midterm 2 Flashcards
SAUROPODOMORPHA
- most sophisticated animals
- lived for 160 million years, from the beginning of dinosaur history until its close.
- They were present on every continent
- Sauropodomorpha is a saurischian dinosaur. Contains Sauropoda and Prosauropoda
- Sauropodomorphs are split roughly one- third to two-thirds between prosauropods and sauropods
PROSAUROPODA
SAUROPODOMORPHA
-small heads, long necks, large bodies, and long tails
- Late Triassic through early Jurassic, from all continents except Australia
- The front limbs were shorter than the hindlimbs, and all had five digits.
- Prosauropod hands had a large, half-moon-shaped thumb claw
The skulls no chew. the jaw joint is slightly lower than the tooth row. The teeth are generally separated, leaf-shaped, and reveal few grinding marks, suggesting puncturing as the dominant function.
- herbivore or carnivor because the prosauropod teeth lack herbivore specializations
- Grinding took place via gastroliths
- The history of prosauropods parallels the rise of gymnosperms.
Eggs and nests are known for the prosauropods Mussaurus (Argentina) and Massospondylus (South Africa). Clutches tended to be small (10 eggs), and the hatchlings small sized. Adult prosauropods are roughly 500–1,000 times larger than the hatchlings.
- Prosauropods represent the first appearance on Earth of the modern ecosystem that is with us today
SAUROPODA
SAUROPODOMORPHA
- remained unique and little changed during their 140 million years on Earth
- skull was distinctive: the tooth row was not inset, didn’t have a lot of teeth
- skulls were delicately built, with large openings. The external nares, instead of residing at the tip of the snout, tended to migrate upward, toward the top of the head
- neck was made up of a complex system of girders and air pockets that maximized lightness and strength. Sauropods had Y-shaped neural arches on the vertebrae
- Sauropods were quadrupeds, having secondarily evolved a quadrupedal stance
- The forefeet (the hands) were digitigradefingers were arranged in a nearly symmetrical horseshoe-shaped semicircle, and the first digit (the thumb) carried a large claw
- foot was asymmetrical, and generally had three large claws. Sauropod footprints spanned as much as 1 m!
- SMALL BRAINs FOR THEIR BODIES
- . Because the thorax and the lungs would be under a column of water some six or more meters deep, unless sauropods had exceedingly powerful chest muscles, they would have been unable to inhale.
- the heart of a Brachiosaurus must have pumped with a pressure exceeding that known in any living animal –it would take a very muscular heart –as much as 400kg
- Diplodocus and other long-necked sauropods may have gained access to foliage at high levels in the trees by adopting a tripodal posture, third leg tail
- . Some sauropods have cavities, called pleurocoels, in their backbones, suggesting the possibility of air sacs and avian-style unidirectional breathing
- The endosymbionts would have chemically broken down the cell walls of the plant food
info/summary
- OC Marsh defined Sauropoda in 1842
- Sacrum wedged more than 10° (NEW SYNAPOMORPHY!!!!!)
- Lived for >160 Ma (one of the longest living dinosaurs)
- Basal sauropodomorphs = prosauropods
- Found on every continent
- 1st Sauropoda body fossils found in late Triassic
- 1st Sauropodomorpha body fossils found in early part of the late Triassic
- Larger sauropods had more air sacs/pleurocoels
PROSAUROPODS Lec 10
- Thecodontosaurus + Plateosaurus + Massospondylus + Megalosaurus
- Some of the earliest dinos
- Heads became smaller; necks longer; quadrupedal stance with legs of similar lengths
- Herbivory parallels the rise of tall gymnosperm forests
- Late Triassic to early Jurassic
- Small skull (less than 5%)
- Elongate lanceolate teeth
- At least 10 neck vertebrae; long neck
- Dorsal and caudal verts add to sacrum
- All limbs have 5 digits – digit one of the manus has a large claw
- Nests with at least 10 eggs
- Adults are 500 to 1000 times larger than hatchlings
- Jaw joint below the tooth row suggests chewing
- Separated leaf-shaped teeth suggests puncture chewing (Plateosaurus)
- Barrel shaped torsos and gastroliths suggest fermentary gut
- Pencil shape (Diplodocus) and scapula/chisel shaped teeth (Camarasaurus)
SAUROPODA
Monophyletic clade comprised of the most recent ancestor of Vulcanodon, Saltosaurus, and all its descendants
Metacarpal V is longest in manus and weight-bearing
Tibia <70% femur lengths
Metatarsal 3 longest in pes
ANATOMY AND BIOLOGY
SAUROPODOMORPHA
- Bifurcated neural spines of cervical vertebrae contain nuchal ligament to passively support the neck
- Graviportal legs – meaning straight up and down like a column
- Columnar metacarpals – maximize supporting weight
- Forelimb digitigrade
- Hindlimb semi-plantigrade – metacarpals are almost parallel to the ground, but they don’t quite touch it
- Narrow stance; no tail dragging
- To eat they stood in one spot, cleared it, and moved on
- Dung left behind fertilized seeds
- A large titanosaur required 100,000 calories a day – means eating 450kg a day
- Sauropods continuously replaced their teeth
HOW DID SAUROPODS GET SO LARGE
- Long neck allowed feeding on plants that smaller dinos couldn’t
- Pneumatic bones reduced their weight by 10%
- Efficient breathing
- Large size protected healthy adults from attacks by predatory dinos
GROWTH AND REPRODUCTION
- Communal nesting site – mulitpke layers of 15 to 34v eggs
- Incubated with vegetations
- R-strategists (many offspring but few survive)
- Sexual maturity in 30 years
- Max life span = 100 years
- We know that all sauropods, regardless of their end-point body size, started out small hatching from eggs. Eithe absolute size difference between adult and hatchlings is greater than for any other terrrestiral vertebrae.
- Known eggs are usually ~15 cm diameter, up to 25 cm, and hatchlings are hypothesized to have been less than a m long and wghed under 10 kg.
EUSAUROPODA
- Broadly rounded snout
- Wrinkled tooth enamel
- At least 12 cervical verts
- Metacarpals arranged in U-shaped colonnade
- Shunosaurus has (1) nostrils forward, (2) small spatulate teeth = shows primitive sauropodomorph condition
NEOSAUROPODA
- Pedal digit IV with 2 or fewer phalanges
- Snout broadens
- Lower jaw strengthened
- Grinding wear facets on teeth
- 2 clades = Macronaria (Camarasaurus + Brachiosaurus) and Diplodocoidea (Diplodocus)
DIPLODOCOIDEA
Elongate; ectomorphic
Longest animals to ever live on earth
Longer skulls than Macronarians
Fully retracted external nares
Sub-rectangular snout
Pencil-like teeth
Late Jurassic, SW USA (morrison formation)
Up to 32m; 15 tons
14 cervical verts held parallel to ground
8- caudal verts
Dermal spines
Diplodocids held their necks horizontal to the ground.
The Vertebral Column of Diplodocus (and all sauropods) Was Analogous to A Suspension Bridge.
MACRONARIA
Stocky and plump
Short, tall skulls (strong force)
Narial diameter > wider than orbits
Enlarged jaw muscles
CAMARASAURAMORPHA
Defining character = metacarpal I is longer than MC IV
Most common sauropod in NA
Refers to pleurocoels
TITANOSAURIA
Enlarged radius and ulna
Found all over the globe
Heaviest animal to ever live
Last sauropod group to appear
Argentinosaurus is thought to be the biggest/heaviest dino
Dwarf sauropod Magyarosaurus (smallest sauropods)
Alamosaurus is one of the last sauropod known in NA
No known sauropods in Canada
Futalongosaurus is a large macronarian titanosaur
Small dinosaurs like Shuvuuia were growing 4.5 times faster and larger dinosaurs like Apatosaurus some 33 times. Microraptor 2 x and Argentinosaurus 56 times
For sauropods, theories positing 120 yrs. to adulthood in sauropods using primitive reptilian rates are not supported by this data
