''Tasbacka'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus of sea turtle containing several species. Though the type species, ''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. 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