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What is the first fossil record of mineralization in vertebrates?
The first evidence in the fossil record of mineralization
in vertebrates is pharyngeal tooth-like structures
(conodonts) from jawless fish that appear in the fossil record
540 million years ago. It remains a point of controversy
whether or not the vertebrates that first formed
conodonts had already diverged from the line leading
to tetrapods. Kawasaki et al. argue that the origin of
SPARCL1 coincided with the innovation of mineralized
skeleton and occurred in a genome-wide duplication in
the stem jawed vertebrates (after the divergence of jawless
fish). In contrast, Sire (University Paris, France) et al. in
the second paper, The Origin and Evolution of Enamel
Mineralization Genes, argue for a much more ancient origin
for SPARCL1 .
Sources:
- Molecular Evolution and Genetic Defects of Teeth, Cells Tissues Organs, 2007
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