image credit: Fossilera (mako shark tooth) and George Karbus Photography (mako shark black and white
image credit: Fossilera (mako shark tooth) and George Karbus Photography (mako shark black and white)Q: How old do ya’ll think sharks are?A: Prof. Custard would accept either “425 million years old”, “lived from upper Silurian to recent”, “older than trees”, “older than dinos”, “yes”, or “um not really sure”The interesting thing about sharks is that their skeletons are made of cartilage, not bone. There’s actually a name for these cartilaginous fishes: the class Chondrichthyes. Think sharks, rays, chimaeras. Quick note: There’s acc a class for fish with skeletons made of bone as well - Osteichthyes, or more simply, bony fish. Also ayy we mammals - and also reptiles, amphibians, and birds - inherited our lungs from bony fish so we gotta thank them for that uwuaNYwaYSharks have tough skin covered w dermal teeth (aka hard lil structures on the skin covered w enamel, making them similar to teeth) and breathe through 5-7 pairs of gills. They’ve got teeth embedded in their gums rather than attached to the jaw, and replace them constantly through their lives. The shape of the tooth is pretty dependent on the shark’s diet: sharks that eat primarily things w shells/hard outer layers (e.g. mollusks or crustaceons) have denser and flatter teeth used to crush, which needle-like teeth are used to feed on fish. Some sharks even have biofluresence (swell shark and chain catshark) which is so amazing and cool jajajasmall-custard assessment: 9.1/10. psa: so many living sharks are either vulnerable, endangered, or critically endangered species due to commercial and recreational fishing. they are often v misunderstood as well so pls,, be kind and remind others to be kind to these bbys, don’t bother them if you are lucky enough to see one, stay away, and it is extremely unlikely that they will hurt you. -- source link
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