File:Elrathia kingii fossil trilobite with healed bite mark (Wheeler Formation, Middle Cambrian; House Range, western Utah, USA) 1 (15255121475).jpg

Elrathia kingii (Meek, 1870) trilobite (2.8 cm long) with healed bite mark from the Wheeler Formation (Middle Cambrian) of western Utah’s House Range.

Trilobites are important and common fossils in Paleozoic rocks, especially in the Cambrian. Much is known about their paleobiology, ontogeny, evolutionary patterns, etc. One of the less well known aspects of trilobitology is the significance of malformations, or deformities in the preserved exoskeleton. One category of trilobite malformation is healed bite marks, which can be seen in this specimen.

Elrathia kingii is one of the most abundantly preserved trilobites species on Earth. It is affectionately called “Joe Trilobite” by some trilobite workers. The species is common in the Wheeler Formation of the House Range in northern Millard County, western Utah, USA. Many specimens are commercially prepared and sold throughout America. Occasionally, specimens can be found with healed bite marks. This Elrathia trilobite has a healed bite mark on the left pleural lobe of the posterior thorax. Three pleurae are strongly malformed. Most bites on trilobites are blamed on unsuccessful anomalocaridid predation, but other Cambrian organisms are also known to have preyed on trilobites.

Classification: Arthropoda, Trilobita, Polymerida, Alokistocaridae

Stratigraphy & age: upper Ptychagnostus atavus Interval-zone (= lower Bolaspidella Assemblage-zone), Wheeler Formation, upper Middle Cambrian

Published references on bitten and malformed trilobites:

Babcock & Robison (1989) - Nature 337: 695-696.

Babcock (1993) - Journal of Paleontology 67: 217-229.