| Briggera Temporal range: upper Cretaceous-Lower Miocene, | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| Clade: | Diaphoretickes |
| Clade: | SAR |
| Clade: | Stramenopiles |
| Phylum: | Gyrista |
| Subphylum: | Ochrophytina |
| Class: | Bacillariophyceae |
| Order: | Hemiaulales |
| Family: | Hemiaulaceae |
| Genus: | † Briggera R. Ross & P.A. Sims, 1985 |
Briggera is a genus of diatom known from the fossil record. [1]
A diatom is any member of a large group comprising several genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of the Earth's biomass: they generate about 20 to 50 percent of the oxygen produced on the planet each year, take in over 6.7 billion tonnes of silicon each year from the waters in which they live, and constitute nearly half of the organic material found in the oceans. The shells of dead diatoms can reach as much as a half-mile deep on the ocean floor, and the entire Amazon basin is fertilized annually by 27 million tons of diatom shell dust transported by transatlantic winds from the African Sahara, much of it from the Bodélé Depression, which was once made up of a system of fresh-water lakes.
Navicula is a genus of boat-shaped diatom algae, comprising over 1,200 species. Navicula is Latin for "small ship", and also a term in English for a boat-shaped incense-holder.
Bolidophyceae is a class of photosynthetic heterokont picophytoplankton, and consist of less than 20 known species. They are distinguished by the angle of flagellar insertion and swimming patterns as well as recent molecular analyses. Bolidophyceae is the sister taxon to the diatoms (Bacillariophyceae). They lack the characteristic theca of the diatoms, and have been proposed as an intermediate group between the diatoms and all other heterokonts.
Craticula is a genus of diatom that lies on or in the top layers of sediments in the freshwater to brackish water environments it inhabits. In addition to frustule morphology the genus differs from closely related species by its sexual reproduction and movement in response to light.
Stilus is a genus of diatoms in the family Plagiotropidaceae.
Peridinium is a genus of motile, marine and freshwater dinoflagellates. Their morphology is considered typical of the armoured dinoflagellates, and their form is commonly used in diagrams of a dinoflagellate's structure. Peridinium can range from 30 to 70 μm in diameter, and has very thick thecal plates.
Acanthoceras is a genus of radially symmetric planktonic diatoms comprising two taxonomically accepted species. They do not have any raphe and therefore lack motility. It appears rectangular with two setae extending from each valve. Not much is known about this genus because it is easily destroyed using common preparation techniques. They can be found all over North America in small lakes and short-lasting ponds.
Hystrix is a genus of diatoms.
Odontella is a genus of marine diatoms. Some sources place it in the family Triceratiaceae, others in the family Odontellaceae. It contains the following species:
Hyalodiscus is an extant genus of diatom known also from the fossil record.
Riedelia is a genus of diatoms known from the fossil record, comprising approximately eight species. Many of the species were originally described under the closely allied genus Hemiaulus. Paleontologists Hans-Joachim Schrader and Juliane Fenner, working with fossil specimens obtained from Leg 38 of the Deep Sea Drilling Program in the Norwegian and Greenland Seas, decided that several previous descriptions of diatoms belonging to Hemiaulus were rightfully placed on Riedelia. Schrader and Fenner note that while Hemiaulus diatoms have polygonal areolated valves, Riedelia valves are punctate with isolated punctae. Additionally, Riedelia typically have two spines, while Hemiaulus have only one. These characteristics were used to justify the placement of these species in Riedelia.
The Cymbellales are a diatom order in the class Bacillariophyceae. They include the following families:
Abas is an extinct genus of diatoms consisting of only one known species: Abas wittii. Originally observed as a fossil genus classified with diatom spore forms under the name Syringidium. Abas was observed to be live from the Eocene to Oligocene epoch appearing in tropical sites.
Trinacria is an extinct genus of diatoms present during the early Eocene, named for its triskelion shape.
Bicornis is an extinct genus of diatoms with one known species.
Craspedoporus is a genus of diatoms known from the fossil record. It first appears in the middle Eocene, and exists until the late Miocene.
Braarudosphaera bigelowii is a coastal coccolithophore in the fossil record going back 100 million years to the Late Cretaceous.
Skeletonema is a genus of diatoms in the family Skeletonemataceae. It is the type genus of its family. The genus Skeletonema was established by R. K. Greville in 1865 for a single species, S. barbadense, found in the Barbados deposit [Jung 2009]. These diatoms are photosynthetic organisms, meaning they obtain carbon dioxide from their surrounding environment and produce oxygen along with other byproducts. Reproduce sexually and asexually [Guiry 2011]. Skeletonema belong to the morphological category referred to as centric diatoms. These are classified by having valves with radial symmetry and the cells lack significant motility [Horner 2002]. Skeletonema are cylindrical shaped with a silica frustule. Cells are joined by long marginal processes to form a filament [Horner 2002]. Their length ranges from 2-61 micrometers, with a diameter ranging from 2-21 micrometers [Hasle 1997]. They are found typically in the neritic zone of the ocean and are highly populous in coastal systems [Jung 2009]. The genus is considered cosmopolitan, showing a wide range of tolerance for salinity and temperature [Hasle 1973]. For example, they have been found in various aquatic environments such as brackish or freshwater. Skeletonema are found worldwide excluding Antarctic waters [Hevia-Orube 2016]. Some harmful effects these diatoms may have on an ecosystem are attributed to large blooming events which may cause hypoxic events in coastal systems. Additionally, they are known to cause water discoloration [Kraberg 2010].
Biddulphiaceae is a family of diatom in the order Biddulphiales. The Biddulphiaceae are distinguished from the Eupodiscaceae by their pseudocelli, where the Eupodiscaceae have fully developed ocelli. Both families commonly inhabit the littoral zone of the ocean, close to the shore. Sixteen species of Biddulphiaceae are found on the west coast of India.
Diatoms belong to a large group called the heterokonts, which include both autotrophs such as golden algae and kelp; and heterotrophs such as water moulds. The classification of heterokonts is still unsettled: they may be designated a division, phylum, kingdom, or something intermediate to those. Consequently, diatoms are ranked anywhere from a class, usually called Diatomophyceae or Bacillariophyceae, to a division (=phylum), usually called Bacillariophyta, with corresponding changes in the ranks of their subgroups.
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