Paired gill slits in a fossil with a calcite skeleton

  title={Paired gill slits in a fossil with a calcite skeleton},
  author={Patr{\'i}cio Dominguez and Antone G. Jacobson and Richard P.S. Jefferies},
The chordates, hemichordates (such as acorn worms) and echinoderms (such as starfish) comprise the group Deuterostomia, well established as monophyletic. Among extant deuterostomes, a skeleton in which each plate has the crystallographic structure of a single crystal of calcite is characteristic of echinoderms and is always associated with radial symmetry and never with gill slits. Among fossils, however, such a skeleton sometimes occurs without radial symmetry. This is true of Jaekelocarpus… 

Heterochrony and parallel evolution of echinoderm, hemichordate and cephalochordate internal bars

Critically evaluate the evidence for pharyngeal structures (gill bars) in the extinct stylophoran echinoderms Lagynocystis pyramidalis and Jaekelocarpus oklahomensis using virtual models based on high-resolution X-ray tomography scans of three-dimensionally preserved fossil specimens.

Worms and gills, plates and spines: the evolutionary origins and incredible disparity of deuterostomes revealed by fossils, genes, and development.

The available morphological, palaeontological, developmental, and molecular data are reviewed to establish a framework for exploring the origins of Deuterostomia, and four characteristics most critical for understanding the form and function of the last common ancestor are considered.

The oldest cinctan carpoid (stem-group Echinodermata), and the evolution of the water vascular system

Through the study of original specimens and ‘virtual fossils’ it was possible to reconstruct the palaeobiology of Protocinctus gen. nov.: cinctans are interpreted as pharyngeal basket feeders with a U-shaped gut, using their posterior appendage to aid stability on the sediment surface.

A phylogeny of the hemichordates based on morphological characters

The pterobranchs have lost many of these features as a consequence of evolving a small body size and living in tubes, but these features exist in present-day enteropneusts, suggesting that they are a plausible model for the proximate ancestor of deuterostomes.

Reinterpretation of the enigmatic Ordovician genus Bolboporites (Echinodermata)

Bolboporites is an enigmatic Ordovician cone-shaped fossil, the precise nature and systematic affinities of which have been controversial over almost two centuries. For the first time, a wide range

A paleontological perspective of vertebrate origin

A five-step hypothesis for vertebrate origin is proposed, intended to bridge the longstanding gap between protostomes and vertebrates, and four of the five steps accord with established ideas current in modern evolutionary zoology.

Evolution of deuterostomy – and origin of the chordates

  • C. Nielsen
  • Biology
    Biological reviews of the Cambridge Philosophical Society
  • 2017
The conclusion must be that the chordate mouth (and that of the deuterostomes in general) is homologous to the protostomian mouth and that the latest common ancestor of protostomes and deuterstomes developed through amphistomy, as suggested by the trochaea theory.

Ontogeny and Funtional Morphology of a Lower Cretaceous Carpinid Rudist (Bivalvia, Hippuritoida)

Caprinuloidea rudists are locally abundant and widespread in Lower Cretaceous (Albian Stage) Edwards Formation in Texas. Landward of the shelf margin on the shallow marine Comanche Shelf rudists


It is not possible on current evidence to reach an unequivocal conclusion regarding the phylogenetic position of the vetulicolians, but one possibility is that they are a sister group of arthropods that lost limbs but gained gill structures analogous to those of deuterostomes, but several features remain unexplained by this model.



The youngest carpoid: occurrence, affinities, and life mode of a Pennsylvanian (Morrowan) mitrate from Oklahoma

Abundant, well-preserved specimens of a new peltocystidan mitrate carpoid, Jaekelocarpus oklahomensis n. gen. and sp., have been discovered in the Pennsylvanian (Morrowan Series) Gene Autry Shale


For the purposes of this review the term ‘carpoid’ is used to include such animals, known generally as the cornute and mitrate carpoids, but now either referred to the echinoderm class Stylophora or the chordate subphylum Calcichordata.

Evolution of the chordate body plan: new insights from phylogenetic analyses of deuterostome phyla.

The nesting of the pterobranchs within the enteropneusts dramatically alters the view of the evolution of the chordate body plan and suggests that the ancestral deuterostome more closely resembled a mobile worm-like enteropNEust than a sessile colonial pterOBranch.

An episode in the ancestry of vertebrates: From mitrate to crown‐group craniate

This paper describes a stem-craniate mitrate, and reconstructs, from the shared characteristics of the extant craniates supplemented by evidence from fossils, the latest common ancestor of extant crANIates which it is called “animal x”.

A new stem-group chordate (Cornuta) from the Llandeilo of Czechoslovakia and the cornute-mitrate transition

It is concluded that P. mergli reinforces the view that the convex surface of the mitrates was ventral in life, and a new homology proposed between the anterior ventral fore-tail plates of cornutes and what were formerly called plates g and j of mitrates.

Brief review of the stylophoran debate

  • M. Ruta
  • Biology
    Evolution & development
  • 1999
Stylophorans may lie at the base of the echinoderm clade and primitively lack pentameral symmetry, therefore casting light on the near‐ancestral body organization of the phylum.

Echinoderm phylogeny and evolutionary biology

This book discusses the phylogeny of the cystoids, the evolutionary palaeoecology of the Blaistoidea, and the early evolution of the Crinoidea ontogeny and phylogenY of disparid crinoids, as well as the origins of the deep-sea hoasteroid fauna feeding and respiratory strategies in stylophora.

Animal phylogeny and the ancestry of bilaterians: inferences from morphology and 18S rDNA gene sequences

Because chaetognaths and lophophorates, taxa traditionally allied with deuterostomes, occupy basal positions within their respective protostomian clades, deuterstomy most likely represents a suite of characters plesiomorphic for bilaterians.

In defence of the calcichordates

The present paper answers Philip's criticisms of the calcichordate interpretation and discusses his own proposals and his comments on Ubaghs' views.