Tegopelte gigas, a Second Soft-Bodied Trilobite from the Burgess Shale, Middle Cambrian, British Columbia

The two known specimens of Tegopelte gigas are redescribed, after preparation that revealed the nature of the appendages. The thin exoskeleton was unmineralized, divided into cephalon, three thoracic tergites and a large pygidium; it lacked furrows, and was not articulated; a dorsal lateral eye may have been present. Appendages included one pair of antennae and a series of uniform appendages, the inner branch a walking leg, the outer one a shaft bearing long, slim filaments. The cephalon bore one pair of antennae and probably three pairs of limbs; beneath each tergite were three pairs of limbs (probably four beneath the third tergite), and some twenty pairs of limbs beneath the pygidium. The animal is regarded as a trilobite, and is unlike any other trilobite species; its relationships are obscure. Two additional species of soft-bodied trilobites, one rare and one quite abundant, are preserved under the special conditions of deposition of the Burgess Shale. Such animals may have been far more abundant and widespread than suggested by deposits of the prevailing kind that yield only mineralized shells.