Tuesday, December 4, 2012

Fish In A Rock

When the winter winds start to blow in southern Utah, it’s time for me to gather my pick and paintbrush, sit myself down at the microscope, and start picking at fish. 

Fossil fish, that is. 

Follow the red arrow to the fish fossil

I volunteer at the St. George (UT) Dinosaur Discovery Site at Johnson Farm, the site of world–class dinosaur trackways along with fossil fish, reptiles, and plant life. Each winter, when I’m not working as an interpretive ranger for the National Park Service, I spend quite a few hours each week gazing into the 220–million year old past. 

In the midst of abundant museum shelves full of samples I choose a rock with tantalizing traces of fish scales sandwiched between layers of greenish gray mudstone. Some of these samples were collected on museum property while others were collected during museum–sponsored field trips to similar Chinle Formation locations around Utah. 

Can't wait to find out what is beneath those layers of mud

With a flick of the pick and a few drops of water, the top layers of lithified mud flake off easily. Within an hour or so I have a nice small pile of mud chips which I have hacked away at carefully removed. 

FishFossilIn Mudstone
Dead thing in mud

Soon, a fossil fish tail begins to reveal itself. There are scales and fins seen too, but just barely. It will take some amount of time to know exactly what is hidden within this lovely rock. 

This work takes a steady hand, lots of patience, and nerves of steel! 

Fins, scales, and a tail begin to reveal themselves

Flaking off the top layer of mudstone was the easy part. During the next few months this fish fossil and I will most likely get to know each other quite well.


Come to the museum and check on our progress! And if you happen to be a good carpenter (or know of one) we would love for someone with some time on their hands to build us some wooden boxes. We have lots of scrap lumber. The dinosaur trackways across the street from the museum are just sitting outside while exposed to the elements, weathering away quickly. It would be heartbreaking for all these remarkable fossils to be lost.


  1. So much patience you have to reveal a truly amazing surprise.

  2. Gaelyn - I do love the surprise! You just never know what's going to turn up, under those mud flakes. And you have to be really careful not to lose a good section of scales, fins, etc. It's REALLY meticulous work. Fun, too!