Position of the labrum in agnostid trilobites
Version of Record online: 9 OCT 2007
Volume 16, Issue 4, pages 309–310, October 1983
How to Cite
RITTERBUSH, L. A. (1983), Position of the labrum in agnostid trilobites. Lethaia, 16: 309–310. doi: 10.1111/j.1502-3931.1983.tb02014.x
- Issue online: 9 OCT 2007
- Version of Record online: 9 OCT 2007
- 20th July,1982.
Specimens of Peronopsis and Ptychagnostus from the House Range of western Utah provide new information on the location of the labrum (hypostoma) of agnostid trilobites. A labral position as that described here, beneath the second glabellar lobe, has two implications: (1) anomalous cephalic muscle scars described by previous workers may be interpreted as attachment areas for labral muscles; and (2) the mouth probably migrated posteriorly in agnostids. Posterior displacement of the mouth was probably one of several feeding modifications associated with a pelagic mode of life.