The ancestry of the vertebrates

  title={The ancestry of the vertebrates},
  author={R. Jefferies},
Anatomy, locomotion and ontogeny of the solute Castericystis vali from the Middle Cambrian of Utah
The ontogeny of C. vali resembles that of Cephalodiscus in that the proportions of the head, arm and stalk or tail change in a similar sequence during the development of both taxa. Expand
The anatomy of the solute Girvanicystis batheri (?Chordata) from the Upper Ordovician of Scotland and a new species of Girvanicystis from the Upper Ordovician of South Wales
The gross anatomy of G. batheri supports the hypothesis that it was a suspension feeder and has characters in common with the cornute Ceratocystis perneri, namely large plates of the skeleton of the head, right and left marginal flanges, opposite dorsal fore tail plates and alternate ventralFore tail plates, which suggest that G.batheri may also be a stem chordate. Expand
Evolutionary Origins of Hearts
This chapter discusses various kinds of animal circulatory pumps and utilizes a hierarchical set of concepts to analyze their evolution and defines the position occupied by vertebrate chambered hearts in relation to the other classes of animal pumping organs. Expand
Origin of the isthmus? A comparison of the brains of lancelets and vertebrates
  • R. Northcutt
  • Biology, Medicine
  • The Journal of comparative neurology
  • 2003
The brains of living lancelets, as well as those of living vertebrates, are almost certainly a mixture of primitive and derived features, whose identity can only be determined in the context of an out-group analysis involving other closely related taxa. Expand
The origin of vertebrates and their symmetry, segmentation, chord and tubular nervous system
Development of vertebrata begins with formation of a multicellular organism by ordered repeated division of a reproductive cell and nondisjunction of the new formed cells, which have kept connectionExpand
The anatomy of conodonts
Ten specimens from the Carboniferous Granton shrimp bed of Edinburgh, Scotland, provide the most complete record of conodont anatomy, with evidence of incomplete preservation of ventral soft parts, at least at the anterior end of the specimens. Expand
The gill slits and pre-oral ciliary organ of Protoglossus (Hemichordata: Enteropneusta) are filter-feeding structures
Observations on the hemichordate worm Protoglossus graveolens demonstrate that the gill slits, pre-oral ciliary organ (POCO), and the lining of the cylindrical pharynx are used in filter feeding, suggesting that a wheel organ/ POCO and a filter-feeding pharynX may have been present in the common ancestor to the deuterostomes. Expand
A Trajectory of Increasing Activity and the Elaboration of Chemosensory Modality: A New Perspective on Vertebrate Origins
  • G. Satoh
  • Biology, Medicine
  • Zoological science
  • 2005
This article reviews recent advances in comparative biological studies of vertebrate origins, with the aim of revisiting the long-standing controversy concerning these origins, and focuses on the evolution of respiratory and circulatory systems. Expand
Limbs and tail as evolutionarily diverging duplicates of the main body axis
  • A. Minelli
  • Biology, Medicine
  • Evolution & development
  • 2000
It is suggested that body appendages such as arthropod and vertebrate limbs and chordate tails are evolutionarily divergent duplicates (paramorphs) of the main body axis, that is, its duplicates, albeit devoid of endodermal component. Expand
Molecular evidence from ascidians for the evolutionary origin of vertebrate cranial sensory placodes.
  • F. Mazet, S. Shimeld
  • Biology, Medicine
  • Journal of experimental zoology. Part B, Molecular and developmental evolution
  • 2005
The interpretation of these findings is that vertebrate placodes and sea squirt siphon primordia have evolved from the same patches of specialised ectoderm present in the common ancestor of the chordates. Expand


Punctuated equilibria: an alternative to phyletic gradualism
Editorial introduction. Moving from populations to species. we recall that the process of speciation as seen through the hyperopic eyes of the paleontologist is an old and venerable theme. But theExpand