|This phylum's 'place'
relative to other phyla:
|Selected taxa within this taxon:
48,000 species, 1400 of which are
invertebrates by virtue of not possessing a backbone
Diverse morphologically and relationship with vertebrates is not always obvious.
Includes:Subphylum Cephalochordata (amphioxous or lancelets)
Ascidians - Sessile tunicates with tough protein and polysaccharide tunic or test.
Sessile form is without a notochord, so why is this considered a chordate?
Notochord reabsorbed at a dramatic metamorphosis.
The only chordate characteristics retained in adults are the pharyngeal gill silts.
Is our basic body plan a neotonous condition?
Larvaceans- Tadpole-like zooplankton that secretes a gelatinous 'house' (appear to be an important and overlook pathway in ocean carbon cycles) . Tail with notochord drives water movement for suspension feeding, Notochord retained through out life, but adults are considered neotonous.
Thaliaceans- Highly transparent, planktonic salps and doliolids. May form aggregates that reproduce asexually.
Based on one fossil group (the "calcichordates"),
has been made that vertebrates evolved from a clacified
echinoderm-like ancestor. However the proponderance of
evidence unites the chordates as a single clade, excluding
Traditionally, numerous morphological similarities used to argue Cephalochordata as the sister group of Vertebrata.
Is the metameric chordate body plan as a late-comer on the evolutionary scene?
So, what is left is
the animals that are not 'invertebrates'
The remaining 'non-invertebrate' groups (the Subphylum Vertebrata or Craniata) represent a mere 1/20 of the splendid kingdom of animals!
However, it does contain one species whose activities have impacted the diversity of life more than any other species since the beginning of life. But this species also has the ability to consciously decide to be stewards over that creation.