A drill removes only a few milligrams from the fossil tooth.
Phosphoric acid converts enamel carbonate into carbon dioxide.
A mass spectrometer resolves rare carbon-and-oxygen combinations in the CO₂.
A calibrated relationship turns the measured clumping signal into an estimate.
The symbols show the direction of the relationship, not molecule counts from an individual tooth.
The signals remained distinct. Wholesale resetting in the same formation would tend to pull both kinds of enamel toward one common apparent temperature.