FIRST REPORT OF A LARVAL SHELL REPAIR SCAR ON A LINGULATE BRACHIOPOD: EVIDENCE OF DUROPHAGOUS PREDATION IN THE CAMBRIAN PELAGIC REALM?

A dorsal valve of an Upper Cambrian Ungulate brachiopod exhibits a repair scar on the anterior lateral edge of its larval shell. This species is characterized by an abrupt change in ornamentation from larval to postlarval growth. Shell material secreted in the injured area after the damage occurred exhibits ornamentation that is characteristic of postlarval growth, although equivalent growth exhibits characteristics of the larval stage. A break in the edge of the shell is visible, and the growth lines of the larval and postlarval shell were distorted until the broken area was filled in. Damage to the surface of the shell is interpreted to have been caused by the same event. Modern ungulate brachiopod larvae are planktotrophic and are interpreted to have been so throughout their long geologic history. Therefore, an environmental cause of shell damage seems unlikely and the injuries are interpreted to have been caused by an unknown durophagous predator. This specimen offers evidence that Ungulate brachiopod larvae were able to survive shell breakage and repair their shells.