Protostega was a large sea turtle the lived in the ocean that covered Kansas and central North America 80 million years ago. New research by FHSU paleontologist Dr. Laura Wilson shows that the bone tissue microstructure (osteohistology) of Protostega reveals growth patterns similar to modern leatherback sea turtles (the largest sea turtles alive today) with rapid growth to large body size. Leatherbacks don’t have a typical reptile metabolism; they have high resting metabolic rates and can hold a body temperature higher than their surroundings. If Protostega had similar bone growth patterns to leatherbacks, it’s hypothesized they had a similar metabolism.
What’s more, for sea turtles rapid growth to adult body size also means rapid growth to reproductive maturity. Growing quickly and reproducing early are great survival strategies in an ocean filled with big bony fish, bigger sharks, and even bigger mosasaurs.
Comparing Protostega to its more basal relative Desmatochelys shows that not all protostegid sea turtles had the same growth patterns. Desmatochelys had a slower growth rate more similar to living green and loggerhead sea turtles. Rapid growth to large size evolved late within the lineage, perhaps in response to the evolution of large tylosaurid mosasaurs. Given uncertainties in the phylogenetic placement of protostegids relative to living sea turtles, it is unclear if the evolution of rapid growth rates and possible elevated metabolism is convergent with modern leatherbacks or if the two are more closely related.
This resaerch was publised in the open-access journal PeerJ and can be read for free: https://peerj.com/articles/14864/