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Figure 1. Vertebrate phylogeny and the evolution of skeletal mineralization. Many extinct vertebrates (dashed lines) split from our ancestral lineage after the modern jawless vertebrates (lampreys and hagfish), but before cartilaginous fish (Chondrichthyes). The most ancient mineralized tissue has been found in conodonts. Subsequent jawless vertebrates evolved a dermal skeleton. The tooth arose before the divergence of cartilaginous fish. Two WGDs are thought to have taken place, first, in the stem jawless vertebrates (WGD1) and, second, in the stem jawed-vertebrates (WGD2). SPARCL1 arose from SPARC through the WGD2. SCPP genes originated from SPARCL1, but have been found only in teleosts and tetrapods to date. The initial SCPP gene arose before the divergence of ray-finned fish and lobe-finned fish. The vertebrate phylogeny is based on Donoghue et al.(2006).

J DENT RES, Vol. 87, No. 6, 520-531 (2008)
DOI: 10.1177/154405910808700608

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