Spotted gar, L. oculatusWIKIMEDIA, TINO STRAUSSEnamel is the hardest tissue in the body—and nearly all land animals produce it to protect their teeth. But until now, its origins had remained a mystery. In a Nature study published this week (September 23), researchers offered evidence for early enamel in the scales of fish that lived more than 400 million years ago.
Researchers from Sweden and China first examined the recently sequenced genome of a fish called the spotted gar (Lepisosteus oculatus) and discovered two of the three genes associated with enamel production in other animals. These genes were expressed in the gar’s skin, where its scales produce an enamel-like substance called ganoine.
Investigating whether enamel could have originated in fish scales, the team used scanning electron microscopy to take a closer look at an ancient bony fish, Psarolepis romeri. The researchers observed incremental lines and crystals in the scales and skull of a fossil sample, which indicated the presence of enamel—though not on the fish’s teeth. Previously, researchers had also observed enamel in the fossilized scales of another ancient fish, Andreolepis.
“In us, enamel is only ...
