The Trigonoceratoidea are a superfamily within the
Nautilida
The Nautilida constitute a large and diverse order of generally coiled nautiloid cephalopods that began in the mid Paleozoic and continues to the present with a single family, the Nautilidae which includes two genera, ''Nautilus'' and ''Allonauti ...
that ranged from the
Devonian
The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...
to the
Triassic
The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...
, thought to have contained the source for the
Nautilaceae
The Nautilaceae form one of five superfamilies that make up the Nautilida according to Bernard Kummel (1964), and the only one that survived past the Triassic. The Nautilaceae comprise six families: Nautilidae, Paracenoceratidae, Pseudonautilidae ...
in which ''
Nautilus
The nautilus (, ) is a pelagic marine mollusc of the cephalopod family Nautilidae. The nautilus is the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina.
It comprises six living species in t ...
'' is found.
Trigonoceratoidea are characterized by open-spiraled,
gyroconic, to closed,
nautiliconic shells in which the
Whorl
A whorl ( or ) is an individual circle, oval, volution or equivalent in a whorled pattern, which consists of a spiral or multiple concentric objects (including circles, ovals and arcs).
Whorls in nature
File:Photograph and axial plane floral ...
section is
quadrate in primitive forms; the
venter typically narrow to acute, the dorsum broad. In some advanced forms, the venter may become concave or broad and rounded, and in some, the surfaces may be strongly
lirate.
Classification and phylogeny
The Trigonoceratoidea are based on the family
Trigonoceratidae of
Alpheus Hyatt
Alpheus Hyatt (April 5, 1838 – January 15, 1902) was an American zoologist and palaeontologist.
Biography
Alpheus Hyatt II was born in Washington, D.C. to Alpheus Hyatt and Harriet Randolph (King) Hyatt. He briefly attended the Maryla ...
, 1884, with which other
phylogenetic
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...
ally related families are combined, and are equivalent to the abandoned Centroceratida of Flower in Flower and Kümmel 1950, and to the Centroceratina of
Shimanskiy 1957, revised to the Centrocerataceae, Shimanskiy 1962.
The Trigonoceratoidea combine five families, the type, Trigonoceratidae, along with the
Centroceratidae
The Centroceratidae is the ancestral family of the Trigonoceratoidea and of the equivalent Centroceratina; extinct shelled cephalopods belonging to the order Nautilida
Diagnosis
The Centroceratidae, which range from the Middle Devonian to the ...
,
Grypoceratidae,
Permoceratidae, and
Syringonautilidae. Phylogenetic study and age show that the Centroceratidae are the root stock in spite of having been first recognized 16 years after the Trigonoceratidae were first described.
The Centroceratidae gave rise to the Trigonoceratidae and Grypoceratidae in the early
Mississippian, while continuing until the very
Early Permian 01 or '01 may refer to:
* The year 2001, or any year ending with 01
* The month of January
* 1 (number)
Music
* '01 (Richard Müller album), 01'' (Richard Müller album), 2001
* 01 (Son of Dave album), ''01'' (Son of Dave album), 2000
* 01 (Urban ...
. The Trigonoceratidae which ranged into the Permian left no descendants. The Grypoceratidae which ranged almost to the end of the Triassic gave rise to two small families, the Permian Permoceratidae and the Triassic Syringonautilidae. The Syringonautilidae, in turn, are the source for the Nautilidae (Nautilaceae) which contain the genus ''Nautilus''.
Families
The
Trigonoceratidae, type family, named by Hyatt, 1884, are loosely coiled to
evolute
In the differential geometry of curves, the evolute of a curve is the locus of all its centers of curvature. That is to say that when the center of curvature of each point on a curve is drawn, the resultant shape will be the evolute of that curv ...
, with oval to