Dem Bone, Dem Bones

Dem Bones, Dem Bones 

By Jackie Howland 

(with thanks to Gateway’s volunteer paleontologist, Bradley, for his input)

For several years now, Gateway Museum has had various paleontologists working on specimens of prehistoric remains in the demo lab. One of the coolest things about this is that visitors can ask questions as the paleontologist works. I’ve asked some questions myself on the days I volunteer at the museum. And their work has triggered more questions for me about fossils – I thought I knew quite a bit about this subject, but it turns out I just had a surface understanding.  

My association with Gateway has certainly added to my general knowledge of fossils. If you’re like I used to be, you may think fossils are the hard bits of animals like bones, teeth, horns, hooves or shells. In many cases, they are. But fossils can also be from things that have no hard bits, like this fossilized mushroom, which is 115 million years old.  

Other examples of “fossils” that we might not think about are preserved tracks of ancient animals or preserved outlines of plant materials. Paleontologists can search for and study so much more than just T. Rex skeletons!

One of my questions was triggered by what was inside some of the “jackets” they’re working on. Jacket in this case refers to the cast that’s put around the remains in the field (along with some other protective materials), much like a cast is put on a broken leg or arm. The cast protects the remains as they are transported to a lab. Then people in the lab cut part of the cast off and begin to remove the surrounding dirt and rock, which they sometimes refer to as the matrix, to expose the remains. These aren’t always fossilized; they may still be mostly bone and can easily crumble. So just how long does it take for something to fossilize?

Depending on various factors, the process can take thousands of years or millions of years. It turns out how quickly a dead organism is buried and what it’s buried by is really important. Most things that die never become part of the fossil record because they get “recycled” – all the bits and pieces that were assembled during the organism’s life get broken back down and returned to become part of something else’s life. Certain soils, such as loam, are much more likely to aid in this recycling.

But if something gets quickly covered by mud, rock or sand, recycling cannot take place. Over time, the weight of the covering material presses down on the organism, and water and gases are expelled. Then a complex chemical process of mineral exchange can begin to occur – minerals from the surrounding material begin to fill the porous bits of the organism – and even the hardest bits have plenty of microscopic porous parts. Given more time, the surrounding material replaces everything so that it becomes a stone replica of the original. Then, eh, voila! We have a fossil.

Other means of natural preservation exist of course, so we can also learn about things that lived long ago by finding these ancient remains that aren’t fossils, which may be studied by other kinds of scientists. One preservation that’s fairly well-known is an animal, or a human, getting frozen in a glacier. With global climate change, such finds, are becoming more common. This freezing is a form of mummification because it involves desiccation – extreme dying – along with pressure from the ice. Entire Wooly Mammoths have been found in the ice, perfectly preserved.

Many people are also aware of another form of preservation because of the first Jurassic Park movie – amber, which is basically dried out tree resin. It can contain insects. Of course, but also bits of dinosaurs, plant parts and even frogs. It’s yet another means for scientists to piece together the puzzles of the past.

Things can also be preserved in natural tar, as in the well-known Labrea tar pits. Many ice age animals’ remains have been recovered from this pit. Stumbling into a tar pit would be sure death for any animal. Interestingly enough, natural concrete and asphalt also exist and may cover fossilized remains. And here we thought humans came up with these things on our own!

A rather surprising form of preservation of ancient creatures occurs in caves found in arid locations. The following looks like a picture of a living bat. It’s not. It’s one of many dead bats that have been found in caves in such areas as the Grand Canyon. These bats may be older than radiocarbon dating testing allows, which is about up to 60,000 years old. Many of the ancient bats found in the caves are around 30,000 years old. Quite amazing!

A mummified myotid bat at its last perch among the gypsum crystals in Double Bopper Cave.

It’s not just the bats that are found in these caves. It may be rodents such as pack rats or mammals that made their home there. And preserved seeds can be found since seeds were a food source for some of these creatures. Here are the remains of a ringtail cat (which is not actually a cat – it’s more closely related to raccoons).  

A mummified ringtail cat found in a cave in the Grand Canyon. 

All of these forms of preservation help us understand not just past life forms; it also reveals how local and global climate changes affect animals, plants, and fungi. The popular theory about how dinosaurs became extinct is that they were affected by a large meteor. But much more relevant to the concerns of today is how global cooling or warming leads to major changes in plant and animal life.  Creatures such as saber tooth cats, American lions, and camels were prevalent in North America during the last ice age. But they’re all gone now. 

Even for people who don’t want to think about climate change, the remains of ancient life can be fascinating. Perhaps it’s because they are in stark contrast to the fragile and fleeting nature of life. To see a perfectly preserved creature from 30,000 years ago is amazing. To see fossilized remains of a creature that existed 300 million years ago or more is simply mind boggling. So if you get a chance, be sure to come to Gateway when the paleontologists are there and thank them, even if it’s just because people like them made the Jurassic Park movies possible.