Paleontologists
have discovered an 11th Archaeopteryx fossil. The 150-million-year-old dinosaur
bones are the oldest yet to be attributed to the transitionary genus.
The
discovery -- detailed this week in the journal PeerJ -- could help scientists
more easily differentiate between the group of bird-like dinosaurs and their
closest relatives.
The fossil
was found in ancient rock in the Altmühl River valley of Northern Bavaria. The
strata from which the latest specimen was excavated represents the Late or Upper
Jurassic epoch.
"Specimens
of Archaeopteryx are now known from three distinct rock units, which together
cover a period of approximately 1 million years," Oliver Rauhut, a
professor and paleontologist at Ludwig-Maximilian University of Munich, said in
a news release.
The
Archaeopteryx genus describes a group of dinosaurs that bridged the
evolutionary gap between feathered dinosaurs and modern birds. The newest
discovery boats several unique features, further expanding the diversity of an
already varied group.
"Among
other things, they reveal that Archaeopteryx was very similar to advanced
predatory dinosaurs in many respects," Rauhut said.
Differentiating
between the transitionary genus and its closest relatives, non-avialan theropod
dinosaurs and basal birds, remains difficult. But scientists believe their
analysis of the 11th Archaeopteryx specimen offers a more definitive way to
identify members of the genus.
In taking
stock of the attributes that define the Archaeopteryx genus, scientists realized
the first-ever Archaeopteryx fossil, the Haarlem specimen, discovered in 1861,
does not really belong to the group.
Though
scientists may now have an easier team identifying Archaeopteryx members, the
genus remains an unusually varied collection. Some scientists suggest the
diversity is a result of intraspecific developmental polymorphism, variety
within each species. Others suggest the varied nature of the group is a product
of evolutionary experimentation.
"The
high degree of variation in the teeth is particularly striking -- none of the
specimens shows the same pattern of dentition as any other, which could reflect
differences in diet," Rauhut said. "This is very reminiscent of the
famous case of Darwin's finks on the Galapagos, which show remarkable variation
in their beak shapes."
Some
scientists believe these transitionary bird-like dinosaur species may have even
evolved their unique attributes on a variety of islands.
"In
that case, the Archaeopteryx fossils could represent a species flock, a Jurassic
analog of Darwin's finches," Rauhut said.
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