Scansoriopteryx
Name:
Scansoriopteryx
(Climbing wing).
Phonetic: Scan-sor-e-op-the-riks.
Named By: S. A. Czerkas & C. Yuan
- 2002.
Synonyms: Epidendrosaurus ninchengensis.
Classification: Chordata, Reptilia, Dinosauria,
Saurischia, Theropoda, Paraves, Scansoriopterygidae.
Species: S. heilmanni
(type).
Diet: Insectivore?
Size: Holotype about 13.5 centimetres long.
Second specimen (formerly Epidendrosaurus)
about 16.2
centimetres long. Both specimens are of juveniles, true adult size
is still unknown.
Known locations: China - Tiaojishan Formation
(Precise discovery site of holotype is unknown).
Time period: Most probably Mid to Late Jurassic
(refer to main text).
Fossil representation: Two individuals known from
partial remains, both juveniles.
If there has ever been a genus that has been a serious source of confusion for people, it’s Scansoriopteryx. We’ll start with the correct name for this genus regarding whether it should be Scansoriopteryx or Epidendrosaurus. We are certain that both of these genera are one and the same and therefore synonymous. However, both were named in 2002, very close to one another, but in different ways. Epidendrosaurus was named first, but the name was published online. Scansoriopteryx was second but named in a more traditional sense of an actual printed publication. Normally the first name to be established should have priority, however at this time the ICZN, the body that governs the naming of animals, did not recognise online sources, and therefore sided with Scansoriopteryx as the valid genus since that one fulfilled the parameters then set for establishing a scientific binomial name.
This
triggered a debate amongst publishers, the internet and publication
of journals online instead of hard copy printing was the future and
today you can almost always buy a paper in either printed or
downloadable format. Indeed in 2004 J. D. Harris proposed an
amendment to the rules governing the naming of animals. However
because at the time the ICZN did not have online sources as valid,
Scansoriopteryx continues to be held up as valid by
most researchers,
though a small number continue to insist upon keeping Epidendrosaurus
as the valid name., and Scansoriopteryx as a
synonym.
One
problem regarding the study of Scansoriopteryx is
that we are still not
very confident about how old the genus is. The Holotype specimen was
bought from a fossil collector who didn’t keep a record of where it had
come from, and age estimates ranged from late Jurassic to early
Cretaceous, with the original describers citing the Yixian Fomration
as the probable source. The former Epidendrosaurus
specimen was a bit
better in that it was known to have come from the Daohugou Beds,
however, at the time the exact age of the Daohugou Beds was
unknown, though today it is thought to be part of the Tiaojishan
Formation which runs from the mid to late Jurassic.
When
first named by Czerkas and Yuan in 2002, Scansoriopteryx
was
described as a tree climbing maniraptoran dinosaur. However,
Scansoriopteryx does display a few features
previously unseen or rare
in dinosaurs. Firstly the third finger of the hand is more than
double the length of the second finger, the one that it usually the
longest. The lower jaw bones may have been fused together,
something only known in oviraptosaurs.
Additionally Scansoriopteryx
had a non-perforated hip socket that was more open than most other
dinosaurs. Scansoriopteryx did have small downy
feathers over its
body, and larger feathers.
In
2014 Stephen Czerkas and Alan Feduccia published a new paper on
Scansoriopteryx regarding how it fitted in with the
origin of birds.
Feduccia is well none for his support of the alternate theory that
birds are not descended from dinosaurs but rather from tree climbing
archosaurs. This paper highlights the features not commonly seen in
dinosaurs as well as a forward facing pubis which they took as a very
primitive feature. The theory about Scansoriopteryx
being a
non-dinosaurian archosaur and ancestor of birds does not end there
though, but what are currently classed as maniraptoran dinosaurs
would actually be descended from birds and not actual dinosaurs at all.
Already
this theory has proven controversial, and the 2014 study has also
not been widely accepted, either by palaeontologists or by numerous
writers on internet blogs. If the discoveries of the early
twenty-first century have shown us anything then the appearance of
birds is most likely housed within the dinosaurs, but the actual
appearance of birds is also murky. To begin with, where do you draw
line between what is a dinosaur and what is a bird? The opinion
varies, with dozens of possible interpretations, and discoveries
now show us that while some forms went forward, some took a step
back, while others went down evolutionary dead ends.
As
far as Scansoriopteryx is concerned it is in a bit
of a grey area,
but most consider it to still be a dinosaur. Scansoriopteryx
is now
also the type genus of its own though small group called the
Scansoriopterygidae. Currently the only other
members of this group
are Epidexipteryx
and Yi.
As far as being a living breathing animal
is concerned, Scansoriopteryx was almost
certainly an arboreal tree
climber. The long fingers as well as the extended third finger would
have been a significant benefit in reaching around tree trunks and
branches and climbing along them. There has also been past
speculation that the long fingers may have been used to dig out grubs
that were hidden within crevices and under bark on the trunk.
Scansoriopteryx had no backwards facing toe on the
foot, but is
thought to have still had a limited perching ability.
The
exact feather covering on Scansoriopteryx is
unknown, in part due to
incomplete remains on some parts of the body, but also since the only
known specimens are juvenile, adults might have had a different
and/or more developed plumage. While downy feathers did cover the
body, larger feathers seem to have been present upon the arms.
While powered flight is unlikely given that there was no deep keel on
the breast bone (am attachment point for flapping wing muscles),
Scansoriopteryx may have still been able to glide
for short
distances. Pebbly scale impressions are known from the feet
suggesting that these probably didn’t have any feathers.
Small
fossilised eggs discovered in Thailand are now no longer thought to be
from Scansoriopteryx.
Further reading
- An arboreal maniraptoran from northeastern China. Feathered
Dinosaurs and the Origin of Flight. The Dinosaur Museum Journal 1.
- The Dinosaur Museum, Blanding, UT 63-95. - S. A.
Czerkas & C. Yuan - 2002.
- A juvenile coelurosaurian theropod from China indicates arboreal
habits. - Naturwissenschaften 89(9):394-398. - F. Zhang,
Z. Zhou, X. Xu & X. Wang - 2002.
- Are current critiques of the theropod origin of birds science?
Rebuttal to Feduccia (2002). - The Auk, 120(2),
550-561. R. O. Prum - 2003.
- Jurassic archosaur is a non-dinosaurian bird. - Journal of
Ornithology, 1-11. - S. A. Czerkas & A. Feduccia
- 2014.
- ‘Published works' in the Electronic Age: recommended amendments
to Articles 8 and 9 of the Code. - Bulletin of Zoological
Nomenclature 61(3): 138-148. - J. D. Harris - 2004.
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