Compsognathidae:
The compsognathid dinosaurs

What are compsognathid dinosaurs‭?
       The compsognathid dinosaurs were a distinct group of the dinosaurs that lived mostly from the late Jurassic through to the early Cretaceous.‭ ‬They were smaller predatory theropod dinosaurs that are typically classed under the Tyrannoraptora group of theropods.‭ ‬This makes the compsognathid dinosaurs cousins to other theropods such as tyrannosaurs and ornithomimosaurs.

How big were compsognathid dinosaurs‭?
       When compared to other kinds of theropod dinosaurs,‭ ‬compsognathids were pretty small.‭ ‬Some were under a meter,‭ ‬while others such as Sinocalliopteryx were over two meters long.‭ ‬Most known genera fall somewhere in‭ ‬between.‭ ‬Some fossils attributed to the Compsognathidae suggest slightly larger sizes,‭ ‬but their placement within the group can also be uncertain and‭ ‬at times‭ ‬even disputed.

What did compsognathid dinosaurs look like‭?
       As theropod dinosaurs,‭ ‬compsognathids were bipedal dinosaurs,‭ ‬very lightly built and suited for agility and quick bursts of speed.‭ ‬For a long time compsognathids were thought to have‭ ‬had‭ ‬bare reptilian skin,‭ ‬an idea based from the early days of the type genus reconstruction of‭ ‬Compsognathus when the science of palaeontology was very much still in its infancy.‭ ‬Newer discoveries towards the end of the twentieth and early twenty-first centuries revealed many new discoveries about this group of dinosaurs.
       First was that new study techniques and better preserved fossils meant that it was finally confirmed that many compsognathids had primitive hair-like protofeathers covering their bodies.‭ ‬In some genera the hair seems to have covered just the body,‭ ‬in others it went all the way down the tail.‭ ‬There seems to be a high level of variation between compsognathid genera regarding how much feathers grew and in what parts of the body they appeared.‭ ‬While some of these protofeathers seem to be insulatory they also seem to have served a display purpose.‭ ‬The‭ ‬2020‭ ‬description of Ubirajara identified an extensive mane that could be raised and lowered as required as well as‭ ‬pairs of spike-like projections sticking out from the sides.
       Studies of the compsognathid dinosaur genus Sinosauropteryx were amongst the first insights into what colour dinosaurs actually were.‭ ‬Melanosomes,‭ ‬colour pigments in feather impressions associated with the fossil,‭ ‬were compared to those seen in living animals today.‭ ‬This comparison revealed that in life Sinosauropteryx may have had an alternating pattern of white and brown bands down the tail,‭ ‬and that Sinosauropteryx had darker colour on the upper portions of its body,‭ ‬and lighter colour on the underside.‭ ‬This is classic camouflage patterning,‭ ‬as the countershading of the main body would mean that the dinosaur would blend in more with the background even when lit from above,‭ ‬while the banding of the tail would break up its shape so that the eyes of a predator would be less likely to detect it.‭ ‬It’s possible that other compsognathids displayed similar patterns and colours as Sinosauropteryx,‭ ‬though equally possible that other generas had their own specific variations of colour and pattern,‭ ‬though the countershading principle of dark on top and light underneath is common in nature.
       There are many compsognathid genera that lack evidence of feathers,‭ ‬though it would be foolhardy to insist that these genera had none at all,‭ ‬especially without hard fossil evidence to prove one or the other.‭ ‬As a group,‭ ‬there is growing evidence to suggest that compsognathid dinosaurs were mostly feathered,‭ ‬at least in some areas of the body.




What did compsognathid dinosaurs eat‭?
       Being towards the smaller end of the size spectrum compsognathids were probably exclusive hunters of small animals.‭ ‬Indeed,‭ ‬fossil remains of what seem to be partially eaten lizards have been found within what would have been the gut of some better preserved compsognathid individuals.‭ ‬Other possible prey animals for compsognathids could include small mammals,‭ ‬juveniles of other dinosaurs,‭ ‬and perhaps even larger invertebrates like insects.‭ ‬Compsognathids would have also certainly scavenged the bodies of dead animals,‭ ‬perhaps picking clean the kills leftover from larger dinosaurs.‭ ‬In some popular media compsognathid dinosaurs have been portrayed as pack hunters,‭ ‬though at the time of writing paleontological evidence for this idea is severely lacking for this‭ ‬specific‭ ‬dinosaur group.

When and where did compsognathid dinosaurs live‭?
       Compsognathid dinosaur fossils are most plentiful in late Jurassic to Early Cretaceous aged fossil deposits.‭ ‬As a group compsognathid dinosaurs are known from across the world,‭ ‬especially China and Europe,‭ ‬but also North and South America.‭ ‬It seems reasonable that when seen as a group,‭ ‬compsognathid dinosaurs may have had a global distribution.
       The Chinese and European fossils deposits where compsognathid dinosaur fossils are often found seem to have been densely forested areas during the Mesozoic,‭ ‬suggesting that compsognathids were more at home amongst the trees and dense undergrowth.‭ ‬This would make sense given that the generally small size of compsognathids would allow them to move and hunt amongst the dense forest growth mostly unhindered,‭ ‬while remaining quite well hidden from anything that might be interested in hunting them.
       It is of course not impossible that some genera may have adapted to live in different environments.‭ ‬After all,‭ ‬in the world of palaeontology it only takes one fossil discovery to turn accepted thinking upside down on its head.




List of some compsognathid dinosaur genera
Note‭* ‬This list should not be considered complete,‭ ‬and may contain dinosaur genera with a disputed placement within the Compsognathidae.

Aniksosaurus‭?
Aristosuchus
Beipiaognathus
Calamosaurus‭?
Compsognathus
Huaxiagnathus
Juravenator‭?

Mirischia
Sinocalliopteryx
Sinosauropteryx
Scipionyx‭?
Tugulusaurus
Ubirajara
Xunmenglong

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