Trilobite malformations and the fossil record of behavioral asymmetry

Malformations of trilobites are classified as healed injuries, teratological conditions, and patholog improved method of recognizing such malformations combines information about the conditions under which the processes by which animal tissues react to injury, and trilobite morphology. Study of healed injuries of polymeroid trilobites shows that injuries attributed to sublethal predation tend to preserved on the pleural lobes, the posterior half of the body, and the right side. Statistically significant diffe of predation scars between the right and left sides is interpreted as evidence of right-left behavioral asymmet of trilobites or the trilobites themselves. Asymmetrical, or lateralized, behavior in present-day animals is on handedness, and is usually related to a functional lateralization of the nervous system. Evidence of behavioral Paleozoic predators or prey suggests that those organisms also possessed lateralized nervous systems. Right-left dif predation scars on trilobites date from the Early Cambrian (Olenellus Zone), and are the oldest known ev asymmetry in the fossil record. Other examples of structural or behavioral asymmetry from the fossil record of animals are cited. Lateraliz representatives of the Arthropoda, Annelida, Bryozoa, Echinodermata, Cnidaria, Mollusca, Chordata, and Con fossi