Determining Diet

Dinosaur jaws and skeletons provide insights into dietary habits.
In the absence of teeth, alternative methods must be employed to deduce diet.
Specific lineages lacking teeth include:
- Ornithomimids (swan-like, ostrich-mimicking dinosaurs)
- Oviraptorids (unusual looking, toothless dinosaurs)

Ornithomimids found with stones in body cavities.
Gastric Mill:
- Definition: A muscular pouch in the digestive tract (near stomach) that holds stones called gastroliths.
- Function: As muscles grind stones against each other, they process food similarly to chewing.
Many modern birds (also toothless) have a similar gastric mill function.

Ankylosaurs and Sauropods:
- Example Species:
- Euplocephalus (Ankylosaurus example)
- Diplodocus (Sauropod example)
- Characteristic Teeth:
- Teeth are relatively small.
- Dental forms included leaf-shaped teeth, which are ineffective for chewing.
- Sauropods possess small heads with pencil-like teeth that also don't function well for chewing.

Large body size compensates for poor chewing ability:
- Large gut cavities allow for longer digestion times.
- Essential for breaking down cellulose from plant material (leaves and branches).
Cellulose Breakdown:
- No vertebrate can digest cellulose independently.
- Symbiotic gut bacteria break down cellulose, extracting nutrients akin to fermentation.

Some hadrosaur fossils found with theropod shed teeth.
Bite marks and scratches on bones indicate theropod predation:
- Bite Marks:
- Parallel scratches indicate tooth tips’ movement across bones.
- Serration marks perpendicular to scouring marks often found.
Uncertainty in predation versus scavenging:
- Cannot definitively distinguish if theropods were hunters or scavengers.
- Example: Modern hunters like lions also scavenge, while scavengers like hyenas may hunt.

Cololites:
- Definition: Fossilized mass of partially digested food preserved in the digestive tract.
- Found in some hadrosaur and ankylosaur fossils.
Expected Contents of Hadrosaur or Ankylosaur Cololites:
- Plant material, as these dinosaurs were herbivorous.
Carnivorous theropod gut contents:
- Examples:
- Compsignathus, Sinoceropteryx: Preserved with lizard and mammal bones.
- Sinocaliopteryx: Kept partially digested remains of other theropod dinosaurs and birds.
- Baryonyx: Stomach contents contained fish scales and bones.
- Baryonyx skull adapted for fish-eating—long, low snout with conical teeth, similar to modern fish-eaters like Gharials.

Pisivore: Fish-eating carnivore; correct answer to identify this dietary type is C.

Coprolites:
- Fossilized dinosaur droppings used to deduce dietary habits.
- Coprolites with plant remains indicate presence of hadrosaurs/ceratopsians.
- Example: A large, 0.5-meter-long coprolite found in Saskatchewan with bone remnants likely belonged to Tyrannosaurus rex.
Tyrannosaurus Diet:
- Deeper jaws and sturdy, rounded teeth suited to bone-crushing compared to slicing teeth of other theropods.

Dinosaurs exhibited an incredibly diverse range of diets.
Paleontologists often rely on comparative anatomy to understand diets based on morphological features, observing modern animal counterparts.