| In similar reciprocal comparisons assuming minimum evolution, the arthropod map is united with the chordate map by three transformations. |
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| Although they retain the chordate characters as adults gill slits are present only in the embryonic stages of land vertebrates. |
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| Thus amphioxus is the only chordate species in which distinct insulin and IGF genes have not been found. |
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| As an initial matter, the echinoderms and chordate phyla have been arranged in almost every possible phylogenetic order. |
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| The timing of expansion coincides with proposed large-scale duplication event in the chordate lineage. |
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| Surely a more penetrating expedition into invertebrate diversity was required to dig up the precursors of the chordate characteristics. |
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| The Cambrian Explosion, for example, is the first time we are able to distinguish a chordate from an arthropod. |
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| A primitive chordate gill is present in tunicates and cephalochordates, where it serves in both respiration and feeding. |
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| Scenarios of pituitary evolution traditionally focused on the base of the chordates consistent with the exclusively chordate nature of the pituitary structure. |
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| At present, the oldest known fossil chordate is Pikaia gracilens, a primitive cephalochordate dated to approximately 505 million years ago. |
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| Unfortunately, a change in the genetic code of the mitochondrial genome in both enteropneusts and echinoderms strongly rejects chordate affinities of the hemichordates. |
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| Notably, the oldest known Early Cambrian chordate Yunnanozoon had its metameric muscular units located dorsally of the notochord, although its body was laterally compressed. |
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| The vertebrate ancestor no doubt had more arches than this, as some of their chordate relatives have more than 50 pairs of gills. |
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| The vertebrates are the only chordate group to exhibit cephalisation, the concentration of brain functions in the head. |
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| Such a scenario would also explain why the lancelet amphioxus, a 'primitive' chordate, has a notochord with both cartilage and muscle. |
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| They found that the cells form a muscle that runs along the animal's midline, precisely where the notochord would be if the worm were a chordate. |
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| It is a member of the chordate family, a group that today includes fish, amphibians, birds, reptiles and mammals. |
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| Whether the ancestral chordate was more like a cephalochordate or a tunicate is debatable, because features absent in tunicates could mean that they never have been present or could mean that they have been lost. |
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| Pikaia has myotomes and what looks like a notochord, indicating that it is a chordate, but only its shape suggests that it is a lancelet rather than a fish. |
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| The chordate body is supported by fluid in the body cavities. |
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| In developing the primary organ rudiments mentioned above, the embryo acquires a definite organization clearly recognizable as that of a chordate animal. |
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| Most chordate features disappear at metamorphosis. |
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| The oldest unequivocal chordate remains come from the Lower Cambrian of south China, where small jawless fish similar to present-day lamprey and hagfish occur as part of the Chengjiang Biota. |
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| What does the term chordate mean when applied to animal species? |
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| The extinct Pikaia gracilens has been confirmed as the oldest known member of the chordate family, which includes all modern vertebrates including humans. |
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| Molecular structures and the aligned amino acid sequences of different lectins isolated from various crustaceans, chordate, mollusca, and marine algae are quite different. |
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| Tables in the appendix list the DNA content of chordate cell nuclei, the RNA and DNA content of vertebrate cell nuclei, and other quantitative data. |
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