''Jurellana tithonia'', the only species in the genus ''Jurellana'', is a fossil

crab Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all the ...

. It was found in

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

rocks from the Ernstbrunn Formation in

Austria Austria, , bar, Östareich officially the Republic of Austria, is a country in the southern part of Central Europe, lying in the Eastern Alps. It is a federation of nine states, one of which is the capital, Vienna, the most populous ...

, which have been dated to the

Tithonian In the geological timescale, the Tithonian is the latest age of the Late Jurassic Epoch and the uppermost stage of the Upper Jurassic Series. It spans the time between 152.1 ± 4 Ma and 145.0 ± 4 Ma (million years ago). It is preceded by the K ...

(late

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...

). It was originally thought to be the world's oldest

porcelain crab Porcelain crabs are decapod crustaceans in the widespread family Porcellanidae, which superficially resemble true crabs. They have flattened bodies as an adaptation for living in rock crevices. They are delicate, readily losing limbs when attack ...

, but was later determined to actually be a true crab.

Taxonomy and stratigraphy

''Jurellana tithonia'' was described in 2010 by

palaeontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...

s Carrie Schweitzer and Rodney Feldmann, as the only species in the genus. The genus' name was based on the name of the

type genus In biological taxonomy, the type genus is the genus which defines a biological family and the root of the family name. Zoological nomenclature According to the International Code of Zoological Nomenclature, "The name-bearing type of a nominal f ...

of the porcelain crabs, ''

Porcellana ''Porcellana'' is a genus of Decapoda, decapod crustaceans in the widespread family (biology), family Porcellanidae, the porcelain crabs, which superficially resemble true crabs. The genus ''Porcellana'' includes the following species: * ''Por ...

'', and the word

. The

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

' also refers to the age during which the animal lived – in this case, the

. The

type specimen In biology, a type is a particular wiktionary:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to a ...

s were discovered near

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. The castle became the seat of the Ernstbrunn branch of the Counts of Sinzendorf ...

Lower Austria Lower Austria (german: Niederösterreich; Austro-Bavarian: ''Niedaöstareich'', ''Niedaestareich'') is one of the nine states of Austria, located in the northeastern corner of the country. Since 1986, the capital of Lower Austria has been Sankt P ...

, and are now held at the

Naturhistorisches Museum The Natural History Museum Vienna (german: Naturhistorisches Museum Wien) is a large natural history museum located in Vienna, Austria. It is one of the most important natural history museums worldwide. The NHM Vienna is one of the largest museum ...

Vienna en, Viennese , iso_code = AT-9 , registration_plate = W , postal_code_type = Postal code , postal_code = , timezone = CET , utc_offset = +1 , timezone_DST ...

. The rocks that contained the specimens have been dated to the Tithonian based on the

ammonite Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) ...

s they contain; they also contain a number of

s. This makes ''Jurellana'' the oldest known porcelain crab. However, a 2019 study found it to be a true crab instead, belonging to the new family Jurellanidae along with the newly described genus '' Ovalopus.''

Description

Two specimens of ''Jurellana tithonia'' are known, one considerably larger than the other. The larger one has a

carapace A carapace is a Dorsum (biology), dorsal (upper) 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 tor ...

long and wide, with a distance between the orbits of the eyes of . The smaller specimen has a carapace long and wide, and orbits apart. ''J. tithonia'' differs from other porcelain crabs in that its

rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ships * Ros ...

, rather than extending forwards from the front of the carapace, is turned 90° downwards. It is wide in the larger specimen, and wide in the smaller specimen. The

appendage An appendage (or outgrowth) is an external body part, or natural prolongation, that protrudes from an organism's body. In arthropods, an appendage refers to any of the homologous body parts that may extend from a body segment, including anten ...

s of the animal have not been preserved in either specimen.

References

{{Taxonbar, from=Q16754023 Porcelain crabs Jurassic crustaceans Monotypic arthropod genera Fossil taxa described in 2010 Prehistoric animals of Europe