Beipiaosaurus inexpectus harassed by a band of indeterminate dromaeosaurs, with Caudipteryx, Sinosauropteryx and Confuciusornis in the foreground.
We owe to China, Ji Quang, Phil Currie and Mark Norell (amongst other paleontologists) for the definitive hard evidence that we needed to culminate the radical change and review of the anatomy, lifestyle and evolutionary relationships of dinosaurs that started with John Ostrom back in the sixties.
The artwork presented here shows a summary of the different stages of avian evolution. Not all the animals were contemporary so I used artistic license to recreate an allegorical landscape that would depict the full circle of theropod evolution.
It reconstructs fot the first time mid-size therinosaurs: Beipiaosaurus inexpectus(see Asian Dinosauria for an alternative view of gigantic therizinosaurs) covered in the bristle (protofeathery?) insulation based on a recently discovered Chinese specimen described in a long-awaited paper by Xing Xu, Zhi-lu Tang and Xiao-lin Wang and published in the journal Nature on the 27th of May 1999 (No 6734).
The combination of the typical Therizinosaur anatomy and the bristle covering give us a radical new view of this controversial animal: a cross between a strange goose and extinct ground sloths. It pays tribute to the foresight of Dale Russell, who was the first in speculating the mammal convergence features in these dinosaurs.
Greg Paul described Therizinosaurs as the 'Sumo-dinosaurs' (because of the enormous and conspicuous bellies). It inspired me to reconstruct them with well armoured bellies so they would be less vulnerable to killer claws and teeth.
The discovery of Caudipteryx, with its arms and tail display fans of non flight feathers, incredibly short tail and peg-like teeth represented the ultimate realisation of Ostrom's dream, and Greg Paul's heretic feathered dinosaurs.
Feathered and insulated dinosaurs are no more a matter of speculation, and the Chinese discoveries shed light to clarify the intricate patterns of advanced avian evolution. Fully clawed but short tailed, beaked and toothless Confuciusornis is a good example with its mosaic of advanced and primitive features and its typical avian sexual dimorphism. The perfectly preserved fossil 'males' sport a dramatically long set of tail feathers as a display.
For more details on Sinosauropteryx see the page devoted to it in this Website.
Philip Currie backs the ground-up theories on the origin of flight. Luis Chiappe, Kevin Padian and Jacques Gauthier have been adamantly favouring the same theory for a long time... they see flight as a byproduct of the predatorial stroke from ancient dromaeosaurs that were already insulated and developed flight feathers. And they feel that all the hard evidence available at the moment and cladistic analyses agrees with them.
Others like Sankar Chattarjee, believe that some primitive dromaeosaurs took to the trees and became volant forms... and George Olshevsky who sees Caudipteryx and Protarchaeopteryx as secondarily flightless... just as the rest of the dinosaurs, who descended from arboreal forms in different stages of evolution.
What all of them (and the majority of paleontologists) agree now is that all of these animals are part of the clade known as the Dinosauria and are branches and twigs of the complicated evolutionary that gave rise to what we know as the modern Avian clade. Aves are simply the last surviving branch that has kept diversifying into a myriad of species, far back in time. Now even a fossil parrot has been found in Cretaceous sediments!
I have been advocating for a long time the old proposal to reconsider Dinosauria as a class, with Aves as a subclass. A bird can always be recognised as a bird... but a Sauropod, a Ceratopsian and a bird seem incongruous as close relatives... and yet, they are all Dinosauria.
The enormous variety of species that we consider dinosaurs merits this review.
With each new discovery, the depiction of dinosaurs is changing every minute. It is clear that we know very little about the external appearance of dinosaurs and some familiar-looking creatures may turn out to be more exotic and strange than we ever thought.
Quoting my expert friend Cristiano Dal Sasso** at the Society of Vertebrate Paleontology meeting this year: "We are barely starting to know dinosaurs... and there are too many surprises still waiting to be discovered..."
So... as Angela Milner would say "Watch this space!"
** Paleontologist at the Natural History Museum of Milan and original researcher and describer of Scipionyx samniticus, the perfectly preserved (guts and all) little Italian maniraptoran dinosaur.
Near background From left to right:
1.- A pair of Psittacosaurus (Ornithischia): Beaked, primitive relative
of ceratopsians. A new psittacosaur specimen from the Yixian formation
has been described in Germany. It's been found with preserved external
integument . This is so far the first ornithischian with what seems
unequivocally dermal long quill-like structures lining up a good part of
the top of the tail. The quills (90 to 100 in this specimen) were 1 to 2
mm thick and possibly hollow, some of them reaching nearly 20 or 30 cm
long and look well flexible, falling over the tail like a fountain. The
rest of the skin is naked and covered with typical ceratopsian scaly skin
( a mosaic of larger non-overlapping round scutes surrounded by many small
ones). This time there were not feathers or protofeathers as in the well
known theropods, but I'm not discounting that one day we'll see furry
ornithischian juveniles since the adults had these tail quills! For me
this shows that quill-like skin structures were probably endemic (as a
way of insulation) in all groups of dinosaurs and a main characteristic of
the Dinosauria. The muscle and fat are preserved in a carbonized layer
surrounding the whole body (a fact that makes the fossil look remarkably
similar to any mammal from the Messel deposits in Germany 50 million
years later) showing precisely how muscle and other soft tissues were
preserved in the Yixiang deposits (contra Ruben et al) and further
demonstrating that accusing theropod feathers or skin structures of being
traces of dried muscular tissue (collagen fibers) is baloney. The
silhouetted carcass shows that the animal might have been somewhat stocky.
Other psittacosaur specimens with gut contents (including bones and
stones) have been found giving credence to the idea that indeed
psittacosaurs were probably 'fat porcupine mimics'. We may also like to
speculate that the quills were venomous as a way of defence. But we may
never know. There's still a lot of work to be done to help us have a
completely accurate picture of this new landmark discovery and further
investigation may change our view of it in the future.
2.- A couple of displaying "BPM 1 3-13" (Cryptovolans) newly described by Mark Norell and still unnamed dromaeosaur specimen that looks very much like Microraptor. What is striking about these new ones is that the tip of the tail feathers are up to 20 cm long, adding extraordinary length to a tail that was already long. I depicted them here as rather ornamental, spectacular display structures but their usefulness is anybody's guess. They may also have served as rudders for balancing the short body and long limbs when on top of the trees as they jump from branch to branch .
The(corrected) Chinese Revolution Part 2.
With the discovery of perfectly preserved specimens of Microraptor
gui and its long metatarsal feathers, a reappraisal of the genus Cryptovolans was very much needed.
The evidence was there from the start (seeing now the fossil it's even clearer): Cryptovolans clearly did show those tarsal feathers from the very beginning and may be nothing more than just another version of Microraptor!
I
personally think that Microraptor and Cryptovolans are one and the
same(skeletal differences are minimal). Accordingly, I have corrected and added
the spectacular fans of leg feathers to the two displaying animals on background (right), giving them also a different dimension:
Feathers not just for flight, but (very importantly) for display too.
Far background:
A couple of Beipiaosaurus feed from some trees while a plethora of birds
and pterosaurs dominate the skies of the nearby lagoon.
Foreground (right side): a couple of Sinosauropteryx approach the scene.
Extreme Foreground:
Two male Confuciusornis sanctus in full display.
The picture of bird evolution that is coming our of the Yixian today is
extremely complex. Confuciusornis was beaked and toothless and had rather
typical small bird body with an avian pygostile (males had two long
feathers attached to it) but powerful arm-wings that show fully functional three clawed fingers with little sign of becoming a fully digit-fused
modern avian wing. But recently, new specimens of birds -like the
recently described Jeholornis that were contemporaries of Confuciusornis-
show that other groups were instead still toothed and with long bony
tails, but the forelimbs and hand bones started showing signs of fusion on
a trend to become a more advanced, typical bird wing,. Much more than
Confuciusornis' wing itself but keeping a more 'primitive' lower part of
the body and head! The contemporary picture of bird evolution is still
hotly debated. Investigating what group of birds is the one that gave rise
to all the contemporary descendants we know today is becoming a complex
puzzle... an amazing mosaic of evolution possibilities still to be
clarified.
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EPIDENDROSAURUS(=SCANSORIOPTERYX, foreground) AND A NEW RECONSTRUCTION OF
MICRORAPTOR.
Acrylics and inks on cardboard.
Click on the picture to see 2 closeups!
The series of paintings called "New Chinese Revolution" were intended to
follow up closely the enormous variety of dinosaur discoveries coming
from the Yixian deposits in the Liaoning Province (China) expecting that
there will always be new discoveries around the corner. And we haven't
been disappointed. This new instalment is dedicated exclusively to the
hypothetical dinosaur life high in the trees. Precious little is known
about arboreal dinosaurs. Even if the probability of their arboreality
has always remained more than an educated possibility, fully
convincing hard evidence has been lacking for a very long time... That
finally had to change with the discovery of animals like Epidendrosaurs
(=Scansoriopteryx) a tiny, fully feathered theropod hatchling with
apparent prehensile feet and opposable hallux, but with a difference: The
third hand digit is almost twice the size of the second digit giving it a
strange (almost pterosaurian!) look. An animal with such a specialised digit
most probably represents the first hard evidence of dinosaur arborealism.
It is difficult to think of a terrestrial animal with such enormous,
specialised hands. I have depicted a couple of Epidendrosaurus (adults)
here using their hypertrophied, specialised third digit for spearing grubs
like a modern Aye-aye lemur. Some primitive characteristics of the
skeleton (including a pelvis even more primitive than Archaeopteryx)
are probably due to the fact that the fossil is a hatchling.
In the background, a troupe of Microraptors jump and glide from branch to
branch using their "four wings" as battering parachutes. The long feathers
lined around the arms and the whole of the leg probably acted in a
similar way as the rigid tufts of matted hair around the body of the
modern lemur Propithecus (as reported in Feduccia 93) that helped the
animal "glide" and to withstand the falls, while keeping strong legs,
fully cursorial locomotor faculties and bipedalism. Is this the origin of
the kind of flight we see today in modern birds? It seems more feasible
than an exclusively cursorial ground-up theory... and the hard evidence
seems to back up this theory (as recently presented in Ken Dial's video
shown as part the itinerant "Feathered Dinosaurs" exhibition of how
birds "run-up" trees instead "flying up" them, see more details in the
article "A reappraisal of possible scenarios for dinosaur and bird
evolution" in this website). Incredibly as it seems the theories of how
flight and birds evolved have gone full circle: Now we have the famous
"Proavis" as envisioned by Gerhard Heilmann in 1927... only not in the same
way. Heilmann's "Proavis" has become a sort of prophecy in its time of
what we know now as just another dromaeosaurid dinosaur.
Click on image to see more detail! (There are 3 areas within this picture.)
Foreground: A nesting Caudipteryx being harassed by several Jixiangornis (newly discovered long tailed birds) Middle ground: A flamboyant, multicoloured Jeholornis gets a
mild warning from a lazy, nesting Psittacosaurus. Jeholornis is
notable for having a long bony tail while the wing digits -even if two
of them are clawed- are showing signs of fusion.
Far background: a flock of Microraptor gui in four-winged flight
motion.
The latest installment of the Chinese saga. If there’s a perfect
picture of evolution in the works it must be the ancient Yixian deposits.
Every possible (no matter how outlandish) stage in dinosaur flight development
can be documented. And much more is still to come.
while a Sinosauropteryx tries to get
to the eggs.
I studied the possibilities of how this animal could (or if) have really
flown and opted for the ‘biplane’ theory instead of full flapping flight
using both forelimbs and backlimbs. The leg flight feathers were
spread but held at a different plane from the battering arm wings.
Probably not a sophisticated flyer, it must have had clumsy flight
capabilities but would have been a spectacular sight nevertheless. I don't think
Microraptor was necessarily an ancestor of any known birds... it
was just yet another dead end: One of many evolutionary trials on how to
fly. An evolutionary triumph that didn't last until our days, but a triumph
nevertheless.
