aptychus

English

Etymology

Modern Latin, from a- + Ancient Greek πτυχή (ptukhḗ, “fold, layer”).

Noun

aptychus (plural aptychi)

1. (paleontology) A hard calcareous plate forming part of the body of an ammonite.
   • 2017, Danna Staaf, Squid Empire, ForeEdge, →ISBN, page 95:

     It wasn't until the 1970s that paleontologists had amassed enough evidence to be certain that aptychi were modified lower jaws.

Related terms

• anaptychus