Some scientists have hypothesized that the first vertebrates, which were fish, may have evolved from an ancestral tunicate that became sexually mature in the larval form. they suggest that these reproducing larvae were successful and natural selection reinforced the absence of metamorphosis to the adult. which of the following statements does not support the hypothesis that vertebrates evolved from a sexually mature larval tunicate? some living urochordates are free-swimming only as larvae. the vertebral column of adult vertebrates replaces the notochord present in embryonic vertebrates. adult tunicates are sessile and larval tunicates are free-swimming. many invertebrates, all tunicate larvae and adults, and the earliest vertebrates are or were filter feeders.