Toothy Mammal Named 'Luck' Coexisted with Dinosaurs

A scrappy, furry plant-lover named Luck coexisted with dinosaurs and provides important new insights into the evolution of Earth's earliest mammals.

A veggie-eating mammal appropriately named "Luck" somehow managed to live alongside several large carnivorous dinosaurs in Madagascar during the Late Cretaceous, according to a new study.

The 66-70-million-year-old mammal, described in the latest issue of the journal Nature, is one of the largest known Dinosaur Era mammals. Named Vintana ("Luck") sertichi, it weighed about 20 pounds, or roughly twice the size of a modern day groundhog, which it resembled.

"This is enormous for a Mesozoic mammal, most of which were shrew or mouse-sized, living in the shadow of dinosaurs," project leader David Krause told Discovery News.

"There were both large (such as Majungasaurus) and small (such as Masiakasaurus and Rahonavis) carnivorous dinosaurs that lived alongside Vintana, not to mention large sauropod dinosaurs (Rapetosaurus, Vahiny), seven different types of crocodiles, both large and small snakes, a giant frog, 6–7 species of birds, a lizard, several fishes and more," added Krause, who led the research and is a professor in the Department of Anatomical Sciences at Stony Brook University.

Joseph Sertich, a former graduate student of Krause's, found Vintana's nearly complete cranium by fortuitous accident in a sandstone block otherwise filled with fish fossils. The block was unearthed in what is now Madagascar.

The cranium represents the first such fossil ever discovered for any gondwanatherian mammal. "Gondwanatherian" refers to an early group of mammals that previously were among the most enigmatic of all prehistoric animals.

Comprehensive analysis of Vintana's teeth, eye sockets, nasal cavity, braincase and inner ears reveals that it was a toothy and agile large-eyed animal with keen senses of hearing and smell.

The researchers had never seen anything comparable to this skull before, however.

"Throw together some anatomical features from ancient mammal-like reptiles, Pleistocene ground sloths, an extant rodent, and maybe a few bits and pieces from the Muppets on 'Sesame Street' and you might get something that resembles the cranium of Vintana," Krause said.

However unusual, the herbivorous animal managed to scurry around its treacherous-carnivore landscape. At the time, the area where it lived was a lowland coastal floodplain.

Vintana shows that gondwanatherians are related to two other early groups of mammals known as multituberculates and haramiyidans. Together, they form a larger group called Allotheria.

Because haramiyidans, which date back to the Late Triassic, are now classified as being in Allotheria, the origin of mammals has just been pushed back by about 25 million years.

"Luck" has therefore proven to be a very lucky find for paleontologists, and the animal might have been lucky in life too. Krause said it is possible that it might have survived the mass extinction event that wiped out all of the non-avian dinosaurs, although fossils confirming that have not yet been found. Other gondwanatherians are known to have survived the extinction around 65 million years ago, perhaps by hibernating underground.

Anne Weil, an associate professor of anatomy at the Oklahoma State University Center for Health Sciences, authored an accompanying "News & Views" article in Nature. She told Discovery News that Vintana "substantially expands our knowledge of the forms that mammals evolved during the Mesozoic, and the ecological roles they played."

Both she and Krause shared that "Luck" has no living descendants.

It instead was, as Krause said, "an early evolutionary experiment in mammalness."

An artist's reconstruction of Vintana sertichi within the context of the tidal, estuarine paleoenvironment and fauna of the Late Cretaceous of Madagascar.

Aug. 30, 2011 --

Evolution and natural selection have played a role in the ever-changing landscape of plants, animals, bacteria and fungi. Although species evolve as they find their niche and adapt to new opportunities, some animals have remained relatively unchanged over the course of history. These animals are known as living fossils. Compared to the animals on this list, humans are relative newcomers to this planet. Homo sapiens emerged out of Africa a mere 200,000 years ago. Many living fossils are considerably older than humans and other mammals; some have even outlasted the dinosaurs. In this slideshow, take an up-close look at animals that have persevered virtually unchanged through the ages and continue to thrive today. We begin with the platypus, an unusual egg-laying animal with fur, a bill and a venomous bite. Charles Darwin himself coined the term "living fossil" while observing the platypus. Native to eastern Australia, the animal is the only surviving example of its family, Ornithorhynchidae. This group of animals is believed to have split from mammals some 166 million years ago.

The horseshoe crab could hold the distinction of being the oldest animal species still in existence. Dating back to the Paleozoic era, the horseshoe crab existed on Earth before the dinosaurs and soldiered on through several mass extinction events. In 2008, a horseshoe crab fossil, the oldest in existence found so far, dated back to around 445 million years ago, according to a report by LiveScience.

The tadpole shrimp, Triops cancriformis, is another contender for the title of oldest living animal species. This shrimp is related to the horseshoe crab so its longevity should come as no surprise. According to a report by The Telegraph, the tadpole shrimp as it appears today is virtually identical to a fossil of a specimen that lived some 200 million years ago just as dinosaurs rose to prominence. Despite the animal's remarkable endurance, the tadpole shrimp is currently listed as an endangered species.

Once thought to be extinct in the same event that killed off the dinosaurs some 65 million years ago, the coelacanth is a lobe-finned fish that sparked a debate over whether this species represented a missing link between aquatic animals and four-legged terrestrial creatures, according to National Geographic. The animal was rediscovered in 1938 and only two species of coelacanth still exist today. In 2007, a fossilized coelacanth fin was found dating back roughly 400 million years.

Snapping turtles as we know them first walked the earth some 40 million years ago, but they have been virtually unchanged over the past 215 million years of their evolution, according to Tortoise Trust. Although not among the most endangered tortoises and turtles according to the Turtle Conservation Coalition, the snapping turtle is listed as threatened.

The more than 20 species of alligators and crocodiles living today have evolved beyond their more primitive ancestors. But the basic physical design of these reptiles has remained essentially the same for the past 320 million years or so. Alligators and crocodiles share a common ancestry, though the two groups separated from each other some 60 million years ago.

The nautilus is the most primitive cephalopod in existence, a group that includes the most complex squid and octopus. Dating back to more than half a billion years ago, the nautilus reached the high point in its evolution during the Paleozoic era about 505 million to 408 million years ago. Several species of nautilus still survive today -- relatively unchanged from their ancestral counterparts.

Goblin sharks are rare, deep-sea dwellers with a unique elongated nose that distinguishes them from other sharks. They're also ancient, and are between 112 million to 124 million years old as a species. Around 2,000 different species of fossil sharks have been discovered, according to the ReefQuest Centre for Shark Research. The earliest sharks predate the dinosaurs by more than 200 million years.

The cockroach is famous for being a survivor. These insects can survive for weeks without their heads and even withstand the fallout following a nuclear blast. Cockroaches are also an especially long-surviving animal. Roaches have thrived on Earth for some 320 million years, with an estimated 5 million to 10 million individual species ranging in shape, size and habitat. This photo shows Blaberus giganteus, one of the largest species of cockroach on Earth.

Hagfish may have had to endure a less-than-flattering name since scientists first described them in the 18th century. However, these famously ugly marine animals have existed for about half a billion years. The hagfish also represents an important evolutionary step in the development of vision. These ancient fish may have been among the earliest animals to evolve more complex, camera-like eyes as opposed to the strictly photosensitive vision possessed by more primitive species. As such, the hagfish represents a kind of missing link in the evolution of the eye.

Compared to other animals on this list, the mouse deer, better known as a chevrotain, is a relative newcomer. For a large mammal, however, it's relatively old. This animal is among the only survivors of a group of hoofed mammals that lived some 35 million years ago.