Shark Evolution Goes Back 450 Million Years, Before Trees and Saturn’s Rings
Shark-like animals appeared 420 to 450 million years ago, before land vertebrates and trees, while a 150-million-year-old fossil shows how specialized sharks became.
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Sharks have an evolutionary history stretching roughly 420 to 450 million years, putting their early relatives far ahead of trees and land vertebrates. Much of that history is reconstructed from teeth and scales because shark skeletons are mainly cartilage, which rarely fossilizes well. That makes unusually complete fossils especially valuable. One striking example is Protospinax annectans, a roughly 150-million-year-old Jurassic shark fossil from what is now southern Germany. Its preserved body outline shows that ancient sharks were not simply unchanged versions of modern sharks. This animal had unusually large pectoral fins and specialized teeth suited to crushing hard-shelled prey such as crustaceans and mollusks. The fossil therefore adds evidence that sharks and their relatives repeatedly evolved specialized body plans to fit changing environments. The broader fossil record also shows that the word shark can be misleading when applied to very ancient shark-like animals, because some early forms were evolutionary relatives of sharks, rays, and chimaeras rather than modern sharks in the strict sense. The key story is not that sharks stopped evolving, but that their long history includes substantial changes and adaptations that helped different lineages persist through major changes in Earth’s oceans.
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