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Embrio reptil tertua yang pernah ditemukan

kembali 280 juta tahun atau lebih , .... fosil tertua diketahui embrio reptil telah digali di Uruguay dan Brasil . Mereka termasuk reptil air kuno , mesosaurs . Studi tentang fosil ini sangat terawat baik menunjukkan bahwa mesosaurs entah vivipar ( mendorong kembali mode reproduksi ini oleh 60 juta tahun ) atau bahwa mereka meletakkan telur dalam stadium lanjut pengembangan ...........read more.

Oldest-ever reptile embryos unearthed

Date:

April 11, 2012

Source:

CNRS (Délégation Paris Michel-Ange)

Summary:

Dating back 280 million years or so, the oldest known fossil reptile
embryos have been unearthed in Uruguay and Brazil. They belong to the ancient
aquatic reptiles, mesosaurs. The study of these exceptionally well-preserved
fossils suggests that mesosaurs were either viviparous (pushing back this mode
of reproduction by 60 million years) or that they laid eggs in advanced stages
of development.

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Dating back 280
million years or so, the oldest known fossil reptile embryos have been
unearthed in Uruguay and Brazil. They belong to the ancient aquatic reptiles,
mesosaurs. The study of these exceptionally well-preserved fossils suggests
that mesosaurs were either viviparous[1] (pushing back this mode of
reproduction by 60 million years) or that they laid eggs in advanced stages of
development.

These finds, published in the journal Historical Biology,
were revealed by an international team including Michel Laurin, CNRS senior
researcher at the Centre de Recherche sur la Paléobiodiversité et les
Paléoenvironnements (CNRS/Museum national d’histoire naturelle/UPMC).



Although the oldest known adult amniote[2] fossils date back some 315 million
years, very few collections of fossil eggs and embryos are available to
paleontologists. The discovery by an international team including Michel
Laurin, from the Centre de Recherche sur la Paléobiodiversité et les
Paléoenvironnements (CNRS/Museum national d’histoire naturelle/UPMC), of
fossilized embryos of mesosaurs, ancient aquatic reptiles that lived ca. 280
million years ago, sheds light on these animals' reproductive mechanism. 
 

In Brazil, the team uncovered a fossil specimen in gestation, which
revealed that mesosaur embryos were retained in the uterus during most of their
development. These reptiles, therefore, were probably viviparous1.

In addition, the same researchers unearthed 26 adult mesosaur specimens in
Uruguay, all of which were associated with embryos or very young individuals,
dating from the same period as the Brazilian fossil.  Although these more
or less disarticulated specimens are difficult to interpret, most of them are
probably embryos in the uterus, thus backing up the hypothesis that mesosaurs
were viviparous. The largest of these fossils may be young animals that were
looked after by at least one of the parents, pointing to the existence of
parental care. However, one isolated mesosaur egg (see photograph below)
was also found at the Uruguayan site. This find casts doubt on the hypothesis
of viviparity (which, in theory, excludes the laying of eggs). It suggests that
the Uruguay mesosaurs laid eggs at an advanced stage of development, which then
hatched shortly afterwards (several minutes to days later).

This research therefore reveals the oldest known fossil amniote embryos
from the Paleozoic (543 to 250 million years BP) and the first examples of
embryo retention (and perhaps viviparity), pushing back this reproductive
mechanism by some 60 million years. But do the reproductive characteristics of
mesosaurs highlighted in this study reflect their aquatic way of life (since
viviparity is frequent in aquatic reptiles), or was it rather a fairly
widespread condition among early reptiles?

Notes:

(1) : Animals that keep their embryos inside their bodies and give birth to
their offspring.

(2) : Amniotes are vertebrates whose embryo is surrounded by a membrane
called the amniotic membrane: they include mammals and reptiles







Story Source:

The above story is based on materials provided
by CNRS (Délégation Paris Michel-Ange). Note:
Materials may be edited for content and length.







Journal Reference:

1.   
Graciela Piñeiro, Jorge Ferigolo, Melitta Meneghel, Michel Laurin. The
oldest known amniotic embryos suggest viviparity in mesosaurs. Historical
Biology, 2012; 1 DOI:10.1080/08912963.2012.662230

 sumber

http://www.sciencedaily.com/releases/2012/04/120411120356.htm

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