An invertebrate animal belonging to a group of phyla that are distinguished by the lack of a well-developed coelom and blood vessels. Most are minute wormlike animals, including the nematodes, rotifers, and water bears.
Phylum Nematoda and about seven minor phyla, formerly placed in a phylum Aschelminthes‘Since aschelminths all lack substantial hard parts, their fossil record is extremely spotty.’
- ‘Clearly, the status of several traditional ‘aschelminthes’ groups awaits further confirmation.’
- ‘An alternative explanation is that it was a kind of aschelminth (pseudocoelomate worm), as indicated for example by its asymmetrical mouth.’
From modern Latin Aschelminthes (former phylum name), from Greek askos ‘sac’ + helminth ‘worm’ (from the former belief that animals of this group had a fluid-filled internal sac).