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Metcalfe 1981 (P1 element) |
Studies of the microfossil group conodonts
Ian Metcalfe
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Metcalfe 1981 (P1 element) |
Conodont species are generally represented in the fossil record by tiny phosphatic tooth-like elements that formed the oral apparatus of a slender free-swimming fish-like animal about seven centimetres long which has chordate affinities (Aldridge and Purnell, 1996) and has been suggested by some to be a primitive vertebrate (Sansom et al., 1992; Briggs, 1992; Janvier, 1995; Donoghue et al., 1998; Donoghue et al., 2000). The phosphatic elements of the oral apparatus generally comprise between seven and nine different morphological types, the most distinctive of which is the P1 (Pa) element an example of which, from the Carboniferous of northern England, is illustrated above.
Conodont fossils appeared in the Cambrian period some 530 million years ago and became extinct at the end of the Triassic period about 200 million years ago. They are one of the most useful fossil biostratigraphic groups for dating Palaeozoic and Triassic marine sedimentary rocks and have been used extensively by the International Union of Geological Sciences (IUGS) for defining the formal Paleozoic and Triassic boundary global stratotype sections and points (GSSPs) for international stratigraphic timescale divisions (Systems, Series, Stages). Some conodont species have very short stratigraphical ranges and can be used as age index fossils. Hindeodus changxingensis is one such age index fossil that very narrowly straddles the end Permian mass extinction and Permian-Triassic boundary levels:
The index conodont fossil Hindeodus changxingensis Wang that narrowly straddles the Permian-Triassic Boundary at the global reference section at Meishan, China and other sections globally (see Metcalfe et al., 2007 for details).
Current studies on conodonts include: