''Tasbacka'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

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, loggerh ...

containing several species. Though the

type species In International_Code_of_Zoological_Nomenclature, 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 spe ...

, ''T. aldabergeni'', has only been found in Kazakhstan and in

Rostov Oblast Rostov Oblast ( rus, Росто́вская о́бласть, r=Rostovskaya oblastʹ, p=rɐˈstofskəjə ˈobləsʲtʲ) is a federal subjects of Russia, federal subject of Russia (an oblast), located in the Southern Federal District. The oblast ...

Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...

, ''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 northern Denmark from Silstrup via Mors and Fur to Ertebølle, and can be seen in many cliffs and ...

. 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