Conulariida
Encyclopedia
The Conulata, also known as conulariids, form a poorly understood clade of extinct scyphozoa
n cnidaria
ns.
s preserved as shell-like structures made up of rows of calcium phosphate rods, resembling an ice-cream cone with fourfold symmetry, usually four prominently-grooved corners. New rods were added as the organism grew in length; the rod-based growth falsely gives the fossils a segmented appearance. Exceptional soft-part preservation has revealed that soft tentacles protruded from the wider end of the cone, and a holdfast
from the pointed end attached the organisms to hard substrate. The prevailing reconstruction of the organism has it look superficially like a sea anemone
sitting inside an angular, hard cone held perpendicular to the substrate.
Setting aside for the moment the Precambrian
vendoconulariids, which may or may not be conulariids at all, the Conulata fossil record begins with undoubted specimens in the Upper Cambrian
(Hughes et al., 2000) and extends without significant break through numerous major mass extinctions. The Conulariids finally disappear from the rock record during the Lower Triassic
stage of the Triassic Period (~).
In North America, conulariids are generally least uncommon in rocks of Ordovician
and Carboniferous
age.
waters, such as the oceans and inland seas. Fossils are commonly found in rocks representing offshore, even anoxic
, marine bottom environments. This has led some scientists to infer that these animals may have drifted plankton
ically for some or all of their lives, ultimately being buried in the anoxic sediments beneath the oxic waters in which they lived. However, basic functional considerations (such as the great weight of the shell) make such interpretations difficult to maintain.
The conulariids were originally thought to be anthozoa
n cnidarians. However, the lack of septa or other features diagnostic of anthozoans led researchers to abandon this hypothesis. Ivantsov and Fedonkin (2002) posit that the conulariids were ancestrally tri-radially symmetrical, as typified with Vendoconularia
, typical of the structure seen in Vendozooans. Conulariids are, however, not generally thought to be a part of the Ediacaran biota as their fossil record starts at Middle Ordovician. The conulariids are now thought to be most closely related to the Scyphozoa
, or the "true jellyfish".
It is now also thought that the conulate trilobozoans derived their fourfold symmetry from a sixfold symmetry, as seen in Vendoconularia. This in turn, is thought to be originally derived from an ancestral disk-like trilobozoa
n three-fold symmetry.
Conulariids are generally thought to be of Cnidaria
n affinity, occupying a position near the base of the Cnidarian family tree. However, the nature of Conulariids and their phylogenetic relationships to other organisms remain poorly understood, and the supposed cnidarian affinity remain speculative.
s within their shells, similar to the way molluscs such as oysters, other pelecypods, and some gastropods do today. These pearls give a clue as to the internal anatomy of the conulariid animal. But due to their calcium phosphate
composition, their crystal structure, and their extreme age, these pearls tend to be rather unattractive for use in decorative objects.
Scyphozoa
Scyphozoa is a class within the phylum Cnidaria, sometimes referred to as the "true jellyfish".The class name Scyphozoa comes from the Greek word skyphos , denoting a kind of drinking cup and alluding to the cup shape of the organism....
n cnidaria
Cnidaria
Cnidaria is a phylum containing over 9,000 species of animals found exclusively in aquatic and mostly marine environments. Their distinguishing feature is cnidocytes, specialized cells that they use mainly for capturing prey. Their bodies consist of mesoglea, a non-living jelly-like substance,...
ns.
Structure
The conulariids are fossilFossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s preserved as shell-like structures made up of rows of calcium phosphate rods, resembling an ice-cream cone with fourfold symmetry, usually four prominently-grooved corners. New rods were added as the organism grew in length; the rod-based growth falsely gives the fossils a segmented appearance. Exceptional soft-part preservation has revealed that soft tentacles protruded from the wider end of the cone, and a holdfast
Holdfast
A holdfast is a root-like structure that anchors aquatic sessile organisms, such as seaweed, other sessile algae, stalked crinoids, benthic cnidarians, and sponges, to the substrate. ...
from the pointed end attached the organisms to hard substrate. The prevailing reconstruction of the organism has it look superficially like a sea anemone
Sea anemone
Sea anemones are a group of water-dwelling, predatory animals of the order Actiniaria; they are named after the anemone, a terrestrial flower. Sea anemones are classified in the phylum Cnidaria, class Anthozoa, subclass Zoantharia. Anthozoa often have large polyps that allow for digestion of larger...
sitting inside an angular, hard cone held perpendicular to the substrate.
Fossil record
Precambrian
The Precambrian is the name which describes the large span of time in Earth's history before the current Phanerozoic Eon, and is a Supereon divided into several eons of the geologic time scale...
vendoconulariids, which may or may not be conulariids at all, the Conulata fossil record begins with undoubted specimens in the Upper Cambrian
Cambrian
The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...
(Hughes et al., 2000) and extends without significant break through numerous major mass extinctions. The Conulariids finally disappear from the rock record during the Lower Triassic
Triassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...
stage of the Triassic Period (~).
In North America, conulariids are generally least uncommon in rocks of Ordovician
Ordovician
The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...
and Carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
age.
Lifestyle
Conulariids apparently lived only in normal-marineMarine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
waters, such as the oceans and inland seas. Fossils are commonly found in rocks representing offshore, even anoxic
Anoxic sea water
Anoxic waters are areas of sea water or fresh water that are depleted of dissolved oxygen. This condition is generally found in areas that have restricted water exchange....
, marine bottom environments. This has led some scientists to infer that these animals may have drifted plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
ically for some or all of their lives, ultimately being buried in the anoxic sediments beneath the oxic waters in which they lived. However, basic functional considerations (such as the great weight of the shell) make such interpretations difficult to maintain.
Phylogeny
About 20 genera and 150 species are known,http://www.zoobank.org/advancedquery.htm?searchType=tree&pp=10&so=a0&q=Conulariida but except for local occurrences, Conulariids are relatively uncommon.The conulariids were originally thought to be anthozoa
Anthozoa
Anthozoa is a class within the phylum Cnidaria that contains the sea anemones and corals. Unlike other cnidarians, anthozoans do not have a medusa stage in their development. Instead, they release sperm and eggs that form a planula, which attaches to some substrate on which the cnidarian grows...
n cnidarians. However, the lack of septa or other features diagnostic of anthozoans led researchers to abandon this hypothesis. Ivantsov and Fedonkin (2002) posit that the conulariids were ancestrally tri-radially symmetrical, as typified with Vendoconularia
Vendoconularia
Vendoconularia is a genus of Ediacaran organism consisting of a hexagonal cone, which is thought to have housed a tentaculate organism. Three longitudinal bands are interspersed between the six sides of the cone. The discovery of vendoconulariids in Proterozoic strata of Russia confirmed a 1987...
, typical of the structure seen in Vendozooans. Conulariids are, however, not generally thought to be a part of the Ediacaran biota as their fossil record starts at Middle Ordovician. The conulariids are now thought to be most closely related to the Scyphozoa
Scyphozoa
Scyphozoa is a class within the phylum Cnidaria, sometimes referred to as the "true jellyfish".The class name Scyphozoa comes from the Greek word skyphos , denoting a kind of drinking cup and alluding to the cup shape of the organism....
, or the "true jellyfish".
It is now also thought that the conulate trilobozoans derived their fourfold symmetry from a sixfold symmetry, as seen in Vendoconularia. This in turn, is thought to be originally derived from an ancestral disk-like trilobozoa
Trilobozoa
Trilobozoa is an extinct taxon of organisms which displayed tri-radial symmetry. Trilobozoans were most dominant during the Ediacaran period — prior to the Cambrian explosion of modern life forms....
n three-fold symmetry.
Conulariids are generally thought to be of Cnidaria
Cnidaria
Cnidaria is a phylum containing over 9,000 species of animals found exclusively in aquatic and mostly marine environments. Their distinguishing feature is cnidocytes, specialized cells that they use mainly for capturing prey. Their bodies consist of mesoglea, a non-living jelly-like substance,...
n affinity, occupying a position near the base of the Cnidarian family tree. However, the nature of Conulariids and their phylogenetic relationships to other organisms remain poorly understood, and the supposed cnidarian affinity remain speculative.
Conulariid pearls
Conulariids produced pearlPearl
A pearl is a hard object produced within the soft tissue of a living shelled mollusk. Just like the shell of a mollusk, a pearl is made up of calcium carbonate in minute crystalline form, which has been deposited in concentric layers. The ideal pearl is perfectly round and smooth, but many other...
s within their shells, similar to the way molluscs such as oysters, other pelecypods, and some gastropods do today. These pearls give a clue as to the internal anatomy of the conulariid animal. But due to their calcium phosphate
Calcium phosphate
Calcium phosphate is the name given to a family of minerals containing calcium ions together with orthophosphates , metaphosphates or pyrophosphates and occasionally hydrogen or hydroxide ions ....
composition, their crystal structure, and their extreme age, these pearls tend to be rather unattractive for use in decorative objects.
List of Genera
- Aciconularia
- Adesmoconularia
- Anaconularia
- Archaeoconularia
- Australoconularia
- Barbigodithreca
- Calloconularia
- Circonularia
- Climacoconus
- Conchopeltis
- Conomedusites
- Conulariella
- Conularina
- Conulariopsis
- Ctenoconularia
- Diconularia
- Eoconularia
- Exoconularia
- Flectoconularia
- Garraconularia
- Glyptoconularia
- Gondaconularia
- Hexangulaconularia
- Holoconularia
- Mabianoconullus
- Mesoconularia
- Metaconularia
- Neoconularia
- Notoconularia
- Palaenigma
- Paraconularia
- Pseudoconularia
- Quadrosiphogonuchites
- Reticulaconularia
- Tasmanoconularia
External links
- http://www.uga.edu/strata/cincy/fauna/conulariida/Conularia.html