dinosaur’ archosaurs referred to as dinosauriforms herein. © David Norman.
	Figure 2. (a) Lagosuchus talampayensis: A skeletal reconstruction of the Middle Triassic dinosauriform archosaur from Argentina (body length 40 cm). © G. S. Paul. (b) A ‘typical’ xiphodont (sword-shaped) carnivore's tooth, the tip is pointed to pierce flesh and the sharp leading and trailing edges have small, sharp, serrations that aid slicing (just like the blade of a steak knife). © David Norman.
	Figure 3. Silesaurus opolensis: (a) Skeletal reconstruction of this dinosauriform from the Late Triassic, approximately 230 Ma in the Carnian Stage of what is now Poland. Silesaurus measured approximately 2.3 m long, light and built for speed. The teeth were small, conical and serrated. The tip of the lower jaw has no teeth, and may have been covered by a keratinous beak. © Scott Hartman. (b) Isolated tooth showing its blunt form and coarse serrations, both of which are more typical of a herbivore than a carnivore. © David Norman.
	Figure 4. (a) @Herrerasaurus ishigualastensis: A Late Triassic basal dinosaur (as indicated in Figure 1 – some have argued that it is a genuine theropod, but there is no current resolution to this issue) from Argentina (body length 2 m). © G. S. Paul. (b) The Early Jurassic theropod dinosaur @ Coelophysis bauri (body length 2 m). © G. S. Paul.
	Figure 5. (a) Plateosaurus engelhardti: A Late Triassic sauropodomorph dinosaur from Europe (body length ranges up to 8 m). © G. S. Paul. (b) Melanorosaurus readi: A Late Triassic sauropodomorph of larger size and more robust construction from the Karoo Basin of southern Africa. © Scott Hartman.
	Figure 6. Eocursor parvus: A skeletal reconstruction of this small (1 m long) Late Triassic ornithischian from the Karoo Basin of southern Africa. Some of the key anatomical features are highlighted: (1) The toothless predentary beak. (2) The pubic shaft has rotated backward, to lie parallel to the ischium. (3) The spine is supported and strengthened by bundles of thin bony rods (ossified tendons). (4) The preacetabular process of the ilium is also characteristically extended forward as a narrow bar of bone and may have provided an attachment area for leg moving muscles, and for gut-supporting ligaments. © David Norman.
	Figure 7. (a) Compsognathus longipes, a small (70 cm long) coelurosaurian theropod from the Late Jurassic of Europe. © G. S. Paul. (b) Allosaurus fragilis, a large (8 m long) allosauroid theropod from the Late Jurassic of North America. The hinge in the lower jaw is adjacent to the large window-like opening (mandibular fenestra). © G. S. Paul.
	Figure 8. Deinonychus antirrhopus: A skeletal reconstruction of this, very bird-like, 2 m long (deinonychosaurian) theropod. Note the thin tail, stiffened by long bony rods derived from the enormous elongation of the zygapophyses and chevrons of the tail vertebrae; the reversed pubic shaft (see Figure 6); the ‘primed’ sickle-shaped claw on the second digit of the foot; the long arms and taloned grasping hands and the large predatory head. © Scott Hartman.
	Figure 9. Tyrannosaurus rex: From the Late Cretaceous, and probably close to the largest size that any bipedal carnivore could attain (body length 14 m). © G. S. Paul.
	Figure 10. (a) Gallimimus bullatus: From the Late Cretaceous of Mongolia, this toothless ornithomimosaurian theropod is similar in size and shape to a modern ostrich (body length 3 m) but of course unlike the ostrich it has a long bony (counterbalancing) tail and long grasping arms. © G. S. Paul. (b) Khaan mckennai: From the Late Cretaceous of Mongolia, another toothless oviraptorosaurian theropod (body length 2 m). Both of these types of animals probably had omnivorous diets. © G. S. Paul.
	Figure 11. (a) Nothronychus mckinleyi: From the mid-Cretaceous of North America. A very bizarre (very probably herbivorous) therizinosaur theropod (body length up to 5 m). The small head has jaws lined with blunt, leaf-shaped teeth, and the abdomen is large and barrel-shaped (and the pubis is rotated backward to enlarge this area of the body) as if to accommodate a large gut, essential for plant digestion. (b) Baryonyx walkeri: From the Early Cretaceous of Britain, is a large (7 m long) spinosauroid theropod. The crocodile-like snout, lined with narrow pointed teeth and the gaff-like claws on the forelimbs suggest that this was a piscivore, although it may well have scavenged carcasses as well. © Scott Hartrman.
	Figure 12. Diplodocus carnegiei: (a) A large diplodocoid sauropod from the Late Jurassic of North America (body length in excess of 25 m). © Scott Hartman. (b) The skull of a juvenile Diplodocus to show the small and pencil-shaped teeth that are clustered at the front of the jaws. © The Society of Vertebrate Paleontology & John Whitlock.
	Figure 13. Nigerosaurus taqueti: A medium-sized (11 m long) specialised diplodocoid from the Cretaceous of North Africa. © Scott Hartman.
	Figure 14. Brachiosaurus altithorax: A large macronarian sauropod (20 m or more long). © Scott Hartman. Camarasaurus lentus: The skull of this macronarian sauropod to show the large size of the nostrils and the large, spoon-shaped teeth. © David Norman.
	Figure 15. Edmontosaurus regalis: (a) A skull reconstruction of a hadrosaurian ornithopod showing the broad toothless beak and behind it a pouch-like recess that would have been covered in life by a fleshy cheek. (skull length 85 cm). (b) An internal view of the right lower jaw to show the ‘magazine’ comprising 100 s of individual teeth that are cemented together to form a grindstone-like ‘megatooth’. © David Norman.
	Figure 16. Calibrated phylogeny of ornithischians. The Ornithischia have their origins in the Late Triassic (Norian) based on the discovery of a poorly preserved and fragmentary specimen of Pisanosaurus from Argentina. Heterodontosaurs and less-specialized forms such as Eocursor represent a Late Triassic-Early Jurassic diversification of the ornithischian body plan. The principal lineages: Thyreophora (armoured and plated forms) and Cerapoda (ornithopods and the horned and frilled forms of ornithischian) diversified through the remaining Jurassic and Cretaceous periods. Toward the close of the Cretaceous period the hadrosaurian and ceratopian groups of ornithischian were very abundant and diverse. © David Norman.
	Figure 17. Heterodontosaurus tucki: A small (1 m long) basal ornithischian from the Early Jurassic of southern Africa. (a) The 1.5 m long skeleton is lightly built; this was a fast-running agile animal. The long tail counterbalanced the front part of the body, and the pelvis is typically ornithischian in that the pubic shaft is rotated to lie parallel to the ischium. The hands are grasping a taloned, rather like a theropod and the jaws have enlarged stabbing ‘caniniform’ teeth near the front point toward a meat-bsed diet. (b) The 10 cm long skull, however, also shows the presence of a toothless predentary and a keratinous beak at the tip of upper and lower jaws as well as cheek teeth, set back within deep cheek recesses, that form chisel-like cutting blades, all of which seems to indicate a plant-based diet. The likelihood is that this was an opportunistic omnivore. © David Norman.
	Figure 18. (a) Edmontonia rugosidens: A Late Cretaceous thyreophoran anklyosaur, large (6 m long), heavily armoured and relatively slow-moving. © Scott Hartman. (b) Stegosaurus stenops: A Late Jurassic thyreophoran stegosaur, large (7 m long), bearing large polygonal plates along its back and elongate tail spikes. The latter were undoubtedly defensive weapons, but the polygonal plates are more problematic and have been suggested to be for use in body heat regulation and/or for use in behavioural signalling. © Scott Hartman.
	Figure 19. (a) Psittacosaurus mongoliensis: A small (1.5–2 m long) Early Cretaceous cerapodan (a basal ceratopian) form Mongolia, that is sufficiently generalised to combine many of the anatomical attributes of ceratopian, pachycephalosaur and ornithopod dinosaurs. (b) Triceratops prorsus: A large (8 m long) Late Cretaceous ceratopian cerapodan demonstrating the massive body, powerful pillar-like legs and massive skull. The jaws are tipped by an unusually narrow and curved (parrot-like) beak and behind this are massive jaws containing magazines of teeth that cut like a pair of guillotine blades. Although there seems little doubt that these were herbivores, it is unclear what particular plants their jaws were adapted to dealing with. These types of large ceratopian became particularly abundant and diverse in the Late Cretaceous of North America. © Scott Hartman.
	Figure 20. Parasaurolophus walkeri: A large (12 m long) crested (lambeosaurine) hadrosaurian cerapodan of Late Cretaceous age. Hadrosaurs became extremely abundant and diverse in the Late Cretaceous of Northern Hemisphere continents and may well have formed substantial herds in the same way that some ungulate mammals do today. © Scott Hartman.

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Further Reading
	book Brusatte SL (2012) Dinosaur paleobiology. Oxford: John Wiley & Sons.
	book Fastovsky DE and Weishampel DB (2009) Dinosaurs a concise natural history. Cambridge, UK: Cambridge University Press.
	book Weishampel D, Dodson P and Osmolska H (eds) (2004) The Dinosauria. Berkeley, CA: California University Press.

Article Title:	Dinosaur Feeding
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Dinosaur Feeding

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