Megalosauroidea

Megalosauroidea

Discussion
Ask a question about 'Megalosauroidea'
Start a new discussion about 'Megalosauroidea'
Answer questions from other users
Full Discussion Forum
 
Encyclopedia
Megalosauroidea is a group of tetanuran
Tetanurae
Tetanurae, or "stiff tails", is a clade that includes most theropod dinosaurs, as well as birds. Tetanurans first appear during the early or middle Jurassic Period.-Definition:...

 theropod dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

s that lived from the Middle Jurassic
Middle Jurassic
The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from 176-161 million years ago. In European lithostratigraphy, rocks of this Middle Jurassic age are called the Dogger....

 to the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...

 period.

Classification


The clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

 Megalosauroidea is defined as Megalosaurus bucklandii
Megalosaurus
Megalosaurus is a genus of large meat-eating theropod dinosaurs of the Middle Jurassic period of Europe...

and all taxa sharing a more recent common ancestor with it than with Allosaurus fragilis or Passer domesticus.

The name Spinosauroidea is sometimes used in place of Megalosauroidea. The superfamily
Taxonomic rank
In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...

 Spinosauroidea was named in 1915 by Ernst Stromer
Ernst Stromer
Ernst Freiherr Stromer von Reichenbach was a German paleontologist.He described the following Cretaceous dinosaurs from Egypt: Aegyptosaurus, Bahariasaurus, Carcharodontosaurus, and the largest known theropod, Spinosaurus aegyptiacus...

. It is a synonym of Megalosauroidea in almost all modern phylogenetic analyses, and it is therefore redundant. Spinosauroidea was defined as a clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

 in 1998 by Paul Sereno
Paul Sereno
Paul Callistus Sereno is an American paleontologist from the University of Chicago who discovered several new dinosaur species on several continents. He has conducted excavations at sites as varied as Inner Mongolia, Argentina, Morocco, and Niger...

 as the node clade containing the common ancestor of Spinosaurus
Spinosaurus
Spinosaurus is a genus of theropod dinosaur which lived in what is now North Africa, from the lower Albian to lower Cenomanian stages of the Cretaceous period, about 112 to 97 million years ago. This genus was first known from Egyptian remains discovered in 1912 and described by German...

and Torvosaurus
Torvosaurus
Torvosaurus is a genus of large theropod dinosaur that lived during the Late Jurassic period...

and all its descendants. Thomas Holtz in 2004 defined a branch clade with the same name containing all species closer to Spinosaurus than to Passer
Passer
Passer is a genus of Old World sparrows. These sparrows are plump little brown or greyish birds often with black, yellow or white markings. Typically 10–20 cm long, they have short tails and stubby conical beaks...

 domesticus
. The ICZN
International Commission on Zoological Nomenclature
The International Commission on Zoological Nomenclature is an organization dedicated to "achieving stability and sense in the scientific naming of animals". Founded in 1895, it currently comprises 28 members from 20 countries, mainly practicing zoological taxonomists...

 holds that even clade names (which do not yet have any governing body) should be replaced if having a traditional taxon suffix and being synonyms of ranked taxa at or below the superfamily level. The seniority of Megalosauroidea was not followed in most paleontological literature during the 1990s and early 2000s. A series of papers supporting the validity of Megalosaurus
Megalosaurus
Megalosaurus is a genus of large meat-eating theropod dinosaurs of the Middle Jurassic period of Europe...

as a genus, the relationships of megalosauroids, and the placement of "spinosauroids" among them, published between 2008 and 2010 argued that Megalosauroidea was in fact the valid name for the group.

The classification of megalosauroids follows a study by Benson in 2010. Note that several "wildcard" taxa that are probably megalosauroids were excluded from the final tree, including Magnosaurus
Magnosaurus
Magnosaurus was a genus of basal tetanuran theropod dinosaur from the Middle Jurassic of England. It is based on fragmentary remains and has often been confused with or included in Megalosaurus.-History and taxonomy:...

, Piveteausaurus
Piveteausaurus
Piveteausaurus is a genus of theropod dinosaur known from a partial skull discovered in the Middle Jurassic Marnes de Dives formation of Calvados, in northern France.-History and description:...

and Streptospondylus
Streptospondylus
Streptospondylus is a genus of tetanuran theropod dinosaur known from the Middle Jurassic period of France, 161 million years ago. It was a medium-sized predator.-Discovery and naming:...

. Later, Magnosaurus
Magnosaurus
Magnosaurus was a genus of basal tetanuran theropod dinosaur from the Middle Jurassic of England. It is based on fragmentary remains and has often been confused with or included in Megalosaurus.-History and taxonomy:...

and Streptospondylus
Streptospondylus
Streptospondylus is a genus of tetanuran theropod dinosaur known from the Middle Jurassic period of France, 161 million years ago. It was a medium-sized predator.-Discovery and naming:...

were added in the final tree. These are known from remains too fragmentary to be reliably classified. Some of these 'wildcard' taxa, such as Poekilopleuron
Poekilopleuron
Poekilopleuron is an extinct genus of large basal tetanuran theropod dinosaur, perhaps belonging to the clade Allosauroidea. It measured 9 metres long and 1 ton in mass...

and Megaraptor
Megaraptor
Megaraptor is a genus of large theropod dinosaur that lived in the Coniacian stage of the Late Cretaceous. Its fossils have been discovered in the Patagonian region of Argentina...

, have been considered possible megalosauroids in the past, but the analysis found that they are more likely allosauroids.