EASC 103 Lecture 6 - Dinosaur Ancestry

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Questions and Answers

Which group of reptiles includes the lineage that leads to modern lizards and snakes?

Lepidosaurs (correct)

Archosaurs

Euryapsids

Diapsids

What major evolutionary change is associated with archosaurs?

Changes to the ankle structure (correct)

Increasing size of body armor

Development of fully aquatic forms

Formation of jaw structures

Which of the following is NOT a characteristic of diapsid reptiles?

Possession of adaptations for fully upright postures

Development into the mammal-like reptiles (correct)

Divisions into Lepidosaurs and Archosaurs

Ankle adaptations leading to semi-upright postures

Which lineage under archosaurs includes pterosaurs and dinosaurs?

Avemetatarsalia Signup and view all the answers

Which type of fish is considered a precursor to amphibians?

Lobe-finned fishes Signup and view all the answers

What group do lobe-finned fish belong to in the context of evolutionary steps leading to dinosaurs?

Tetrapod ancestors Signup and view all the answers

What significant evolutionary innovation allowed early reptiles to lay eggs on land?

Development of the amniotic egg Signup and view all the answers

Which of the following is considered the first true vertebrate?

Primitive jawless fishes Signup and view all the answers

What feature distinguishes amphibians from earlier tetrapod ancestors?

Development of robust limb bones Signup and view all the answers

What characteristic do lobe-finned fish possess that is crucial for their adaptation to terrestrial environments?

Articulated bones in fins Signup and view all the answers

Which of the following statements about early reptiles is NOT true?

They could reproduce in aquatic environments. Signup and view all the answers

What was a key feature of transitional species like Tiktaalik?

Gills and lungs for air and water breathing Signup and view all the answers

The earliest chordates, such as Pikaia, evolved during which geological period?

Cambrian Signup and view all the answers

What is the meaning of the name Pteranodon longiceps?

Winged, toothless, long-headed Signup and view all the answers

During which geological period did pterosaurs exist from the Late Triassic to the end of the Cretaceous?

Triassic to Cretaceous Signup and view all the answers

What adaptation is primarily associated with pterosaurs?

Powered flight Signup and view all the answers

What is the estimated wingspan of Quetzalcoatlus, one of the largest pterosaurs?

11 meters Signup and view all the answers

Which of the following is a key characteristic of pterosaur wings?

A membrane of skin, tissues, and muscles Signup and view all the answers

Which group is considered the sister clade to the dinosaurs?

Pterosaurs Signup and view all the answers

What is a characteristic feature of archosaurs distinct from other reptiles?

Changes to the ankle Signup and view all the answers

Which group includes both dinosaurs and birds?

Archosauria Signup and view all the answers

Within diapsids, which group represents reptiles with a fully upright posture?

Archosauria Signup and view all the answers

Which of the following is NOT a member of the Archosauria group?

Lobefins Signup and view all the answers

What does the term 'avemetatarsalia' refer to within the context of archosaur diversity?

The lineage leading to birds Signup and view all the answers

Which characteristic is shared by pterosaurs and dinosaurs?

They are both classified under Archosauria. Signup and view all the answers

What group includes the largest dinosaurs and their relatives?

Saurischia Signup and view all the answers

Study Notes

Dinosaur Ancestry

Tetrapods evolved from primitive fish, with the Cambrian period marking the appearance of early chordates like Pikaia (~510 million years ago).
The first vertebrates were jawless fishes, followed by diversification into various fish types, including lobe-finned fish with both gills and lungs.
Lobe-finned fish could "walk" on riverbeds and travel overland to access water, breathing through lungs.

Evolution of Tetrapods

Amphibians were the first true tetrapods, exhibiting robust limb bones and represented by transitional species like Tiktaalik.
Reptiles evolved from amphibians, showcasing adaptations such as skeletal modifications for life on land and the development of the amniotic egg, which allows eggs to be laid on land.

Tetrapod Family Tree

Ancestral lineage includes: Pikaia, jawless fishes, placoderms, cartilaginous fishes, ray-finned fishes, lobe-finned fishes, amphibians, and reptiles.
Reptile diversification includes various classes: anapsids, euryapsids, synapsids (leading to mammals), and diapsids.

Diapsid Reptiles

Diapsids split into two main groups: Lepidosaurs (modern lizards and snakes) and Archosaurs (crocodilians and avemetatarsalia, which includes pterosaurs and dinosaurs).
Archosaurs show key evolutionary innovations, particularly alterations to the ankle for different postures: semi-upright in pseudosuchia and fully upright in avemetatarsalia.

Pterosaurs

Pterosaurs, known as "winged lizards," form a sister clade to dinosaurs and existed from the Late Triassic to the end of the Cretaceous (228-66 million years ago).
Notable pterosaurs include Pteranodon longiceps, known for its wingspan of over 6 meters (20 feet) and its toothless, long-headed structure.

Azhdarchids

Azhdarchids represent some of the largest pterosaurs. Notable examples include Quetzalcoatlus, with an impressive wingspan reaching 11 meters.
Fossils suggest Quetzalcoatlus lived in North America around 85 million years ago.

Adaptations for Flight

Pterosaur wings are constructed from a membrane of skin, tissues, and muscles, indicating significant adaptations for powered flight.
Odd body dimensions in pterosaurs further complement their flight capabilities, showcasing evolutionary adaptations specific to their ecological niches.

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Description

This quiz covers Lecture 6 of EASC 103, focusing on the evolutionary steps leading to dinosaurs. Explore the diversification of tetrapods, the construction of their family tree, and examine diapsid reptiles and pterosaurs, which are closely related to dinosaurs.