Mirischia

Mirischia is a small (two meter-long) genus of compsognathid theropod dinosaur from the Albian stage (Early Cretaceous Period) of Brazil.

Mirischia
Temporal range: Early Cretaceous, 108 Ma
Mirischia asymmetrica by Ademar Pereira
Hypothetical Model
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Family: Compsognathidae
Genus: Mirischia
Naish et al., 2004
Species:
M. asymmetrica
Binomial name
Mirischia asymmetrica
Naish et al., 2004

Discovery and naming

In 2000 David Martill and Eberhard Frey reported the find of a small dinosaur fossil present in a chalk nodule, illegally acquired by the German Staatliches Museum für Naturkunde Karlsruhe from an illegal Brazilian fossil dealer who had indicated the piece had been uncovered in the Chapada do Araripe, specifically at Araripina, Pernambuco.[1] In 2004 the type species Mirischia asymmetrica was named and described by Martill, Frey and Darren Naish. The generic name combines the Latin mirus, 'wonderful', with "ischia", the Latinised plural of Greek ἴσχιον, ischion, 'hip joint'. The specific name asymmetrica refers to the fact that in the specimen the left ischium differs from its right counterpart.[2]

The holotype, SMNK 2349 PAL, has its probable provenance in the Romualdo Formation of the Santana Group, dating from the Albian. 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 right tibia and fibula. In front of the pubes, a piece of a petrified intestine is present. The specimen represents a subadult individual.[2]

Description

Cratoavis and misrischia
Cratoavis being attacked by Mirischia

Mirischia was a small bipedal predator. Its length was in 2004 estimated at 2.1 metres.[2] In 2010 Gregory S. Paul estimated the weight at seven kilogrammes.[3] The holotype of Mirischia is notable for having asymmetrical ischia. 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, and Mirischia seems to confirm that. Another notable trait is the exceptional thinness of the bone wall of all skeletal elements.[2]

Phylogeny

In 2004 Mirischia was assigned to the Compsognathidae, as closely related to Compsognathus from the Upper Jurassic of Europe and Aristosuchus from the Lower Cretaceous of 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 the Tyrannosauroidea.[4]

References

  1. ^ 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 Sciences 37(6): 891-900
  2. ^ a b c d e 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
  3. ^ Paul, G.S., 2010, The Princeton Field Guide to Dinosaurs, Princeton University Press p. 123
  4. ^ Naish, Darren. 2010. Tetrapod Zoology Book One. CFZ Press

External links

2004 in paleontology

Paleontology or palaeontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 2004.

Air sac

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 of air) in their bones. Theropods, like Aerosteon, have many air sacs in the body that are not just in bones, and they can be identified as the more primitive form of modern bird airways. Sauropods are well known for the amount of air pockets in their bones (especially vertebra), although one theropod, Deinocheirus, shows a rivalling amount of air pockets.

Coeluridae

Coeluridae is a historically unnatural group of generally small, carnivorous dinosaurs from the late Jurassic Period. For many years, any small Jurassic or Cretaceous theropod that did not belong to one of the more specialized families recognized at the time was classified with the coelurids, creating a confusing array of 'coelurid' theropods that were not closely related. Although they have been traditionally included in this family, there is no evidence that any of these primitive coelurosaurs form a natural group with Coelurus, the namesake of Coeluridae, to the exclusion of other traditional coelurosaur groups.

Compsognathidae

Compsognathidae is a family of coelurosaurian theropod dinosaurs. They were small carnivores, generally conservative in form, hailing from the Jurassic and Cretaceous Periods. The bird-like features of these species, along with other dinosaurs such as Archaeopteryx inspired the idea for the connection between dinosaur reptiles and modern-day avian species. Compsognathid fossils preserve diverse integument — skin impressions are known from four genera commonly placed in the group, Compsognathus, Sinosauropteryx, Sinocalliopteryx, and Juravenator. While the latter three show evidence of a covering of some of the earliest primitive feathers over much of the body, Juravenator and Compsognathus also show evidence of scales on the tail or hind legs.

The first member of the group, Compsognathus, was discovered in 1861, after Johann A. Wagner published his description of the taxon. The family it was created by Edward Drinker Cope in 1875. This classification was accepted by Othniel Charles Marsh in 1882, and added to the Coelurosauria clade by Friedrich von Huene in 1914 after additional fossils had been found. With further discoveries, fossils have been uncovered across three different continents, in the countries of China, France, Germany, Italy, and Brazil. Assignment to Compsognathidae is usually determined through examination of the metacarpal, which is used to separate Compsognathidae from other dinosaurs. However, classification is still complicated due to similarities to the body of several other theropod dinosaurs, as well as the lack of unifying, diagnostic features that are shared by all compsognathids.

Compsognathus

Compsognathus (; Greek kompsos/κομψός; "elegant", "refined" or "dainty", and gnathos/γνάθος; "jaw") is a genus of small, bipedal, carnivorous theropod dinosaur. Members of its single species Compsognathus longipes could grow to around the size of a turkey. They lived about 150 million years ago, during the Tithonian age of the late Jurassic period, in what is now Europe. Paleontologists have found two well-preserved fossils, one in Germany in the 1850s and the second in France more than a century later. Today, C. longipes is the only recognized species, although the larger specimen discovered in France in the 1970s was once thought to belong to a separate species and named C. corallestris.

Many presentations still describe Compsognathus as "chicken-sized" dinosaurs because of the size of the German specimen, which is now believed to be a juvenile. Compsognathus longipes is one of the few dinosaur species whose diet is known with certainty: the remains of small, agile lizards are preserved in the bellies of both specimens. Teeth discovered in Portugal may be further fossil remains of the genus.

Although not recognized as such at the time of its discovery, Compsognathus is the first theropod dinosaur known from a reasonably complete fossil skeleton. Until the 1990s, it was the smallest-known non-avialan dinosaur, with the preceding centuries incorrectly labelling them as the closest relative of Archaeopteryx.

Compsognathus was the first dinosaur genus to be portrayed with feathers, by Thomas Henry Huxley in 1876.

Crato Formation

The Crato Formation is a geologic formation of Early Cretaceous (Aptian) age in northeastern Brazil's Araripe Basin. It is an important Lagerstätte (undisturbed fossil accumulation) for palaeontologists. The strata were laid down mostly during the early Aptian age, about 113 million years ago, in a shallow inland sea. At that time, the South Atlantic was opening up in a long narrow shallow sea.

The Crato Formation earns the designation of Lagerstätte due to an exceedingly well preserved and diverse fossil faunal assemblage. Some 25 species of fossil fishes are often found with stomach contents preserved, enabling paleontologists to study predator-prey relationships in this ecosystem. There are also fine examples of pterosaurs, reptiles and amphibians, invertebrates (particularly insects), and plants. Even dinosaurs are represented: a new maniraptor was described in 1996. The unusual taphonomy of the site resulted in limestone accretions that formed nodules around dead organisms, preserving even soft parts of their anatomy.

Cratoavis

Cratoavis is a genus of enantiornithine birds. The type and only currently described species is C. cearensis, from the Early Cretaceous of Araripe Basin, Ceará, Brazil. The fossil, an articulated skeleton with feathers attached to the wings and surrounding the body, extends considerably the temporal record of the group at South America.The genus was named after the Crato Formation, in which the specimen was found.

Darren Naish

Darren Naish is a British vertebrate palaeontologist and science writer. He obtained a geology degree at the University of Southampton and later studied vertebrate palaeontology under British palaeontologist David Martill at the University of Portsmouth, where he obtained both an M. Phil. and PhD. He is founder of the blog Tetrapod Zoology, created in 2006.

Irritator

Irritator is a genus of spinosaurid theropod dinosaur that lived in what is now Brazil during the Albian stage of the Early Cretaceous Period, about 110 million years ago. It is known from a nearly complete skull found in the Romualdo Formation of the Araripe Basin. Fossil dealers had acquired this skull and illegally sold it to the State Museum of Natural History Stuttgart. In 1996, the specimen became the holotype of the type species Irritator challengeri. The genus name comes from the word "irritation", reflecting the feelings of paleontologists who found the skull had been heavily damaged and altered by the collectors. The species name is an homage to the fictional character Professor Challenger from Arthur Conan Doyle's novels.

Many paleontologists regard Angaturama limai—known from a snout tip that was described later in 1996—as a potential junior synonym of Irritator. Both animals hail from the same stratigraphic units of the Araripe Basin. It was also previously proposed that Irritator and Angaturama's skull parts belonged to the same specimen. Although this has been cast into doubt, more overlapping fossil material is needed to confirm whether they are the same animal or not. Other spinosaurid skeletal material, some of which could belong to Irritator or Angaturama, was retrieved from the Romualdo Formation, allowing for a replica skeleton to be made and mounted for display at the National Museum of Rio de Janeiro in 2009.

Estimated at between 6 and 8 meters (20 and 26 ft) in length, Irritator weighed around 1 tonne (1.1 short tons), making it one of the smallest spinosaurids known. Its long, shallow and slender snout was lined with straight and unserrated conical teeth. Lengthwise atop the head ran a thin sagittal crest, to which powerful neck muscles were likely anchored. The nostrils were positioned far back from the tip of the snout, and a rigid secondary palate on the roof of the mouth would have strengthened the jaw when feeding. Belonging to a subadult, Irritator challengeri's holotype remains the most completely preserved spinosaurid skull yet found. The Angaturama snout tip expanded to the sides in a rosette-like shape, bearing long teeth and an unusually tall crest. One possible skeleton indicates it, like other spinosaurids, had enlarged first-finger claws and a sail running down its back.

Irritator had been mistaken initially for a pterosaur, and later a maniraptoran dinosaur. In 1996, the animal was identified as a spinosaurid theropod. The holotype skull was thoroughly prepared before being redescribed in 2002, confirming this classification. Both Irritator and Angaturama belong to the Spinosaurinae subfamily. A generalist diet—like that of today's crocodilians—has been suggested; Irritator might have preyed mainly on fish and any other small prey animals it could catch. Fossil evidence is known of an individual that ate a pterosaur, either from hunting or scavenging it. Irritator may have had semiaquatic habits, and inhabited the tropical environment of a coastal lagoon surrounded by dry regions. It coexisted with other carnivorous theropods as well as turtles, crocodyliforms, and a large number of pterosaur and fish species.

List of South American dinosaurs

This is a list of dinosaurs whose remains have been recovered from South America.

List of dinosaur genera

This list of dinosaurs is a comprehensive listing of all genera that have ever been included in the superorder Dinosauria, excluding class Aves (birds, both living and those known only from fossils) and purely vernacular terms.

The list includes all commonly accepted genera, but also genera that are now considered invalid, doubtful (nomen dubium), or were not formally published (nomen nudum), as well as junior synonyms of more established names, and genera that are no longer considered dinosaurs. Many listed names have been reclassified as everything from birds to crocodilians to petrified wood. The list contains 1559 names, of which approximately 1192 are considered either valid dinosaur genera or nomina dubia.

Mirisch

Mirisch is a Jewish surname. Notable people with the surname include:

Harold Mirisch (1907–1968)

Marvin Mirisch (1918–2002)

Walter Mirisch (born 1921), American film producer

Physiology of dinosaurs

Overall, dinosaurs are reptiles. However preliminary note: In this article "dinosaur" means "non-avian dinosaur," since birds are a monophyletic taxon within the clade Dinosauria and most experts regard birds as dinosaurs.The physiology of dinosaurs has historically been a controversial subject, particularly their thermoregulation. Recently, many new lines of evidence have been brought to bear on dinosaur physiology generally, including not only metabolic systems and thermoregulation, but on respiratory and cardiovascular systems as well.

During the early years of dinosaur paleontology, it was widely considered that they were sluggish, cumbersome, and sprawling cold-blooded lizards. However, with the discovery of much more complete skeletons in western United States, starting in the 1870s, scientists could make more informed interpretations of dinosaur biology and physiology. Edward Drinker Cope, opponent of Othniel Charles Marsh in the Bone Wars, propounded at least some dinosaurs as active and agile, as seen in the painting of two fighting "Laelaps" produced under his direction by Charles R. Knight.In parallel, the development of Darwinian evolution, and the discoveries of Archaeopteryx and Compsognathus, led Thomas Henry Huxley to propose that dinosaurs were closely related to birds. Despite these considerations, the image of dinosaurs as large reptiles had already taken root, and most aspects of their paleobiology were interpreted as being typically reptilian for the first half of the twentieth century. Beginning in the 1960s and with the advent of the Dinosaur Renaissance, views of dinosaurs and their physiology have changed dramatically, including the discovery of feathered dinosaurs in Early Cretaceous age deposits in China, indicating that birds evolved from highly agile maniraptoran dinosaurs.

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 Santana Formation, named after the village of Santana do Cariri, lies at the base of the Araripe Plateau. It was discovered by Johann Baptist von Spix in 1819. The strata were deposited during the Albian stage of the Early Cretaceous in a lacustrine rift basin with shallow marine incursions of the proto-Atlantic. At that time, the South Atlantic was opening up in a long narrow shallow sea.

The Romualdo Formation earns the designation of Lagerstätte due to an exceedingly well preserved and diverse fossil faunal assemblage. Some 25 species of fossil fishes are often found with stomach contents preserved, enabling paleontologists to study predator–prey relationships in this ecosystem. There are also fine examples of pterosaurs, reptiles and amphibians, invertebrates (particularly insects), crocodylomorphs, and plants. Even dinosaurs are represented (Spinosauridae, Tyrannosauroidea, Compsognathidae). The unusual taphonomy of the site resulted in limestone accretions that formed nodules around dead organisms, preserving even soft parts of their anatomy. In preservation, the nodules are etched away with acid, and the fossils often prepared by the transfer technique.Local mining activities for cement and construction damage the sites. Trade in illegally collected fossils has sprung up in the last decade, driven by the remarkable state of preservation and beauty of these fossils and amounting to a considerable local industry. An urgent preservation program is being called for by paleontologists.

In addition, the weathering of Romualdo Formation rocks has contributed soil conditions unlike elsewhere in the region. The Araripe manakin (Antilophia bokermanni) is a very rare bird that was discovered only in the late 20th century; it is not known from anywhere outside the characteristic forest that grows on the Chapada do Araripe soils formed ultimately from Romualdo Formation rocks.

Scipionyx

Scipionyx (pronounced "SHIH-pee-oh-nicks" or "ship-ee-OH-nicks") is a genus of compsognathid theropod dinosaur from the Early Cretaceous of Italy, around 113 million years ago.

There is only one fossil known of Scipionyx, discovered in 1981 by an amateur paleontologist and brought to the attention of science in 1993. In 1998 the type species Scipionyx samniticus was named, the generic name meaning "Scipio's claw". The find generated much publicity because of the unique preservation of large areas of petrified soft tissue and internal organs such as muscles and intestines. The fossil shows many details of these, even the internal structure of some muscle and bone cells. It was also the first dinosaur found in Italy. Because of the importance of the specimen, it has been intensely studied.

The fossil is that of a juvenile only half a metre (twenty inches) long and perhaps just three days old. The adult size is estimated to have been about two metres (6.5 feet). Scipionyx was a bipedal predator, its horizontal rump balanced by a long tail. Its body was probably covered by primitive feathers but these have not been found in the fossil, that is without any skin remains.

In the guts of the fossil some half-digested meals are still present, indicating Scipionyx ate lizards and fish. Perhaps these had been fed to the young animal by its parents. Several scientists have tried to learn from the position of the internal organs how Scipionyx breathed, but their conclusions often disagree.

Thalassodromeus

Thalassodromeus is a genus of pterosaur that lived in what is now Brazil during the Early Cretaceous period, about 100 million years ago. Thalassodromeus had one of the largest known skulls among pterosaurs, around 1.42 m (4 ft 8 in) long, with one of the proportionally largest cranial crests of any vertebrate. Though only the skull is known, the animal is estimated to have had a wing span of 4.2 to 4.5 m (14 to 15 ft). The crest was lightly built and ran from the tip of the upper jaw to beyond the back of the skull, ending in a unique V-shaped notch. The jaws were toothless, and had sharp upper and lower edges. Its skull had large nasoantorbital fenestrae (opening that combined the antorbital fenestra in front of the eye with the bony nostril), and part of its palate was concave. The lower jaw was blade-like, and may have turned slightly upwards.

The original skull, discovered in 1983 in the Araripe Basin of northeastern Brazil, was collected in several pieces. In 2002, the skull was made the holotype specimen of Thalassodromeus sethi by palaeontologists Alexander Kellner and Diogenes de Almeida Campos. The generic name means "sea runner" (in reference to its supposed mode of feeding), and the specific name refers to the Egyptian god Seth due to its crest being supposedly reminiscent of Seth's crown. Other scholars have pointed out that the crest was instead similar to the crown of Amon, and Seth did not wear such a crown. A jaw tip was assigned to T. sethi in 2005, moved to the new genus Banguela in 2014, and assigned back to Thalassodromeus as the species T. oberlii in 2018. Another species (T. sebesensis) was named in 2015 based on a supposed crest fragment, but this was later shown to be part of a turtle shell. The closest relative of Thalassodromeus was Tupuxuara; both are grouped in a clade that has been placed within either Tapejaridae (as the subfamily Thalassodrominae) or within Neoazhdarchia (as the family Thalassodromidae).

Several theories have been suggested to explain the function of Thalassodromeus's crest, including thermoregulation and display, but it likely had more than one function. The crests of thalassodromids appear to have developed late in growth (probably correlated with sexual maturity) and they may have been sexually dimorphic (differing according to sex). As the genus name implies, Thalassodromeus was originally proposed to have fed like a modern skimmer bird, by skimming over the water's surface and dipping its lower jaws to catch prey. This idea was later criticised for lack of evidence; Thalassodromeus has since been found to have had strong jaw musculature, and may have been able to kill and eat relatively large prey on the ground. The limb proportions of related species indicate that it may have adapted to fly in inland settings, and would have been efficient at moving on the ground. Thalassodromeus is known from the Romualdo Formation, where it coexisted with many other types of pterosaurs, dinosaurs and other animals.

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