PALEO 200 Glossary Terms Module 7-12

Abelisaurids

A group of ceratosaurid theropods that thrived throughout Gondwana during the Middle Jurassic to Late Cretaceous; characterized by short forelimbs, small teeth, and ornamented skulls; e.g. Carnotaurus, Majungasaurus, and Rugops

Alfred Wegner

German meteorologist who devised the theory of continental drift

Anapsids

A group of amniotes that have no skull fenestra; turtles are a modern example; the validity of this clade is contested among paleontologists

Ankylosaurs

Heavily-armored quadrupedal ornithischian dinosaurs; e.g. Ankylosaurus, Edmontonia, Polacanthus

Antorbital fenestra

Opening in the skull in front of the orbits; characteristic of archosaurs

Archean Eon

Division of the Geologic Timescale from 4-2.5 billion years ago; during this time the atmosphere likely lacked free oxygen and stromatolites first appeared

Archosauromorpha/Archosauromorphs

A group of diapsids that includes archosaurs and many more primitive groups; first evolved during the Late Permian

Aves

The clade containing birds

Binomial name

The two part scientific name of a species; composed of a genus name and a species epithet; written in italics

Biological species concept

A group of organisms that can interbreed

Branches

Lines on a cladogram that show how descendants from a common ancestor diverged to become unique species

Cambrian Explosion

The rapid appearance of most of the major animal groups around 540 million years ago

Cambrian Period

Division of the Geologic Timescale from 542-490 million years ago

Carboniferous Period

Division of the Geologic Timescale from 355-300 million years ago

Carcharodontosaurids

A group of theropod dinosaurs with teeth that somewhat resemble those of modern sharks; lived during the Late Jurassic to the Late Cretaceous; e.g. Giganotosaurus, Carcharodontosaurus, Concavenator

Carl Linnaeus

18th century Swedish naturalist who created binomial nomenclature

Cenotes

Sinkhole formed from the collapse of limestone; a circular arrangement of cenotes mark the rim of the Chixulub crater

Cenozoic Era

Division of the Geologic Timescale from 66 million years ago to the present; often called “The Age of Mammals”

Coelurosaurian theropods

A group of theropod dinosaurs closely related to and including birds; e.g. Compsognathus, Tyrannosaurus, Velociraptor

Convergent feature/evolution

Similar structures that independently evolve in unrelated species because the two species are faced with similar survival challenges

Crust

The outermost solid layer of the Earth; between 5-25 km thick

Cynodonts

A group of synapsids that led to modern day mammals; first evolved in the Late Permian

Devonian Period

Division of the Geologic Timescale from 420-355 million years ago

Diapsida/Diapsids

A group of amniotes with two pairs of skull fenestra: supratemporal and laterotemporal fenestrae; includes crocodiles, lizards, snakes, tuataras, dinosaurs, birds, and many extinct groups

Dicynodonts

A group of herbivorous synapsids with characteristic tusks and beaks; first evolved in Permian and thrived during the Triassic

Diplodocids

A group of sauropod dinosaurs with long necks and long “whip-like” tails; lived during the Middle to Late Jurassic; e.g. Apatosaurus, Diplodocus, Supersaurus

Extant

Species currently alive

Formation

A body of rock composed of a certain rock type or series of types

Geologic Timescale

A standardized system that divides the history of the Earth into discrete temporal units

Gondwana

Former supercontinent composed of South America, Australia, Africa, Antarctica, Madagascar, and India

Gorgonopsids

Group of carnivorous synapsids characterized by sets of elongated fangs; lived from the Middle to Late Permian

Hadeon Eon

Division of the Geologic Timescale from 4.6-4 billion years ago; the first geologic eon

Hadrosaurs

Advanced group of ornithopod dinosaurs with broad beaks and dental batteries; commonly called “duck-billed dinosaurs”; e.g. Edmontosaurus, Maiasaura, Parasaurolophus

Holotype

Specimen used to describe and name a new species

Inner core

The innermost layer of the Earth; a solid mass composed of iron and nickel

Iridium

An element that is rare on Earth but common in meteorites

Jurassic Period

Division of the Geologic Timescale from 201-145 million years ago; the second period of the Mesozoic Era

Laurasia

Former supercontinent comprised of Asia, Europe, and North America

Lepidosauromorpha/Lepidosauromorphs

Group of non-archosaur diapsids that include lizards, snakes, tuatara, and many extinct groups

Lithosphere

Ridged outermost layer of the Earth; composed of the crust and the upper portion of the mantle

Mandibular fenestra

Fenestra in the lower jaws of archosaurs

Mantle

Highly viscous layer of the Earth; layer between the crust and the outer core; roughly 2900km thick

Mesozoic Era

Division of the Geologic Timescale from 252-66 million years ago; contains the Triassic, Jurassic, and Cretaceous periods; during this time dinosaurs, birds, and mammals evolved; commonly called “the Age of Dinosaurs”

Morphological species concept

Concept that defines organisms that look different as belonging to different species and organisms that look the same as belonging to the same species

Mosasaurs

A group of extinct lepidosaurs that were highly adapted to a marine life; evolved in the Late Cretaceous

Nodes

The points on a cladogram that indicate where two lineages shared a common ancestor

Ontogenetic changes

Anatomical changes that occur during an individual’s lifetime

Ordovician Period

Division of the Geologic Timescale from 490-440 million years ago; during this time the first jawed fish evolved; ended with a mass extinction

Ornithomimids

Group of herbivorous and possibly omnivorous theropod dinosaurs characterized by long legs and short beaks; commonly called “ostrich-mimic” dinosaurs; first evolved in the Cretaceous; e.g. Gallimimus, Struthiomimus, Ornithomimus

Outer core

Layer of the Earth composed of molten iron and nickel; roughly 2270 km thick

Oviraptorids

Group of herbivorous and possibly omnivorous theropod dinosaurs characterized by beaks and feather tails fans; evolved during the Cretaceous; e.g. Oviraptor, Gigantoraptor, Caudipteryx

Paleozoic Era

Division of the Geologic Timescale from 542-252 million years ago

Pangaea

Supercontinent comprised of all the Earth’s major landmasses, that formed around 300 million years ago and began breaking up around 200 million years ago

Panthalassa

The giant ocean that surrounded Pangaea

Parsimony/Occam’s Razor

The reasoning that’s the simplest of two or more explanations is most probable; originally expressed by philosopher William of Ockham; commonly summarized as “all other things being equal, the simplest answer is usually the right one”

Permian Period

Division of the Geologic Timescale from 300-252 million years ago; ended in a mass extinction

Phanerozoic Eon

Division of the Geologic Timescale from 542 million years ago to the present

Phylogenetic tree/cladogram

Diagram that visually depicts the pattern of evolutionary relationships among a group of organisms

Plate tectonics

Scientific theory that explains and describes the motion of the Earth’s lithosphere

Plesiosaurs

A group of diapsids specially adapted to a marine life; lived during the Early Jurassic to late Cretaceous; e.g. Dolichorhynchops, Elasmosaurus, Kronosaurus

Principle of Superposition

The basic principle of stratigraphy that when sedimentary layers are horizontal the oldest layer will be on the bottom with progressively younger layers above it

Proterozoic Eon

Division of the Geologic Timescale from 2.5 billion years to 542 million years ago

Pseudosuchians

Group of archosaurs that includes modern crocodilians and all archosaurs more closely related to crocodilians than to birds; “crocodile-line” archosaurs

Pterosaurs

Group of flying archosaurs closely related to dinosaurs; lived during the Late Triassic to the Cretaceous; the first group of vertebrates to evolve flight; commonly called “pterodactyls”; e.g. Pteranodon, Quetzalcoatlus, Rhamphorhynchus

Radiometric dating

The use of isotopic ratios to calculate age of a rock

Rule of Priority

The first name formally given to an organism is the one that stands

Sexual dimorphism

Differences between males and females of a given species

Shared derived character/synapomorphy

Characteristic common to the members of a phylogenetic group and not present in more primitive ancestral species outside the group; character that defines a phylogenetic group

Shocked quartz

Quartz whose internal structure has deformed due to intense pressure; known to be produced from the shockwaves of atomic blasts and meteorite impacts

Silurian Period

Division of the Geologic Timescale from 440-420 million years ago

Stratigraphy

Branch of geology that studies rock layers

Synapsids

A group of amniotes with only one pair of fenestra; includes mammals and their extinct close relatives

Taxonomy

The science of classifying organisms

Tektites

Earthly debris that was superheated by a meteorite impact and cooled to form a natural glass

Therizinosaurs

A group of herbivorous and possibly omnivorous theropod dinosaurs characterized by long necks, elongated forelimbs, elongated hand claws, and four forward-directed toes; lived during the Cretaceous; e.g. Therizinosaurus, Segnosaurus, Falcarius

Titanosaurs

Group of advanced sauropod dinosaurs; lived during the Late Jurassic to Late Cretaceous; globally distributed but most abundant in Gondwana; e.g. Argentinosaurus, Saltosaurus, Alamosaurus

Triassic Period

A division of the Geologic Timescale from 252-200 million years ago; first period of the Mesozoic Era; the start and end are marked by mass extinctions; dinosaurs and animals first appeared in the Late Triassic