aptychus
English edit
Etymology edit
Modern Latin, from a- + Ancient Greek πτυχή (ptukhḗ, “fold, layer”).
Noun edit
aptychus (plural aptychi)
- (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.