Taxonomic Dictionary

mutation: any event that changes genetic structure.
taxon: a particular group of organisms of any taxonomic rank, e.g. a phylum, a genus, or a species.

taxonomy: the science of finding, describing and categorising organisms.

sister group: the two clades resulting from the splitting of a single lineage are called sister groups.
anagenesis: evolutionary change of characteristics within a line without an increase in the number of groups.

cladogenesis: branching of lineages during phylogeny.

clade: a group of biological taxa or species that share features inherited from a common ancestor.
homology: any similarity between characters that is due to their shared ancestry.

analogy: two structures that perform the same or similar function by a similar mechanism but evolved separately.

homoplasy: a correspondence between the parts or organs of different species acquired as the result of parallel evolution or convergence.
apomorphy: any feature novel to a species and its descendants.

synapomorphy: an apomorphy shared by two or more species or clades.

plesiomorphy: a character state that is present in both outgroups and in the ancestors.
monophyly: a group that includes an ancestral species and all its descendants.

paraphyly: excluding some descendants of the common ancestor.

polyphyly: convergent evolution describes the acquisition of the same biological trait in unrelated lineages.
phylogeny: the evolutionary history of an organism.

ontogeny: refers to the history of an organism from birth.

cladogram: a branching treelike graphical representation of the phylogenetic relationships between organisms showing which species have branched from common ancestors.

phylogram: differs from a cladogram in that the branches are drawn proportional to the amount of inferred character change.
holotype: the single physical example (or illustration) of an organism, known to be used when the taxon was formally described.

paratype: a specimen of an organism that is used as the basis of a taxonomic description.

allotype: a specimen that exemplifies the opposite sex of the holotype.

syntype: any of two or more specimens listed in a species description where a holotype was not designated.

neotype: a specimen later selected to serve as the single type specimen when an original holotype has been lost or destroyed, or where the original author never cited a specimen.

lectotype: a specimen later selected to serve as the single type specimen for species originally described from a set of syntypes.