Multiple-Rusophycus assemblage from the Parnaíba Basin (NE Brazil) reflects trilobites as tracemakers and molting behavior

Trilobites inhabited all environments of Paleozoic seas, ranging from estuaries to continental slopes, and were globally distributed. Although their functional morphology phylogenetic relations are established by well-preserved body fossils, the behavior trilobites has received less attention. Three well-known trace fossils interpreted be produced trilobitomorphs when preserved in rocks, Rusophycus (a resting trace), Cruziana furrowing Diplichnites locomotion trace). Those unveil some aspects trilobite behavior, but they not investigated test paleoecologic strategies based on morphometric parameters. This study uses access storm-dominated shallow marine deposits Pimenteira Cabeças formations (Middle Upper Devonian, Parnaíba Basin, Brazil). It was conducted a detailed analysis specimens section that represents transition between (Parnaíba Basin). The width length measured, statistical analyses performed understand population characteristics. Relatively small-sized dominant such deposits, suggesting dominance young tracemakers inferred r-strategist populations. here reported multiple- assemblage reveals population, tiers relationship (cross-cutting epistratal shallow-tier as Bergaueria , Palaeophycus Protopaleodictyon ) indicate deep . main reason for those burrowing activities substrate might protection during ecdysis. Thus, random distribution, lack hunting evidence, depth suggest molting activity trigger production storm-influenced beds Formation, probably calmoniids or homalonotids.