Notes on Triassic and Jurassic Evolution, Fossil Records, and Dinosaurs.

Surprising Findings of Triassic Animals
- Many species resembled modern animals but were not closely related.
- Example: Drepanosaurs with chameleon-like features, including grasping feet and bird-like heads.
Drepanosaurus Characteristics
- Bird-like heads with disproportionately small features.
- The new genus Avicranium named for its superficial resemblance to birds.
- Lacked ear drums resembling early reptiles instead of birds.
Rate of Evolutionary Change
- Rate of change is influenced by competition in the environment.
- Fewer competitors lead to rapid species diversification (known as adaptive radiations).
- Adaptive radiations usually occur after mass extinctions.
Examples of Reptile Lineages Filling Niches
- Drepanosaurs occupied distinct niches quickly evolving into their own lineage after the end-Permian extinction.

Fossil Groups in Haida Gwaii T-J Boundary
- Notable groups: Ammonites, Conodonts, Radiolarians.
- Conodonts went extinct during the end-Triassic mass extinction.
Lifestyle and Importance of Radiolarians
- Radiolarians are predatory protists useful as biostratigraphic markers.
- Their rapid evolutionary changes help correlate geological time.
Ammonites as Dating Tools
- Despite poor preservation, they are crucial for relative dating and correlating sections globally.

Plants in Jurassic
- Dominant plants were gymnosperms (conifers, cycads, ginkgos) with ferns and horsetails present, while angiosperms were scarce.
- Angiosperms develop seeds in fruits, enabling more targeted animal pollination.
Theropod Dinosaurs
- Example: Coelophysis, a fast, agile predator with several adaptations:
- Hollow bones, keen eyesight, and a good sense of smell.

Morphological Features of Coelophysis
- Hollow bones for weight reduction.
- Adapted for bipedal locomotion.
Rapid Burial of Coelophysis at Ghost Ranch
- Drought led to congregations near water, sudden floods caused mass burial and exceptional fossil preservation.
Diversity of Dinosaurs and Predators
- The concept of Predator-Gap explained by lack of medium-sized predators in fossil records.
Darwin's Finches as an Example of Adaptive Radiation
- Similar principles applied to dinosaur evolution and diversification.

Mesozoic Paleogeography
- Pangea started fragmenting into Laurasia and Gondwana, creating new ocean basins.
Hispanic Corridor
- A seaway between North and South America facilitating dispersal of organisms and influencing evolution.
Formation of Rocky Mountains
- Collision of terranes (e.g., Wrangellia) caused crustal compression and the creation of mountain ranges.

Triassic-Jurassic Mass Extinction
- 22% marine families, 76-84% of species went extinct.
- Causes: falling sea levels, volcanic activity from Central Atlantic Magmatic Province (CAMP).
Recovery of Ecosystems
- Gradual increase in biodiversity following mass extinctions; coral reefs re-establishing, mammals evolving.

Dinosaur Classification and Characteristics
- Saurischia vs. Ornithischia based on pelvis structure.
- Evidence points to a range of adaptable physiologies and behaviors among dinosaurs.
Parental Care in Dinosaurs
- Evidence from nests and juvenile care suggests some species, like Maiasaura, demonstrated parental behavior.

Pterosaur Anatomy and Flight
- Evolution marked by the development of lightweight skeletal structures for powered flight.
- Divided into rhamphorhynchoids and pterodactyloids, which exhibit varying sizes and adaptations.

Bird Evolution from Theropods
- Evidence of feathers and specialized bone structures support the link between modern birds and theropod dinosaurs.
- Archaeopteryx as a transitional form showing characteristics of both birds and reptiles.