Synechodontiformes is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

order of prehistoric

shark Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimo ...

s, known from the

Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleoz ...

to the

Paleogene The Paleogene ( ; British English, also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period, geologic period and system that spans 43 million years from the end of the Cretaceous Period million yea ...

. They are considered to be members of

Neoselachii Elasmobranchii () is a subclass of Chondrichthyes or cartilaginous fish, including sharks (superorder Selachii), rays, skates, and sawfish (superorder Batoidea). Members of this subclass are characterised by having five to seven pairs of gi ...

, the group that contains modern sharks and rays. Their placement in the group is uncertain, some authors have considered them to be galeomorph

crown-group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...

sharks, while others have considered them to represent a

stem-group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...

to modern sharks. They have sometimes been considered a

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

grouping, but Klug (2010) recovered the group as

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...

. Members of the clade are united by two synapomorphies, "pseudopolyaulacorhize tooth root pattern present; labial root depression in basal view present". The oldest possible member of the clade are teeth from the early Permian (

Cisuralian The Cisuralian is the first Series (stratigraphy), series/Epoch (geology), epoch of the Permian. The Cisuralian was preceded by the Pennsylvanian (geology), Pennsylvanian and followed by the Guadalupian. The Cisuralian Epoch is named after the w ...

) of the Ural Mountains.

Taxonomy

Primarily after Klug (2010) * †

Orthacodontidae Orthacodontidae is an extinct family of sharks in the order Synechodontiformes. It contains twelve species within three genera. Some authors included it into Hexanchiformes or Lamniformes. Species * '' Occitanodus'' Guinot, Cappetta & Adnet, 20 ...

de Beaumont, 1960 ** †'' Sphenodus'' Agassiz, 1843 Early Jurassic - Paleocene **†'' Occitanodus'' Guinot, Cappetta & Adnet, 2014, France, Early Cretaceous (

Valanginian In the geologic timescale, the Valanginian is an age or stage of the Early or Lower Cretaceous. It spans between 139.8 ± 3.0 Ma and 132.9 ± 2.0 Ma (million years ago). The Valanginian Stage succeeds the Berriasian Stage of the Lower Cretaceou ...

) * † Pseudonotidanidae Underwood & Ward, 2004a ** †''

Welcommia ''Welcommia'' is an extinct genus of shark. It contains only two species - ''Welcommia bodeuri'' and ''Welcommia cappettai'', described from the middle Oxfordian of Germany Germany,, officially the Federal Republic of Germany, is a ...

'' Cappetta, 1990 ** †'' Pseudonotidanus'' Underwood & Ward, 2004a * †

Palaeospinacidae Paleospinacidae is an extinct family of prehistoric sharks in the extinct order Synechodontiformes Synechodontiformes is an extinct order of prehistoric sharks, known from the Permian to the Paleogene. They are considered to be members of Neo ...

Regan, 1906 ** †'' Antrigoulia'' Guinot, Cappetta, & Adnet, 2014 France, Early Cretaceous (

) **†''

Synechodus ''Palaeospinax'' is an extinct genus of shark which lived from the Early Triassic to the end of the Eocene epoch. Although several species have been described, the genus is considered ''nomen dubium'' because the type-specimen of the type specie ...

'' Woodward, 1888 Rhaetian-Paleocene ** †'' Palidiplospinax'' Klug & Kriwet, 2008 *†Paraorthacodontidae Klug, 2010 **†''

Paraorthacodus ''Paraorthacodus'' is an extinct genus of cartilaginous fish. An unidentified species has been found in the Hasle Formation of Bornholm, Denmark ) , song = ( en, "King Christian stood by the lofty mast") , song_type = National and royal ...

'' Glikman, 1957, **†''

Macrourogaleus ''Macrourogaleus'' is a genus of palaeospinacid shark from the Late Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preser ...

'' Fowler, 1947 * ''Incertae sedis'' ** †''

Rhomphaiodon ''Rhomphaiodon'' is an extinct genus of prehistoric sharks in the order Synechodontiformes that has been found in Late Triassic and Early Jurassic deposits located in Europe.G. Cuny and S. Risnes. 2005. The Enameloid Microstructure of the Teeth ...

'' Duffin, 1993a ** †'' Mucrovenator'' Cuny et al., 2001 **†'' Safrodus'' Koot & Cuny, 2014 Early Triassic, Oman **†'' Polyfaciodus'' Koot & Cuny, 2014 Early Triassic, Oman

References

External links

* * Prehistoric cartilaginous fish orders Permian first appearances Lopingian taxonomic orders Early Triassic taxonomic orders Middle Triassic taxonomic orders Late Triassic taxonomic orders Early Jurassic taxonomic orders Middle Jurassic taxonomic orders Late Jurassic taxonomic orders Early Cretaceous taxonomic orders Late Cretaceous taxonomic orders Paleocene taxonomic orders Paleogene extinctions {{paleo-shark-stub