| Loganelliids | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Infraphylum: | Agnatha |
| Class: | † Thelodonti |
| Order: | † Thelodontiformes |
| Family: | † Loganelliidae Karatajūtė-Talimaa 1997 |
| Synonyms | |
Loganiidae Karatajūtė-Talimaa 1978 | |
Loganelliidae is an extinct family of thelodonts in the order Thelodontiformes. [1] They are distinguished by the star or cross shaped ridges located on their head scales.
The head scales possess cross shaped or star shaped ridges, transitional scales are rhomboidal, and trunk scales are horizontally elongated. The crown is notably posteriorly pointed, with the apex extending beyond the base. The main crown surface is flat and smooth, and can be inclined in either horizontal direction. The base of the crown possesses a short spine which points downwards and anteriorly. [2] [3]
The family contains the following genera: [4]
Eurypterus is an extinct genus of eurypterid, a group of organisms commonly called "sea scorpions". The genus lived during the Silurian period, from around 432 to 418 million years ago. Eurypterus is by far the most well-studied and well-known eurypterid. Eurypterus fossil specimens probably represent more than 95% of all known eurypterid specimens.
Thelodonti is a class of extinct Palaeozoic jawless fishes with distinctive scales instead of large plates of armor.
Anaspida is an extinct group of jawless fish that existed from the early Silurian period to the late Devonian period. They were classically regarded as the ancestors of lampreys. Anaspids were small marine fish that lacked a heavy bony shield and paired fins, but were distinctively hypocercal.
Thelodus is an extinct genus of thelodont agnathan that lived during the Silurian period. Fossils have been found in Europe, Asia and North America. Unlike many thelodonts, species of Thelodus are known not only from scales, but from impressions in rocks. Some species, such as the Canadian T. inauditus, are thought to be comparable in size to other thelodonts, i.e., from 5 to 15 centimeters in length. The scales of the type species, T. parvidens of Silurian Great Britain, however, reach the size of coins, and, if proportioned like other thelodonts, such as Loganellia, the living animal would have been about one meter in length.
Birkenia is a genus of extinct anaspid fish from Middle Silurian strata of Northern Europe, and Middle Silurian to possibly Earliest Devonian strata of Arctic Canada. Birkeniid anaspids are covered by a series of small plates on the head and rod-shaped scales in a cheveron-like pattern on the trunk.
Phlebolepis is an extinct thelodont agnathan genus belonging to the family Phlebolepididae. Whole fossils are found in Late Silurian aged strata from Saaremaa, Estonia. Phlebolepis elegans was average-sized for a thelodont, 7 cm long.
Eusthenodon is an extinct genus of tristichopterid tetrapodomorphs from the Late Devonian period, ranging between 383 and 359 million years ago. They are well known for being a cosmopolitan genus with remains being recovered from East Greenland, Australia, Central Russia, South Africa, Pennsylvania, and Belgium. Compared to the other closely related genera of the Tristichopteridae clade, Eusthenodon was one of the largest lobe-finned fishes and among the most derived tristichopterids alongside its close relatives Cabonnichthys and Mandageria.
Furcacauda is a genus of thelodontid agnathan from the Lower Devonian of Canada, and is the type genus of the order Furcacaudiformes. Furcacaudiform thelodontids were deep water jawless vertebrates with symmetrical fork and lobed-finned tails and scales smaller than typical loganellid and nikoliviid thelodonti scales. Furcacaudiform thelodonts are noted as having a laterally compressed body, large anterior eyes, slightly posterior, lateral, and vertical to a small mouth, and a condensed curved row of branchial openings (gills) directly posterior to the eyes. Many but not all had laterally paired fins. Wilson and Caldwell also note the presence of a caudal peduncle and a long caudal fin made of two large lobes, one dorsal and one ventral separated by 8 to 14 smaller intermediate lobes, giving the appearance of a striated half-moon shaped tail resembling the tail of a heterostracan. A large square cavity within the gut connecting a small intestine to an anal opening lead many to believe that it is this genus that exhibits the first vertebrate stomach. According to Wilson and Caldwell their discovery, based on sediment infillings of fossils of the Furcacauda heintze, gives credence to the evolutionary development of stomach before jaws.
A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scales, which can also provide effective camouflage through the use of reflection and colouration, as well as possible hydrodynamic advantages. The term scale derives from the Old French escale, meaning a shell pod or husk.
Longodus is an extinct genus of thelodont, placed in its own family – Longodidae – which existed in what is now Estonia during the Ludlow epoch of the upper Silurian period. The type and only species is Longodus acicularis. They are most noted for their long, needle-like scales, which run vertically along their trunk.
Loganellia is a genus of jawless fish which lived between 430 and 370 million years ago, during the Silurian and Devonian periods of the Paleozoic. Loganellia belonged to the Thelodonti class and like other Thelodonts possessed scales instead of plate armor.
Furcacaudiformes is an extinct order of jawless fish in the class Thelodonti.
Thelodontiformes is an extinct order of jawless fish of the Silurian.
Archipelepidiformes is an order of extinct jawless fishes in the class Thelodonti.
Archipelepis is a genus of extinct thelodont agnathans, and are the most primitive recognized thelodonts of which whole body fossils are known. Fossils of bodies and scales are currently known from Late Telychian to Wenlock-aged marine strata of northern Canada.
Phlebolepididae is an extinct thelodont agnathan family in the order Phlebolepidiformes.
Erepsilepis is an extinct thelodont agnathan genus in the family Phlebolepididae.
Vernonopterus is a genus of eurypterid, a group of extinct aquatic arthropods. Fossils of Vernonopterus have been discovered in deposits of the Carboniferous period in Scotland. The name of the genus derives from the location where the only known fossil has been discovered, Mount Vernon near Airdrie in Lanarkshire, Scotland. A single species of Vernonopterus is recognized, V. minutisculptus, based on fragmentary fossilized tergites, segments on the upper side of the abdomen. The species name minutisculptus refers to the ornamentation of scales that covers the entirety of the preserved parts of the eurypterid.
Oeselia mosaica is a fossil jawless fish and is the only species in its genus and in the family Oeseliidae. It is a member of an extinct family of thelodonts or jawless fishes. The family and genus were established along with the description of the species by Tiuu Märss in 2005.
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