Albian: The interval of geologic time from approximately 112 to 99 million years ago.
Allopatry: When two species do not occur together, but exclude each other geographically.
Alpine Tethyan Sea: An oceanic basin, located where the western Alps presently are, that opened in the Early Jurassic (following the opening of the Atlantic Ocean) and closed during the Tertiary.
Altriciality: The kind of vertebrate ontogeny that is characterized by a short gestation and the birth of relatively underdeveloped, helpless young.
Alvarezsauridae: A node-based taxon defined as the most recent ancestor of Mononykus and Alvarezsaurus, and all the descendants of this ancestor. This clade is diagnosed by laterally compressed synsacral vertebrae, extreme modification of the forelimbs, and the absence of distal fusion in the pubis and ischium, among other characters. The phylogenetic position of alvarezsaurids is quite controversial. These theropods have been placed on either side of Archaeopteryx, making them either a true avialan clade or a very close outgroup. On the other hand, alvarezsaurids have been identified as the sister group to ornithomimosaurs. Other alvarezsaurids include Shuvuuia, Mononykus, and Patagonykus (Chiappe et al. 2002).
Ammonites: An extinct group of marine cephalopods whose closest living relative is the modern pearly nautilus. Their shells generally are in the form of flat spirals, although others uncoil to produce a straight conical shell. Known worldwide from the Silurian to the end of the Cretaceous, ammonites were among the top predatory invertebrates of their time.
Ankylosauria: The “armored” dinosaurs, a stem-based taxon defined as all eurypodan thyreophorans closer to Ankylosaurus than Stegosaurus. This clade can be diagnosed by numerous features of the skull, vertebral column, pelvis, and armor. Other ankylosaurs include Edmontonia, Ankylosaurus, and Pinacosaurus (Vickaryous et al. 2004).
Ankylosauridae: A stem-based taxon defined as those ankylosaurs more closely related to Ankylosaurus than to Edmontonia, and diagnosed by having a pyramidal squamosal boss, raised nuchal sculpturing, a premaxillary palate that is wider than long, a premaxillary notch, a deltoid quadratojugal boss, a postocular shelf, and a tail club, among other features. Other ankylosaurids include Gobisaurus, Saichania, and Euoplocephalus (Vickaryous et al. 2004).
Apparent polar wandering: The apparent migration, over Earth’s surface, of Earth’s magnetic poles through geologic time. Known from the direction of magnetization of many rocks, apparent polar wandering attests to the movement of continental landmasses and makes it possible to infer the relative movement of various continental blocks over different intervals of geologic time.
Aptian: The interval of geologic time from approximately 121 to 112 million years ago.
Apulia: A region in southeastern Italy, on the Adriatic coast and the Gulf of Taranto. In terms of plate tectonics, it is a microcontinental plate that once formed the promontory of northern Africa, but it detached to eventually suture with several other microcontinents and the Eurasian plate to form Italy, the inner region of Transylvania, and the Banat. See also “Moesia” and “Rhodope.”
Aves: The monophyletic clade of all living birds; crown-group birds.
Avetheropoda: A node-based taxon consisting of Allosaurus fragilis, Passer domesticus (the living English sparrow), their most recent common ancestor, and all of its descendants, diagnosed by broad contact between the quadratojugal and the squamosal, palatine recesses, laterally displaced zygapophyses of the cervical vertebrae, a large and narrow iliac preacetabular fossa, an obturator process that is separated from the pubic plate, and the development of an accessory trochanter on the proximal lateral surface of the femur, among other characters. Other avetheropods include Sinraptor, Carcharodonto-saurus, Archaeopteryx, and modern birds (Holtz and Osmólska 2004).
Avialae: A stem group encompassing living birds and all maniraptorans closer to them than to Deinonychus, a dromaeosaurid. This clade is diagnosed by many features, among them long, narrow, and pointed premaxillae; a quadrate that articulates with the prootic and the squamosal; unserrated teeth that are reduced in size and number; a pronounced acromion process on the scapula; a coracoid with a pronounced sternal process; forelimbs that are nearly as long as or longer than the hind limbs; forearms approximately as long as or longer than the humerus; and modifications of the foot, among other characters. This clade includes Archaeopteryx, Hesperornis, and Aves (Padian et al. 2004).
Azhdarchidae: A stem-based taxon defined as all pterosaurs more closely related to Quetzalcoatlus than to Tapejara, diagnosed by an elongation of the middle cervical vertebrae and the reduction or loss of the neural spines on these cervicals. In addition to Quetzalcoatlus, Azhdarchidae presently includes Azhdarcho (Kellner 2003).
Biogenic Law: Haeckel’s term for his principle that ontogeny recapitulates phylogeny.
Biogeography: The study of the geographic distribution of life.
Biological constraints: The limits or boundary conditions on biological traits whose success or failure depends on alternatives in other organisms with which a species competes. These biological constraints are historical and developmental in their essence, since the ultimate arbiter is competitive advantage, and thus survival is imparted by design.
Biological determinism: A theory that claims that the traits of organisms are entirely determined by the interaction of genetic variation and the overarching control of natural selection.
Bioturbation: The biological activities that occur at or near the sedimental surface that cause the sediment to become mixed. Examples of these activities include burrowing and boring.
Campanian: The interval of geologic time from approximately 83.5 to 71.3 million years ago.
Casichelydia: A stem-based taxon defined as all testudines closer to Crysemys picta (the living painted turtle) than to Proganochelys. This clade is diagnosed by the loss of the lacrimal bone and duct, and a modification of the palate and braincase. Other casicheyids include Kayentachelys and two living turtles, the yellow-spotted Amazon River turtle (Podocnemis unifilis) and the eastern box turtle (Terrapene carolina) (Gaffney and Meylan 1988).
Cenomanian: The interval of geologic time from approximately 99 to 93.5 million years ago.
Ceratopsia: A stem clade defined as all of Marginocephalia closer to Triceratops than to Pachycephalosaurus, which is diagnosed by a high external naris separated from the ventral border of the premaxilla by a flat area, a rostral bone, an enlarged premaxilla, well-developed lateral flaring of the jugal, wide dorsoventral length of the infraorbital ramus of the jugal, and contact of the palatal extensions of the maxillae rostral to the choana. Other ceratopsians include Psittacosaurus, Protoceratops, and Styracosaurus (You and Dodson 2004).
Ceratosauria: A stem-based taxon defined as those theropods more closely related to Ceratosaurus nasicornis than to birds. This clade can be diagnosed by modifications of the vertebral column and pelvis, among others. Other ceratosaurians include Coelophysis, Syntarsus, and Carnotaurus. There is some question about the monophyly of this group (Tykoski and Rowe 2004).
Cimmerian block: An elongate and narrow continental block that, when it began its northern motion approximately 280 million years ago, extended from modern-day Gibraltar to the eastern margin of Australia, where it formed the southern margin of the Paleotethyan Ocean. The Cimmerian block docked with the Eurasian continental landmass, thereby creating the largest extent of the Neotethyan Ocean, about 200 million years ago.
Clade: A group of biological taxa that includes all the descendants of a single common ancestor.
Cladistics: A system of biological taxonomy that defines taxa by shared unique characteristics not found in ancestral groups and uses inferred evolutionary relationships to arrange taxa in a branching hierarchy, such that all members of a given taxon have the same ancestors. See also “Phylogenetic systematics.”
Cladogram: A branching diagrammatic tree used in cladistic classification to illustrate phylogenetic relationships.
Coelacanth: Usually
refers to the living form, Latimeria, and its two species (L. chalumnae and L. menadoensis), as well as their closest (but extinct) relatives. See also “Actinistia.”
Coevolution: Evolution involving successive changes in two or more ecologically interdependent species that affect their interactions.
Comparative anatomy: The study of the anatomy of several groups of organisms.
Cope’s Rule: The tendency for size increases to occur in evolutionary lineages.
Court Jester hypothesis: A model of extinction in which changes in the physical environment are the initiators of major changes in organisms.
Crocodylia: A node-based (crown-group) taxon defined as the common ancestor of the living Alligator mississippiensis and the living Gavialis gangeticus, and all the descendants of this common ancestor. This clade is diagnosed by the construction of the skull roof and the mandible. Modern crocodilians include alligators, crocodiles, gavials, and caimans, among others (Buscalioni et al. 2001).
Crown group: The clade made up of all living members of the group, the ancestor of that clade, and all the descendants of that ancestor. Examples include Mammalia, Aves, and Archosauria.
Cryptodira: The hidden-necked turtles, a node-based taxon defined as the common ancestor of Kayentachelys and Crysemys picta (the living painted turtle), and all the descendants of this common ancestor. This clade can be diagnosed by several features of the palate, the jaw system, and the skull roof, as well as the turtle’s unique way of folding its neck. Other cryptodires include Meiolania, living soft-shelled freshwater turtles, and the modern Galápagos giant tortoise (Geochelone nigra) (Gaffney and Meylan 1988).
Dacians: The people who inhabited the region known as Dacia (in what is now Romania, Moldova, and parts of Serbia, Bulgaria, Hungary, and Ukraine) between the second century BCE and the second century CE, when they were conquered by the Romans.
Definition: A statement about the membership of a clade, based on common ancestry.
Dental battery: Upper and lower dentition, composed of abundant (up to 60 tooth positions), closely packed cheek teeth and consisting of one to three functional teeth and up to five replacement teeth per tooth position. Dental batteries are known in hadrosaurid dinosaurs.
Diagnosis: The list of features that are synapomorphies, delimiting the taxon that has been defined.
Diastema: A space between teeth in a jaw, usually referring to the gap between the front of the jaws and the cheek teeth (as seen in hadrosaurids), or the gap between the incisors and premolars (in horses).
Dinosauria: A node-based taxon consisting of Triceratops, Neornithes, their most recent common ancestor, and all their descendants. It is diagnosed by the loss of the postfrontal, elongated deltopectoral crest on the humerus; a brevis shelf on the ventral surface of the postacetabular part of ilium; an extensively perforated acetabulum; a tibia with a transversely expanded, subrectangular distal end, as well as a caudolateral flange and a depression for the astragalus; and an ascending astragalar process on the cranial face of the tibia (Benton 2004).
Dromaeosauridae: A node-based taxon defined as all the descendants of the most recent common ancestor of Microraptor zhaoianus, Sinornithosaurus milleni, and Velociraptor mongoliensis. This clade can be diagnosed by features of the skull roof, the vertebrae, and a sickle-shaped claw on the second digit of the foot, among others. Other dromaeosaurids include Saurornitholestes and Deinonychus (Norell and Makovicky 2004).
Dsungaripteroidea: A node-based pterosaur taxon defined as the most recent common ancestor of Nyctosaurus and Quetzalcoatlus, and all of its descendants, diagnosed by edentulous jaws, a notarium, and a pneumatic foramen on the proximal humerus, among other features. Other dsungaripteroids include Pteranodon, Noripterus, and Anhanguera (Kellner 2003).
Euhadrosauria: The true hadrosaurids, a node-based taxon defined as the common ancestor of Edmontosaurus and Corythosaurus, and all the descendants of this common ancestor. The clade is diagnosed by modifications of the jaws. Other euhadrosaurs include Gryposaurus, Parasaurolophus, and Charonosaurus (Horner et al. 2004).
Eusuchia: The true suchians, a node-based taxon defined as the common ancestor of Hylaeochampsa and Alligator, and all the descendants of this common ancestor. This clade can be diagnosed by modifications of the palate and the vertebrae. Other eusuchians include Alligator, Caiman, and Gavialis (Buscalioni et al. 2001).
Foraminifera: A group of large, chiefly marine protozoans—usually having calcareous shells that often are perforated with minute holes for the protrusion of slender pseudopodia—that form the bulk of chalk and nummulitic limestone.
Founder effect: The principle that the founders of a new, isolated population carry a gene pool that is not representative of that of the population as a whole.
Functional morphology: The study of how biological structures work, which, in paleontology, entails the use of analogies with mechanical and extant animal models.
Ghost lineage: The lineage of an organism for which there is no physical record, but whose existence can be inferred by phylogeny calibrated by stratigraphy. The length of time incorporated into a ghost lineage is known as its ghost lineage duration (GLD).
Gondwana: The region consisting of the once-connected Indian subcontinent and the landmasses of the Southern Hemisphere.
Hadrosauridae: The duck-billed dinosaurs, a node-based taxon defined as the common ancestor of Telmatosaurus and Corythosaurus, and all the descendants of this common ancestor. This clade can be diagnosed by numerous features involving dentition, the skull and palate, the vertebral column, and the appendicular skeleton. Other hadrosaurids include Gryposaurus, Edmontosaurus, and Parasaurolophus (Horner et al. 2004).
Hadrosaurinae: The non-lambeosaurine euhadrosaurians, a stem-based taxon defined as all euhadrosaurs more closely related to Edmontosaurus than to Corythosaurus. This clade can be diagnosed on the basis of modifications of the nasal region of the skull. Other hadrosaurines include Gryposaurus, Maiasaura, and Saurolophus (Horner et al. 2004).
Hadrosauroidea: A stem-based taxon defined as all iguanodontians more closely related to Corythosaurus than to Iguanodon. This clade is diagnosed by modifications of the facial skeleton, the tail vertebrae, the pelvis, and the hind foot. Other hadrosauroids include Shuangmiaosaurus, Altirhinus, and Eolambia (You et al. 2003).
Heterochrony: Evolutionary differences in the features of organisms due to ontogenetic changes in the relative rates or timing of the development of organismal traits. When a descendant is ontogenetically less well developed than its ancestor, the resulting morphology is termed paedomorphic. When its development goes beyond that of its ancestor, the resulting morphology is called peramorphic. See also “Paedomorphosis” and “Peramorphosis.”
Hierarchy: In evolutionary biology, the ordering of organisms by a pattern of common descent; clades within clades.
Histology: The study of tissue structure or organization.
Historical contingency: The conditions by which the details of evolutionary history are unpredictable, that is, determined by chance events and/or by improbable events with large consequences.
Homology: A similarity between two organisms, due to the inheritance of the same feature from a common ancestor.
Homoplasy: A similarity between two organisms, due to separate and independent inheritances from different ancestors. Evolutionary convergence is one kind of homoplasy.
Iguanodontia: A stem-based taxon defined as all euornithopods closer to Edmontosaurus than to Thescelosaurus. This clade can be diagnosed by numerous modifications of the snout, the sternum, the pelvis, and the manus. Other iguanodontians include Dryosaurus, Ouranosaurus, and hadrosaurids (Norman 2004).
Insularity: As used in this volume, the state or condition of being cut off or isolated from other organisms.
Island Rule: The common pattern of a dwarfing of mammals evolving on islands.
K selection / strategy: Selection on individuals in populations at or near the carrying capacity of their environm
ents, usually favoring the production of a few, slowly developing young that are well adjusted in form and function to their (usually stable) environment. K-selected individuals are good competitors in conditions of density-dependent mortality.
Lambeosaurinae: The hollow-crested hadrosaurids, a stem-based taxon defined as all euhadrosaurs more closely related to Corythosaurus than to Edmontosaurus. This clade can be diagnosed by modifications of the jaw system and the skull roof. Other lambeosaurines include Lambeosaurus, Corythosaurus, and Tsintaosaurus (Horner et al. 2004).
Laurasia: The region consisting of the once-connected landmasses of the Northern Hemisphere, except for the Indian subcontinent.
Laws of physics: From an evolutionary perspective, the universal/ahistorical laws that dictate the general configuration of biological forms. These laws arise from the physical tenets of geometry, scaling laws, and packing principles.
Life-history strategies: Selected sets of adaptations to local environments, involving such quantitative aspects of life history as fecundity, the timing of maturation, and the frequency of reproduction. Responses to r and K selection represent two different life-history strategies.
Lithosphere: The solid, outer part of Earth’s core, composed of rock essentially like that exposed at the surface and usually considered to be about 80 km thick.
Living fossil: An organism that has remained essentially unchanged from much earlier geologic times and whose close relatives are usually extinct. Living fossils are descendants of extinct organisms greatly removed in time from their sister group (i.e., having a large GLD) and with very little character transformation over that GLD.
Lycian Sea: A small oceanic basin, located along the southwestern coast of Anatolia in northern Turkey. The Lycian Sea opened in the late Early Cretaceous as a second basin adjoining that of the Vardar Sea, and it persisted into the Tertiary.
Maastrichtian: The interval of geologic time from approximately 71.3 to 65 million years ago.
Maniraptora: A stem-based clade consisting of Passer domesticus (the living English sparrow) and all taxa closer to it than to Ornithomimus velox. This clade is diagnosed by the presence of ossified sternal plates, changes in the elbow, a semilunate carpal, modification of the hand, changes in the pelvis (including the rearward rotation of the pubis), and broad pennaceous feathers on the forelimb and tail, among other characters. Other maniraptorans include troodontids, oviraptorosaurs, and dromaeosaurids (Holtz and Osmólska 2004).
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