| Helenoconcha polyodon | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Gastropoda |
| Subclass: | Heterobranchia |
| Order: | Stylommatophora |
| Family: | Charopidae |
| Genus: | Helenoconcha |
| Species: | †H. polyodon |
| Binomial name | |
| †Helenoconcha polyodon Sowerby, 1844 | |
†Helenoconcha polyodon was a species of small air-breathing land snails, terrestrial pulmonate gastropod mollusks in the family Charopidae.
This species was endemic to Saint Helena. It is now extinct.
Paddlefish are a family of ray-finned fish belonging to order Acipenseriformes, and one of two living groups of the order alongside sturgeons (Acipenseridae). They are distinguished from other fish by their elongated rostra, which are thought to enhance electroreception to detect prey. Paddlefish have been referred to as "primitive fish" because the Acipenseriformes are among the earliest diverging lineages of ray-finned fish, having diverged from all other living groups over 300 million years ago. Paddlefish are almost exclusively North American and Chinese, both extant and in the fossil record.
The American paddlefish is a species of ray-finned fish. It is the last living species of paddlefish (Polyodontidae). This family is most closely related to the sturgeons; together they make up the order Acipenseriformes, which are one of the most primitive living groups of ray-finned fish. Fossil records of other paddlefish species date back 125 million years to the Early Cretaceous, with records of Polyodon extending back 65 million years to the early Paleocene. The American paddlefish is a smooth-skinned freshwater fish with an almost entirely cartilaginous skeleton and a paddle-shaped rostrum (snout), which extends nearly one-third its body length. It has been referred to as a freshwater shark because of its heterocercal tail or caudal fin resembling that of sharks, though it is not closely related. The American paddlefish is a highly derived fish because it has evolved specialised adaptations such as filter feeding. Its rostrum and cranium are covered with tens of thousands of sensory receptors for locating swarms of zooplankton, its primary food source. The only other species of paddlefish that survived to modern times was the Chinese paddlefish, last sighted in 2003 in the Yangtze River in China and considered to have gone extinct no later than 2010.
The Chinese paddlefish, also known as the Chinese swordfish, is an extinct species of fish that was formerly native to the Yangtze and Yellow River basins in China. With records of specimens over three metres and possibly 7 m (23 ft) in length, it was one of the largest species of freshwater fish. It was the only species in the genus Psephurus and one of two recent species of paddlefish (Polyodontidae), the other being the American paddlefish. It was an anadromous species, meaning that it spent part of its adult life at sea, while migrating upriver to spawn.
Petrochromis polyodon is a species of cichlid endemic to Lake Tanganyika found in areas with rocky substrates where it can graze on algae. This species coexists with other herbivorous cichlids such as Tropheus moorii and Telmatochromis temporalis. Individuals can reach lengths of 40cm or 16 inches and 1kg in weight. They can be found in the aquarium trade.
†Helenoconcha leptalea is an extinct species of small air-breathing land snails, terrestrial pulmonate gastropod mollusks in the family Charopidae.
Helenoconcha is a genus of small air-breathing land snails, terrestrial pulmonate gastropod mollusks in the family Charopidae endemic to the island of Saint Helena, hence the genetic epithet. All species save for H. relicta, are extinct.
Helenoconcha minutissima is an extinct species of gastropod in the family Charopidae. It was endemic to Saint Helena.
†Helenoconcha pseustes was a species of small air-breathing land snails, terrestrial pulmonate gastropod mollusks in the family Charopidae.
†Helenoconcha sexdentata was a species of small air-breathing land snails, terrestrial pulmonate gastropod mollusks in the family Charopidae.
Pristerognathus is an extinct genus of therocephalian, known from the late Middle Permian (Capitanian) of South Africa. It lends its name to the Pristerognathus Assemblage Zone of the Beaufort Group of South African geological strata. Pristerognathus was a medium-sized therocephalian with a 25 cm (9.8 in) skull and a total length up to 1.5 m.
Chiloglanis polyodon is a species of upside-down catfish endemic to Sierra Leone where it is only known from the headwaters of the Bagbwe River. This species grows to a length of 5.2 centimetres (2.0 in) TL.
Synodontis polyodon is a species of upside-down catfish native to Gabon where it occurs in the Ogowe River basin. It was first described by French zoologist Léon Vaillant in 1895, based upon a holotype discovered in the Ogooué River, near Adouma, Gabon. The specific name "polyodon" comes from the Greek words poly, meaning "many" and odon, meaning "tooth", referring to the many teeth in this species.
Abida polyodon is a species of air-breathing land snails, a terrestrial pulmonate gastropod mollusc in the family Chondrinidae.
Antarctosuchus is an extinct genus of capitosauroid temnospondyl known from the Middle Triassic upper Fremouw Formation in the Transantarctic Mountains of Antarctica. It contains a single species, Antarctosuchus polyodon.
The Ammonite Snail is a species of small air-breathing land snails, terrestrial pulmonate gastropod mollusks in the family Charopidae. The species is endemic to Saint Helena Island, and is the only Helenoconcha species remaining.
The sturddlefish is a hybrid of the American paddlefish and the Russian sturgeon, accidentally created by researchers in 2019 and announced in 2020. Obtaining living hybrids through breeding individuals from different families is unusual, especially given that the two species' last common ancestor lived 184 million years ago. The hybrids were created accidentally during attempts to induce gynogenesis, a type of parthenogenic reproduction where a sperm cell must be present to trigger embryogenesis but does not genetically contribute to the offspring. Hundreds of hybrid fish were created, of which about two-thirds survived over one month, and about 100 survived for one year. As of July 2020, all living hybrid fish are living in captivity at the research lab in Hungary. There are no current plans to create new sturddlefish.
