What characters define the sauropodomorpha?
- long necks: at least 10 neck vertebrae
- small head: not so smart
- additional vertebrae in front of and behind sacrum: hips
- enormous thumb with large claw
- long femur
The saurpodomorpha lived for the entire time of the dinosaurs and was found on all continents, they spanned over
100 species.
For the sauropodomorpha, over time
their necks became longer, their heads became smaller, and their hind legs and front legs became equal in length.
True or false, sauropodomorphs were the first large dinosaurs and eventually reached gigantic proportions
True
2 groups of sauropodomorpha
Prosauropoda
Sauropoda
Sauropoda
- big, quadrupedalism
- herbivore
- as trees got bigger so did these dinosaurs
- first to take advantage of tall plant life
- bad chewers
- large animals with small mouths, they would have had to have been constantly eating
- digestive system like a conveyor belt
- claw may have aided in ripping vegetation into smaller pieces
Why were the sauropoda so big?
As a defence mechanism or simply because they could
What are some of the qualities that allowed the sauropoda to get so big??
- presence of pneumatic bone kept the upper skeleton light (hollow bones)
- skulls are small and delicate and light
Prosauropoda
Bi pedal, small
Evolutionary steps that led to the sauropoda
What was the basis for the subdivision of sauropods into the Diplodocoidea and Macronaria
External nares migrated to the top of the skull.
Diplodocoidea
Subdivision of the sauropods
- sub rectangular snout
- fully retracted external nares above eyes
- peg like teeth along front of jaw: tooth comb
(slides: a is diplodocoidea)
Macronaria
Subdivision of the sauropods
- nares as large as or larger than orbit
- nares move toward top of skull
- shortening/elevation of skull: more powerful biting force
(slides: b is macronaria)
What were the scientific theories to try and explain why sauropods had nostrils at the top of their heads?
- snorkel: however we only found trackways on terrestrial sediments
- trunks: like an elephant? But they lack a large facial nerve that would suggest the presence of a trunk, also, the mobile trunk is supposed to compensate for a short neck. Comparisons with modern crocodiles and turtles showed the probable location of cartilage, blood vessels, and other soft tissues that made up the extinct creature’s nasal cavities.
- we don’t know
What did sauropod trackways suggest?
- that they lived on land, trackways where only found in terrestrial sediments
- no tail drag marks were found so the tail must have been held off the ground
- sauropods travel in herds, trackways found together and not crossing. This is also supported by the discovery of bone beds. Trackways also indicate that the young would have walked in the middle.
Abundance of ____ for blood vessels and nerves indicates fleshy nostrils further down the face and closer to the mouth than the eyes.
Abundance of foramina for blood vessels and nerves indicates fleshy nostrils further down the face and closer to the mouth than the eyes.
4 ways to make a long neck
- Make really long vertebrae in the neck
- Recruit vertebrae from the back into the neck
- Increase number of neck vertebrae
- A combination of the above
Different sauropods did different things or a combination of these things.
The suspension bridge that holds the sauropod’s neck up
Interlocking system of girders.
The nuchal ligament prevents the long necks of sauropods from falling forward: Elastic rope of connective tissue that ran down the neck and the back to support the head so the muscles didn’t have to work as hard.
Y shaped neural arches on vertebrae held nuchal ligament.
Physiological demands of the long neck
The sauropods would need exceptionally high blood pressure to pump blood above the heart and not faint. Blood pressure would have to be twice as high as giraffe’s. This would burst capillaries!
How does this work?
- multiple hearts along the neck?
- special siphons?
- single giant heart with thick, muscular walls?
- cervical ribs flexed while dino walked, so neck doesn’t sway, compression may have put pressure on the vertebral artery, helping to pump blood to the neck.
Why couldn’t the sauropods rear up on their hind legs?
This could cause fainting because the head would be so high above the heart.
The shape of the pelvis would not have allowed for this anyway, especially in brachiosaurus.
What implications do hollow bones in sauropods have on breathing?
Sauropods have long necks, if they breathed bi directionally, like humans, there would have been a lot of unused air in their necks.
They could have breathed unidirectionally, like birds: air will follow a loop, goes into air sac to lungs to air sac to out, resulting in a constant flow of air. Some of these air sacs are in their hollow bones.
Long neck means more food with little
energy. More food means larger, larger means harder to take down.
Eggs and nests
Soccer ball sized, perfectly round, hard shelled eggs.
In 1997, Patagonia, nest sites were discovered with embryonic skeletons and skin. Several layers of eggs suggested that the mother came back to the same location to lay eggs every year.
Mothers either buried their eggs and left the site, or communally guarded them.
Laid lots of eggs to increase chances of survival.
