A POSSIBLE LATE CAMBRIAN VERTEBRATE FROM AUSTRALIA

摘要

THE fossil record of early vertebrates starts with certainty with the dermal armour of agnathan fish from the Early-Middle Ordovician of Australia(1,2). Recent controversial acceptance that conodonts(3) and the fragments called Anatolepis(4,5) may be vertebrate remains(6), extends their fossil record back to the Late Cambrian. Now a new type of phosphatic skeleton from Australia shows a three-layered structure that indicates vertebrate affinity, but with several unique features not known in other vertebrates. The new evidence challenges the most widely accepted current theory for the development of the vertebrate skeleton(7-11), which assumes the odontode (skin denticle) to be the primitive patterning component. The Australian material provides an alternative model for early vertebrate dermal armour with which to assess the vertebrate-like hard tissues in conodonts(12,13) and the dermal armour of Anatolepis(4-6,14). [References: 29]