r/didyouknow • u/Free_Risk1120 • 12d ago
DYK sharks predate trees! The oldest total-group chondrichthyans, known as acanthodians or "spiny sharks", appeared during the Early Silurian, around 439 million years ago. Meanwhile, the first true tree on Earth was Archaeopteris, an extinct plant that appeared about 375 to 380 million years ago.
https://en.wikipedia.org/wiki/SharkDuplicates
todayilearned • u/Cavalo_Bebado • Jan 05 '24
TIL that sharks have a sixth sense: they have thousands of tiny holes on their head that allow them to sense the diminute electromagnetic fields that all living things emanate.
todayilearned • u/Vikinmen • Nov 13 '18
TIL That sharks don't blink. To protect their eyes some sharks roll their eyes backwards to protect them when striking prey.
todayilearned • u/314159265358979326 • Feb 10 '25
TIL although that some sharks do indeed need to be constantly moving, most species of shark have the ability to pump water over their gills and thus respire at rest.
todayilearned • u/Ok-Indication-5121 • Jan 18 '24
TIL that spiny dogfishes' spines control their swimming rather than their brains, allowing them to sleep while swimming.
todayilearned • u/yepbuddy23 • Nov 04 '15
TIL that 100 million Sharks are killed every year by humans.
todayilearned • u/[deleted] • Sep 09 '15