About 500 million years ago, not a single creature had a skull. Over time, these bony plates evolved into the structural marvels that vertebrates—animals with spinal cords, aka you, me, and your pug, ...

https://siris-libraries.si.edu/ipac20/ipac.jsp?&profile=liball&source=~!silibraries&uri=full=3100001~!743001~!0#focus ...