Postosuchus

*Postosuchus kirkpatricki*

***Postosuchus*** was a basal archosaur which lived in what is now North America during the middle through to the late Triassic period (228-202 million years ago). It was a rauisuchian, a cousin of crocodiles and came from the same ancestry as dinosaurs. Its name means "crocodile from Post", named after the Post Quarry in Texas, where many fossils of the species were found. It was one of the top predators of its area during the Triassic, larger than the small dinosaur predators of its time (such as *Coelophysis*). It was a hunter which probably preyed on dicynodonts and many other creatures smaller than itself.

*Postosuchus* was a quadrupedal reptile with a wide skull and a long tail. This carnivore attacked with its large curved claws. It was about 4-5 meters long (12-15 feet), and was held up by columnar legs (a quite uncommon feature in reptiles). A crocodile-like snout, filled with many large-sized dagger-like teeth, was used to kill its prey. Rows of protective plates covering its back formed a defensive shield.

## General Description

*Postosuchus* was one of the largest carnivorous reptile species of the Triassic, reaching 5-7 meters (16-23 ft) long 2 to 3.5 meters tall and weighed 300–600 kg (550-660 lbs). It had a massively built skull, bearing powerful jaws and dagger like teeth that can easily kill its quarry by cutting through its flesh and ripping off pieces. Rows of protective osteoderms covering its back formed a defensive shield, protecting it from other predators and dangerous prey.

### Skull

 File:Postosuchus profile.jpg

The skull of *Postosuchus* was constructed narrow in front and extended wide and deep behind. It was 55 cm in length and 21 cm broad and deep. There are many fenestrae (openings) present in the bones that lighten the skull, providing space for the muscles. Like more derived archosaurs, the lower jaw had mandibular fenestrae (openings at the lower jaw), formed by the junction of the dentary with other jaw bones (surangular and angular). *Postosuchus* had very good long distant sight, due to large orbits, supporting large and sharp eyes, and strong olfaction provided by elongated nostrils. Inside the skull, under the nostrils, there was a hollowing that probably was for the Jacobson's organ, an olfactory sensory organ sometimes referred as the "sixth sense".[8] The jaws held large and sharp serrated teeth and in some points were developed even larger to operate as hooked sabers. A complete tooth found among *Postosuchus* remains in North Carolina measured about 7.2 cm in height.[10] Postosuchus possessed heterodonty dentition, which means each tooth was different in size and shape from the others. The upper jaw composed of seventeen teeth, with each premaxilla bore only four teeth and each maxilla thirteen teeth.[9] In the lower jaw were counted over thirty teeth. Replacement activity in *Postosuchus* was different from that of crocodiles, since the replacement tooth didn't fit directly in the pulp cavity of the old tooth, but grew until resorption of the old tooth was complete.

### Limbs and posture

*Postosuchus's* forelimbs were over half the size of its hind legs, this characteristic of short forelimbs can usually be seen in bipedal reptiles. Chatterjee suggested that *Postosuchus* could walk in an erect stance, since the short forelimbs were used probably only during slow moving locomotion. However, in 1995, Robert Long and Phillip A. Murry claimed that *Postosuchus* was a stocky quadruped. There is a debate over whether *Postosuchus* was either a biped or a quadruped as scientists aren't sure yet. However, some paleontologists suggested that *Postosuchus* was probably a facultative biped, meaning that it altered between bipedally and quadrupedally. Some early depictions show the Postosuchus stalking around on its hind legs, with its front legs hanging irregularly from their joints as it walked.

### Postcranial anatomy

The neck of *Postosuchus* consists of at least eight cervical vertebrae followed by sixteen dorsals, while four co-ossified sacral vertebrae supported the hips. It is thought to be over thirty vertebrae in the tail decreasing in size to the end. The pelvis with the hooked pubis and the rod-like ischium looked like those of carnosaur dinosaurs. Along with remains of the skeleton, paleontologists also identify osteoderms, which were thick plates forming scales. These were on its back, neck, and possibly above or under the tail. The ribcage of Postosuchus had typical archosaur structure, composed of large and slender, curved ribs. In some discoveries ribs were found associated with gastralia, dermal bones which located in the ventral region of the body.[15] The limbs were located underneath the body giving *Postosuchus* an upright stance.[5] With the forelimbs being approximately 64% of the hindlimbs, Postosuchus had small hands bearing five toes. Only the first toe bore a large claw, which was used as an offensive weapon, and the forelimbs were robust, probably to hold the prey. Peyer et al. 2008, argued that the thick pectoral girdle served for locomotion of the forelimbs.[16] However, this doesn't detract from the theory that Postosuchus could walk bipedally. The feet were much larger than the hands, with the fifth metatarsal forming a hook shape. The halluxes were more slender than the other toes and the marginal ones couldn't touch the ground. As crurotarsan, the heel and ankle of *Postosuchus* resemble those of modern crocodiles.

## *P. alisonae*

A partial skeleton of *Postosuchus* from Durham County, North Carolina was discovered in 1994 and named in 2008 as new species *P. alisonae*. The specific name is in reference to Alison L. Chambers, who worked to popularize paleontology in North Carolina. The skeleton of *P. alisonae* consists of a few cranial bones, seven neck, one back, and four tail vertebrae, ribs, gastralia ("belly ribs"), chevrons, bony scutes, much of the shoulder girdles, most of the forelimbs except the left wrist and hand, most of the hindlimbs except for the thigh bones, and pieces from the hip. This specimen is unusual in preserving gut contents: bones from at least four other animals, including a partial skeleton of an aetosaurid, a snout, coracoid, and humerus of the traversodontid cynodont *Plinthogomphodon*, two phalanges from a dicynodont, and a possible temnospondyl bone. Furthermore, the *Postosuchus* was positioned on top of a skeleton of the sphenosuchian *Dromicosuchus*, which included tooth marks on the skull and neck.

## Appearance in other media

### *Jurassic Park*

* *Postosuchus* is a super rare amphibian that can be created in *Jurassic World: The Game*, even though in real life it was a terrestrial reptile. It was added as part of the March 16th, 2016 update and can be acquired in a Super Rare pack, or by completing Battle Stage 70. When *Postosuchus* is in its pen, its tail rests on the ground. While other crocodiles did this, it is unlikely *Postosuchus* did this. With the legs under its hips like a dinosaur and unlike a semi aquatic crocodile, *Postosuchus'* tail had to be above the ground for balance. Also, *Postosuchus* is shown to walk on four legs, whereas recent research suggests it likely walked on two, but this is still being debated.
* *Postosuchus* does appear in *Jurassic World: Alive*. *Postosuchus* is shown to walk on four legs, whereas recent research suggests it likely walked on two. It is a Rare dinosaur and can be achieved by darting 100 Postosuchus DNA.

## Links

https://web.archive.org/web/20050307005256fw\_/http://www.jpinstitute.com/dinolab/dino\_academy/art\_gallery\_class\_gallery.jsp?CLASSID=5

## References

1. ↑ 1.0 1.1 Template:Cite book
2. ↑ Template:Cite journal