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Table 1 Ecological niches of trilobites based on morphological or sedimentary evidence

From: Beyond memorization: an intermediate-level paleontology activity that integrates anatomy, ecology, and macroevolutionary theory using trilobites

Fossil Evidence Interpretation Inferred lifestyle or behavior
Reduced thorax and pygidium; smoothed cephalon; downward projecting spines; facies independence Light, streamlined body allows fast swimming. Spines prohibit effective movement on the sediment surface. Distribution controlled by water column characteristics rather than sediment characteristics. Pelagic lifestyle/swimming
Smooth exterior, broad & flat axial lobe Reduce friction Burrowing
Larger muscle attachments Stronger limb motions to move sediments
Eyes reduced or absent Darker conditions, less need/no need for keen eyesight Living in deep water
Wide bodies, genal spines
Added support for soupy substrate
Well-developed limbs, flexible hypostome, Cruziana feeding traces Food passed anteriorly towards the mouth during the course of movement, flexible hypostome used as a scoop. Particle feeding
Unusual occipital angle, pitted fringe Pits allow water to flow through cephalon from leg-generated currents Filter feeding
Rigid, strongly braced hypostome; forked hypostome projections Ability to process relatively large food particles Predatory, feeding on soft bodied worms