''Cothurnocystis'' is a genus of small enigmatic

echinoderm An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the sea ...

s that lived during the Ordovician. Individual animals had a flat boot-shaped body and a thin rod-shaped appendage that may be a stem, or analogous to a foot or a tail. Fossils of ''Cothurnocystis'' species have been found in Nevada, Scotland, Czech Republic, France and Morocco.

Taxonomy

The position of the

Stylophora The stylophorans are an extinct, possibly polyphyletic group allied to the Paleozoic Era echinoderms, comprising the prehistoric cornutes and mitrates. It is synonymous with the subphylum Calcichordata. Their unusual appearances have led to a va ...

, of which ''Cothurnocystis'' is a prominent representative, has been in a state of flux. Some scientists claim to be able to see a structurally very basic

notochord In anatomy, the notochord is a flexible rod which is similar in structure to the stiffer cartilage. If a species has a notochord at any stage of its life cycle (along with 4 other features), it is, by definition, a chordate. The notochord consis ...

in the tail, and consequently consider the Stylophora to be a group of primitive

chordate A chordate () is an animal of the phylum Chordata (). All chordates possess, at some point during their larval or adult stages, five synapomorphies, or primary physical characteristics, that distinguish them from all the other taxa. These fiv ...

s, calling them the "Calcichordata". Alternatively these animals are considered related to

s, as the shell (or

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), ...

) is similar in structure and composition to the tests of echinoderms. However, stylophorans are asymmetric organisms that lack either the

radial symmetry Symmetry in biology refers to the symmetry observed in organisms, including plants, animals, fungi, and bacteria. External symmetry can be easily seen by just looking at an organism. For example, take the face of a human being which has a pla ...

typical of most echinoderms, or the

bilateral symmetry Symmetry in biology refers to the symmetry observed in organisms, including plants, animals, fungi, and bacteria. External symmetry can be easily seen by just looking at an organism. For example, take the face of a human being which has a pla ...

of the chordates.

Etymology

* ''C. americana'' refers to the continent where it was found. * ''C. curvata'' is named for the curved form of its theca. * ''C. elizae'' honors Elizabeth Gray, who collected the specimens upon which the description of this species is based.

Distribution

* ''C. americana'' is known from the Lower Ordovician of Nevada (lowest Tremadocian, Whipple Cave Formation, near Lund, White Pine County). * ''C. curvata'' occurs at the Upper Ordovician of Scotland ( Starfish Bed of the

Drummock Group The Drummock Group is a geologic group in Scotland. It preserves fossils dating back to the Ordovician period. See also * List of fossiliferous stratigraphic units in Scotland See also *Lists of fossiliferous stratigraphic units in Europ ...

, ''Dicellograptus anceps''-zone, Thraive Glen, Girvan, Ayrshire). * ''C. elizae'' has been collected in the Lower Ordovician of Morocco (highest Tremadocian to mid Floian, Zagora region), the Upper Ordovician of Scotland (Starfish Bed of the Drummock Group, ''Dicellograptus anceps''-zone, Thraive Glen, Girvan, Ayrshire). * ''C. fellinensis'' is found at the Lower Ordovician of France ( Saint-Chinian Formation, Montaigne Noire).

Description

The body of ''Cothurnocystis'' consists of a chalice (or theca) and a stem (tail or foot). The theca is flattened, boot-shaped and asymmetrical. The edges of the flat sides of the theca seem to consist of 14 elements, 11 defining the outline of the theca, and 3 are processes, one forming a "toe"-spike, a second a heel-spike and a third a lip-spike. The so-called "obverse"-side ("toe" pointing left), is covered with one thin integument, at the "reverse"-side the integument is interrupted by a "strut" formed by a branch of an element near the attachment of the stem, and a branch of an element at the top of the theca. Approximately from the attachment of the stem to the "toe"-spike, is a structure reminiscent of a windpipe, that has been interpreted as a series of slits in the integument. The attachment of the stem seems to consist of four sets of left and right elements, becoming narrower further from the theca. Further down single and uniform elements of the stem seem comparable to the anatomy of sealily stems. The "instep" of the boot seems to hold both the mouth and the anus.

References

* D. Lambert, D. Naish and E. Wyse (2001) "Encyclopedia of Dinosaurs and prehistoric life", p. 32, Dorling Kindersley Limited, London. {{Taxonbar, from=Q4459847 Homalozoa Prehistoric echinoderm genera Ordovician echinoderms Prehistoric echinoderms of Africa Ordovician Africa Fossils of Morocco Ordovician echinoderms of Europe Ordovician France Ordovician Scotland Fossils of the Czech Republic Fossils of France Fossils of Great Britain Ordovician echinoderms of North America Ordovician geology of Nevada Fossils of the United States Wheeler Shale Fossil taxa described in 1913