Warning: In today’s column I will be writing about fossils and fossilized materials such as plants and animals that have evolved over a time scale called Geologic Time that begins with the Earth’s oldest known rocks currently dated to 3.9 billion years ago. If you are a Young Earth Creationist you might want to stop reading now so as not to become upset.
In November 1994, Richard Thompson, a UA mathematics student, and Gordon Nelson were out reconnoitering a sandstone ridge in the Whetstone Mountains looking for petrified wood. Instead, what they found in the Turney Ranch Formation from the Cretaceous Period of 65 to 142 million years ago were the bones of what they thought might be a dinosaur.
Their discovery was brought to the attention of Ronald Paul Ratkevich, a paleontologist at the Arizona-Sonora Desert Museum, and plans were made for a dig to recover the bones in the spring of 1995.
After much study and conjecture, and a trip to the American Museum of Natural History in New York, Ratkevich proclaimed the bones to be those of a plant eating sauropod, a clade of creatures characterized by long necks (think Budweiser bottles) and large bodies (think Orcas).
As this was a previously unknown dinosaur, the naming rights fell to Ratkevich and he christened the find genus Sonorasaurus, literally Sonoran lizard, of type species S. thompsoni in honor of the discoverer.
The Whetstone’s own Sonorasaurus was not a particularly large dinosaur by sauropod standards but it still came in at 49’ length, head to tail, 26’ tall and a hefty 35 tons weight. In 2018 Sonorasaurus was declared to be the official dinosaur of the state of Arizona after a letter instigating the process was written by 11 year old Jax Weldon of Phoenix.
Like any child I passed through a fascination with dinosaurs phase early on in my life. I still have fond memories of the one trip my family made to the Museum of Natural History on Central Park West. I can recall happily running from exhibit to exhibit, from diorama to diorama, from dinosaur bone to dinosaur bone shouting, “Hey Dad, look at this.” I remember the echo in that great Museum’s chambers, the dimmed lights, the excitement at the discovery of the shape and scope of this world.
I didn’t return to that museum for another 25 years, until I had my own child to run through those halls with. As soon as my young ones were out of diapers, and into their grammar school years, we would make a day of it to go there to see what had been discovered, contemplated and cataloged.
Skip ahead now some more decades, the zipping past, to the present, and I am an even older adult, living in Arizona, pursuing a newly found interest in rocks. I had never collected any fossils, even though they were all around me, because I had not yet trained my eyes to see them.
In 2021 I picked up and saved one piece of fossilized wood on a walk across some property in the Grosvenour Hills, about seven miles as the crow flies from Patagonia. Before I made that discovery, I thought that the Petrified Forest was the only place in Arizona where you could find that stuff and that Arizona was the only place in the world where it could be found. News Flash: (to me anyway) wood turned into agate has been found on every continent. Hello Antarctica!
Being unaware of the history of the discovery of fossils in Arizona I was delighted to find out on a recent visit to the Arizona-Sonora Desert Museum that many important dinosaur remains have been found all over this state and that from my backyard I can look and see the places where fossils exist. The mountains and hills of the Whetstones, the Santa Ritas, and the Mustangs are loaded with the limestone that is always a candidate for holding ancient sea creatures such as seashells as well as crinoids and brachiopods. I have finally learned to see the fossilized coral on hilltops high above the ocean bottom where they once thrived before dying and becoming mineralized only to be thrust upward by geologic forces.
Recently, on the advice of a book that I recommend for novice rockhounds, “Gem Trails of Arizona,” by James R. Mitchell, I took a trip to look for fossils in the Whetstone Mountains of Sonorasaurus fame. The place is a couple of miles of rough trail off State Road 90 on the east side between Benson and Whetstone. The destination’s name was French Joe Canyon, which made me smile as I imagined some long ago migrant insisting that his name was Jacques even as his friends and acquaintances called him French Joe.
If you turn west towards the mountains at milepost 301 and continue straight for about 1.5 miles to a T intersection and then turn right and continue on for another .25 mile you will come to the canyon area. Here and there on the ground, you can find many examples of fossilized coral. I’ve seen evidence of shell imprints and even something called Devil’s Toenail, a type of ancient mollusk.
The rocks feel dense and weighty in my hands. Some of them glow deep reds and green under ultraviolet light, a process that I am still trying to understand. Mostly though, fossils remind me of the passage of all that time and of my own journey. I feel it every time I am confronted with a new technology, or I attempt to buy something online or I have to remember or create a new password. There I am, well on my way to becoming a fossil.