''Mirischia'' is a small (two meter-long)

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of compsognathid

theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

from the

Albian The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous Epoch/ Series. Its approximate time range is 113.0 ± 1.0 Ma to 100.5 ± 0 ...

stage Stage or stages may refer to: Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly British theatre newspaper * Sta ...

( Early Cretaceous

Period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...

) of

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

Discovery and naming

In 2000 David Martill and

Eberhard Frey Eberhard is an old Germanic name meaning the strength or courage of a wild boar. People First name *Eberhard of Friuli (815–866), Duke and key figure in the Carolingian Empire *Eberhard of Béthune (died 1212), Flemish grammarian *Eberhard I, Du ...

reported the find of a small dinosaur fossil present in a chalk nodule, illegally acquired by the German

Staatliches Museum für Naturkunde Karlsruhe The State Museum of Natural History Karlsruhe (german: link=no, Staatliches Museum für Naturkunde Karlsruhe), abbreviated SMNK, is one of the two state of Baden-Württemberg's natural history museums. Together with the State Museum of Natural H ...

from an illegal Brazilian fossil dealer who had indicated the piece had been uncovered in the

Chapada do Araripe The Chapada do Araripe, also known as the Serra do Araripe, is a ''chapada'' ( plateau) in northeastern Brazil. The chapada forms the boundary of Ceará and Pernambuco states, and forms the watershed between the Jaguaribe River of Ceará, which fl ...

, specifically at

Araripina Araripina is a Brazilian municipality in the state of Pernambuco. Has an estimated population in 2020 of 84,864 inhabitants according with IBGE. Total area of 1.847,5 km and is located in the state mesoregion of Sertão, at 622 meters abov ...

Pernambuco Pernambuco () is a States of Brazil, state of Brazil, located in the Northeast Region, Brazil, Northeast region of the country. With an estimated population of 9.6 million people as of 2020, making it List of Brazilian states by population, sev ...

. In 2004 the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specime ...

''Mirischia asymmetrica'' was named and described by Martill, Frey and

Darren Naish Darren William Naish is a British vertebrate palaeontologist, author and science communicator. As a researcher, he is best known for his work describing and reevaluating dinosaurs and other Mesozoic reptiles, including '' Eotyrannus'', '' Xenop ...

. The generic name combines the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

''mirus'', 'wonderful', with "ischia", the Latinised plural of

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

ἴσχιον, ''ischion'', 'hip joint'. The specific name ''asymmetrica'' refers to the fact that in the specimen the left ischium differs from its right counterpart. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of sever ...

, SMNK 2349 PAL, has its probable provenance in the

Romualdo Formation The Romualdo Formation is a geologic Konservat-Lagerstätte in northeastern Brazil's Araripe Basin where the states of Pernambuco, Piauí and Ceará come together. The geological formation, previously designated as the Romualdo Member of the Sa ...

of the

Santana Group The Santana Group is a geologic group, formerly included as the middle part of the Araripe Group, in the Araripe Basin of northeastern Brazil. The group comprises the Crato, Ipubi and Romualdo Formations and is dated to the Aptian to Albian stag ...

, dating from the

. It consists of a partial articulated skeleton, largely consisting of the pelvis and incomplete hind limbs, including two posterior dorsal vertebrae, a rib,

gastralia Gastralia (singular gastralium) are dermal bones found in the ventral body wall of modern crocodilians and tuatara, and many prehistoric tetrapods. They are found between the sternum and pelvis, and do not articulate with the vertebrae. In thes ...

, partial ilia, pubes and ischia, partial thigh bones and the upper parts of the right

tibia The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...

and

fibula The fibula or calf bone is a leg bone on the lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones. Its upper extremity i ...

. In front of the pubes, a piece of a petrified intestine is present. The specimen represents a subadult individual.

Description

''Mirischia'' was a small bipedal predator. Its length was in 2004 estimated at 2.1 metres. In 2010

Gregory S. Paul Gregory Scott Paul (born December 24, 1954) is an American freelance researcher, author and illustrator who works in paleontology, and more recently has examined sociology and theology. He is best known for his work and research on theropod dino ...

estimated the weight at seven kilogrammes. The holotype of ''Mirischia'' is notable for having asymmetrical

ischia Ischia ( , , ) is a volcanic island in the Tyrrhenian Sea. It lies at the northern end of the Gulf of Naples, about from Naples. It is the largest of the Phlegrean Islands. Roughly trapezoidal in shape, it measures approximately east to west ...

. Quoting from Naish et al. (2004): "The ischia of ''Mirischia'' are 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-cranial

air sacs Air sacs are spaces within an organism where there is the constant presence of air. Among modern animals, birds possess the most air sacs (9–11), with their extinct dinosaurian relatives showing a great increase in the pneumatization (presence ...

, and ''Mirischia'' seems to confirm that. Another notable trait is the exceptional thinness of the bone wall of all skeletal elements.

Phylogeny

In 2004 ''Mirischia'' was assigned to the

Compsognathidae Compsognathidae is a family of coelurosaurian theropod dinosaurs. Compsognathids were small carnivores, generally conservative in form, hailing from the Jurassic and Cretaceous Periods. The bird-like features of these species, along with other d ...

, as closely related to ''

Compsognathus ''Compsognathus'' (; Ancient Greek, Greek ''kompsos''/κομψός; "elegant", "refined" or "dainty", and ''gnathos''/γνάθος; "jaw") is a genus of small, bipedalism, bipedal, carnivore, carnivorous theropoda, theropod dinosaur. Members o ...

'' from the Upper

Jurassic The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...

of Europe and ''

Aristosuchus ''Aristosuchus'' is a genus of small coelurosaurian dinosaur whose name was derived from the Ancient Greek, Greek ἄριστος (meaning bravest, best, noblest) and ''σουχος'' (the Ancient Greek corruption of the name of the Ancient Egypt ...

'' from the Lower

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

of England. It would then be the only compsognathid known from the Americas.Naish, 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: 1-14 http://dx.doi.org/10.1080/08912960410001674200 In 2010 Naish suggested it may have instead been a basal member of the

Tyrannosauroidea Tyrannosauroidea (meaning 'tyrant lizard forms') is a superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinen ...

.Naish, Darren. 2010. ''Tetrapod Zoology Book One''. CFZ Press

References

External links

The Theropod Database

{{Portal bar, Dinosaurs, Cretaceous Compsognathids Albian life Early Cretaceous dinosaurs of South America Cretaceous Brazil Fossils of Brazil Romualdo Formation Fossil taxa described in 2004 Taxa named by Darren Naish