Megalosauridae

Opisthokonta

Megalosaurids Temporal range: Middle - Late Jurassic, 170–148 Ma PreЄ Є O S D C P T J K Pg N
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Superorder:	Dinosauria
Order:	Saurischia
Suborder:	Theropoda
Superfamily:	†Megalosauroidea
Family:	†Megalosauridae Huxley, 1869
Type species
†Megalosaurus bucklandii Mantell, 1827
Genera
†Streptospondylus
Synonyms
Torvosauridae Jensen, 1985 Eustreptospondylidae Paul, 1988 Streptospondylidae Kurzanov, 1989

Megalosauridae was a family of relatively primitive tetanuran theropod dinosaurs, order Saurischia. They were small-to-large carnivores with sharp teeth and three claws on each hand. Some members of this group were Megalosaurus, Eustreptospondylus, Streptospondylus and Torvosaurus. Megalosaurids first appeared in the mid Jurassic and seemed to have been displaced and replaced by other theropods by the end of that period; their fossils are known from Europe, North America, South America and Africa. They are considered by most researchers (Sereno 2005, Olshevsky 1995, Holtz 2004, etc.) to be close relatives of the spinosaurs.

Classification

Like Megalosaurus itself, the family Megalosauridae, coined by Huxley in 1869, had traditionally been used as a 'wastebasket' group, which included a wide variety of unrelated species (such as Dryptosaurus, Ceratosaurus, Indosaurus, and even Velociraptor). Because of this traditionally polyphyletic use, some scientists, such as Paul Sereno, reject the family name Megalosauridae in favor of Torvosauridae (coined by Jensen in 1985), despite the fact that Megalosauridae has priority under the ICZN rules governing family-level names in zoology.^[1] While a 2008 review of Megalosaurus by Benson and colleagues also found that the relationships of Megalosaurus to other theropods could not be determined, and that the assignment of basal spinosauroids to the family Megalosauridae should be discontinued,^[2] further work by Benson reversed this position, finding a well-supported Megalosauridae in phylogenetic analyses.^[3]

Phylogeny

The clade Megalosauridae was first given a phylogenetic definition by Allain in 2002. According to Allain's definition, a megalosaurid is any dinosaur that shares a common ancestor with Poekilopleuron valesdunensis (since reclassified as Dubreuillosaurus), Torvosaurus, and Afrovenator.^[4] In 2004, Holtz and colleagues proposed a new definition: all dinosaurs more closely related to Megalosaurus than to Spinosaurus, Allosaurus, or modern birds (represented by Passer domesticus).^[5] In 2005, Sereno rejected the use of Megalosauridae as a clade altogether, due to the fragmentary nature of Megalosaurus, and used the name Torvosauridae instead, using the same definition as Holtz but replacing Megalosaurus with Torvosaurus.^[1]

The cladogram presented here follows Benson (2010) and Benson et al. (2010).^[3][6]

Megalosauridae	Eustreptospondylus Magnosaurus Streptospondylus Megalosaurinae Duriavenator Afrovenator Dubreuillosaurus Megalosaurus Torvosaurus

References

1. ^ ^{a b} Sereno, P.C. (2005). Stem Archosauria—TaxonSearch [version 1.0, 2005 November 7]
2. ^ Benson R.B.J., Barrett P.M., Powell H.P., Norman D.B. (2008). "The taxonomic status of Megalosaurus bucklandii (Dinosauria, Theropoda) from the Middle Jurassic of OxfordshireE, UK.". Palaeontology 51 (2): 419–424. doi:10.1111/j.1475-4983.2008.00751.x. 
3. ^ ^{a b} Benson, R.B.J. (2010). "A description of Megalosaurus bucklandii (Dinosauria: Theropoda) from the Bathonian of the UK and the relationships of Middle Jurassic theropods". Zoological Journal of the Linnean Society 158: 882. doi:10.1111/j.1096-3642.2009.00569.x. 
4. ^ Allain R (2002). "Discovery of megalosaur (Dinosauria, Theropoda) in the middle Bathonian of Normandy (France) and its implications for the phylogeny of basal Tetanurae". Journal of Vertebrate Paleontology 22 (3): 548–563. doi:10.1671/0272-4634(2002)022[0548:DOMDTI]2.0.CO;2. 
5. ^ Holtz, T.R., Molnar, R.E., Currie, P.J. (2004). "Basal Tetanurae." In Weishampel, D.B., Dodson, P., & Osmolska, H. (Eds.). The Dinosauria (2nd Edition). Berkeley: University of California Press. Pp. 71-110.
6. ^ Benson, R.B.J., Carrano, M.T and Brusatte, S.L. (2010). "A new clade of archaic large-bodied predatory dinosaurs (Theropoda: Allosauroidea) that survived to the latest Mesozoic". Naturwissenschaften 97 (1): 71–78. Bibcode 2010NW.....97...71B. doi:10.1007/s00114-009-0614-x. PMID 19826771.  Supporting Information

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