Geology

dailyfossil:

Brontosaurus 

Mounted skeleton was on display at the American Museum of Natural History

Reconstruction by Charles Knight

When: Holocene (1879 to 1903) 

Where: Scientific literature and museums on the east coast of the USA. Found even today in public consciousness and outdated dinosaur books. 

What: Brontosaurus is perhaps the most well known of the sauropod dinosaurs. Too bad it never really existed!  The history of this name and why it became so popularized starts in 1877 when the paleontologist Othniel Charles Marsh applied the name Apatosaurus to a sauropod specimen. This specimen was not very complete and mostly represented by vertebrae and a pelvis.  Two years later he erected the name Brontosaurus based on an almost complete skeleton that was missing its head.  Headless sauropod skeletons are fairly common, but in this case this missing head only served to make the story even more complicated.

This missing head was obviously a problem when the Peabody Museum of Natural History at  Yale wanted to mount its specimen of Brontosaurus for display. There was great debate over which head to use, which some camps wanting to use one that resembled Diplodocus but others rallied behind a Brachiosaurus type skull. This latter skull was what  Marsh had envisioned in his publications on Brontosaurus, so after much heated debate a Brachiosaurus type skull was attached to the previously headless skeleton.  This skeleton was unveiled to the public in 1905 to great fanfare and soon after the American Museum of Natural History in New York City had its own Brontosaurus on display, with an identical head to the Yale specimen. 

So the general public had a firm concept of the dinosaur Brontosaurus! It was an easy to remember and pronounce name, this is what it looked like, and hey look we even have all of these lovely reconstruction showing these great lumbering beasts in prehistoric swamps. Too bad everything was wrong. And even worse, it was KNOWN to be wrong by some workers who were shouted down by others. In 1903, two years before the specimen was mounted at Yale,  a paper was published Elmer Riggs at the Field Museum of Chicago that declared that the bones known for Apatosaurus that overlapped with those of Brontosaurus showed that these two animals were the same. He concluded that Brontosaurus was not a valid name as it was two years younger than Apatosaurus. Even worse, remember the great head debate? Totally wrong. Later fossil finds have confirmed that a Diplodocus style head should have been used. These skulls are much more elongated and flatter than the high domed skull that was used for the Brontosaurus mount. 

So not only is the name not valid, but the anatomy of the animal isn’t even anything that ever existed in nature! It is a chimera of different species. Also sauropods were not aquatic swamp dwellers, they were 100% terrestrial creatures. 

Poor Brontosaurus. 

vena-nicea:

-Danxia Landform near Zhangye in South East China

dailyfossil:

Ambulocetus

Reconstructions by Carl Buell 

When: Eocene (~50 to 48 million years ago)

Where: Pakistan 

What: Ambulocetus is fossil whale relative. This beast was about 10 feet (~3 meters) long, and not very agile in either the land or the water. It was capable of movement on land, but it would have been rather slow and lumbering, as its forelimbs were shortened compared to its fully terrestrial ancestors. In the water it would have been capable of swimming with some speed, but it would not have been able to make quick turns as it chased its prey. Therefore, it has been reconstructed as an ambush-style predator, in the same niche as the modern crocodile. It would have laid in wait in the water, with its relatively dorsal eyes and nose peeking above the sufrace, able to see and smell approaching prey. Once a prey animal got close enough, Ambulocetus would launch itself from the water and try to catch the animal in its powerful jaws, such as is shown above. I think it is some form of basal horse that is trying to avoid the snapping jaws of Ambulocetus. This ambush style strategy could have also worked with aquatic prey, such as schools of fish. Ambush predation is seen in some species of whales today, Orcas (the killer whales) have been recorded ambushing seals on ice flows. 

Ambulocetus lived on the edge of the Tethys Sea (a body of water between India and Asia) in what is now Pakistan. At the time this region was one of many islands off the shore of the island continent of India, which had not yet collided with Asia (this would not happen for tens of millions of years). This warm seaway was full of mammals starting to return to the seas, including other lineages of whale relatives. In the cetacean family tree, Ambulocetus falls between Indohyus and modern whales; it was carnivorous - as all modern whales are-, and far more adapted for aquatic locomotion than Indohyus was, with shortened legs and a much more powerful tail.