Having a mineralized skeleton is not enough to ensure that a biological archive continuously records the spectrum of seasonal variations. Leaving aside the physiology, i.e. the molecular mechanism producing the shell, factors related to growth and ecology are crucial to record the seasonality of temperatures.
In a study recently published in the context of the STAMINA project, we actually observed that juvenile shells of Calloria inconspicua show a continuous growth pattern throughout the year, allowing a better resolution and plausible estimate of the seasonal temperature variation. Once they reach a certain size, probably linked to reaching the adult phase, the growth of the shell continues but for a limited period of the year.
This finding has clearly important implications for the use of brachiopods to reconstruct past climate seasonality. You can read the full article here and download the accepted version of the manuscript below.
