A 150 MYA Jurassic feeding frenzy, Wyoming Dinosaur Center

The Something Interesting (S.I.) quarry in Thermopolis, Wyoming, Warm Springs Ranch Dig Sites, These hills contain thousands of dinosaur bones dating back to the Late Jurassic Period, 150 – 146 million years ago. One of the most unique dinosaur sites ever discovered: a dinosaur skeleton surrounded by dozens of dinosaur footprints. This incredible quarry captured a Late Jurassic feeding frenzy, where a massive carcass was torn apart by hungry scavengers.

150 million years ago, a young Camarasaurus died and was deposited on the shore of a prehistoric lake. Attracted by the smell of decaying flesh – and the promise of an easy meal – hungry carnivores arrived to feed on the carcass. In the ensuing feast, the scavengers dismembered and scattered the skeleton, and left dozens of footprints in the mud. Soon after they finished their meal, sediment covered the tracks, teeth, and remaining bones in more layers of mud. Today, that mud makes up the rock of the Morrison Formation, one of the richest fossil deposits on the planet.

Excavations began in 1993 and right away it was clear something was interesting about the site – thus, the name. Once dinosaur bones are discovered, they are meticulously mapped so a complete picture of the site can be assembled. This allows paleontologists to revisit the site, long after the bones are excavated and taken back to the museum. In the case of the S.I. Quarry, the map revealed the story of the Jurassic feast.

The size and shape of the bones reveal that the scavenged carcass belonged to a Camarasaurus, a long – necked sauropod. A full grown Camarasaurus could grow up to 60 feet long and weigh as much as 20 tons. These bones are too small to belong to a fully grown adult – this Camarasaurus was only about half grown at the time of its death.

Once the bones has been stripped clean of flesh, they were left to rot in the mud; some were trodden upon by dinosaurs walking along the shore of the lake. In addition, the skeleton preserved at the S.I. Quarry isn’t complete. Parts of the carcass may have been dragged or carried away by scavengers seeking a private spot to eat.

This is the mounted skeleton of a Camarasaurus, excavated in Thermopolis, WY, but not in the S.I. Quarry. The Camarsaurus in the S.I. Quarry was about half the size of the one pictured here.

A trackway is a complete sequence of footprints (right, left, right, left.) There are no complete trackways in the S.I. Quarry. The dinosaurs were constantly stepping over the existing footprints in their feeding frenzy. As a result – even though the mudstone layer is covered in tracks – only a few of them are completely intact. Most were left behind by the feeding allosaurs, but a few tracks belong to a large sauropod.

Three long toes indicate this footprint was left behind from a theropod – a bipedal carnivorous dinosaur. The exact identity of the culprit is unknown, but was mostly like a medium – sized Allosaurus.

Tail bones from a young Camarasaurus, strewn throughout the site. Many of these bones have deep scratches on the surface – traces of the teeth and claws of hungry scavengers.

This is the partial skull of an Allosaurus was found in a different fossil quarry in Thermopolis, WY. Other than teeth, no Allosaurus bones were discovered in the S.I. Quarry. This lack of allosaur bones supports the theory that the young Camarasaurus was not killed at the site. There is no sign of a hunt the site itself, and even a young Camarasaurus could kill or seriously wound a Allosaurus. While the idea of a prehistoric battle is exciting, the evidence collected at the S.I. Quarry suggests a scavenging site, rather than a kill site.

Carnivorous dinosaurs continuously shed and regrew teeth, just like modern sharks. These teeth – and dozens of others – were found during the excavation of the S.I. quarry. The size and shape indicate that many different sized Allosaurus – juveniles to fully grown adults – stopped in to feed on the Camarasaurus carcass. Allosaurus was the most common large carnivore from the Late Jurassic Period, and their shed teeth are often found in Late Jurassic dinosaur quarries.

These grooves are the result of an Allosaurus using its serrated teeth to gouge the surface of the bone – undeniable evidence of a voracious meat – eater trying to get every piece of meat from the bone.

These gastroliths were discovered in the stomach area of the SI Camarasaurus. Sauropods didn’t have molars, or chewing teeth, to process their food – they swallowed vegetation whole. To assist in digestion, they also swallowed small stones to grind the food in their stomachs. The smooth, shiny surface is the result strong stomach acids polishing the gastroliths.

During the excavation of the S.I. Quarry, a dinosaur bone was discovered inside one of the large sauropod footprints. The bone had clearly been stepped on and crushed by the tremendous weight of the sauropod. But instead of shattering or snapping (how bones usually break) this bone was completely flattened – like a pancake. The bone in question – a caudal vertebrae, or tail bone – should be as large and round as a can of soda. Why did this bone flatten instead of shattering?

Further analysis of the S.I. Quarry solved the Mystery of the Crushed Caudal. The geochemistry of the mudstone layer containing the bones and tracks was analyzed, in order to determine the mineral present in the water at the time the feeding frenzy occurred. The water of the prehistoric lake was alkaline, and slowly leeched away the minerals – such as calcium – which keep bones hard and strong; just like keeping a chicken bone in a jar of vinegar for a few days. The bone was so soft by the time sauropod stepped on it that it was squashed flat, rather than breaking.

The Camarasaurus caudal in question. The conditions which caused this bone to flatten – and the circumstances in which the flattening occurred – make this the only fossil of its kind in the world.

The verdict is out: The S.I. Quarry is one of the most unique paleontological sites ever discovered. Many of the discoveries in this quarry are one of a kind – and that discovery is ongoing. Excavations at the S.I. Quarry continue, and many of the bones have been left exactly where they were discovered. These can be viewed during the summer excavations at the Wyoming Dinosaur Center.

For more information on the analysis of the S.I. Quarry.