Stories tagged Madagascar

Dec
02
2011

Rapetosaurus krausi: The Cretaceous titanosaur is dwarfed by the massive leg bones of its larger Jurassic cousin Apatosaurus. Field Museum of Natural History.
Rapetosaurus krausi: The Cretaceous titanosaur is dwarfed by the massive leg bones of its larger Jurassic cousin Apatosaurus. Field Museum of Natural History.Courtesy Mark Ryan
Paleontologist Kristina Curry Rogers, a former curator here at the Science Museum of Minnesota, has dedicated much of her career studying sauropod dinosaurs, their behaviors, and the histology of their bones. Sauropods are a diverse group of large, long-necked dinosaurs that include, among others, the popular Apatosaurus (Brontosaurus), Diplodocus, Barosaurus, and Brachiosaurus. The four-legged, herbivorous sauropods made their first appearance in the Late Triassic Period about 220 million years ago, then rose to prominence during the Late Jurassic, growing to 80 tons or more. The Jurassic giants gave way to the titanosaurs in the Cretaceous, a group that thrived until 65 million years ago when a major extinction event wiped out all the mega-fauna dinosaurs.

Osteoderms in a modern reptile: Bumps of bony armor seen embedded in the skin of a Gila Monster  (Heloderma sp.)
Osteoderms in a modern reptile: Bumps of bony armor seen embedded in the skin of a Gila Monster (Heloderma sp.)Courtesy Fritz Geller-Grimm via Wikipedia Creative Commons
Now an assistant professor at Macalester College in St. Paul, Curry Rogers' latest research centers on titanosaur osteoderms. Osteoderms are bony deposits embedded in the skin and used as defensive protection or for other functions such as temperature regulation. The bumpy armor can be seen today in alligators, crocodiles and many other reptilian forms (see photo). So far, titanosaurs are the only sauropod dinosaurs known to have had osteoderms.The smaller ornithopod dinosaurs such as ankylosaurs and stegosaurs used osteoderms to create bony exteriors to strengthen their hide against attack. On the predator side of the equation, the carnivore Ceratosaurus is the only theropod dinosaur found with osteoderms.

Curry Rogers has been studying the osteoderms of two titanosaur specimens (Rapetosaurus krausi), one from an adult and the other from an immature individual. Both specimens were found in the 1990s in the sandstones of the Maevarano Formation exposed on the northwest corner of the island of Madagascar. During the Late Cretaceous the climate in the region was seasonal with periods of rain and drought alternating with periods of semi-arid conditions.

Heads up: Rapetosaurus krausi stands before Charles R. Knight's classic rendition of its Jurassic ancestor, Apatosaurus
Heads up: Rapetosaurus krausi stands before Charles R. Knight's classic rendition of its Jurassic ancestor, ApatosaurusCourtesy Mark Ryan
That a 50-foot adult Rapetosaurus would even need osteoderms at first mystified the paleontologist. A full-grown Rapetosaurus was just too enormous to require body armor.

Using a CT scanner and core-sampling to analyze the two samples, Curry Rogers found that the juvenile osteoderm had a thick, dense outer lining on the outside and was filled with a spongy bone on the inside. The larger adult osteoderm - 22 inches in length and the largest ever found - appeared much the same from the outside but surprisingly the shell wasn’t as thick and the inside was almost completely hollow. Microscopic examination of the inside lining of the outer structure showed signs of it being resorbed into the body

The new data made the paleontologist wonder. Why would the osteoderms appear one way in an earlier life stage and change into another form in adulthood? Did their functions change as the titanosaurs passed through different stages of life?

Eventually the paleontologist came up with a hypothesis: the osteoderms were probably used as armor when the Rapetosaurus was small and still growing, and easy prey for predators. But as it neared adult size the osteoderms were no longer needed for protection and instead could have served as reservoirs for minerals, such as calcium and phosphorus. These would have been useful as the dinosaurs' size increased or when the adult titanosaurs needed extra minerals during times of environmental stress (like the frequent droughts occurring on Madagascar during the Late Cretaceous). Drawing minerals from its arm or leg bones would have weakened them making it difficult for the multi-ton animals to stand or walk. The mineral stores could also be used during reproduction when calcium was necessary for egg shell production.

Curry Rogers and her colleagues have published their findings in the online journal Nature Communications and can be downloaded here.

SOURCES and LINKS
Sauropod Dinosaur Osteoderms from the Late Cretaceous of Madagascar
Smithsonian’s Dinosaur Tracking "Inside Sauropod Armor
Star Tribune story
Macalester College news release

Another sad day for wildlife lovers as yet another one of the world’s beautiful creatures is declared extinct. The Alaotra grebe from Madagascar was added to a growing list of modern day extinctions of bird species, nearly 190 total out of the 10,000 bird species remaining in the world. I shudder to think how the threatened and endangered list will change with this terrible oil spill in the gulf.

Jun
10
2008

Melon-headed whale
Melon-headed whaleCourtesy Minerals Management Service

Fifty-five melon-headed whales, a species tropical dolphin, have beached themselves in Madagascar and died. This is the first time these creatures are known to have visited the island.

Whales and dolphin periodically strand themselves on beaches, individually or in groups. No one knows why. They sometimes get "lost," swimming far inland up rivers. We have discussed such incidents on Science Buzz before: here and here and also here.

Feb
28
2008

Huge frog: Fossilized remains have been found in Madagascar of the Devil Toad, a bowling-ball-sized frog that was likely capable of eating small, young dinosaurs.
Huge frog: Fossilized remains have been found in Madagascar of the Devil Toad, a bowling-ball-sized frog that was likely capable of eating small, young dinosaurs.Courtesy wikipedia
It sounds like the name of some gnarly rock band: Devil Toad.

But it’s actually the latest fossil discovery made by researchers from New York’s Stony Brook University. Fossils of the creature (which is actually a frog despite its name), about the size of a bowling ball and equipped with a mouthful of teeth, has been discovered in Madagascar. It’s official name is Beelzebuf, which translates from Latin into Devil Toad.

Here's a link to a story with a great artist's sketch of what Beelzebuf might have looked like with size comparisons to regular everyday frogs and a pencil.

Examining the fossils, researchers figure that the Devil Toad is a close relative to similar frogs currently found in South America. The old frogs would have lived around the same time as dinosaurs, got to a size of 10 pounds and stretched 16 inches long.

And if the ancient version of the frogs were anything like their contemporaries, they were some tough-as-nails amphibians, being able to capture and eat hatchling dinosaurs.

The fossil remains date back about 70 million years ago, putting them in the late Cretaceous period. Also found in the same area were dinosaur and crocodile fossils.

On top of all of that, the Devil Toad’s skull appears to especially thick and includes ridges and grooves that could have made up some type of protective shield.

Harvard scientists working in Madagascar recently collected a 10-inch long pink snake. Examining the creature back at the lab, they realized they had re-discovered a species which hadn't been seen in over 100 years. The snake is not only extremely rare, but it lives underground and avoids light, making it extra difficult to find.

Oct
15
2006

Coral in trouble: photo from NOAA via Wikimedia
Coral in trouble: photo from NOAA via Wikimedia

Oceans appear unhealthy

What if Earth's oceans get so sick they start a chain reaction of death? Zones of death are showing up in the Gulf and off the coast of Oregon. The coral reefs off Madagascar, Australia, and Belize are dying.

More than 90 percent of the earth’s living biomass (weight of living matter) is found in the oceans, and 90 percent of that is made up of single cell and microbial species. ...
There are signs that marine life is failing right at the bottom of the food web as the result of global warming, which could start a series of aggravating feedback effects on climate change. Institute of Science in Society

"Increasing carbon dioxide in the atmosphere has had effects in the ocean, where it's causing increased acidity," says director of NSF's biological oceanography program, Phil Taylor, "This increasing acidity has the potential to disrupt the calcifying processes that lead to coral reef development, for example, as well as disrupt those same processes in the microscopic plankton that form the center of the ocean's food web." National Science Foundation

Cacium carbonate depends upon non-acidic ocean

Since the industrial revolution began, ocean pH has dropped by approximately 0.1 units, and it is estimated that it will drop by a further 0.3 - 0.4 units by 2100 as the ocean absorbs more anthropogenic CO2 (Caldeira and Wickett, 2003; Orr et al., 2005) (via Wikipedia). Ocean life which use calcium carbonate find themselves dissolving when their environment is too acidic.

More research needed

In a recent study, scientists discovered several small reefs near Madagascar with corals that appeared to be resilient to rising sea temperatures. These resilient areas could be used to reseed damaged reefs ensuring the continued existence of coral reefs around the world and the marine species that rely upon them for survival.

Coral bleaching should serve as a red flag warning us that we need to understand the complex interactions between changing ocean chemistry and marine ecology. We need to develop research strategies to better understand the long-term vulnerabilities of sensitive marine organisms to these changes.