Two smaller Phyla, the Onychophora and Tardigrada,
myriapods), Nematoda, and several smaller Phyla.
Phylum Chordates Arthropods.
owing to many morphological and genetic differences between the two Phyla.
The phylum is typically divided into 8 or 9 taxonomic classes,
Many modern animal Phyla became clearly established in the fossil record
which may be treated as Phyla, are listed in the taxobox, upper right.
Sponges lack the complex organization found in most other animal Phyla; their cells are differentiated,
to put in any modern group, at the end of the Cambrian most modern Phyla were already present.
study of terrestrial animals in other arthropod groups or other Phyla, such as arachnids, myriapods, earthworms, land snails, and slugs.