Mirischiais a small (two meter-long)genusofcompsognathidtheropoddinosaurfrom theAlbianstage(Early CretaceousPeriod) ofBrazil.
| Mirischia Temporal range:Early Cretaceous,
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| Hypothetical Model | |
Scientific classification
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Family: | †Compsognathidae |
| Genus: | †Mirischia Naishet al.,2004 |
| Species: | †M. asymmetrica
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| Binomial name | |
| †Mirischia asymmetrica Naishet al.,2004
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Discovery and naming
editIn 2000David MartillandEberhard Freyreported the find of a small dinosaur fossil present in a chalk nodule, illegally acquired by the GermanStaatliches Museum für Naturkunde Karlsruhefrom an illegal Brazilian fossil dealer who had indicated the piece had been uncovered in theChapada do Araripe,specifically atAraripina,Pernambuco.[1]In 2004 thetype speciesMirischia asymmetricawas named and described by Martill, Frey andDarren Naish.The generic name combines theLatinmirus,'wonderful', with "ischia", the Latinised plural ofGreekἴσχιον,ischion,'hip joint'. Thespecific nameasymmetricarefers to the fact that in the specimen the leftischiumdiffers from its right counterpart.[2]
Theholotype,SMNK 2349 PAL,has its probable provenance in theRomualdo Formationof theSantana Group,dating from theAlbian.It consists of a partial articulated skeleton, largely consisting of the pelvis and incomplete hind limbs, including two posterior dorsal vertebrae, a rib,gastralia,partial ilia, pubes and ischia, partial thigh bones and the upper parts of the righttibiaandfibula.In front of the pubes, a piece of a petrified intestine is present. The specimen represents a subadult individual.[2]
Description
editMirischiawas a small bipedal predator. Its length was in 2004 estimated at 2.1 metres.[2]In 2010Gregory S. Paulestimated the weight at seven kilogrammes.[3]The holotype ofMirischiais notable for having asymmetricalischia.Quoting fromNaishet al. (2004): "The ischia ofMirischiaare asymmetrical, that on the left being perforated by an oval foramen while that on the right has an open notch in the same position. "The specimen is also unusual in that it preserves some soft tissue remains: apart from the intestine, what the describers interpreted to have been an air sac was preserved between its pubic and ischial bones in the form of a vacuity. Previous workers had suggested that non-avian theropods might — like birds — possess post-cranialair sacs,andMirischiaseems to confirm that. Another notable trait is the exceptional thinness of the bone wall of all skeletal elements.[2]
Phylogeny
editIn 2004Mirischiawas assigned to theCompsognathidae,as closely related toCompsognathusfrom the UpperJurassicof Europe andAristosuchusfrom the LowerCretaceousof England. It would then be the only compsognathid known from the Americas.[2]In 2010 Naish suggested it may have instead been a basal member of theTyrannosauroidea.[4] In 2024, Andrea Cau published a study on the phylogenetics of compsognathids that recoveredMirischia,along with four other proposedCompsognathidsin a polytomy within basalCoelurosauria.This polytomy notably did not includeComposognathusproper, which would make none of these speciesCompsognathids.[5]
This is a simplified version of the phylogeny in Cau (2024), withMirischiain bold.
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References
edit- ^D.M. Martill, E. Frey, H.-D. Sues and A.R.I. Cruickshank, 2000, "Skeletal remains of a small theropod dinosaur with associated soft structures from the Lower Cretaceous Santana Formation of northeastern Brazil",Canadian Journal of Earth Sciences37(6): 891-900
- ^abcdeNaish, D., Martill D.M., and Frey, E., 2004, "Ecology, Systematics and Biogeographical Relationships of Dinosaurs, Including a New Theropod, from the Santana Formation (?Albian, Early Cretaceous) of Brazil",Historical Biology.2004: 1-14http://dx.doi.org/10.1080/08912960410001674200
- ^Paul, G.S., 2010,The Princeton Field Guide to Dinosaurs,Princeton University Press p. 123
- ^Naish, Darren. 2010.Tetrapod Zoology Book One.CFZ Press
- ^Cau, Andrea (2024)."A Unified Framework for Predatory Dinosaur Macroevolution"(PDF).Bollettino della Società Paleontologica Italiana.63(1): 1-19.doi:10.4435/BSPI.2024.08(inactive 2024-11-20).
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