Pin the Nose on the Dinosaur

Brachiosaurus was not a swampbound dinosaur. The magnificent “arm lizard”, over 80 feet long from snout to tail tip, trod over Late Jurassic, fern-covered floodplains now preserved in the 150 million year old rock of the American west. Still, when my much younger self first saw Zdeněk Burian’s restoration of BrachiosaurusZdeněk Burian’s restoration of Brachiosaurus submerged almost up to its head, I couldn’t deny that the illustration just looked right. It wasn’t so much the dinosaur’s bulk, but that the sauropod’s nose was atop its head – why would such an enormous herbivore need a dorsal nose unless the dinosaur hid its girth underwater?

The sauropod snorkel wasn’t an ad hoc invention to explain amphibious dinosaurs. Nasal bones on sauropod skulls really do open up further back on the skull, far from the snout and closer to the eyes. If the nasal opening was there, researchers reasoned, then the external nostrils must have been in the same place. Even as paleontologists rehabilitated sauropods and moved them out of Mesozoic bogs, the noses of Brachiosaurus, Diplodocus, and kin remained atop their heads in art and scientific restorations, and expression of the bony architecture underneath.

But, contrary to the long-running tradition of “shrink-wrapping” dinosaurs in a minimum of muscle and skin, the skulls of sauropods and the anatomy of living animals indicates that the dinosaurs had “rostral nostrils” far forward of the nasal openings in their skulls. In 2001, paleontologist Lawrence Witmer compared clues about soft tissue from dinosaur skulls to the anatomy of crocodylians, birds, and other amniotes to determine where dinosaur noses actually were.

All the animals Witmer investigated had fleshy nostrils at the front of the skeletal opening, and sometimes even further forward. The external nasal openings in dinosaurs almost certainly followed the same rule – their noses were at the front of the bony nasal opening, not pushed all the way back. A common, ancient trait shared among modern animals meant that dinosaurs followed the same rule.

So Brachiosaurus didn’t have a snorkel. Based on the anatomy of living animals, and the pattern of blood vessels that dotted the dinosaur’s skull, the dinosaur’s nose probably sat near the front of its snout, the airway going back up into the bony nasal opening. (Don’t get carried way, though – there’s no evidence that Brachiosaurus, Diplodocus or other sauropods had trunksthere’s no evidence that Brachiosaurus, Diplodocus or other sauropods had trunksthere’s no evidence that Brachiosaurus, Diplodocus or other sauropods had trunksthere’s no evidence that Brachiosaurus, Diplodocus or other sauropods had trunksthere’s no evidence that Brachiosaurus, Diplodocus or other sauropods had trunks.) This isn’t just about dinosaur cosmetics. To understand how dinosaurs breathed, we need to accurately reconstruct their noses. The same goes for their sense of smell. Parsing dinosaur mysteries requires researchers to restore prehistoric anatomy as precisely and accurately as possible.

As weird as non-avian dinosaurs were, they were still real animals that were connected to other creatures by evolutionary history. By pairing hints from soft tissues with ancient bones, we can’t start to approach tantalizing aspects of how these lost animals actually lived.

References:

Knoll, F., Galton, P., López-Antoñanzas, R. 2006. Paleoneurological evidence against a proboscis in the sauropod dinosaur DiplodocusPaleoneurological evidence against a proboscis in the sauropod dinosaur Diplodocus. Geobios. 39: 215-221

Witmer, L. 2001. Nostril position in dinosaurs and other vertebrates and its significance for nasal function. Science. 293: 850-853