Mesozoic Era Flashcards

These flashcards provide vocabulary and key concepts for the Mesozoic Era, covering tectonic changes, biological evolution across the Triassic, Jurassic, and Cretaceous periods, and the terminal mass extinction.

Mesozoic Era

An era known as middle life that extends from about $252$ to $65\text{ Ma}$, beginning with recovery from a mass extinction and finishing with another mass extinction.

Triassic Period

A period spanning $252-201\text{ Ma}$ during which reptiles evolved, dinosaurs and crocodylomorphs appeared, and the breakage of Pangaea began.

Pangaea

The supercontinent that began to break up at the end of the Triassic and split apart during the Jurassic.

Megachirella

A stem lizard that lived approximately $240\text{ Ma}$, was about $15\text{ cm}$ long, and is part of the earliest squamate group (geckos).

Therapsida

A group of synapsid reptiles that were stem ancestors to mammals, characterized by mammal-like traits such as a walking stance and dental characteristics.

Archosauria

Diapsid reptiles that were stem ancestors to birds, crocodiles, pterosaurs, and dinosaurs; characterized by skull openings in front of the eyes and socketed teeth.

Cynodonts

A suborder of therapsids that are stem ancestors to mammals, featuring mammalian traits like hair, warm-bloodedness, and a mammal-like abdomen for breathing.

Pseudosuchia

A major archosaur division containing crocodiles and their relatives, characterized by $4-5$ digits on the hands and feet and a closed acetabulum (hip socket).

Avemetatarsalia

A major archosaur division with bird-like foot bones and higher ankle flexibility/mobility compared to Pseudosuchia.

Rauisuchia

The dominant land predators of the Triassic, with the largest species (G Fasolasuchus) reaching over $6\text{ meters}$ long.

Pterosauria

The earliest flying vertebrates in geologic history, featuring wings formed by a membrane of skin stretching from the ankle to an elongated $4\text{th}$ finger.

Nyasasaurus

A creature from Tanzania that lived approximately $246\text{ Ma}$ and is considered a candidate for the first dinosaur.

Jurassic Period

A period spanning $202-145\text{ Ma}$ characterized by continued dinosaur evolution, the appearance of the first birds, and the earliest true mammals.

Laurasia

The northern landmass formed when Pangaea split into two parts between $215-175\text{ Ma}$.

Gondwana

The southern landmass formed when Pangaea split into two parts between $215-175\text{ Ma}$.

Ornithischian

Mainly herbivorous dinosaurs featuring a bird-like hip bone structure where the pubis bone points tailward; they involve an open acetabulum.

Saurischian

A group including carnivorous dinosaurs and modern birds characterized by a lizard-like hip bone structure where the pubis bone points forward.

Sauropods

Huge, four-legged herbivorous dinosaurs with disproportionate heads; they are known as the largest land creatures to ever live.

Theropods

Bipedal dinosaurs characterized by hollow bones and three-toed limbs; they include carnivores, herbivores, and the ancestors of modern birds.

Juramaia

The earliest known placental mammal from the late Jurassic ($~160\text{ Ma}$), which was a small shrew-like animal up to $10\text{ cm}$ long.

Marsupial

A mammal type with a uterus and yolk sac-like placenta where underdeveloped babies are produced after a minimal time in the womb.

Monotreme

A mammal that lacks a uterus and produces young through a hard egg rather than live birth, such as the duckbill platypus.

Placental

A mammal type that uses a temporary organ (placenta) to connect the fetus to the uterus, allowing for maximal time in the womb and developed offspring.

Archaeopteryx

A transitional creature appearing around $150\text{ Ma}$ that is between feathered dinosaurs and birds, featuring wings and feathers but also teeth and a long bony tail.

Cretaceous Period

A period spanning $145-66\text{ Ma}$ when dinosaurs flourished, the first primates and flowering plants appeared, and primitive modern continent shapes formed.

Ankylosaurus

A heavily armored Cretaceous dinosaur with a tail club, specimens of which have been found in the Carlsbad area of California.

Nevadan Orogeny

A mountain-building event in western North America between $155-145\text{ Ma}$ that formed the Sierra Nevada and Klamath Mountains.

Sevier Orogeny

A simultaneous mountain-building period with the Laramide ($~140-50\text{ Ma}$) involving thin-skinned style deformation and compression in central Utah.

Laramide Orogeny

A mountain-building period ($~80-35\text{ Ma}$) in western North America featuring thick-skinned style deformation of deep basement rock and deep-seated faults.

K-Pg Extinction

A mass extinction event approximately $65\text{ Ma}$ where at least 75\text{%} of species died out, marked by a worldwide sediment layer high in iridium.

Chicxulub Crater

An impact crater in the Yucatán Peninsula discovered in the $1990\text{s}$ that correlates with the timing of the K-Pg extinction event.

Deccan Traps

Large volcanic features in India that formed around $65\text{ Ma}$; their eruptions released gases like $SO_2$ that contributed to sudden global cooling.