''Tasbacka'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

sea turtle Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the flatback, green, hawksbill, leatherback, loggerhe ...

containing several species. Though the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen( ...

, ''T. aldabergeni'', has only been found in Kazakhstan, ''Tasbacka'' had a wide distribution. ''T. ruhoffi'' was found in the eastern USA, ''T. danica'' in modern Denmark, ''T. ouledabdounensis'' in modern Morocco, ''T. salisburgensis'' in modern Austria, and ''T. germanica'' in modern Germany. In 2008, researchers found a well-preserved, juvenile specimen of ''T. danica'' in Denmark's

Fur Formation The Fur Formation is a marine geological formation of Ypresian ( Lower Eocene Epoch, c. 56.0-54.5 Ma) age which crops out in the Limfjord region of Denmark from Silstrup via Mors and Fur to Ertebølle, and can be seen in many cliffs and quarries ...

. Some of the fossil's soft tissues remained. The specimen, dating back to 54 Ma, contained eumelanin. This pigment would've given the hatchling a dark shell while it was alive. Modern sea turtle hatchlings also have dark shells; while a hatchling floats on the ocean's surface, its dark coloring enables it to absorb heat from the sun and avoid predatory birds. The existence of similar pigment on an ancient specimen suggests sea turtles evolved this survival trait millions of years ago.

References

Chelonioidea Fossils of Denmark Paleocene turtles Extinct turtles Turtle genera Fur Formation Fossil taxa described in 1987 Fossils of Austria {{paleo-turtle-stub