''Pelanechinus'' 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 Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

sea urchin Sea urchins () are spiny, globular echinoderms in the class Echinoidea. About 950 species of sea urchin live on the seabed of every ocean and inhabit every depth zone from the intertidal seashore down to . The spherical, hard shells (tests) of ...

s in the order

Echinothurioida The Echinothurioida are an order of sea urchins in the class Echinoidea. Echinothurioids are distinguished from other sea urchins by the combination of a flexible test and hollow spines. The membrane around the mouth contains only simple plates, ...

. It is placed in the family Pelanechinidae and is in the

stem group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...

of echinoids.

Species

''Pelanechinus corallina'' † (Wright, 1858) – known from the Oxfordian and

Late Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the name ...

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

. ''Pelanechinus oolithicum'' † (Hess, 1972) – known from the

Bajocian In the geologic timescale, the Bajocian is an age and stage in the Middle Jurassic. It lasted from approximately 170.3 Ma to around 168.3 Ma (million years ago). The Bajocian Age succeeds the Aalenian Age and precedes the Bathonian Age. Stratig ...

and

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 ...

Switzerland ). Swiss law does not designate a ''capital'' as such, but the federal parliament and government are installed in Bern, while other federal institutions, such as the federal courts, are in other cities (Bellinzona, Lausanne, Luzern, Neuchâtel ...

. It was originally described as ''Pelanodiadema oolithicum'' Hess, 1972 (Pelanodiademinae Hess, 1972) but ''Pelanodiadema'' is now considered to be a synonym of ''Pelanechinus''. ''Pelanechinus triceps'' † Quenstedt 1858 – known from the

Jura Mountains The Jura Mountains ( , , , ; french: Massif du Jura; german: Juragebirge; it, Massiccio del Giura, rm, Montagnas da Jura) are a sub-alpine mountain range a short distance north of the Western Alps and mainly demarcate a long part of the Frenc ...

. It was originally described as ''Leptocidaris triceps'' but the genus ''Leptocidaris'' is now considered to be 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 ''Pelanechinus''.

''Pelanechinus corallina''

''Pelanechinus corallina'' is the

type species In 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 species that contains the biological type specimen ...

of the genus and was originally described from Yorkshire, England from a single

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

ised specimen in which only the oral part of the

test Test(s), testing, or TEST may refer to: * Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities Arts and entertainment * ''Test'' (2013 film), an American film * ''Test'' (2014 film), ...

was preserved. Members of the Echinothurioida, including ''Pelanechinus'', have flexible tests. In ''P. corallina'' the plates are fused in groups of three with a central large plate and two half-sized ones on either side. The groups of plates overlap in the way that roof tiles do. There is a large

tubercle In anatomy, a tubercle (literally 'small tuber', Latin for 'lump') is any round nodule, small eminence, or warty outgrowth found on external or internal organs of a plant or an animal. In plants A tubercle is generally a wart-like projection ...

on every second or third central plate. Another incomplete specimen found later in the

coral rag Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and sec ...

Calne Calne () is a town and civil parish in Wiltshire, southwestern England,OS Explorer Map 156, Chippenham and Bradford-on-Avon Scale: 1:25 000.Publisher: Ordnance Survey A2 edition (2007). at the northwestern extremity of the North Wessex Downs h ...

, England had a test with a diameter of and was somewhat dorso-ventrally flattened. That specimen was well-preserved with a single

ambulacral Ambulacral is a term typically used in the context of anatomical parts of the phylum Echinodermata or class Sea star, Asteroidea and Edrioasteroidea. Echinoderms can have ambulacral parts that include Ossicle (echinoderm), ossicles, plates, spines ...

area and most of two interambulacral areas present. The mouthparts and teeth were distinct with small overlapping plates surrounding the mouth is the peristomal area .

''Pelanechinus oolithicum''

''Pelanechinus oolithicum'' is known from Schinznach, Switzerland where well preserved fossils have been found. The plates are similarly fused in groups of three in the ambulacral area but there are three tubercles on the set, the central one being the largest. The pore pairs come in groups of three. The interambulacral areas are about three times as wide as the ambulacral areas and have one perforated primary and several secondary tubercles on each plate. The spines are slender and filled with a spongy material.

''Pelanechinus triceps''

''Pelanechinus triceps'' is known from the Jura. The type specimen has a diameter of and a height of . The primary tubercles are perforated and smooth.

References

{{Taxonbar, from=Q7161176 Echinothurioida Prehistoric echinoid genera Jurassic echinoderms Extinct animals of Europe Bajocian first appearances Late Jurassic extinctions