The teeth of sharks can be difficult to identify in isolation. Those at the front of the jaw (anteriors) are often straight with an inflection in the lateral view. The teeth at the side of the jaw (laterals) may be curved backwards in many species. In reality, a tooth from one part of a shark’s jaw may look similar to a tooth from another part of the jaw of a different species. There are also some species which have quite unique teeth. This tooth is an anterior tooth from a Goblin Shark, Anatomadus species. It can easily be confused with the teeth of Odontaspis species, the tiger shark.
To enable comparison of fossil material, it is often wise to cast specimens. The casts can then be carried arround without the risk of damaging the original specimen. This is an unusual fossil of the inside of a trilobite carapace, exposed for inspection. It is Phillipsia gemmulifera from the carboniferous.
There are a lot of fossil teeth out there, especially from large marine predators like sharks, which shed their teeth naturally, and marine reptiles which break their teeth on hard prey. Most of the teeth are like this one, isolated and out of context. I would call this an indeterminate fossil tooth, but some would call it plesiosaur, ichthyosaur, pterosaur, etc… Who knows what it is from?
Rhamphorhynchus was a long-tailed pterosaur from the Upper Jurassic. This bone is the Humerus of the wing of Rhamphorhynchus Longiceps. The original fossil humeri are embedded in shale and this represents a reconstruction of the whole bone based on the actual specimen. This allows the bone to be handled and rotated for comparison with other specimens.