Is this titanosaur the biggest dinosaur ever?

When it comes to asking what were the biggest land animals ever to walk the Earth, there's no confusion. It was the dinosaurs. End of story. Next question!

Okay. But when the next question is: What was the biggest dinosaur ever? Well ... that is an answer that is shrouded in mystery. That's because there were a lot of very large dinosaurs. Known as the titanosaurs, these were the largest of the long-necked dinos, or sauropods. Top heavyweights from this group include Argentinosaurus and Patagotitan.

Now new fossil evidence from a dig in Patagonia (southern South America) is introducing a new challenger to the title. The unnamed species is definitely enormous. But biggest dinosaur ever? Let's take a look!

The problem with fossils

This skeleton of Patagotitan looks complete, but it has been based on known fossils that are added on to bones known from similar species. (Wikimedia Commons)

The main challenge in trying to figure out anything about dinosaurs is that fossils are almost never complete. In fact, most dinosaurs are known only from fragments. (We discuss this in more detail in this video.) This is especially true when you're dealing with such massive creatures like titanosaurs. Over millions of years, parts of this skeleton get washed away—paleonotologists must make do with what they can find.

Some leg bones. Parts of the neck and back. A few ribs. Maybe half of the skull. Only by comparing the bones they have with other dino fossils—as well as similar creatures that are alive today—can experts begin to piece together what a complete skeleton would actually look like.

This is why we still don't know which dinosaur was the biggest ever. The two main candidates—Argentinosaurus and Patagotitan—are both only known from bits and pieces. Experts know they were huge animals—estimated to be around 15 metres (50 feet) tall and to weigh 62 metric tons (think about twelve elephants). But it's not as though they can just grab a tape measure and go nose to tail.

They just don't have enough of the bones.

A curious case

The new fossil is in a location that is very difficult to remove bones from. This makes getting answers extra challenging. (Alejandro Otero and José Luis Carballido)

Enter this new fossil. First discovered in 2012, paleontolgists have been spending years examining what they have found. These bones date back around 98 million years ago. They include a large section of the tail and parts of the pelvic and pectoral area (hips and chest). Sadly, they haven't yet found the leg bones, which are key to determining a sauropod's size.

They still haven't named the dinosaur because they can't say for sure yet if it is a new species or not. But according to a new paper led by researchers in Argentina, this fossil's bones belong to a land animal that is bigger than any found before—including the same bones on Argentinosaurus and Patagotitan.

Of course, for this dinosaur to really take the title of biggest dinosaur ever—as well as get a name!—more research has to be done. The hope is that further excavations can unearth the truth of just how big dinos were.