BISC 120 - Lecture 15: Mesozoic and Cenozoic Evolution

Vocabulary practice flashcards covering Mesozoic reptiles, dinosaur groups, synapsid and mammal evolution, the end-Cretaceous mass extinction, and Cenozoic climate trends from BISC 120 Lecture 15.

Mesozoic Era

Geologic era occurring about 250-65 mya, referred to as the Age of Reptiles.

Triassic climate

Climatic conditions early in the Mesozoic that were still hot and dry.

Late Jurassic-Early Cretaceous climate

Climate that was warmer and more humid than the Triassic climate.

Mesozoic continental drift

The ongoing movement in which continents continued drifting apart throughout the Mesozoic.

Archosaurs

Reptile group that includes crocodilians, birds, and extinct dinosaur groups.

Triassic archosaurs

Archosaurs that gave rise to the earliest crocodilians, pterosaurs, and dinosaurs.

Early dinosaurs

Dinosaurs that were originally small and bipedal.

Early Mesozoic mammals

Mammals that evolved during the Triassic but remained small and mostly nocturnal.

Late Triassic dinosaur diversification

Major evolutionary radiation where dinosaurs diversified greatly and continued through the Jurassic and Cretaceous.

Theropods

Mostly bipedal dinosaurs, many of which were carnivorous, such as Tyrannosaurus and Allosaurus.

Sauropods

Usually quadrupedal herbivorous dinosaurs; some reached enormous body sizes.

Jurassic-Cretaceous sauropods

Sauropods that reached their maximum sizes during the Jurassic and Cretaceous periods.

Feathered dinosaurs

Dinosaurs that had fluff or feathers in addition to scales.

Bird origin

Evolutionary event in which a group of small feathered theropod dinosaurs gave rise to birds during the Jurassic.

Archaeopteryx

Early bird featuring airfoil-shaped feathers alongside dinosaur-like teeth, claws, and tail.

Pterosaurs

Flying Mesozoic reptiles that are not dinosaurs.

Plesiosaurs

Marine Mesozoic reptiles that are not dinosaurs.

Ichthyosaurs

Marine Mesozoic reptiles that are not dinosaurs.

Mesozoic Synapsida

Therapsids that continued evolving and became smaller and more mammal-like during the Triassic.

Cynodonts

Advanced, mammal-like therapsid synapsids that were important in the origin of mammals.

Tetracynodon

Triassic therapsid synapsid highlighted as an example of a cynodont.

Early synapsid jaw joint

Jaw joint articulation formed by the quadrate and articular bones.

Early synapsid lower jaw

Lower jaw structure that contained many bones, among which the dentary was the largest.

Dentary

The largest lower-jaw bone in early synapsids, which becomes the single lower-jaw bone in mammals.

Early synapsid teeth

Teeth that were relatively similar in morphology rather than strongly specialized.

Early synapsid middle ear

Middle ear in which only the stapes was present as an auditory bone.

Cynodont jaw transition

Evolutionary modification where the dentary increasingly articulated directly with the skull, as seen in mammals.

Articular to malleus transition

Evolutionary transformation where the early synapsid articular jaw bone became the malleus of the mammalian middle ear.

Quadrate to incus transition

Evolutionary transformation where the early synapsid quadrate jaw bone became the incus of the mammalian middle ear.

Mammalian lower jaw

Jaw structure in which only one bone remains: the dentary, known as the mandible in humans.

Mammalian differentiated teeth

Specialized dentition consisting of incisors, canines, premolars, and molars.

First mammals

Mammals that arose from advanced cynodont synapsids around the Triassic-Jurassic boundary (~200 mya).

Early mammal brain

Organ that underwent expansion in size as mammals evolved.

Morganucodon

An early mammal example that was small, insectivorous, active, endothermic, and egg-laying.

Early mammal hearing

Sensory function resulting from new middle-ear anatomy that yielded sensitive hearing across many frequencies.

Early mammal and dinosaur coexistence

Ecological co-occurrence in which early mammals lived alongside dinosaurs throughout the Jurassic and Cretaceous.

Major mammal groups (~160 mya)

The three groups present by about 160 mya: monotremes, marsupials, and placental mammals.

Monotremes

Living mammal group characterized by laying eggs.

Marsupials

Living mammal group characterized by the presence of a pouch.

Placental mammals

Living mammal group characterized by the presence of a placenta.

Cretaceous mass extinction

Mass extinction event occurring 65-66 mya that ended the Mesozoic and began the Cenozoic.

Cretaceous extinction cause

An asteroid impact in Mexico that caused worldwide environmental effects.

Iridium layers

Geological evidence associated with the end-Cretaceous asteroid impact.

Cenozoic continental movement

The progression of continents toward modern positions, including the collision of India with Eurasia to form the Himalayas.

Early Cenozoic climate

Climate regime that began warmer than today and subsequently cooled.

Paleocene and Eocene

The warmest climatic intervals identified in the Cenozoic climate overview.

Eocene-Oligocene boundary

Geologic transition marked by a large temperature drop associated with the Grande Coupure, or Big Cut.

Grande Coupure

A major extinction event (also termed the Big Cut) associated with climatic cooling near the Eocene-Oligocene boundary.

Middle Miocene cooling

Major temperature drop occurring around ~15 mya during which the climate became cooler and drier.

Antarctic ice sheet

Permanent ice mass that expanded as the climate cooled, contributing to lowered global ocean levels.

Cenozoic climate trend

Long-term climatic pattern characterized by warm and humid conditions early, shifting to cooler, drier, and more variable conditions later with glaciations.