With a total length of up to 5.5m, the tiger shark is one of the largest predatory sharks known today. This shark is a cosmopolitan species found in all the oceans of the world. It is characterized by a striped pattern on the back, which is well marked in juveniles but generally fades in adults.
An international team of researchers led by Julia Türtscher from the University of Vienna examined the fossil records of these top predators and found that modern tiger sharks are older than previously thought and that several species of tiger sharks exist. in the past compared to unique species living today. The results of this study are published in the journal Paleobiology.
The fossil history of modern sharks dates back to the Permian, around 295 million years ago. Complete fossil shark skeletons are very rare – the skeleton, which consists almost entirely of cartilage, is only preserved under very special circumstances during the fossilization processes. Due to the continuous replacement of teeth throughout life, most extinct sharks are therefore only known by their well mineralized teeth, which, nonetheless, can provide in-depth information about their evolutionary history.
The teeth of the modern tiger shark are unique: they have a large double-toothed edge that allows them to even easily cut the shells of sea turtles. Tiger shark teeth have been known in the fossil record for around 56 million years. Based on these fossil teeth, more than 22 species of extinct tiger sharks have been described.
An international team of researchers led by Julia Türtscher from the University of Vienna has now examined the fossil history of the tiger shark and its missing relatives. Using geometric morphometry, scientists were able to show that only 5 of 22 known fossil tiger sharks actually represent valid species. Nevertheless, tiger sharks were more diverse in the past and only one species has survived until today.
Another intriguing detail in the tiger shark fossil record emerged during this study. Until now, it was assumed that the modern tiger shark originated from ca. 5.3 million years ago. However, the team was able to identify several 13.8 million year old fossil teeth as belonging to this shark, demonstrating that it was born much earlier than previously thought.
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