麻豆传媒

Fig. 2: A collection of fossilised shark and ray teeth. Hand of an adult for size comparison. Left: Otodus megalodon; First row f.l.t.r. Palaeocarcharodon orientalis, Galeocerdo aduncus, Myliobatidae indet., Upper and lower tooth Notorhynchus primigenius; Second row f.l.t.r. Otodus obliquus, Otodus angustidens, Squalicorax pristodontus; third row f.l.t.r. Upper and lower tooth Notidanodon loozi, Isurus oxyrinchus, Carcharodon hastalis.

Fig. 3: Diversity curve of neoselachians (modern sharks and rays and the extinct synechodontiform sharks) from the Triassic to the Holocene in millions of years. The curve shows "sampling standardised range through" diversity. This diversity approach takes into account the fact that the probability of finding and preserving a fossil depends on several factors, such as the size of the organism, the type of sediment and geological processes. It also takes into account the fact that the amount of fossil material collected is often not representative of the actual diversity of species, for example because fossils are more intensively searched for in certain areas than in others, or because some species are simply easier to find, e.g. because of their abundance or size. As a result, the true diversity of organisms in the past can easily be overestimated or underestimated.