Paleontologists uncover the deep past of our planet by piecing together the story of life from fragmented remains. Each fossil discovery serves as a clue, helping researchers understand the origins of ancient creatures. Unraveling the initial appearance of dinosaurs on Earth involves navigating immense spans of geologic time, stretching back hundreds of millions of years. Scientists continue to search for the earliest evidence, pushing back the timeline of when these animals first walked the Earth.
Meet the Earliest Known Dinosaur Contender
The primary candidate for the world’s earliest known dinosaur is Nyasasaurus parringtoni. This ancient reptile is recognized from a limited collection of remains: a single upper arm bone (humerus) and several vertebrae from its backbone. These sparse fragments provide clues about one of the earliest animals on the dinosaur lineage.
The fossils of Nyasasaurus parringtoni were discovered in the 1930s in Tanzania’s Ruhuhu Valley near Lake Nyasa. Based on available evidence, scientists estimate this creature was relatively small, about 7 to 10 feet (2 to 3 meters) long, including a long tail. It was roughly the size of a Labrador retriever. Without a recovered skull, its diet cannot be definitively determined, but it is thought to have been an insectivore or carnivore. Nyasasaurus parringtoni inhabited the Earth during the Middle Triassic Period, approximately 240 to 245 million years ago, when all continents were conjoined into the supercontinent Pangaea.
Dating a Dinosaur From Millions of Years Ago
Determining the age of a fossil like Nyasasaurus parringtoni involves a process called stratigraphy, the study of rock layers. The bones were found embedded within the Manda Formation, a geological layer in southwestern Tanzania. This rock layer has been dated, placing the Nyasasaurus fossil at approximately 243 million years old.
Scientists examine the internal structure of the bones for biological indicators. A cross-section of the humerus reveals rapid bone growth, a characteristic associated with dinosaurs and their immediate relatives. Its bone tissue shows a high density of bone cells and blood vessels, similar to fast-growing animals today, such as some mammals or birds. This anatomical evidence from the bones, combined with the geological dating of the surrounding rock, supports its placement as a very early member of the dinosaur lineage.
Why the “Oldest” Title is Still Debated
Despite the evidence, the scientific community continues to debate whether Nyasasaurus parringtoni holds the title of the oldest dinosaur. The debate stems from the incomplete fossil record; only a few bones have been recovered, making conclusive classification challenging. With such limited material, it is difficult to discern all features that define a true dinosaur.
Some paleontologists classify Nyasasaurus as a “dinosauriform,” a group of dinosaur-like reptiles that are close relatives, existing just before true dinosaurs. They share many characteristics with dinosaurs but may lack one or more defining features. Other early dinosaur fossils, such as Eoraptor and Herrerasaurus from South America, are known from more complete skeletons. These were previously considered the oldest dinosaurs, dating to around 230-237 million years ago. The more extensive remains of these animals offer clearer anatomical evidence, providing a benchmark against which more fragmentary finds like Nyasasaurus are compared.