Irritator Facts for Kids

Quick facts for kids Irritator Temporal range: Lower Cretaceous

Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Sauropsida
Superorder:	Dinosauria
Order:	Saurischia
Suborder:	Theropoda
Family:	Spinosauridae
Genus:	Irritator Martill et al., 1996
Species:	I. challengeri Martill et al., 1996 (type)

Irritator is a genus of theropod dinosaur which was discovered in the Lower Cretaceous of the Santana Formation.

The first identifiable dinosaur from Brazil and the first non-avian from South America, Irritator has teeth similar to Spinosaurus. It has a slender jaw with nostrils well back from the front of the snout (all consistent with fish eating). It also had a large crest on the quadrate bone on top of the skull. It was named due to the feelings of the scientists who described it when they found that the snout had been artificially lengthened to resemble a plesiosaur.

Current estimations indicate a length of 8 meters (26 feet). In 2010, Gregory S. Paul gave lower estimations of 7.5 metres and one tonne. It was found in Brazil. Irritator was a theropod with an unusually shaped crest at the rear of its head, and most likely consumed fish.

So far the only fossil that has been found was an 80 centimeter long fossil skull in the Romualdo Member, a layer member of the Santana Formation. This skull strongly resembles the skulls of Suchomimus and Spinosaurus. The genus is often regarded today as identical (synonymous) with Angaturama, which lived in the same time and the same place as Irritator. In the year 2004 parts of a spinal column were discovered in the Santana Formation. These have been assigned, due to their structure, to the Spinosauridae. With very high probability these fossils belong to Irritator, since this is the so far the only well-known spinosaurid in the formation.

Irritator probably nourished itself on fish, like the pterosaurs found in large number in the Santana Formation. Irritator was probably, like today's crocodiles, a food generalist, eating all other animals that it could catch besides fish. A tooth belonging to Irritator still inserted into a fossil neck vertebral column of a pterosaur, indicates that Irritator ate pterosaurs as well, although it is not known if it actively hunted these animals, or simply scavenged the remains.

Images for kids

Map showing the Northeast Region of Brazil, with the discovery sites of three spinosaurine fossil specimens in the Araripe and São Luís-Grajaú Basins marked. From top to bottom: Oxalaia, Irritator, and Angaturama.
Outdated reconstruction of the holotype skull (top) based on the interpretations of Martill and colleagues in 1996. Depictions (similar to the one at the bottom) based on this reconstruction were later featured in many dinosaur books and encyclopedias.
Known skull elements of Irritator as interpreted by paleontologist Jaime A. Headden; the snout tip is from the Angaturama specimen.
Holotypes of Irritator challengeri and Angaturama limai in place, showing the latter's larger skull size and overlapping third left maxillary tooth, as proposed by Sales and Schultz in 2017
Spinosaurine pelvis and sacral vertebrae (specimen MN 4819-V), National Museum of Rio de Janeiro
Holotype skull of Irritator challengeri from left (top) and right side views
Life restoration combining specimens of Irritator and Angaturama
Closeup of Irritator's upper jaw and dentition
Holotype of Angaturama limai from various angles
Hand and arm bones of specimen MN 4819-V, the most complete spinosaurid hand known
Diagram illustrating skull elements from Irritator (bottom) and other spinosaurids, comparing the relative positions of the external nares, or bony nostrils, (labeled e.n.)
Head of an Indian gharial, which has similarities to the head of Irritator
Closeup of reconstructed skull and neck
Skeleton mounted as attacking an anhanguerid pterosaur, National Museum of Rio de Janeiro
CT scan of the holotype showing endocast and endosseous labyrinth
Restoration of the head
Restoration of Irritator walking down a coastline in the Romualdo Formation environment
Generalized locations of spinosaurid fossil discoveries from the Albian-Cenomanian, 113 to 93.9 million years ago, marked on a map of that time span

Irritator facts for kids

Images for kids

See also