An Asteroid wrapped up the Age of the Dinosaurs. But How ...

What’s Happening

Breaking it down: Researchers are uncovering the evolutionary steps that set the stage for dinosaurs to rule the planet An Asteroid wrapped up the Age of the Dinosaurs.

But How Did Their Reign Begin? Mysterious Early Reptiles May Hold the Answer Researchers are uncovering the evolutionary steps that set the stage for dinosaurs to rule the planet Amy McDermott, PNAS Front Matter 10:10 a. (yes, really)

Paleontologists have found early examples of theropods, the group that would at some point include tyrannosaurs.

The Details

But precisely how another group of dinosaurs, known as the bird-hipped ornithischians, evolved remains a major question in paleontology. Roger Harris / SPL via This piece first appeared in the Front Matter section of the Proceedings of the National Academy of Sciences .

A small but fierce jawbone sits in Argentina’s natural science museum in Buenos Aires. Six inches long and studded with backward-curving fangs that would have hooked into flesh to rip it open, the fossil contains teeth not unlike those of the fearsome Komodo dragon of today, says paleontologist Martín Ezcurra , a researcher at the museum.

Why This Matters

But this jaw is no Komodo dragon bone: The 236-million-year-old fossil belonged to an extinct reptile called Lewisuchus admixtus , which ran across Triassic northern Argentina, a world of cycads and ferns that thrived long before grass existed. Lewisuchus stood about knee-high, was roughly five feet long from nose to tail and hunted the cousins of early mammals. It lived about 30 million years before the well-known dinosaurs first roamed the Argentine plains.

Scientists and researchers are watching this development closely.

Key Takeaways

• So was Lewisuchus a early dinosaur?
• Or was it a cousin of the dinosaurs, one of many reptile groups skittering over Earth at the time?
• Lewisuchus is embroiled in an ongoing debate that could help resolve enduring mysteries about the dawn of the dinosaurs.

The Bottom Line

Lewisuchus is embroiled in an ongoing debate that could help resolve enduring mysteries about the dawn of the dinosaurs. Placing it and related reptiles on the tree of life could reveal the early steps in dinosaur evolution, how their rise was shaped plans and how they interacted with other species.

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