acron

acron

[′ak‚rän]

(evolution)

Unsegmented head of the ancestral arthropod.

(invertebrate zoology)

The preoral, nonsegmented portion of an arthropod embryo.

The prostomial region of the trochophore larva of some mollusks.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.