Great environmental changes may affect the survival capability of a variety of organisms.
Testudinidae is the most diverse family of terrestrial chelonians within the whole
order (Testudines). Interestingly, however, the number of extinct species overcome
the extant ones. In order to understand better how the diversification process of
this family occurred, this work used the PyRate software, which estimates both the
preservation and diversification processes in a continuous time interval. For such,
the software used a list of fossil occurrences obtained from the Paleobiology Database
whereas the extant species list was obtained from Catalogue of Life. This way, the
software was able to infer the probability of the ancestral clade having resulted
in these species during its evolutionary history. The analyses generated graphs containing
the diversification, extinction and speciation curves and their respective associated
95% credibility intervals. A great rise in the extinction rate was observed starting
6 million years ago. This rise is believed to be related to the drop of atmospheric
CO2 all over the globe at the end of the Miocene, about 8-6 million years ago. This
event led to a turnover of the vegetation composition on the warmer areas of the planet,
with plants that used C3 metabolism giving way to C4 plants. In terms of landscape,
grasses and herbal vegetation, such as savannas, started dominating. As for other
animal groups, those herbivores with grazing habits were more successful than those
used to only browsing or that did not have enough flexibility of choice.