compsognathus

Schoenesmahl

Schoenesmahl dyspepsia was a lizard that lived in what is now Europe during the late Jurassic, about 150 million years ago. Around 30cm long (~1′), it had a fairly small head, elongated hind limbs, and a very long tail – proportions that suggest it was an agile animal capable of fast running.

Only one specimen is known, most notable for being preserved inside the stomach of the dinosaur Compsognathus. For a long time it was classified as an example of Bavarisaurus, but it was finally recognized as representing a distinct type of lizard in 2018, with recent studies placing it as an early member of the gecko lineage closely related to ardeosaurids and eichstaettisaurids.

First discovered in the 1850s, Compsognathus longipes was the first theropod dinosaur known from a fairly complete skeleton, and also the smallest known non-avian dinosaur for over 130 years.

(A second specimen was also, briefly, the “first” aquatic non-avian dinosaur, but that’s another story.)

Living in what is now Europe during the late Jurassic, about 150 million years ago, it was a lightly built animal with long legs and a long tail, growing to around 1.2m long (~4′). Its hands seem to have had only two functional fingers, with the third being vestigial and possibly not even having a claw.

Skin impressions from about a third of the way along its tail show small bumpy scales – but since other compsognathids like Sinosauropteryx are known to have been covered in fur-like feathers, this likely means that just that particular region of Compsognathus’ body wasn’t fluffy.

Some of Compsognathus‘ diet is known for certain, since preserved gut contents show it fed on smaller vertebrates like lizards and rhynchocephalians. The remains of a lizard in the stomach of one specimen were even identified as belonging to a previously-unknown species, Schoenesmahl dyspepsia, with the dismembered nature of the skeleton suggesting Compsognathus tore its prey into bite-sized chunks in a similar manner to modern predatory birds.

April Fools 2022: The Aquatic Dinosaur That Wasn’t

So, Spinosaurus wasn’t technically the first known aquatic non-avian dinosaur.

That title instead temporarily went to Compsognathus corallestris.

While the idea that hadrosaurs and sauropods were wallowing swamp-dwellers had been completely abandoned at the start of the Dinosaur Renaissance, the new view of dinosaurs as active sophisticated animals led to a surprising aquatic hypothesis during the early days of this paleontological revolution.

A specimen of the small theropod Compsognathus discovered in southeastern France in the early 1970s was only the second skeleton ever found of this dinosaur, and came over a century after the first. It was initially thought to represent a new species since it was about 50% larger than the German specimen of Compsognathus longipes, and it seemed to have something very unusual going on with its hands – its forelimbs were somewhat poorly-preserved and distorted, and had traces of some sort of large fleshy structure around the hands that was interpreted as representing elongated three-fingered flippers used for swimming.

This wasn’t necessarily as ridiculous of an idea as it might sound. Compsognathus lived during the Late Jurassic, about 150 million years ago, at a time when Europe was a group of islands in a shallow tropical sea. A semiaquatic dinosaur specialized to swim and dive, hunting the abundant aquatic prey in its environment, and easily able to island-hop all around the European archipelago seemed at least somewhat plausible, and reconstructions of fin-handed C. corallestris even appeared in several popular dinosaur books of the time.

But it didn’t last.

Within just a few years doubt was being cast on this idea, and further studies of both known Compsognathus skeletons in the late 1970s and early 1980s concluded that C. corallestris was actually a fully-grown adult individual of the juvenile C. longipes. The French Compsognathus had normal-looking hands for its kind after all, with two large clawed fingers and a vestigial third finger, and the “flipper” impressions had just been ripples in the fossil slab.

For a long time after that the general view became that there just weren’t any aquatic non-avian dinosaurs at all – but more recent discoveries like the new Spinosaurus material and Halszkaraptor are starting to suggest that some of these animals were much more at home in the water than previously thought.

Something resembling Compsognathus corallestris might still surprise us in the future.