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Lecture 3

GSC 102 Lecture Notes - Lecture 3: Feathered Dinosaur, Tyrannosaurus, Central Atlantic Magmatic Province

Geological Sciences
Course Code
GSC 102
Leech Peter

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Exam 3 Notes 11/2/2016 3:24:00 PM
24. Triassic (252-201 million years ago)
First period of the Mesozoic
Amphibians made it thru the Permian-Triassic extinction event
Early Triassic the temnospondyls gave rise to genus Triadobatrachus (in
o AKA proto-frog
o Evolution of the modern frog
Lystrosaurus is a dicynodont (a type of synapsid) which survived the PT
o During Early Triassic, make up 95% of all terrestrial vertebrates
Mammal having a dentary-squamosal joint
o Have one jaw bone, three ear bones
o Reptiles have more jaw bones and one ear bone
During the Triassic (200 million years ago), first mammal like animals
appear like the Megazostrodon
o Mammals are characterized by having modified sweat glands called
mammary glands
Pangea is arid; Sauropsids may conserve water better than synapsids
Living descendents of the synapsids have glandular skin and need to flush
out their nitrogen waste with water
Sauropsids split into:
o LEPIDOSAURS include the modern snakes and lizards (the “scaly
o ARCHOSAURS include the dinosaurs and crocodilians
Lepidosaurs give rise to the MESOZOIC MARINE REPTILES (not dinosaurs)
o Lepidosaurida (possibly) produced the first ICHTHYOSAURS during
the Triassic (probably)
o Ichthyosaurs are one of three main kinds of MMR we’ll see
Organisms which attached to the sea floor and were easily plucked off
(like the Paleozoic crinoids and brachiopods) did not do well
o They are largely replaced by organisms which can cling tightly to
the substrate
The Triassic land is dominated by NONDINOSAUR ARCHOSAURS
o The top carnivores are relatives of the early ancestors of the
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The first crocodylomorph archosaurs show up near the end of the Triassic
Non-dinosaur archosaurs also dominate the herbivores
Members of order Rhynchosaur may have made up 40-60% of animals in
certain places during the Triassic
Pterosaurs make an appearance during the Late Triassic (not dinosaurs)
o Early pterosaurs are distinguished by their tails, which later
pterosaurs do not have.
Dinosaurs are defined as everything which evolved from the most recent
common ancestor of Triceratops and birds, minus the birds
The earliest true dinosaur is probably something like Eoraptor (“Dawn
o Small, bipedal, omnivorous
Alternatively, the dinosaurs are all of the archosaurs which are not
crocodilian or pterosaurs
The dinosaurs are split into two main groups:
o ORNITHISCHIA (bird-hipped dinosaurs)
o SAURISCHIA (lizard-hipped dinosaurs)
This distinction is exactly what it sounds likea fundamental
difference in the structure of the hip
By the end of the Triassic, the lizard-hipped dinosaurs had split into two
main groups:
Diplodocus is a SAUROPOD from the Late Jurassic
Pisanosaurus, from 220 Ma, represents an early bird-hipped dinosaur
o 3-4 feet long
Bird-hipped dinosaurs will include every dinosaur that is not a therapod or
o Stegosaurus is a bird-hipped dinosaur from the Late Jurassic
o Triceratops is a bird-hipped dinosaur from the Late Cretaceous
The end of the Triassic is marked by the production of the CENTRAL
o New Jersey Palisades are part of CAMP
25. Jurassic (200-145 million years ago)
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Pangaea begins to break into LAURASIA to the North and GONDWANA to
the South, separated by the TETHYS SEA
Climate is generally warm, non-glaciated, with low seasonality
In the enclosed basin of the Gulf of Mexico and the Western Interior
Seaway, salt and gypsum began to accumulate
Salt, under high pressure, tends to flow. It is also low in density
compared to other rocks, so it tends to push up through newer sediments
and form SALT DOMES
o As salt domes rise up, they form bulges in the overlying sediment.
Oil and gas float to the top of these bulges
o One of the key locations of the Bone Wars was the MORRISON
FORMATION, an extremely fossil-rich Jurassic sedimentary rocks
Sauropods (lizard-hipped, quadrupedal, long-necked herbivores) evolved
from small, bipedal ancestors
Almost all dinosaurs, even quadrupedal dinosaurs, had back legs bigger
than their front legs
Cope’s Rule suggests that population lineages get larger over time. Large
size has many advantages (up to a point)
o Sauropods become very large, very quickly, and then mostly
plateau through the Cretaceous
Evolutionary cascade models suggest multiple causes and feedbacks
contributing to increasing size in sauropods
Sauropod neck posture is still a controversial issue, and involves
questions of neck flexibility, energy expenditure, and blood pressure
o A recent hypothesis puts Diplodocus’s neck at around 45°
In contrast to the diplodocoids, the TITANOSAURIFORMS tended to have
longer front legs, a more upright neck, and shorter tails
o Titanosauriforms include Brachiosaurus
Amphicoelias fragillimus may be the largest land animal of all time, at
200 feet long and 120 tons
o Amphicoelias fragilimus is only known from a drawing of a partial
vertebrate made in the 1870s. (The actual fossil is thought to have
Sauropods had relatively small heads, and small, peg-like teeth
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