''Stenochirus'' 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 decapod crustaceans that lived from the Callovian to

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 ...

stages of the Jurassic period. Its fossils have been found in Germany and France.

Discovery and naming

Remains of ''Stenochirus'' have been described before the genus was named.

Georg zu Münster Count Georg Ludwig Friedrich Wilhelm zu Münster (german: Georg Graf zu Münster; 17 February 1776 – 23 December 1844) was a German paleontologist. Biography Münster was born on 17 February 1776, in Langelage near Osnabrück. In 1800, he be ...

established the genus ''Bolina'' in 1839 and assigned to species to it, ''B. angusta'' and ''B. pustulosa'' (the type species), both originating from the

-aged Solnhofen Limestone in Bavaria. 22 years later in 1861, Albert Oppel points out that the genus name ''Bolina'' is

preoccupied The Botanical and Zoological Codes of nomenclature treat the concept of synonymy differently. * In botanical nomenclature, a synonym is a scientific name that applies to a taxon that (now) goes by a different scientific name. For example, Linn ...

by a cnidarian, and reassigns the two species into separate genera. He erects the new genera ''Stenochirus'' and ''

Pseudastacus ''Pseudastacus'' (meaning "false ''Astacus''", in comparison to the extant crayfish genus) is an extinct genus of decapod crustaceans that lived during the Jurassic period in Europe, and possibly the Cretaceous period in Lebanon. Many speci ...

'', which ''B. angusta'' and ''B. pustulosa'' became the type species of respectively, the former now renamed as ''Stenochirus angustus''. In addition to the type species, two other species have been assigned to the genus. Oppel described a second species in 1862, which he named ''Stenochirus mayeri'' after Charles Mayer-Eymar, based on one specimen preserved showing its underside collected from the Solnhofen Limestone. The specific name has been misspelled as ''meyeri'' in some publications, due to mistakenly believing the species is named after Hermann v. Meyer. In 2006, the third species ''Stenochirus vahldieki'' was named from remains found in the lagerstätte at La Voulte-sur-Rhône, France. This site dates back to the Callovian stage of the

Middle Jurassic The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from about 174.1 to 163.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relatively rare, but geological formations co ...

period, making ''S. vahldieki'' the oldest known species of the genus.

Description

Measuring around long, ''Stenochirus'' was a small crustacean with a

crayfish Crayfish are freshwater crustaceans belonging to the clade Astacidea, which also contains lobsters. In some locations, they are also known as crawfish, craydids, crawdaddies, crawdads, freshwater lobsters, mountain lobsters, rock lobsters, mu ...

-like build and smooth exoskeleton. The

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 ...

is cylindrical, with a deep cervical groove stretching across the top and sides, as well as two shallow grooves behind it running parallel to each other. The back of the carapace has slightly convex margin. The rostrum is long and has four forward-pointing teeth on its sides. A pair of short stalks connect the compound eyes to the head. The antennae are very long, exceeding the rest of the body in length. Stenochirus claws

The frontmost pair of

pereiopod The decapod (crustaceans such as a crab, lobster, shrimp or prawn) is made up of 20 body segments grouped into two main body parts: the cephalothorax and the pleon (abdomen). Each segment may possess one pair of appendages, although in various g ...

s are very long and slender, ending with pincers. Both "fingers" of each pincer have rows of elongated teeth-like serrations and curve at the tip. In ''S. angustus'', the frontmost pereiopods are six times as long as they are wide, and the pincer "fingers" are equal in length. Meanwhile, the frontmost pereiopods of ''S. mayeri'' are narrower, being 12 times longer than they are wide, and the movable pincer "finger" is longer than the fixed one. The first abdomen segment is smaller than the others, which are around the same length and subrectangular in shape. The telson also has a subrectangular shape, as well as a weak groove, two pairs of spines and two ridges starting at the front of the upper surface which end with small spines on the side margins. Both the endopods and

exopod The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments (called podomeres) are of Latin origin, and may be confused with terms for bones: ''coxa'' (meaning hip, plur ...

s of the uropods have weak ridges, the latter additionally having a small spine on the outer margin.

Classification

''Stenochirus'' is the type genus of the family Stenochiridae, assigned as such when the family was established without formal diagnosis by

Karl Beurlen Karl Beurlen (17 April 1901 – 27 December 1985) was a German paleontologist.Rieppel, Olivier. (2012). ''Karl Beurlen (1901-1985), Nature mysticism, and Aryan Paleontology''. ''Journal of the History of Biology'' 45: 253-299. Beurlen was born in ...

in 1928. Beurlen initially erected it as a

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end subfamily botanical names with "-oideae", and zoologi ...

named Stenochirinae, but would elevate it to family level in 1930. Although

Martin Glaessner Martin Fritz Glaessner AM (25 December 1906 – 23 November 1989) was a geologist and palaeontologist. Born and educated in the Austro-Hungarian Empire, he spent the majority of his life in working for geoscientific institutes in Austria, Russia ...

assigned ''Stenochirus'' to Erymidae in 1929, he later placed it as an indeterminate astacidean when writing for the '' Treatise on Invertebrate Paleontology'' in 1969. Garassino & Schweigert (2006) would resurrect the taxon Stenochiridae and give the family a formal diagnosis, reassigning ''Stenochirus'' as its only genus. In 2013, analysis by Karasawa ''et al.'' found that the supposed family Chilenophoberidae is

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

, as ''Stenochirus'' is nested within as a sister taxon to ''

''. They therefore declared Chilenophoberidae as a

junior synonym The Botanical and Zoological Codes of nomenclature treat the concept of synonymy differently. * In botanical nomenclature, a synonym is a scientific name that applies to a taxon that (now) goes by a different scientific name. For example, Linna ...

of Stenochiridae, and thus more genera were moved into the family. The following cladogram shows the placement of ''Stenochirus'' within Stenochiridae according to the study:

References

External links

* {{Taxonbar, from1=Q123575455 Jurassic crustaceans Solnhofen fauna Fossil taxa described in 1861 Decapod genera