extinct
Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
genus
Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of
bivalve
Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...
in the
extinct
Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
family
Praenuculidae
Praenuculidae is an extinct family of prehistoric bivalves in the superfamily Nuculoidea. Praenuculidae species lived from the early Ordovician, Arenig stage through the Early Devonian Emsian stage.
. The genus is one of eleven genera in the subfamily
Praenuculinae
Praenuculinae is an extinct subfamily (biology), subfamily of prehistoric bivalves in the family (biology), family Praenuculidae. Praenuculinae species lived from the middle Ordovician through the late Devonian.Late Ordivician,
Caradoc
Caradoc Vreichvras (; Modern , ) was a semi-legendary ancestor to the kings of Gwent. He may have lived during the 5th or 6th century. He is remembered in the Matter of Britain as a Knight of the Round Table, under the names King Carados and C ...
epoch, fossils found in South America. ''Trigonoconcha'' currently contains a
single
Single may refer to:
Arts, entertainment, and media
* Single (music), a song release
Songs
* "Single" (Natasha Bedingfield song), 2004
* "Single" (New Kids on the Block and Ne-Yo song), 2008
* "Single" (William Wei song), 2016
* "Single", by ...
accepted species, ''Trigonoconcha acuta''.
Description
''Trigonoconcha acuta'' was first described in 1999 by Teresa M. Sánchez from fossils from sediments of the late Middle Ordivician, Caradocian aged Don Braulio Formation. The formation outcrops on the flank of Sierra de Villicum in the
Argentina
Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...
precordillera
Precordillera is a Spanish geographical term for hills and mountains lying before a greater range, similar to foothills. The term is derived from ''cordillera'' (mountain range)—literally "pre-mountain range"—and applied usually to the Andes.
...
.The Paleobiology database "Sierra de Villicum" entry accessed 11 February 2012
The shells of ''Trigonoconcha'' have anterior and posterior sides which meet at an angle of no more than sixty-five degrees. While this is similar to the related genera '' Palaeoconcha'' and '' Similodonta'', they are both noted for anterior-posterior angles of no less than ninety degrees. The presence of an auricle, a finger-like projection on the underside of the umbo, in ''Palaeoconcha'' also distinguishes specimens from ''Trigonoconcha''. ''Similodonta'' is distinguished from both other genera by an edentulous space, a region on the hinge that lacks teeth. The umbo of ''Trigonoconcha'' is located at the vertex formed by the anterior and posterior sides and the ventral margin forms a broad curving edge. On smaller shells, possibly from immature specimens, the ventral margin curves abruptly to meet the anterior and posterior margins creating a triangular shell outline.
The anterior edge is host to up to fifteen teeth while the posterior edge has a maximum of ten. The ''Trigonoconcha'' ranges in shell length from and has a height between . When described, the genus name ''Trigonoconcha'' was chosen by Sánchez in reference to the triangle created by the anterior and posterior margins of the shell. Similarly, the species epithet ''acuta'' was coined as a reference to the acute angle formed by the anterior and posterior margins.
''Trigonoconcha'' was described from one
holotype
A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...
specimen, number CEGH-UNC 16158, which is an internal mold of a left valve. A series of twelve other right and left valve molds were also examined and used in the description. The specimens are currently deposited in the Department of Geology
paleontology
Paleontology, also spelled as palaeontology or palæontology, is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use fossils as a means to classify organisms, measure ge ...
collections in the
National University of Córdoba
The National University of Córdoba (), is a public university located in the city of Córdoba, Argentina. Founded in 1613, the university is the oldest in Argentina, the third oldest university of the Americas, with the first university being ...