Sauropods in Argentina kept their eggs warm near geothermal vents

Jun 30, 2010 by Lin Edwards report
(a) A 21 cm egg exposed at SGP. (b) Spatial arrangement of a complete egg clutch implying dug-out holes as 'nests'. (c) A complete egg with typical fractured eggshell. (d) Typical variation of the eggshell thickness in a single egg; (e) SEM image of outer surface of eggshells with nodes and pore apertures. (f) SEM image of radial view of eggshells. Note the spongy appearance, an adaptation to extremely wet environments. (g) Rombohedric acicular calcite crystals with vesicles. (h, i) Transmitted light microscopic views of radial section of an eggshell. Yellow arrows point to the microspar diagenetic calcite, the red arrows to the diagenetic chalcedonic crystals. Image: Nature, doi:10.1038/ncomms1031.

(PhysOrg.com) -- Researchers working in Argentina have found 100-million-year-old neosauropod nesting sites in which clutches of eggs were kept warm by geothermal vents.

Paleontologists from the US and Argentina found the nesting grounds in the Sanagasta Valley in La Rioja Province in northwest Argentina. The nesting sites are the first to show definitively that some neosauropod had specific nesting grounds they returned to year after year, as many do today.

The researchers working in the field last summer were Gerald Grellet-Tinner from the Field Museum in Chicago, US, and doctoral student Lucas Fiorelli, from the Regional Research Center for Scientific Investigation and Technology Transfer (CRILAR) in La Rioja, Argentina. They discovered about 80 clutches of eggs at Sanagasta, all within three meters of . The nests usually contained from 3 to 12 eggs, but some spread wide, with up to 35 eggs stacked in two rows over an area of up to 1.8 square meters. The stacking indicates the clutches were buried in dug-out holes rather than on the surface.

The site is the first Cretaceous site where neosauropod dinosaurs have been shown to have used the and thermoradiance to incubate their eggs. It lies within the Sanagasta Geologic Park, an area of 300,000 square meters characterized by hydrothermal mega structures of alkaline fountain geysers, hydrothermal pipes, druses and vents.

The eggs measured up to 21 centimeters in diameter, and had variable shell thickness ranging from 1.29 to 7.94 millimeters, which implies the shells became thinner during the incubation period. The thick shells of newly laid eggs may have been gradually leached away by the acidic environment near the geothermic vents, making the shells thinner at the end of incubation and easier for the babies to break through. Most of the eggs were in fragments that intricately fit together.

A geochemical analysis of the fossilized eggs yielded an estimation of the of one to two months at temperatures of 60-100°C. The researchers said the elements found in the sediments and eggshells matched those present around 134-110 million years ago in a period known as the Gondwanic hydrothermic cycle, an era characterized by geothermal venting.

So far the researchers have not discovered any fossilized bones or embryos, which would enable them to identify the egg-layers conclusively. The most common herbivorous animals in South America in the Cretaceous period were the sauropods.

The endangered megapode turkey (Megapodius prichardii) in Tonga has a similar nesting behavior today, laying its in burrows volcanically heated burrows.

The paper is available online in the Nature Communications journal.

Explore further: New branch added to European family tree

More information: A new Argentinean nesting site showing neosauropod dinosaur reproduction in a Cretaceous hydrothermal environment, Nature Communications, Volume: 1 ,Article number: 32, DOI: doi:10.1038/ncomms1031

Related Stories

Hundreds of dinosaur nests found in India

Oct 02, 2009

(PhysOrg.com) -- Geologists have discovered hundreds of fossilized nests each containing clutches of eight dinosaur eggs. The eggs were located in sand banks in Tamil Nadu in Southern India.

How birds spot the cuckoo in the nest

Jul 15, 2008

It's not always easy spotting the cuckoo in the nest. But if you don't, you pay a high price raising someone else's chick. How hosts distinguish impostor eggs from their own has long puzzled scientists.

Cuckoo chicks in Zebra finches

Apr 22, 2010

(PhysOrg.com) -- Some female zebra finches foist a part of their eggs on their neighbours. Scientists of the Max Planck Institute for Ornithology in Seewiesen discovered that in every fifth nest there is one ...

Why solitary reptiles lay eggs in communal nests

Sep 03, 2009

Reptiles are not known to be the most social of creatures. But when it comes to laying eggs, female reptiles can be remarkably communal, often laying their eggs in the nests of other females. New research in the September ...

It's a record summer for some turtles

Aug 21, 2006

Italian scientists say an endangered species of marine turtle -- loggerhead turtles -- are appearing along Italy's southern shores in increasing numbers.

Endangered turtles make a comeback

May 14, 2006

Kemp's ridley sea turtles almost became extinct, but 50 nestings have been recorded in Texas and more than 4,000 eggs recovered for incubation this year.

Recommended for you

New branch added to European family tree

Sep 17, 2014

The setting: Europe, about 7,500 years ago. Agriculture was sweeping in from the Near East, bringing early farmers into contact with hunter-gatherers who had already been living in Europe for tens of thousands ...

'Hidden Treasure of Rome' project unveiled

Sep 16, 2014

For more than a century, hundreds of thousands of historical artifacts dating back to before the founding of Rome have been stored in crates in the Capitoline Museums of Rome, where they have remained mostly untouched. Now, ...

NOAA team reveals forgotten ghost ships off Golden Gate

Sep 16, 2014

A team of NOAA researchers today confirmed the discovery just outside San Francisco's Golden Gate strait of the 1910 shipwreck SS Selja and an unidentified early steam tugboat wreck tagged the "mystery wreck." ...

User comments : 0