Beak and Beak Sculpture

Beak, top viewAlasmidonta heterodon

Beak, top view
Alasmidonta heterodon

Beak size, prominence and structure vary among species and may aid in identification. The shape and arrangement of the contours of the beak are known as the beak sculpture, and if present can be seen clearly with a hand lens.  Examples of the beak and its sculpture are depicted below, and others may be seen in the species accounts.

The beak, the oldest part of the animal's shell, may best be seen in a posterior view.

Beak, left valveAnodonta implicata

Beak, left valve
Anodonta implicata

Alasmidonta undulatatriangle floater

Alasmidonta undulata
triangle floater

Ligumia nasutaeastern pondmussel

Ligumia nasuta
eastern pondmussel

It is not necessary to remove the thick outer covering, or periostracum, of the shell in order to reveal the lines and contours of the beak sculpture.
Lampsilis radiataeastern lampmussel

Lampsilis radiata
eastern lampmussel

Strophitus undulatuscreeper

Strophitus undulatus

A specimen of S. undulatus shows the distinct rings of the beak sculpture; although prominent, the double-looped beak sculpture of L. radiata is no longer apparent in this older specimen. Shell wear in older specimens and those from acidic waters may cause the beak sculpture to appear absent or indistinct.