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Overview of phyla and classes

  1. Feb 17, 2017 #1
    Could you suggest any source giving a good systematic overview of all phyla and classes - extant and extinct?
    the list of animal phyla is suggested as 34, but controversies exist
    Some phyla have no fossil record, some fossilize with great luck, some often fossilize.
    While many old fossils are hard to classify and some have been suspected as extinct phyla, there are no generally acknowledged extinct phyla: these suspicious fossils have also been suspected to belong to extinct classes of extant phyla.
    No easily fossilized phylum has appeared after Ordovician, and these may have had poorly fossilized members in Cambrian.
    Listing phyla:
    Easily fossilized:
    1. Cnidaria - since Vendian
    2. Porifera - since Vendian
    3. Annelida - since Cambrian
    4. Arthropoda - since Cambrian
    5. Brachiopoda - since Cambrian
    6. Chaetognatha - since Cambrian
    7. Chordata - since Cambrian
    8. Ctenophora - since Cambrian
    9. Echinodermata - since Cambrian
    10. Entoprocta - since Cambrian
    11. Hemichordata - since Cambrian
    12. Loricifera - since Cambrian
    13. Mollusca - since Cambrian
    14. Nematoda - since Cambrian
    15. Sipuncula - since Cambrian
    16. Tardigrada - since Cambrian
    17. Bryozoa - since Ordovician
    With lucky fossilization:
    1. Rotifera - since Eocene
    2. Onychophora - since Cretaceous
    3. Platyhelminthes - since Permian
    4. Priapulida - since Carboniferous
    No fossil record:
    1. Cycliophora
    2. Gastrotricha
    3. Gnathostomulida
    4. Kinorhyncha
    5. Micrognathozoa
    6. Nematomorpha
    7. Nemertea
    8. Orthonectida
    9. Phoronida
    10. Placozoa
    11. Rhombozoa
    12. Xenacoelomorpha
    Last edited: Feb 17, 2017
  2. jcsd
  3. Feb 17, 2017 #2
    Cnidaria, since Vendian:
    1. Anthozoa - since Vendian
    2. Stauromedusae - since Vendian
    3. Cubozoa - ill preserved
    4. Hydrozoa - ill preserved
    5. Scyphozoa - ill preserved
    6. Polypodiozoa - ill preserved
    7. Malacosporea - ill preserved
    8. Myxosporea - ill preserved
    Porifera, since Vendian (?):
    1. Calcarea - since Cambrian
    2. Hexactinellida - since Cambrian
    3. Demospongia - since Cambrian
    4. Homoscleromorpha - ?
    Annelida, since Cambrian:
    1. Polychaeta - since Cambrian
    2. Clitellata - since Triassic
    3. Echiura - since Carboniferous
    4. Machaeridia - Ordovician to Carboniferous
    Arthropoda, since Cambrian:
    1. Trilobita - Cambrian to Permian
    2. Arachnida - since Silurian
    3. Merostomata - since Ordovician
    Last edited: Feb 17, 2017
  4. Feb 17, 2017 #3


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    Science Advisor

    My response is focused on metazoa (multi-cellular animals) since I don't know a lot about plant and fungal phylogeny.

    Phyla are taxonomic divisions that arose early in evolution, with body plans which, once established at these early times, were rarely changed except in "details" which generated sub-divisions of phyla like classes.

    There are lots of large books (also see) that describe many (but perhaps not all) of the phyla. I would suggest looking through several in a college library. Here is a short article on a few phyla and their relationships. Generally, the larger the books, the more complete will be their coverage the morphological features of the many different phyla. Smaller books might have rather thin discussions of the details of the some phyla. Among animals, they would generally be found under comparative biology or comparative invertebrate biology. These books would include lots of information about the anatomy and physiology of each group or at least the differences between them.

    In the last few years, there has been a revolution in the research on phyla, due to the use of sequence data which can easily provide lots and lots (hundreds, thousands, millions) of informative traits for determining their evolutionary relationships. Before that, traits used in phylogenetic analysis were restricted to anatomical, physiological, developmental, and biochemical traits which are way fewer in number and therefore had less power to resolve phylogenetic relationships.
    Therefore, if you are interested in understanding the evolutionary relationships between these groups, I would avoid the older books now (although they have good anatomical etc descriptions) because many relationships were not as well resolved as now, due to the limitied data that was available when they were written.

    Most smaller, more recently derived taxa (like classes vs. phyla) should appear after the phyla have been established and would be relatively small changes to the body plan of their particular phyla.
    Among the animals, it is commonly assumed that almost all the phyla appeared during the Cambrian or earlier, however, many may not have fossilized well. The many phyla are also assumed to be derived from one (or a few) different precursors in some not entirely known step-wise manner. The relationships between the various phyla should be representative of this ordering of their origins.

    Some molecular estimates indicate phyla evolved earlier, but left few if any fossils due to having small soft bodies that rarely leave good fossils. There are also a lot of "enigmatic" fossils from earlier times whose relations to existing phyla are not obvious to everyone. These may be examples of some of these earlier stages which could have lead to current phyla or might have been evolutionary dead ends (died out without leaving descendants).

    An Evo-Devo view of phyla would describe them as resulting from a step-wise evolution of the developmental processes (embryology) that generate the diverging set (different phyla) with increasingly more complex body plans.
  5. Feb 17, 2017 #4

    jim mcnamara

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    Staff: Mentor

    (not Discovery magazine) --
    For plants you want:
    Wilson N. Stewart 'Paleobotany and the Evolution of Plants'
    Most college libraries will have a copy. There is a discussion on 'missing' Phyla that is really good.
  6. Feb 18, 2017 #5
    Unfortunately, edit rights soon expire. Compiling longer texts is therefore difficult.
    Arthropoda, since Cambrian:
    1. Arachnida - since Silurian
    2. Merostomata - since Ordovician
    3. Pycnogonida - since Cambrian
    4. Chilopoda - since Silurian
    5. Diplopoda - since Silurian
    6. Branchiopoda - since Cambrian
    7. Remipedia - since Carboniferous
    8. Maxillopoda - since Cambrian
    9. Ostracoda - since Ordovician
    10. Malacostraca - since Cambrian
    11. Insecta - since Devonian
    12. Pauropoda - ill preserved, since Eocene
    13. Symphyla - ill preserved
    14. Cephalocarida - ill preserved
    15. Entognatha - ill preserved
    16. Trilobita - Cambrian to Permian
    17. Camptophyllia - Carboniferous
    18. Marrellomorpha - Cambrian to Devonian
    19. Acanthomeridion - Cambrian
    20. Thelxiope - Cambrian
    Note statistics of arthropods:
    Modern diversity is 11 living and easily fossilized classes, plus 4 ill preserved classes.
    Fossil diversity is the fossils of 11 extant classes, plus 1 well recognized class (Trilobita) and 4 more mysterious and less represented groups.
    Last edited: Feb 18, 2017
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