Chapter 9 –Dinosaur Feeding Habits

Importance of Studying Dinosaur Feeding Habits

You are what you eat

What dinosaurs ate is interpreted mostly from their teeth

Supplemented with toothmarks, gastroliths, rarely preserved stomach contents, coprolites and tracks

Most dinosaurs were herbivores

Interrelationships of herbivorous dinosaurs and their food plants a important part of the Mesozoic terrestrial ecosystem

Especially important are the effect that sauropods, hadrosaurids and ceratopsians had in giving an adaptive advantage to fast growing plants

Carnivorous dinosaurs were either predators, scavengers or a mixture of the two and would have been present in smaller numbers than herbivorous dinosaurs

Ratios of herbivorous to carnivorous dinosaurs are comparable to those of modern large-mammal communities and bear on the discussion as to whether dinosaurs were warm- or cold-blooded

 

Dinosaur Teeth and Toothmarks

Basic Tooth Terminology

Chordate teeth

Fish, Amphibians, Reptiles, Mammals

Modern birds don’t, but fossil birds did, and some embryonic birds do

Terms (see Figures 9.1 and 9.2)

Enamel and dentine

Crown and root

The majority of most dinosaur teeth are roots

Lingual and labial sides

Denticles, carinae, serrations and cellae

Occlusion

Heterodont dentition

Tooth shape

Leaf-like, peg-like, conical and bladed

Dental batteries

Secondary wear and lost teeth

Herbivorous Dinosaur Teeth

Leaf-shaped

Prosauropods (roughly serrated), Thyreophorans and Pachycephalosaurs

Nipping off vegetation from limbs and stems

Originally interpreted as carnivorous for prosauropods

Peg-like

Sauropods

Strip vegetation from limbs, like a rake

Leaves and needles are not chewed, but swallowed and processed internally by gastroliths or bacteria

Dental batteries

Ornithopods and Ceratopsians

Well-developed in hadrosaurids

Less elaborate in smaller ornithopods

Carnivorous Dinosaur Teeth

Normally serrated and curved posteriorally

Referred to as ziphodont teeth and restricted to theropods among dinosaurs

Similar to archosaur ancestors of dinosaurs

Plesiomorphic (ancestral) trait

Seen in ancestral dinosaur species like Herrerasaurus and Eoraptor

Adapted for grasping and cutting through flesh and for crushing or punching through bone

Most theropod teeth are conical

Chunks of flesh torn off and swallowed, not chewed

For most theropods, in the same jaw, teeth are the same shape but different sizes

Various levels for cutting flesh

Serrations in theropod teeth, particulary for tyrannosaurids have been related to those of the Komodo Dragon of Indonesia

Fibers of flesh retained by the cellae putrify and produce a septic culture

Bites lead to fatal infection

Variations from strict carnivory

Piscivory

Some theropods, notably spinosaurs and therizinosaurs

Based on their numerous small, similarly shaped teeth, in conjunction with other anatomical features

Omnivory, Insectivory and Egg eating

Some theropods, notably ornithomimosaurs and oviraptorids

Theropod teeth in the bones of other animals

Tyrannosaurus in Hypacrosaurus fibula

Saurornitholestes in pterosaur bone

Dinosaur Toothmarks

Definitions

An impression left by the bite of an animal with teeth, regardless of what was bitten

Scrape vs puncture marks

Puncture marks best for determining the identity of the tracemaker

Can be used to re-create the feeding procedure

Most toothmarks were accidental byproducts of meat eating, not of preferential bone consumption

Examples of toothmarks attributable to specific dinosaurs

Troodon on ceratopsian bones

Saurornitholestes in ornithomimid and Edmontosaurus bones

Tyrannosaurus in Triceratops, Edmontosaurus and Saurornitholestes bones

Albertosaurus in Edmontosaurus bones

NOTEEdmontosaurus didn’t always succomb; Healed tyrannosaurid toothmarks reported for one Edmontosaurus specimen

Can be used to estimate biting force

Tyrannosaurus has a biting force greater than that for any known animal

Taphonomy of Teeth and Toothmarks

Teeth more commonly found separate from their jaws and in relatively great abundance

Can be reworked easily

Often separated by loss during life, as a result of feeding

Replaced subsequently

Risky to name a dinosaur species based only on teeth

Toothmarks preserved only if made in bone and are relatively rare

Bias toward those of larger dinosaurs, both as predators and prey

Might be more common, but overlooked

 

Dinosaur Gastroliths

Gastroliths

Stones used primarily to help in the mechanical breakdown of food within a digestive tract

Modern birds and crocodilians have gastroliths, although crocodilians use theirs for ballast

Definitive dinosaur gastroliths are found within their chest and abdominal cavities

Dinosaur gastroliths generally are smooth, polished, rounded and oblate to semispherical

They range in size from less than 1 cm to as large as 10 cm

They are generally silica rich, like chert or quartzite

Limestone and dolostone would dissolve, and, like shales, are too soft

Gastroliths are trace fossils

History of gastrolith reports

Barnum Brown in the early 20th century for Claosaurus, a hadrosaurid

Friedrich von Huene in 1931 for Sellosaurus, a prosauropod

William Lee Stokes in 1942 for a sauropod

General reluctance to identify gastroliths

Difficult to distinguish from other smooth, rounded stones

Must clearly demonstrate that they are not stream pebbles washed into a carcass deposited in a river setting

Gastroliths can be evidence for dinosaur presence in the absence of body fossils or other trace fossils

Concentrated deposits of well-polished, rounded stones in otherwise fine-grained (muddy or sandy) deposits

Dinosaurs with well-supported evidence for gastroliths

Sauropodomorphs

Nodosaurids (a type of ankylosaur)

Psittacosaurids (primitive ceratopsians)

But had well-developed dental batteries

Theropods

 

Stomach Remains and Digestion

Other Species

Mostly other vertebrates are recognized

Plants and insects unlikely to be preserved

One specimen of Edmontosaurus reported with seeds, twigs and conifer needles

Digestion in dinosaurs

Aided by anaerobic bacteria and specialized organs

Methane a byproduct of this symbiosis with methanogenic bacteria

Examples from theropods

Compsognathus with a complete lizard (Bavarisaurus) from the Late Jurassic Solnhofen Limestone of Germany

Note – this is the same unit that has yielded the specimens of Archeopteryx

Sinosauropteryx with a small mammalian dentary from the Early Cretaceous of China

Daspletosaurus with an etched vertebra from a juvenile hadrosaurid from the Late Cretaceous Two Medicine Formation of Montana

Regurgitates

Can be to rid body of toxins or from poor health or indigestible material

Only one dinosaur example from the Early Cretaceous of Mongolia

Recent report of ichthyosaur regurgitate from the Late Jurassic of England

Cannibalism

Coelophysis

Two adult specimens with remains of smaller, possible juvenile individuals (see Figure 9.6)

 

Dinosaur Coprolites

Terminology

Coprolite – remains of solid or semi-solid fecal material

Coprolites are trace fossils

Important source of information related to the feeding habits of extinct animals

May contain evidence of coprophagy (see Figure 9.7)

Late Cretaceous hadrosaurid coprolite with dung-beetle traces

Pseudocoprolites – inorganically formed deposits that superficially resemble coprolites

Things to look for

Relative flattening

Water content

Height of animal

Size

Large coprolites imply large animal

Small coprolites generally imply small animals, but not always, and small coprolites sometimes will be merged into a larger mass

Surface features

Folding of lower intestines

Coprolite contents

Plant material or bones are convincing evidence for coprolites

Two examples of tyrannosaurid coprolites

Both from the Late Cretaceous of Alberta in tyrannosaurid bearing strata

Both are large - 44-cm and 64-cm long

One has numerous small bone fragments of a juvenile hadrosaurid

The other has 3-d impressions of muscle tissue and finely ground bone

Taphonomy of Coprolites

Rapid phosphatization increases chance of preservation

Especially prevalent for theropod coprolites

Bone or tooth dahllite serves as nucleation sites for phosphatization

Rapid burial increases chance of preservation

Especially good in “aqueous” environments like floodplains, watering holes, and lake or estuary margins

 

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