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.
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