Jurellana

Jurellana tithonia, the only species in the genus Jurellana, is the oldest known fossil porcelain crab. It was found in limestone rocks from the Ernstbrunn Formation in Austria, which have been dated to the Tithonian (late Jurassic). It differs from extant porcelain crabs by the down-turned form of the rostrum, which points forwards in other porcelain crabs.

Taxonomy and stratigraphy

Jurellana tithonia was described in 2010 by the palaeontologists Carrie Schweitzer and Rodney Feldmann, as the only species in the genus. The genus' name was based on the name of the type genus of the porcelain crabs, Porcellana, and the word Jurassic. The specific epithet tithonia also refers to the age during which the animal lived – in this case, the Tithonian.^[1] The type specimens were discovered near Ernstbrunn, Lower Austria, and are now held at the Naturhistorisches Museum in Vienna. The rocks that contained the specimens have been dated to the Tithonian based on the ammonites they contain; they also contain a number of crabs.^[2] This makes Jurellana the oldest known porcelain crab.^[1]

Description

Two specimens of Jurellana tithonia are known, one considerably larger than the other. The larger one has a carapace 10.8 millimetres (0.43 in) long and 9.8 mm (0.39 in) wide, with a distance between the orbits of the eyes of 7.8 mm (0.31 in). The smaller specimen has a carapace 4.0 mm (0.16 in) long and 4.0 mm (0.16 in) wide, and orbits 3.4 mm (0.13 in) apart.^[1] J. tithonia differs from other porcelain crabs in that its rostrum, rather than extending forwards from the front of the carapace, is turned 90° downwards.^[1] It is 5.4 mm (0.21 in) wide in the larger specimen, and 2.2 mm (0.087 in) wide in the smaller specimen.^[1] The appendages of the animal have not been preserved in either specimen.^[1]

References