Jurellana
Encyclopedia
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.
of the porcelain crabs, Porcellana
, and the word Jurassic
. The specific epithet also refers to the age during which the animal lived – in this case, the Tithonian
. 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 ammonite
s they contain; they also contain a number of crab
s. This makes Jurellana the oldest known porcelain crab.
10.8 millimetre (0.425196850393701 in) long and 9.8 mm (0.385826771653543 in) wide, with a distance between the orbits of the eyes of 7.8 mm (0.307086614173228 in). The smaller specimen has a carapace 4 mm (0.15748031496063 in) long and 4 mm (0.15748031496063 in) wide, and orbits 3.4 mm (0.133858267716535 in) apart. 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. It is 5.4 mm (0.21259842519685 in) wide in the larger specimen, and 2.2 mm (0.0866141732283465 in) wide in the smaller specimen. The appendage
s of the animal have not been preserved in either specimen.
Porcelain crab
Porcelain crabs are decapod crustaceans in the widespread family Porcellanidae, which superficially resemble true crabs. They are typically less than wide, and have flattened bodies as an adaptation for living in rock crevices...
. It was found in limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
rocks from the Ernstbrunn Formation in Austria
Austria
Austria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...
, which have been dated to the Tithonian
Tithonian
In the geologic timescale the Tithonian is the latest age of the Late Jurassic epoch or the uppermost stage of the Upper Jurassic series. It spans the time between 150.8 ± 4 Ma and 145.5 ± 4 Ma...
(late Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
). It differs from extant porcelain crabs by the down-turned form of the rostrum
Rostrum (anatomy)
The term rostrum is used for a number of unrelated structures in different groups of animals:*In crustaceans, the rostrum is the forward extension of the carapace in front of the eyes....
, 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 genusType genus
In biological classification, a type genus is a representative genus, as with regard to a biological family. The term and concept is used much more often and much more formally in zoology than it is in botany, and the definition is dependent on the nomenclatural Code that applies:* In zoological...
of the porcelain crabs, Porcellana
Porcellana
Porcellana is a genus of decapod crustaceans in the widespread family Porcellanidae, the porcelain crabs, which superficially resemble true crabs...
, and the word Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
. The specific epithet also refers to the age during which the animal lived – in this case, the Tithonian
Tithonian
In the geologic timescale the Tithonian is the latest age of the Late Jurassic epoch or the uppermost stage of the Upper Jurassic series. It spans the time between 150.8 ± 4 Ma and 145.5 ± 4 Ma...
. The type specimens were discovered near Ernstbrunn
Ernstbrunn
Ernstbrunn is a town in the district of Korneuburg in Lower Austria in Austria. Ernstbrunn takes up about 80.69 square kilometers, 26.99 percent of which is forest.-External links:*...
, Lower Austria
Lower Austria
Lower Austria is the northeasternmost state of the nine states in Austria. The capital of Lower Austria since 1986 is Sankt Pölten, the most recently designated capital town in Austria. The capital of Lower Austria had formerly been Vienna, even though Vienna is not officially part of Lower Austria...
, and are now held at the Naturhistorisches Museum
Naturhistorisches Museum
The Naturhistorisches Museum Wien or NHMW is a large museum located in Vienna, Austria.The collections displayed cover , and the museum has a website providing an overview as a video virtual tour....
in Vienna
Vienna
Vienna is the capital and largest city of the Republic of Austria and one of the nine states of Austria. Vienna is Austria's primary city, with a population of about 1.723 million , and is by far the largest city in Austria, as well as its cultural, economic, and political centre...
. The rocks that contained the specimens have been dated to the Tithonian based on the ammonite
Ammonite
Ammonite, as a zoological or paleontological term, refers to any member of the Ammonoidea an extinct subclass within the Molluscan class Cephalopoda which are more closely related to living coleoids Ammonite, as a zoological or paleontological term, refers to any member of the Ammonoidea an extinct...
s they contain; they also contain a number of crab
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
s. This makes Jurellana the oldest known porcelain crab.
Description
Two specimens of Jurellana tithonia are known, one considerably larger than the other. The larger one has a carapaceCarapace
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...
10.8 millimetre (0.425196850393701 in) long and 9.8 mm (0.385826771653543 in) wide, with a distance between the orbits of the eyes of 7.8 mm (0.307086614173228 in). The smaller specimen has a carapace 4 mm (0.15748031496063 in) long and 4 mm (0.15748031496063 in) wide, and orbits 3.4 mm (0.133858267716535 in) apart. J. tithonia differs from other porcelain crabs in that its rostrum
Rostrum (anatomy)
The term rostrum is used for a number of unrelated structures in different groups of animals:*In crustaceans, the rostrum is the forward extension of the carapace in front of the eyes....
, rather than extending forwards from the front of the carapace, is turned 90° downwards. It is 5.4 mm (0.21259842519685 in) wide in the larger specimen, and 2.2 mm (0.0866141732283465 in) wide in the smaller specimen. The appendage
Appendage
In invertebrate biology, an appendage is an external body part, or natural prolongation, that protrudes from an organism's body . It is a general term that covers any of the homologous body parts that may extend from a body segment...
s of the animal have not been preserved in either specimen.