Glossary A - L


allopatric. Not occurring in the same geographic place.

altricial - Mammals that are born in relatively undeveloped condition (eyes closed and with minimal fur) and require prolonged parental care—as opposed to precocial.

alveolus - A small cavity or pit, as a socket for a tooth. Alveolar length of a tooth-row therefore denotes the length of the row of the teeth, taken from the posteriormost place where the back tooth emerges from the bone to the anteriormost point where the front tooth in the row emerges from the bone—the overall length of the bony sockets for the row of teeth. Plural is alveoli.

annulation - A circular or ring-like formation, as of the dermal scales on the tail of a mammal where one ring of scales that extends entirely around the tail is succeeded, posteriorly, by other rings.

anterolateral dentine tract - An area lacking enamel on the anterolateral portion of the lower first molar of some species of Neotoma.

apomorphic - In cladistics, a character state different from that of an ancestor—that is, derived from a different ancestral state.

apomorphy. A derived character state; a character state that has appeared for the first time in the taxon under consideration or in the nearest common ancestor of two taxa (such shared derived character states are synapomorphies).

arboreal - Inhabiting or frequenting trees—contrasted with fossorial, aquatic, and cursorial.

aspect ratio - Ratio of length to width of a wing. Thus a high aspect ratio wing of 18:1 is long and narrow, while a ratio of 4:1 would be a relatively short and broad wing.

auditory bulla (plural, auditory bullae) - A hollow, bony prominence of rounded form (in most mammals formed by the tympanic bone) partly enclosing structures of the middle and inner ear.

basal length - Distance on skull from the anteriormost inferior border of the foramen magnum to a line connecting the anteriormost parts of the premaxillary bones.

basilar length - Distance on skull from the anteriormost inferior border of the foramen magnum to a line connecting the posteriormost margins of the alveoli of the first upper incisors.

bead - A salient, rounded cord-like projecting ridge of bone, as in certain rodents where the superior border of the orbit is beaded.

biogeography: The study of the distributions of organisms and of the factors resulting in those distributions at any point in time.

braincase - The part of the skull enclosing the brain.

bunodont - Teeth (usually molars) having cusps as relatively low, raised areas. Characteristic of omnivores such as pigs and humans.

calcar - In bats a process connected with the calcaneum (heel bone), helping to support the edge of the fold of skin (the uropatagium) that extends between the leg and tail. In some bats, a flap of skin extends beyond the calcar; the combination is a "keeled calcar".

cancellous - Having a spongy or porous structure.

carnassials - Teeth specialized for slicing meat. The Carnivora is typified by possession of a carnassial pair consisting of upper premolar 4 and lower molar 1.

canine - Of, pertaining to, or designating the tooth next to the incisors in mammals. Of or pertaining to dogs or to the family Canidae.

carnivore - An animal that preys on other animals; an animal that eats the flesh of other animals; especially any mammal of the order Carnivora, but not limited to that order..

cartilage bone - Bone that is preformed in cartilage in the embryo (and often into youth), later becoming ossified. Membrane, or dermal, bone on the other hand ossifies directly within tissue without being preceded by cartilage.

cheek teeth - Teeth posterior to the canines.

common ancestor. A taxon that occurs in the ancestry of all the taxa being considered; usually used in the sense of the last (most recent) common ancestor. If, for example, we followed back our ancestry, eventually we would come to a taxon in the ancestry of both ourselves and of the great apes—this would be the common ancestor.

character - Any attribute of a member of a taxon (e.g., number of teeth, color, number of digits. Sometimes used as any attribute of a taxon that may differ from that in other taxa, but "character state" is a better term; that is, the various states of a particular attribute (e.g., character states of the number of digits might be five, four, three, two, or one).

cloaca - A single opening to the surface for the urogenital and digestive-waste systems. Although most mammals have separate openings, some (including the prototherians and Afrosoricida) have a cloaca.

conch (plural, conchs) - The external ear of a mammal; sometimes the spelling is concha (plural, conchae); the origin of both spellings is conch or konch, originally a bivalve shell of a marine mollusk. Equivalent to "pinna".

condylar (articular) process - On a mandible, the process ending in the articular condyle.

condylobasal length - Least distance on skull from a line connecting the posteriormost projections of the exoccipital condyles to a line connecting the anteriormost projections of the premaxillary bones.

conspecific. Belonging to the same species.

continuous variation. A situation in a population wherein a trait varies through a range without being divided into discrete segments, or clusters. For example, a large sample from a male human population cannot be divided into short, medium, tall, etc., except arbitrarily—there are no discernable natural dividing lines within the continuum.

convergent evolution - The situation where organisms or structures of different organisms have become more similar through evolution (usually in adaptation to similar functions) than they were at an earlier time.

coronoid process - The upward projecting process of the posterior part of the mandible, giving attachment on its outward side to the masseter muscle and on its inner side to the temporal muscle.

cryptic species - Species that are indistinguishable (or nearly so) morphologically but are reproductively isolated from one another and thus are good biological species. Sometimes called sibling species.

cursorial - Adapted for running.

dendrogram. Any branching diagram. Such things as phenograms, phylogenetic trees, and cladograms are dendrograms.

dental formula (plural, formulae) - A brief method for expressing the number and kind of teeth of mammals. The abbreviations i (incisor), c (canine), p or pm (premolar), and m (molar) indicate the kinds in the permanent dentition, and the number in each jaw is written like a fraction, the figures above the horizontal line showing the number in the upper jaw, and those below, the number in the lower jaw. For deciduous teeth, the abbreviation is preceded by "d".

dentine - A calcareous material, harder and denser than bone, which composes the principal mass of a tooth.

dentition - The teeth, considered collectively, of an animal.

dermal bone - Bone that forms directly in dermal layers without being preformed in cartilage. The dermal armor of an armadillo would be an example. Some dermal bones have been integrated into the skull evolutionarily.

deuterocone - One of the cusps of a premolar tooth of a mammal corresponding in position (anteromedial) to the protocone of a true molar.

diaphysis. The main shaft of a long bone, as opposed to separate ossifications at the ends of the bone.

diastema - A vacant place or gap between teeth in a jaw.

digitigrade - Walking on the toes and distal ends of the metapodials, as seen in cats and dogs, for example.

derived - A character state which has arisen (been derived from) a different, ancestral state. See apomorphic.

diurnal - Active by day—opposed to nocturnal.

echolocation - The use of sound waves echoing off of objects determine their location and other pertinent information.

enamel - Of teeth, the hardest substance of the mammalian body and forming a thin layer that caps or partly covers a tooth.

endemic. Occurring only in that place. Thus a plant occurring only in the Franklin Mountains is endemic to that mountain range.

epiphysis. Plural, epiphyses. Separate ossifications in embryos and young mammals at the ends of long bones and vertebrae that are separated from the main shaft of the bone by epiphyseal cartilage. Epiphyses eventually fuse to the shaft (diaphysis).

epipubic bones - Paired bones extending from the anterior side of the pubic bones in prototherians and marsupials.

extinction. The end of existence for a taxon. As used here, it does not include the loss of a taxon by evolution into another taxon. Thus, extinction means that there is one less taxon.

fauna - All the animal inhabitants of some geographic area or geologic time. Thus, "the Pleistocene fauna of North America" refers to the animals present in North America during the Pleistocene Epoch. Sometimes used as a synonym for animals, but better practice restricts it to a collective term (e.g., not "We saw some fauna," but "We tabulated the fauna of the area").

feces - Intestinal excrement.

femur (plural, femora) - The proximal bone of the hind limb.

feral - Wild animals descended from domesticated forms. Thus domestic cats and their descendants that are no longer acting as domestic animals are said to be feral.

flora - All the plants of some geographic area or geologic time. Thus, "the Pleistocene flora of North America" refers to all the plants present in North America during the Pleistocene Epoch. Sometimes used as a synonym for plants, but better practice restricts it to a collective term (e.g., not "We saw some flora," but "We tabulated the flora of the area").

foramen magnum - The large opening in the back of a skull through which the spinal cord passes to become the medulla oblongata of the brain.

forearm - The part of the forelimb between the elbow and wrist.

fossils. Any recognizable trace of past life. Among others, traces may include unaltered remains, parts of organisms that have been replaced by minerals, casts or molds where no part of the original specimen has been preserved but where the shape and ornamentation has been replicated, and tracks.

fossorial - Adapted to digging and generally implying burrowing. At the extreme, an animal that spends most of its life underground.

frontal - Pertaining to or designating the bone (paired) immediately in front of the parietal bone and behind the nasal.

gene flow. Transference of genetic material from one part of a population to another, or from one population to another. It may occur through migration or through breeding with neighbors that, in turn, breed with their neighbors, resulting in a slow movement of genetic material away from the periphery of the source.

genetic drift - Changes in the genetic makeup of a population through chance (sampling error). Just as tossing a coin a number of times often doesn't result in equal numbers of heads and tails, so passage of genes from one generation to another often changes their frequencies in the next generation by chance. In general, the smaller the population, the greater the effect of this; small populations are highly susceptible and the changes may outweigh those caused by natural selection.

genus - A formal obligate rank of the taxonomic hierarchy lying between species and family. A genus consists of one or more species that are believed to be more closely related to one another than any is to any species of a different genus. The plural is genera.

gestation period - The period of carrying young in the uterus, as applied to placental mammals; the period of pregnancy.

grade - Any particular level of morphological adaptation without implication of phylogenetic relationship. E.g., one might speak of the "cursorial grade", meaning those animals that have specialized morphologically for swift running.

guard hairs - The stiffer, longer hairs that grow up through the limber, shorter hairs (fur) of a mammal's pelage.

habitat - The kind of environment in which a species of organism is normally found.

half-life. In regard to radioactive decay, the length of time it takes for half of the radioactive atoms in a sample to decay to the daughter isotope.

hamular process of pterygoid - A hooklike process on the pterygoid bone.

hibernation - Torpidity, especially in winter entered into by some kinds of mammals; the bodily temperature approximates that of the surroundings; the rate of respiration and the heart beat are much slower than in a non-hibernating mammal.

hierarchy. A way of organizing things so that things having common attributes are grouped together. The group thus formed is in turn grouped together with similar groups to form a more inclusive group, etc. Thus similar species are grouped into a genus; similar genera into a family; similar families into an order, etc.

holocene. The current geologic epoch. The transition from the Pleistocene epoch to the Holocene occurred about 10,000 years ago.

homology. Homologous structures, processes, etc., have the basic features inherited from a common ancestor. Example: the forelimb of birds, bats, and humans have the same basic structure because it has been inherited from their common ancestor. Homology is established by such evidence as position, embryonic development, similarity of such features as muscle connections, innervation, etc. Differences between homologous structures sometimes are characterized as "variations upon a theme".

homoplasy. Structures, processes, etc., that appear similar to those of other organisms but which haven't been inherited from a common ancestor and thus are a result of parallel or convergent evolution.

horizontal classification - Classification where similarities at a time horizon are used to classify taxa. E.g., under the current, evolutionary classification, the lobe-finned fishes and the ray-finned fishes are both considered members of the class Osteichthyes even though lobe-finned fishes are considered to be ancestors of the tetrapods (classes Amphibia, Reptilia, Aves, and Mammalia).

horizontal ramus - In a lower jaw, the ramus bearing the teeth, and anterior to the vertical ramus.

hyperspace. Space defined by more than three dimensions. Mathematically, a space may be defined by any number of dimensions, and the position of objects within that space may be located, much as we might locate an object in 3-space on the basis of axes of length, width, and weight.

hypselodont - Rootless, evergrowing teeth. Examples include the incisors of all rodents and lagomorphs, the molars of voles, and all of the cheek teeth of rabbitts.

hypsodont - High-crowned teeth. Teeth in which the crowns (the portion covered by enamel) make up a relatively large portion of the tooth. In taxa with more hypsodont teeth, the crown in a young animal extends deep into the jawbone, gradually emerging as the tooth wears at the surface.

igneous rocks. Rocks that have solidified from a molten condition (that is, from a melted state), such as basalt and other lavas.

incisive foramina - The anterior palatine foramina (singular, foramen), of which there are two, in the bony roof of the anterior part of the cavity of the mouth at the juncture of the premaxillary bones and maxillary bones; transmit nasal branches of palatine arteries and nasopalatine ducts of Jacobson.

incisor - Pertaining to or designating one of the teeth in front of the canine tooth; those in the upper jaw invariably are in the premaxillary bone.

infraorbital canal - A canal through the maxillary bone from the orbit to the face.

inguinal - Pertaining to or in the region of the groin.

insectivorous - Eating insects; preying or feeding on insects.

in situ. In place, not coming from elsewhere.

interfemoral membrane - In a bat the fold of skin stretching from hind legs to tail. The uropatagium.

interorbital constriction - The least distance across the top of the skull between the orbits (eye sockets).

interorbital region - The region between the eye sockets; the region of the skull between the rostrum and the braincase.

interparietal - Pertaining to or designating the bone (rarely paired) immediately in front of the supraoccipital bone and between the two parietal bones.

isotopes. Atoms of an element differing in atomic weight due to different numbers of neutrons. Chemically, the differing isotopes of an element act the same.

jury-rig. To erect, construct, or arrange in a makeshift fashion.

kya. Abbreviation for thousands of years ago.

litter - The two or more young brought forth at one birth by a female mammal.

loph - A combining form used as the terminal part of certain words and denoting the ridges (or areas) composed of several cusps and styles on the occlusal face of a tooth, as protoloph.

Adapted in part from Feldhamer et al. (2004) and Hall (1981)


Last Update: 1 Feb 2008

Centennial Museum and Department of Biological Sciences, The University of Texas at El Paso