Carnivorous chewing
Snakes and komododragons are terrible chewers!
Their teeth a sharp and pointed backward, good for ripping flesh. The teeth are also space out and sheer past each other sequentially as the jaw closes.
The jaw joint is at the same level as the tooth row, so the jaw cannot move side to side, but rather the mouth works like scissors.
This structure is great for ripping apart flesh, digestion occurs internally.
Unique features that allow herbivorous mammals the ability to chew. The herbivorous skull is divided into three main parts:
- cropping section: incisors to bite of chunks of food
- diastema: toothless gap for food manipulation by the tongue
- cheek teeth: molars, able to grind food into paste
Adaptations for chewing
- expansion of bone: coronoid process for jaw muscle attachment
- closely packed teeth with grinding surface
- teeth occlude (fit together tightly top to bottom) for efficient grinding
- an inset tooth row to support cheeks (somewhere to put your cheetos as you chew and snack on them)
- jaw joint is ABOVE not AT the tooth row: allows upper and lower teeth to make contact at the same time. This is a less stable jaw joint but allows for grinding.
What features can we use to determine whether dinosaurs chewed?
- gape
- tooth spacing
- nature of contact between upper and lower teeth
- position of jaw joint
- carnivore or herbivore?
Do carnivores chew their food?
No, they swallow chunks of meat whole, the meat is then digested with stomach acid.
How do herbivores break down food?
- enzyme in their saliva that carnivores do not have, this enzyme helps to break down carbohydrates
- long digestive tracks, this allows for the fermentation needed to break down food (the more chewing you do the less fermentation needed)
How do carnivores break down food?
- digest internally
- single chamber stomach
- short digestive track
Gastroliths
Many animals ingest small stones, stomach rocks, to help mechanically process food. Some animals keep them and others pass them and must replace them.
Gastroliths are also used as a ballast in some aquatic animals.
Theropods and chewing
Theropods would have been terrible chewers.
We think they might have bitten and pulled on larger prey and held on do smaller prey with their huge, backwards facing teeth. Remember they have a jaw like scissors and a digestive tract for meat.
Sauropodomorphs and chewing
Sauropodomorphs would have been relatively bad chewers
- jaw joint is below tooth row
- tooth row is not inset, so no cheeks
- teeth offer few grinding spaces
- dominant tooth function: puncturing vegetation
- barrel shaped guts for fermentation
- gastroliths
Ornithiscians and chewing
Ornithiscians would have been great chewers
- toothless gap
- grinding space
- dental battery: multiple rows of teeth that are stacked up on each other. When teeth wear down there are more teeth coming up behind them to replace the worn down teeth.
- rhamphotheca: cropping is done with a beak made of keratin
How can we determine what dinosaurs ate?
We can look at Coprolites: fossilized poop
We can look at Cololites: gut contents, this is rare and unlikely to fossilize
Indirect evidence:
- assemble all known fossils from an area
- look for teeth marks on bones
- comparative anatomy: ex. a crocodile eats fish and has adaptations to do so, like its carnivorous teeth and long snout for catching fish underwater. Whereas a koala has adaptations for eating plants. We can use these animal’s adaptations and life styles to compare to our dinosaur fossils.
