Bulking up on veggies

Sauropod dinosaurs, like Diplodocus and Brachiosaurus, hold the record for the largest land animals, weighing up to 80 tons, and stretching more than 60 meters from head to tail.

To support their size, these herbivorous dinosaurs must have spent most of their time eating and searching for food.

They had a mouthful of incisors, good for clipping off plants, but not designed for chewing. They had no molars for pulverizing their food, so they must have swallowed their food whole.

The giant bulk of these dinosaurs is more puzzling when considering their relatively tiny heads, but their small heads were supported by long necks, which may have been critical to the sauropod’s success.

Their long necks allowed these dinosaurs to stand in one place and browse vegetation from a large radius, allowing them to collect a lot of food without expending much energy.

Based on research by P. Martin Sander and Marcus Clauss, 2008. Sauropod Gigantism. Science 322: 20-201

Illustration from http://www.scorcher.ru/journal/art/art_pic/diplodocus_2.jpg

Thwarting T. rex

How can an herbivore protect itself from carnivorous predators?

Strategies seen today among predators and prey of the African Serengeti apparently existed among dinosaurs in ancient ecosystems.

Paleontologists from Ohio University counted growth lines in the legbones of hadrosaurs, a group of herbivivorous duck-billed dinosaurs. By counting the number and spacing of growth rings, paleontologists can determing the animals’ age and its relative growth rate—the fast growth seen in juveniles is characterized by widely-spaced growth rings; growth slows or stops at adulthood, shown by close spacing of the growth rings.

The scientists found that hadrosaurs reached their adult size by age 13. In contrast, the carnivorous Albertosaurus reached full size at 20-30 years. Maturing quickly gave hadrosaurs an advantage over their predators, as they could produce offspring at an earlier age, and their offspring grew quickly to maturity.

Source: Drew Lee, Royal Society London B, Aug 5, 2008

Filling an empty niche

Despite the occupation by reptiles of almost every ecological niche during the Mesozoic Era, there were no large planktivorous marine reptiles, the niche filled today by baleen whales.

Recent discoveries in museum drawers may hold the answer to this gap in Mesozoic reptile ecology. Fossils that had lain unstudied or incorrectly identified have been newly identified as suspension-feeding pachycormids, a group of giant bony fish.

These fish were previously thought to have been a short-lived group, limited to the Jurassic Period. Mesozoic marine reptiles may have been excluded from the large-bodied, suspension-feeding trophic niche by these supersized fish.

The pachycormids were extinct by the end of the Cretaceous Period, opening up the planktivorous niche to a new group--the whales.

Matt Friedman, et al., 100-Million-year dynasty of giant planktivorous bony fishes in the Mesozoic Seas. Science 327

A new spin on an ancient predator

More than 100 years after its discovery the Middle Cambrian Burgess Shale of British Columbia Canada, continues to offer up new insight into the history of life.

One of the many enigmatic soft-bodied animals of the 500 million year old Burgess Shale of British Columbia is Nectocaris (fossil shown above) long thought to be a shrimp-like arthropod (reconstruction, above, left), but a recent study shows that the animal is most likely a cephalopod, ancestral to the group includes modern squid, octopus, and the pearly Nautilus (reconstruction above, right).

This re-classification of Nectocaris extends the geologic range of the cephalopods back 30 million years and dramatically changes hypotheses of cephalopod evolutionary history.

Nectocaris does not have an external shell, as did other ancient fossil cephalopods, and this discovery scuttles previous hypotheses that cephalopods evolved the ability to float and then swim after the evolution of their chambered shell. Nectocaris shows that cephalopods shells evolved later in cephalopod evolution, possibly in response to increased predation during the Late Cambrian.

Martin Smith and Jean-Bernard Caron, Nature 2010. Photos by the authors. Reconstructions from Discover Magazine blog

Burgess Shale redux

The Middle Cambrian Burgess Shale of British Columbia, Canada, is famous for the preservation of bizarre and distinctive animal fossils, like Anomalocaris, Hallucigenia, and Marella (shown at right).

Since its discovery over 100 years ago, other Burgess Shale faunas have been found in strata of similar age around the world, but the fauna appeared to have died out by the end of the Middle Cambrian.

The recent discovery of a Burgess Shale type fauna in Morocco from rocks millions years younger than the Burgess Shale breathes life into a fauna that was thought to be long extinct--including animals like Marella, above, left.

The apparent extinction of the Burgess Shale animals was probably a result of the rarity of the exceptional circumstances required to preserve soft-bodied organisms. The discovery opens the door to finding other, younger Burgess Shale type faunas around the world.

Source and photo credit: Peter Van Roy, et al., 2010, Ordovician faunas of Burgess Shale type. Nature 465:215-218.

Happy Anniversary, GeoLog!

365 days and 211 scripts ago, WPRR, public radio in Grand Rapids, Michigan, broadcast the first "GeoLog" program. GeoLog Blog reproduces the scripts along with a photo and links to the original source of the news item or other related website.

Mp3 files of GeoLog programs are now available on iTunes. Check them out at

http://www.publicrealityradio.org/programs/geolog

Tell your local radio station to pick up the program--each piece is only 1 minute long, short enough to run as a PSA (public service announcement).

Spread the word--Earth history rocks!

"Dark Earth"

Astronomers estimate that the sun was up to 30% dimmer early in its history (before its internal fusion engine was up to full power), and as a consequence put out less heat. Therefore, any water on the young Earth should have been frozen.

However, rocks formed during this period of Earth history, the Archean Eon, about 3.8-2.5 billion years ago, give evidence of deposition in liquid water. This discrepancy has been called the “faint young sun paradox”.

Now there is a new explanation for a warmer-than-expected early earth: Continents were smaller and more of the surface of the Earth was covered by ocean, giving the early Earth a darker, less-reflective surface, or low albedo.

Accordingly, the Earth’s surface absorbed more of the sun’s energy than it would have with a more reflective surface, enough to keep its oceans liquid, and keeping the planet hospitable for the development of early lifeforms.

Source: Rosing, Minik T.; Bird, Dennis K.; Sleep, Norman H.; Bjerrum, Christian J., 2010, No climate paradox under the faint early Sun. Nature 464: 744–747. Also reported in Science News April 24, 2010.

Photo credit and more info on the "faint young sun paradox": http://www.astrosociety.org/pubs/mercury/35_06/paradox.html