The 'missing link' which proves the
relationship among dinosaurs and birds may have been found.
It is a widely-held view that dinosaurs and
birds share the same heritage, and an egg exposed in the Montsec area of
Lleida, near Catalonia in Eastern Spain, shares individuality of both species.
The dinosaur egg, dating back 70 to 83
million years, has an oval shape, similar in exterior to a chicken egg, and an
'air bag' inside which birds today use to respire in the last stages of its growth.
The new type of dinosaur egg has been given
the technical name of Sankofa pyrenaica and is the only dinosaur egg in the
world to have an oval shape, alike to that of chicken eggs.
Nieves López Martínez, palaeontologist of
the Complutense University of Madrid, was working on investigate of dinosaur
eggs before her death in December 2010.
Together with Enric Vicens, palaeontologist
of the Universitat Autònoma de Barcelona, the two scientists conducted a thorough
analysis of their detection, now published in the journal Palaeontology.
The South Pyrenean area is rich in dinosaur
egg sites, most of which communicate to sauropod eggs from the upper
Cretaceous, dating back more than 70 million years ago.
During that period, the area was a coastal
area full of beaches and deltas which won land from the sea through residue buildup.
Sand and mud from that period gave way,
millions of years later, to the stonework and marl where dinosaur leftovers now
can be found. On the seashore ridges and flat coastal lands is where a large
group of dinosaurs laid their eggs.
The sites anywhere the discoveries were
made correspond to the upper Cretaceous, between the Campanian and
Maastrichtian periods, some 70 to 83 million years ago.
The fossils found belong to small eggs
measuring some 7 centimeters tall and 4 cm wide, while the eggshell was on standard
0.27mm thick.
Most of the eggs found were broken in small
wreckage, but scientists also discovered more or less complete eggs, which can
be easily deliberate in sections.
The eggs found at the sites all belong to
the same species. The main difference when compare to other eggs from the same
period is their irregular shape, similar to that of chicken eggs.