 As the preservation of soft tissue in "T. eatoni" is excellent, it is probable that it lacked cerci, the most backward pair of extremities known from "Olenoides serratus".Due to the existence of an excellently preserved deposit in the Frankfurt Shale near Rome, New York State, that suggests an entire population of "Triarthrus eatoni" was killed and quickly buried, it has been possible to make a plausible reconstruction of its life history.After hatching, probably from eggs a few tenths of a millimeter (although these are not known in any trilobite), the small protaspid and early meraspid stages supposedly lived between the plankton in the water column.