Deltadromeus

*Deltadromeus agilis*

***Deltadromeus*** (meaning "delta runner") is a genus of large basal ceratosaurian theropod dinosaur from Northern Africa. It had long, unusually slender hind limbs for its size, suggesting that it was a swift runner. The skull is not known. Two fossil specimens of a single species (*D. agilis*, or "agile delta runner") have been described, found in the Bahariya Formation and Kem Kem Beds, which date to the mid Cretaceous Period (mid Cenomanian age), about 95 million years ago. It may be a junior synonym of the contemporary *Bahariasaurus*. Often thought to be a ceratosaurian, the discovery of the theropod *Gualicho shinyae* indicates it is likely a sister taxon to the South American predator.

Being a noasaurid, *Deltadromeus* featured a long neck and legs, with small vestigal arms; it also had a small head and stiff tail. This creature was around 8 meters long with an unknown weight.

Since its body design is that of a runner, it was most likely warm-blooded. It was likely covered in scales or bumps rather than feathers due to it being a member of a more basal theropod family, closely related to *Carnotaurus* and *Ceratosaurus,* and would not need them as an adult since its own size would likely have made it gigantothermic.

Its gracile and relatively fragile frame is not suited for engaged combat and probably attacked the prey with its vicious claws and teeth, slashing the hide and flesh like an axe until the prey died from exhaustion, blood loss, shock or a combination of the three.

## Description

The fairly complete holotype skeleton of *Deltadromeus agilis* (museum catalogue number SGM-Din2) measured an estimated 8 m (26.24 ft) long.

A second specimen (IPHG 1912 VIII) was originally described by Ernst Stromer as a specimen of *Bahariasaurus*,[3] but was designated as a specimen of *Deltadromeus* by Paul Sereno in 1996.[4] This second specimen comes from a much larger individual, with a femur (upper leg bone) length of 1.22 meters, compared to 0.74 meter femur of the holotype.[4]

*Deltadromeus* skeletons have been found in the same formations as those of the giant theropods *Carcharodontosaurus*, *Spinosaurus*, and *Bahariasaurus*, which may be synonymous with *Deltadromeus*. No skull material has been found for either *Deltadromeus* or *Bahariasaurus*, and though carnivore teeth labelled as "Deltadromeus" are commonly sold in rock shops, there is no way of knowing if they actually come from this animal.

*Deltadromeus* is thought to have weighted up to 2 metric tons.

*D. agilis* means 'agile delta runner'. It was unusually slender for a theropod of it's size, which leads to an often interpreted that it was a swift runner. *Deltadromeus* has no known crania, with a single fossil specimen described from the the Kem Kem Beds, which date to the mid-Cretaceous Period, about 95 million years ago. It was once thought to be synonymous with *Bahariasaurus*. SGM-Din2, a partial skeleton 8 meters (26 feet) long, is the holotype. It is little over a ton heavy.

## Classification

*Deltadromeus* was originally described as a large coelurosaur, but more recent studies suggest it was actually a ceratosaur, though exactly what type of ceratosaur remains unknown. One 2003 study suggested it was a member of the Noasauridae,[6] though others have found it to be more primitive, possibly related to the primitive ceratosaurs *Elaphrosaurus* and *Limusaurus*. However more recent studies showed it was a Carnosauria since *Gualicho* was a Sister taxa to *Deltadromeus* which was possibly the same animal as *Aoniraptor*.

The cladogram below follows a 2016 analysis by Oliver Rauhut, and Matthew Carrano.

Different analyses have not found *Deltadromeus* to be a ceratosaur. An analysis of *Gualicho*, a South American theropod belonging to the allosauroid family Neovenatoridae, finds *Deltadromeus* to be *Gualicho's* probable sister taxon. In an analysis of *Aoniraptor*, which may be the same animal as *Gualicho*, *Deltadromeus* was found along with *Aoniraptor* and *Bahariasaurus* to probably form a still poorly known clade of megaraptoran tyrannosauroids different from the Megaraptoridae.

The cladogram below follows a 2016 analysis by Sebastián Apesteguía, Nathan D. Smith, Rubén Juarez Valieri, and Peter J. Makovicky.

## Paleobiology

*Deltadromeus* was contemporaneous with *Carcharodontosaurus*, *Spinosaurus*, *Bahariasaurus*, abelisaurids, crocodylimorphs and pterosaurs. Though theropod teeth labelled as "*Deltadromeus*" are sold in rock shops, this assignment is dubious at best since there is no way to test their identity. *Deltadromeus* had lived through a highly volatile and hostile habitat. The Northern Africa had so many large and potentially dangerous predators, it is often depicted as 'the most dangerous place on Earth'.

## JPInstitute.com Description

Deltadromeus was a fast meat eater, sort of like a very large raptor. It had big claws, strong legs, and lots of sharp teeth. Only one partial skeleton has been found so there is still a great deal about this dinosaur that remains a mystery. To date, a skull hasn't been found, but scientists have uncovered its teeth, and because of this they can only guess at what its head looked like. Much of its body has been found, however, so scientists know how big it was, and by comparing it to similar dinosaurs they can make a good guess as to how it looked when it was alive.

Deltadromeus is known mostly from a single, very fragmented partial skeleton that was found in 1995 by Paul Sereno from the University of Chicago. Bones and sharp, one-inch-long, serrated teeth found in the Baharia Formation have been attributed to this species, but this has yet to be proven as the skull for the species has not been found. Skeletal elements indicate that it was a fast, agile carnivore with many similarities to coelurosaurs like the older Ornitholestes from the Jurassic. Dr. Sereno's National Geographic-sponsored expedition was most successful as he also discovered the only substantial specimen of Carcharodontosaurus.

## Links

http://web.archive.org/web/20040214162141fw\_/http://www.jpinstitute.com/dinopedia/dinocards/dc\_delta.html

## References

1. ↑ 1.0 1.1 https://www.geol.umd.edu/~tholtz/dinoappendix/DinoappendixSummer2008.pdf
2. ↑ 2.0 2.1 Template:Cite journal
3. ↑ Template:Cite journal
4. ↑ https://medium.com/predict/scientists-reveal-the-most-dangerous-place-in-earths-history-562b88cb6681