Compsognathus

About Compsognathus

Features and the Mystery of Classification

Compsognathus was a small carnivorous dinosaur that lived in Europe during the Late Jurassic period, about 150 million years ago. It had a very slender skeleton and was a bipedal theropod.

It was once considered the representative of its own unique group, the "Compsognathidae." However, recent research has pointed out the possibility that many of the dinosaurs classified in this group were actually fossils of juveniles whose skeletons had not yet fully grown. In other words, there is an ongoing debate that the Compsognathidae group itself may not exist, and that juveniles of larger theropods like Allosaurus may have been mistakenly classified due to features they shared when young.

The skull was generally elongated and tapered smoothly towards the tip of the snout. A distinctive feature is the very large orbits (eye sockets), which occupied about a quarter of the skull's length. From these huge eyes, it is known that Compsognathus was a diurnal hunter that relied heavily on vision to hunt.

Habitat and Hunting Methods

At that time, Europe was not a continuous landmass as it is today, but tropical islands (such as the Solnhofen Archipelago) floating in the shallow Tethys Sea. Because these islands did not have enough space or resources for large dinosaurs to live, Compsognathus is thought to have been an apex predator at the top of the ecosystem on these small islands.

It is estimated to have been a fast runner based on the balance of its leg bones, with some simulation studies suggesting a top speed of about 64 kilometers per hour. With this speed and excellent vision, they chased agile prey in open beaches and shrublands.

A small lizard was found inside the stomach of a discovered fossil, indicating that they were carnivorous. The lizard in the stomach was called "Bavarisaurus" for many years, but a 2018 study revealed that it was an early gecko. This lizard was given the unique name *Schoenesmahl dyspepsia* ("beautiful meal that caused indigestion"). The fact that the lizard's bones were disarticulated in the stomach reveals that Compsognathus did not swallow its prey whole like a snake, but held it down with its forelimbs and tore it apart with its jaws before eating.

The Smallest Dinosaur? Growth Stages and Size

For a long time after its discovery, Compsognathus was highly famous as "the world's smallest dinosaur, about the size of a chicken." In fact, the first German specimen discovered was a juvenile fossil less than 1m long.

However, subsequent research revealed that a larger adult specimen found in France showed that a mature Compsognathus grew to the "size of a turkey," about 125-140 cm in total length and weighing 2.5-3.5 kg.

Today, with the successive discoveries of even smaller dinosaur fossils such as Microraptor, it has yielded the title of "smallest dinosaur," but it remains unchanged that they played the role of agile small hunters in the Jurassic ecosystem.

How Many Fingers on the Forelimbs? A History of Debate

The "number of fingers" on the forelimbs of Compsognathus has been a subject of debate for a long time. The first discovered German specimen had poor preservation of the forelimb area, and it appeared to have only two functional fingers. Because of this, Compsognathus was restored for a long time as a "two-fingered dinosaur" like Tyrannosaurus.

However, the discovery of traces of a small third finger in the French specimen found in the 1970s, and a recent reinvestigation of the German specimen using precision equipment, led to the conclusion that it actually had two fully functional fingers (the first and second fingers) and a small, reduced, non-functional third finger. It is now the accepted view that Compsognathus was three-fingered, like other early theropods.

Fossil Discovery History and the Mystery of the "Death Pose"

The first fossil (the German specimen) was discovered in the Solnhofen limestone formation in Bavaria, Germany, in the 1850s and was described by Johann A. Wagner in 1859. Later, around 1971, a second nearly complete skeleton was discovered in southeastern France.

In many dinosaur fossils found in a nearly complete state, including the German specimen, a peculiar posture is seen in which the head is extremely arched backward toward the back, and the tail is also raised toward the back. This is called the "death pose," and was once thought to be caused by agony or asphyxiation spasms just before death.

However, recent taphonomic (fossilization process) research has proven that this posture is due to physical changes after death. When a carcass sinks in water and decays, the muscles relax, and the strong "elastic ligament" stretched from the neck to the back naturally contracts, strongly pulling the neck and tail backward, forming this arched posture.

Compsognathus Integument: Feathers or Scales?

Because traces of simple feathers have been found in closely related dinosaurs (such as Sinosauropteryx), many modern encyclopedias and reconstructions depict Compsognathus with its entire body covered in feathers. However, despite being found in well-preserved limestone, no evidence of feathers has ever been found on Compsognathus's own fossils.

Also, a study claiming there were traces of "scales" on the tail of the French specimen caused debate when published, but the latest research in 2022 confirmed that it was not scales but "simply an abnormal overgrowth of bone" that occurred during fossil preservation, effectively rejecting the scale theory as well.
It remains unsettled whether they had lost their feathers to adapt to the tropical climate, or if the feathers simply did not survive the fossilization process, so the appearance of their integument is still unknown today.

Compsognathus Stamp & Fossil Gallery