Vertebrates

Some articles on vertebrates:

M. Paul Smith
... and the early Palaeozoic radiation of vertebrates ... discovering that conodont teeth were made of bone cells, such as are found only in vertebrates ... This dated the origin of the vertebrates to 515 million years before the present, 40 million years earlier than had been previously thought ...
Lamprey - Characteristics
... skeleton, suggest they are the sister taxon (see cladistics) of all living jawed vertebrates (gnathostomes), and are usually considered the most basal group of the Vertebrata ... which superficially resemble lampreys, are the sister taxon of the true vertebrates (lampreys and gnathostomes) ... function like the T cells and B cells seen in higher vertebrates ...
Cephalaspis - Evolutionary History and Phylogeny
... widely believed to be the sister group to all jawed vertebrates ... was not a direct ancestor of the jawed vertebrates, Cephalaspis and jawed vertebrates nevertheless shared a common ancestor ...