Compsognathus

Credit: Gabriel Ugueto.

*Compsognathus*, further abbreviated to "Compy", is an extinct genus of theropod dinosaur that lived in Europe during the Late Jurassic.

## Description

For many decades, *Compsognathus* was thought to be the smallest known non-avian dinosaur, being as tall as the modern chicken. However, dinosaurs like *Microraptor, Parvicursor* and *Caenagnathasia* and possibly several ichnogenera found since are even smaller. These animals were still small, bouncing around on two slender hind limbs and balancing with a long stiff tail. The forelimbs were considerably shorter than their hind counterparts. Each hand bore two large clawed digits, and possibly non-functional smaller third finger. *Compsognathus* skills are long and delicate, with narrow tapered rostrums. One skull bears give pairs of fenestrae. The largest of which being the orbit, larger in portion to the rest of the entire skull. The mandible lacks mandibular fenestrae, and is slender in shape. This pair or fenestra are commonly seen in most Archosaurs. Each tooth is small but sharp. These are suited towards small vertebrates and invertebrates. The front-most teeth sitting on the premaxilla lack serrations, where ones farther back are flattened and sharp. These help scientists classify *Compsognathus* and closely affiliated. This was described in 2012 by Reisdorf and Wuttke. The total number of digits of *Compsognathus*' forearm has been debated throughout history. Mostly, the dinosaur is depicted with three, typical of Theropods. However, closer analysis shows that the holotype preserves only two functional digits, and one reduced. One study describes webbed hands for paddling in water. This sparked depictions of an amphibious animal specializing in marine food and terrestrial-walking to escape predators. This was debunked, as another specimen was identical to other descriptions (except for size), and that this hypothesis was wrong. These conclusions have since been accepted.

Close relatives to *Compsognathus* are known to have had fur-like protofeathers covering their bodies. *Compsognathus* may have been similarly covered. However, no covering impressions in fossilization are documented. Scales have been reported being preserved on the underside of the tail and in the sides of the legs. However, these claims were disproved by Ostrom, reporting these as being adipocere, a wax that forms on corpses. Some dinosaurs may have had a fewer covering, however the covering lacking the sides of the legs and the underside of the tail may have been common.

## Paleobiology

### Paleopathologies

In 2001 nine elements attributed to *Compsognathus* feet were examined for signs of stress fracture. The results showed none.

### Diet

The remains of a small lizard have been found in the German specimens thoracic cavity. This shows that *Compsognathus* hunted small animals and maybe insects. Marsh, examining the specimen in 1881, thought the remains were an embryo, but was confirmed a lizard by Nopsca in 1903. Ostrom identified the remains as *Brevarisaurus*, a fast-running lizard. This lizard is thought to have been a fast runner, meaning *Compsognathus* would have needed sharp vision and agility to catch the small animal. Later Conrad announced in the press that the lizard was the only holotype of *Schoenesmahl*. The remains are in a single piece, probably swallowed whole. The French specimen has unidentified Sphenodontids and lizards in its gastric contents.

### Eggs

The slate preserving the German remains show several circular shapes, 10 millimeters (0.39 inches) in diameter near the carcass. Griffiths interprets them as eggs in 1993. However, several authors have doubted that these shapes belong to the genus, as they are found outside the actual corpse, belonging to another animal. The closely-related *Sinosauropteryx* bears two oviducts that contain two unlaid eggs. These were larger and there were less of them. Instead of being eggs, Werner in 1964 states that they are spherical gas bubbles, formed and fossilized due to carcass putrefaction.

### Speed

Sellers and Manning placed an estimate of *Compsognathus* speed in 2007 by using a computer model to reconstruct the skeleton and muscles. They placed its speed at 17.8 m/a (40 miles/hour).

## Paleoecology

Late Jurassic of Europe is characteristically dry, and the German archipelago *Compsognathus* lived on edged the Tethys. The fine limestone *Compsognathus* are found in originate from calcite, which further originates from marine animal shells. Both France and German sediments where *Compsognathus* are found were deposited around lagoons, which are surrounded by islands and reefs. *Compsognathus* lived with *Archaeopteryx*, the pterosaur *Rhamphorynchus* and *Pterodactylus*, horseshoe crabs and marine and terrestrial Crocodylomorphs. The reefs were inhabited by echinoderms, fish, crustaceans and molluscs. *Compsognathus* may have been one of the top land predators at this time and place.

Discussion about the taphonomy of the German specimen is complicated. How and when it died are unclear as the exact locality, position and orientation has been lost. The orientation of the specimen can not be truly reconstructed, and, as a compression fossil, it would have been preserved on both upper and lower surfaces of the slabs. One theory states that it was fossilized on its side, and that the left limbs are better articulated than the right. This may mean that the individual was laying on its left side, embedded on the bottom of the upper slab.

The German specimen is very articulated, only the skull, hands, cervical ribs and gastralia being disarticulated. The braincase is displaced, positioned behind the skull. The first tail vertebrae is articulated 90°, breaking between the 7 and 8 vertebrae. The neck curves strongly, the head placed above the pelvis. The spine of the trunk and tail are also curved. It sports the iconic death pose. It is thought that this position is caused by cerebral spasms while the animal is dying. Another theory places this as the Ligamentum elasticum releasing, which curls the animal. The latter would have occurred slowly as muscle tissues were in the process of decay.

## References

* https://en.wikipedia.org/wiki/Compsognathus
* Archaeopteryx: A Jurassic Mystery, Marco Signore and Matteo Bacchin