nomen nudum A published binominal without an adequate description, definition or illustration to permit its official adoption.
nomen oblitum No longer in effect in ICZN after 1973; a name that has not been used in the primary zoological literature for 50 years; a forgotten name.
nomen taxon Any named taxon, objectively defined by its type, whether valid or invalid.
nominalism n. [L. nomen, name; ismus, denoting a condition] Doctrine of nominalists denying the existence of universals, and emphasizing the importance of man-given names for the grouping of individuals.
nominate a. [L. nomen, name] Pertaining to a subordinate taxon that contains the type of the subdivided higher taxon and bears the same name as the original parent taxon.
noncelliferous side of colony (BRYO: Stenolaemata) The reverse or back side of the colony.
noncellular outgrowth A cuticular prominence of the body-wall.
noncoelomate see acoelomate non-congression n. [L. non, not; congressus, meeting] Chromosomes not pairing on the spindle equator.
non-conjunction n. [L. non, not; cum, with; junctus, joined] Absence of meiotic chromosome pairing.
nondimensional species The concept of a species characterized by the noninterbreeding of two coexisting demes, uncomplicated by space and time.
nondisjunction n. [L. non, not; disjunctus, unyolked] The failure to separate of paired chromosomes during meiosis.
non-essential amino acids Amino acids that can be synthesized by animals and not required in their diet.
nonincubatory oysters (MOLL: Bivalvia) Oysters that do not incubate their larvae.
non-medullated nerve A nerve fiber lacking a myelin sheath; non-myelinated.
nonsense codon see nonsense mutation nonsense mutation A mutation that changes a coding triplet into a triplet that codes for no amino acid and terminates the polypeptide chain.
normalizing selection The removal of all alleles that produce deviations from the normal (average) phenotype of a population by selection against all deviant individuals.
nosogenic a. [Gr. nosos, disease; gennaein, to produce] Causing disease; pathogenic.
nosography n. [Gr. nosos, disease; graphos, writing] A branch of pathology dealing with the description of diseases.
nota pl. of notum notacoria n. [Gr. notos, back; L. corium, leather] (ARTHRO: Insecta) A membranous area separating the pleuron and notum in the thorax; sometimes reduced to a suture.
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