 It is currently unclear whether the paracaspases (and caspases) found in eukaryotes are a result from several (at least 2) independent horizontal gene transfer events from prokaryotes or if there has been a convergent evolution of (para)caspases evolved from the metacaspases in several different organisms within the eukaryotes.The "type 2" paracaspases in animals represent the ancestral form which only consists of a caspase-like domain.This form of paracaspase can be found in ctenophora, trichoplax, sponges and cnidarians.