Dinopedia
Advertisement
Ekrixinatosaurus
Temporal range: Cenomanian
Gabriel
Reconstruction of Ekrixinatosaurus by Gabriel Ugueto
Scientific classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Family: Abelisauridae
Genus: Ekrixinatosaurus
Calvo, 2004
Species: E. novasi
Type species
Ekrixinatosaurus novasi
Calvo, 2004

Ekrixinatosaurus (meaning "explosion-born lizard") was a large carnivorous dinosaur from South America, belonging to the family Abelisauridae. It was initially thought to have reached lengths of 9 to 10 meters, making it the largest abelisaurid discovered at the time, however a study in 2016 estimated that it had a more plausible average length of 7.4 meters. Other estimates put its length at 11 meters, however these estimates are only based on the absolute size of the skull alone in comparison to other abelisaurs, not accounting for the fact that it would be highly unlikely for Ekrixinatosaurus to have reached such sizes. The previous largest Carnotaurus is estimated to have an average length of 7.8 meters. So far, the crown of the largest abelisaur belongs to Pycnonemosaurus (around 9 meters long). This large theropod was named as such when its remains were unearthed during an explosion. 

Discovery and naming[]

As suggested by its name, the bones of Ekrixinatosaurus were discovered during a construction-related explosion. It was described in 2004 by Argentian paleontologist Jorge Calvo, and Chilean paleontologists David Rubilar-Rogers and Karen Moreno. The holotype specimen of Ekrixinatosaurus was fairly well-preserved, including in its elements a left and partial right maxillae, both dentaries, a near complete set of teeth, a cervical, dorsal, sacral, and caudal vertebrae, chevrons, ribs, ilia, pubis and proximal ischia, left and distal end of right femur, left tibia and astragalus and calcaneum, proximal end of left fibula and right tibia, metatarsals, phalanges, and a pedal ungual. Due to the astonishing preservation of the specimen, the remains of Ekrixinatosaurus were able to reveal more parts about abelisaurid anatomy as a result of the inclusion of previously unknown or poorly preserved skeletal portions from other abelisaurids.

Classification[]

Ekrixinatosaurus is classified as an abelisaurid within the Carnotaurinae subfamily and subsequent Carnotaurini tribe, putting its placement in the clade as an abelisaur more closely related to Carnotaurus than to Majungasaurus. The closest relative of Ekrixinatosaurus that also resided within Argentina is Skorpiovenator.

Description[]

Ekrixinatosaurus was a fairly large and heavily built abelisaurid, possessing a boxy and comparatively short skull to most other large carnivores of its time, with an estimated approximate length of 83 cm (33 inches). The skull was rather deep and thickly built, meaning that Ekrixinatosaurus would have been equipped with a devastating bite force that could dispatch of most small to medium-sized herbivores living besides it, and even possibly crush the bones of carcasses. Ekrixinatosaurus was initially thought to be the largest of its family at a length of 11 meters (36 feet) based only on the size of the skull in comparison to other abelisaurids, although recent studies more realistically estimated its average length to be about 7.4 meters (24 feet) with a mass of around a tonne (2,205 lbs) based on comparisons of its proportions with others of the Abelisauridae family. Ekrixinatosaurus was as a result quite unusual even among other abelisaurids, as it would have a large head in comparison to the rest of the body, indicating the frontal portion of the body to be more heavily built to support the size of the head and the neck muscles that hold it.

Paleoecology[]

Ekrixinatosaurus was found in the fossil beds of the Candeleros Formation, which has yielded a wide variety of vertebrates. It shared its environment with the titanosaurian sauropod Andesaurus and the rebbachisaurid sauropods Limaysaurus and NopcsaspondylusIguanodont ornithischian remains have reportedly also been found. The carcharodontosaurid Giganotosaurus was possibly the apex predator of the region and may have competed with Ekrixinatosaurus for food. Smaller predators also inhabited the area, including the dromaeosaurid Buitreraptor, the alvarezsaurid Alnashetri, and the basal coelurosaurian Bicentenaria. Other primitive reptiles lived in the area, such as the primitive snake Najash, the crocodile Araripesuchus, along with turtles, fish, pipid frogs, and mammals. Pterosaurs also lived in the area, as evidenced by pterosaur tracks. A wide variety of dinosaur trackways have also been found in the Candeleros Formation, suggesting significant faunal activity in the area.

Recent studies on Gondwanan theropods have interpreted abelisaurids as modest and medium sized dinosaurs that co-occurred with giant carcharodontosaurids during the Early and early Late Cretaceous. It has been hypothesized that it was only after extinction of the carcharodontosaurids that abelisaurids were able to diversify into more robust forms that occupied the niche of top predators of their ecosystems. However, it has been observed that both Giganotosaurus and Ekrixinatosaurus were among the largest of their respective clades in their area yet existed at the same time, which refutes this hypothesis. Both these animals occupied the role of the largest carnivores, however it is uncertain whether they played different ecological roles (such as active predation vs. scavenging), or lived in different habitats and preyed on different animals. In addition, the known distribution of abelisaurids in South America, Madagascar and India brings the hypothesis of a dispersion route between these areas by a terrestrial bridge called the Kerguelen Plateau that formed prior to the separation of Africa and South America.

Gallery[]

Advertisement