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Related Experiment Videos

Conodont affinity and chordate phylogeny.

P C Donoghue1, P L Forey, R J Aldridge

  • 1School of Earth Sciences, University of Birmingham, Edgbaston, UK. p.c.j.donoghue@bham.ac.uk

Biological Reviews of the Cambridge Philosophical Society
|July 6, 2000
PubMed
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Conodonts, ancient jawless vertebrates, are confirmed as the earliest jawed vertebrates (Gnathostomata). Their mineralized skeletons evolved before bone, with complex sensory systems arising multiple times.

Area of Science:

  • Paleontology
  • Vertebrate Evolution
  • Phylogenetics

Background:

  • Conodonts are extinct marine vertebrates known from fossilized tooth-like structures.
  • Previous interpretations of conodont relationships to vertebrates have varied.
  • Recent advances in understanding conodont hard tissues provide new data for phylogenetic analysis.

Purpose of the Study:

  • To re-evaluate the phylogenetic position of conodonts within the Chordata.
  • To investigate the evolution of vertebrate skeletal and sensory systems using conodonts as a model.
  • To establish the earliest origins of mineralized skeletons and jawed vertebrates.

Main Methods:

  • A comprehensive phylogenetic analysis using 17 chordate taxa and 103 morphological, physiological, and biochemical characters.

Related Experiment Videos

  • Inclusion of conodonts as a primary taxon in the analysis.
  • Experimental variations including character coding, taxon deletion, and constraint trees.

    • Main Results:

    • Conodonts are determined to be cladistically more derived than hagfishes and lampreys due to their mineralized dermal skeleton.
    • Conodonts represent the most primitive (plesiomorphic) member of the total group Gnathostomata (jawed vertebrates).
    • The evolution of neuromasts within canals appears to have occurred independently multiple times, and vertebrate mineralized skeletons originated as odontodes.

    Conclusions:

    • Conodonts are basal gnathostomes, providing insights into early vertebrate evolution.
    • The evolution of the vertebrate skeleton and sensory systems was complex, involving multiple independent origins.
    • Phylogenetic analysis predicts the Cambrian existence of hagfishes and lampreys, consistent with fossil evidence.