The tiger shark is without doubt one of the largest predatory sharks recognized right this moment. This shark is a cosmopolitan species occurring in all oceans worldwide. It’s characterised by a striped sample on its again, which is effectively marked in juveniles however normally fades in adults.
The fossil historical past of contemporary sharks reaches again to the Permian, about 295 million years in the past. Full fossil shark skeletons are very uncommon — the skeleton, which consists nearly totally of cartilage, is just preserved beneath very particular circumstances in the course of the fossilization processes. As a result of lifelong steady tooth alternative, most extinct sharks are subsequently solely recognized by their well-mineralized tooth, which, nonetheless, can present deep insights into their evolutionary historical past.
The tooth of the fashionable tiger shark are distinctive: they’ve a broad, double-serrated innovative which even permits them to chop via sea turtle shells with ease. Tiger shark tooth are recognized within the fossil document since about 56 million years. Primarily based on these fossil tooth, over 22 extinct tiger shark species have been described.
A world staff of researchers led by Julia Türtscher from the College of Vienna has now examined the fossil historical past of the tiger shark and its extinct kinfolk. With the assistance of geometric morphometrics, the scientists have been capable of present that solely 5 of the 22 recognized fossil tiger sharks really symbolize legitimate species. However, tiger sharks have been extra numerous previously and solely a single species survived till right this moment.
One other intriguing element within the tiger shark fossil document emerged throughout this examine. So far, it was assumed that the fashionable tiger shark originated ca. 5.three million years in the past. The staff, nevertheless, was capable of establish a number of 13.eight million yr outdated fossil tooth as belonging to this shark demonstrating that it originated a lot sooner than beforehand assumed.
Story Supply:
Materials supplied by University of Vienna. Word: Content material could also be edited for model and size.
Source link
