Jurassic Surprise: Unraveling the Tale of the 'Chicken From Hell,' South Dakota's Newest Dinosaur Discovery

A recent paleontological finding has unveiled a new dinosaur species, playfully dubbed the "Chicken from Hell," shedding fresh light on the dynamics of the dinosaur population prior to their extinction.

Scientific opinions are divided on whether the dinosaur populace had been diminishing before the catastrophic asteroid event that eradicated them from Earth.

Researchers now believe that the identification of this newfound species can contribute valuable insights into this ongoing debate. Similar to the revelation of Tyrannosaurus mcraeensis, a newly identified relative of the formidable T. rex, the fossil of the “Chicken from Hell” was initially misclassified as a juvenile of a known species.

Unearthed in South Dakota within the Hell Creek Formation rocks and dating back to the final 2 million years of the Cretaceous period, the specimen was initially thought to be a juvenile Anzu, the sole recognized caenagnathid species from that era and region.

Caenagnathids, distinguished by birdlike traits such as toothless beaks, long legs and short tails, are believed to be omnivores weighing approximately 450 to 750 pounds.

Upon studying four hindlimb bones — an adult femur, tibia and two metatarsals — paleontologists eventually identified it as an entirely new adult species within the Caenagnathid group. This conclusion was reached through a meticulous examination of the bone rings, analogous to tree rings, where each annual line signifies a period of slowed growth.

According to paleontologists Kyle Atkins-Weltman and Eric Snively, "In a juvenile, we would expect lines of arrested growth in the bone to be widely spaced, indicating rapid growth. Here, we saw that the later lines were spaced progressively closer together, indicating that this animal’s growth had slowed and it was nearly at its adult size," as they wrote in the academic journal The Conversation.

The newly discovered species, named Eoneophron infernalis, meaning "Pharaoh’s dawn chicken from Hell," possesses distinctive features such as ankle bones fused to the tibia and a well-developed ridge on one of its foot bones. These traits differentiate it from a young Anzu, highlighting its uniqueness within the smaller Eoneophron.

This breakthrough prompted further examination of fossils presumed to be Anzu, leading to the identification of a third, similarly distinct "Hell Chicken" species.

"Where once there was one 'chicken from Hell,' now there were two, and evidence for a third: one large (Anzu), weighing as much as a grizzly bear, one medium (Eoneophron), humanlike in weight, and one small and yet unnamed, close in size to a German shepherd," the scientists wrote.

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Contrary to the previous notion of dinosaur decline during the Cretaceous's final phase, this newfound diversity challenges assumptions about dwindling dinosaur populations.

As the scientists expressed, "Our new discovery suggests that this dinosaur group was not declining in diversity at the very end of the Cretaceous. These fossils show that there are still new species to be discovered and support the idea that at least part of the pattern of decreasing diversity is the result of sampling and preservation biases."