Jeholornis
Name:
Jeholornis
(Jehol bird).
Phonetic: Je-hol-or-niss.
Named By: Z. Zhou & F. Zhang -
2002.
Synonyms: Shenzhouraptor.
Classification: Chordata, Aves,
Jeholornithiformes, Jeholornithidae.
Species: J. prima (type), J.
curvipes, J.
palmapenis.
Diet: Herbivore.
Size: Up to 80 centimetres long.
Known locations: China, Hebei Province -
Jiufotang Formation, Liaoning Province - Yixian Formation.
Time period: Aptian of the Cretaceous.
Fossil representation: Few individuals.
Jeholornis
was a primitive bird that is known from both the Hebei and Liaoning
provinces of China where individuals of the genus lived during the
early cretaceous. At eighty centimetres long from the tip of the
snout to the tip of the tail, Jeholornis was
quite a large bird for
the time. An additional bird genus named Shenzhouraptor
is now
regarded as
synonyms to Jeholornis. There has been previous
dispute over whether
Shenzhouraptor should have priority over Jeholornis
since they were
both named so closely together with Shenzhouraptor
appearing in a
monthly journal and Jeholornis in a weekly one,
but Jeholornis is
usually treated as valid since in these circumstances weekly journals
are seen to have technical priority.
Jeholornis
was similar to genera such as Epidexipteryx
and Incisivosaurus
since
those individuals also had short but high skulls. The jaws curved
downwards and depending upon the fossil specimen, show a greatly
reduced amount of teeth. The holotype specimen only possessed three
pairs of reduced blunt teeth in the lower jaw, while another suggests
no teeth at all. These were likely feeding adaptations that allowed
Jeholornis to pluck up and swallow seeds,
something that can be
supported by the discovery of around fifty, eight to ten millimetre
seeds believed to be from the plant genus Carpolithes
inside what was
once the crop of a Jeholornis.
Jeholornis
had better developed wings than earlier bird forms such as
Archaeopteryx,
though they were still not as well adapted for true
flapping flight as the wings of modern birds are. The wings were
still longer than the legs, and the feathers were asymmetrical
similar to modern birds. Like with many primitive forms, gliding
flight would have certainly been possible for Jeholornis,
but it is
still unknown if it could use flapping flight since the arrangement of
the shoulders would have still had a limited range of motion hindering
a flight stroke where the wings passed above the back.
Jeholornis
still lacked a pygostyle and instead had a long more dinosaur-like
tail. This feature would not have made flight impossible, but it
would not have been as good as a pygostyle that supported the growth of
flight feathers from the tail. Analysis of the bones of Jeholornis
also indicate that individuals grew very slowly, another primitive
trait shared with other early bird forms, though as the Cretaceous
period went on birds would develop to become very fast growing animals.
One
of the key important things about Jeholornis is
that the hallux
(first toe) is partially reversed meaning that it was semi
opposable. In modern birds the hallux is completely opposable to the
other toes so that a bird can grip hold of branches, in a similar
manner to how you can hold onto railings by wrapping your thumb and
fingers around them. Jeholornis would not have
been as capable of
this as modern birds, but again more primitive forms such as
Archaeopteryx lacked an opposable hallux all
together and could not
perch like modern birds at all. Therefore the hallux of Jeholornis
shows the continuing transition to the modern bird form, helping to
fill in another gap in the evolutionary theory of dinosaurs to birds.
Further reading
- A long-tailed, seed-eating bird from the Early Cretaceous of
China. - Z. Zhou & F. Zhang - 2002.
- A new species of Jeholornis with complete
caudal integument. -
Jingmai K. O'Connor, Chengkai Sun, Xing Xu, Xiaolin Wang and
Zhonghe Zhou - 2012.
- Jeholornis compared to Archaeopteryx,
with a new understanding of
the earliest avian evolution. - Z. -H. Zhou & F. -C
Zhang - 2003.
- P. Senter - Scapular orientation in theropods and basal
birds, and the origin of flapping flight - 2006.
- Reconstructing the habits of Jeholornis prima.
- Z. Li
& Y. Zhang - 2008.
- A new specimen of a Jeholornis-like long-tailed
bird shows that
Jixiangornis is a junior synonym of Jeholornis
prima. - X. Wang,
G. Dyke & P. Godefroit - 2012.
- A new long-tailed basal bird from the Lower Cretaceous of
north-eastern China. - Biological Journal of the Linnean Society
113:790-804. - U. Lefevre, D. Hu, F. Escuillie, G. Dyke & P.
Godefroit - 2014.
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