Digging Deeper into Dreadnoughtus: Dinosaur Interview with Ken Lacovara

Kenneth Lacovara, PhD with Dreadnoughtus schrani fossils.
Kenneth Lacovara, PhD with Dreadnoughtus schrani fossils.
Kenneth Lacovara, PhD with Dreadnoughtus schrani fossils.

A team led by Drexel University’s Kenneth Lacovara, PhD announced a major new dinosaur discovery with a paper published in the journal Scientific Reports on Sept. 4, 2014. The dinosaur is BIG. So big that we could only fit the highlights and main points of interest into the press release – read that for a general overview of the find. Below is Part I of the extended cut of our interview with Lacovara, featuring more insight into the dinosaur’s anatomy and lifestyle.

What did you discover?

This is a new genus and species of dinosaur, which we named Dreadnoughtus schrani, represented by the most complete skeleton ever found of a supermassive animal. In life if fleshed out, this would have weighed 65 tons. To put that in perspective a full-grown bull African elephant weighs about five tons. So you’re looking at an animal that is equivalent to a dozen giant elephants smooshed into one body. People often ask me, ‘Is this as big as a T. rex?’ Well, a T. rex is maybe eight or nine tons. So you’re looking at seven or seven and a half T. rex again smooshed into one body, so it’s just this titanic beast. No one has ever seen such a complete skeleton for such a large creature before. This contends for the most massive dinosaur ever found. But it’s by far the best example we have of any of the most giant creatures to ever walk the planet.

Can you put this into the context of others of the largest known dinosaurs?

This dinosaur is not the longest ever found. There are some very long dinosaurs with a whip-like tail. It’s not the tallest ever found. There are some dinosaurs with very high shoulders that have almost a giraffe-like posture. But it’s among the most massive dinosaurs ever found. And there’s really only one that could rival this in mass. It’s called Argentinosaurus, but Argentinosaurus is only known from a short series of vertebrae in its mid-back portion and a few other pieces, but not the upper limb bones. And the other really massive dinosaurs are known from just a couple of bones…. Currently, prior to the publication of Dreadnoughtus, the most complete supermassive titanosaur, Futalognkosaurus, is known from a rather complete skeleton in its neck and torso but was not found with most of its limbs, was not found with a tail, was not found with any skull. So Dreadnoughtus dinosaur, which preserves all the body segments, is by far the most complete supermassive dinosaur.

The reconstructed skeleton and body silhouette of Dreadnoughtus, showing fossil bones that were found in white.
The reconstructed skeleton and body silhouette of Dreadnoughtus, showing fossil bones that were found in white. The completeness in terms of types of bones represented is extraordinarily high in comparison to other known supermassive titanosaurs.

 

Tell us more about the features of this dinosaur and the fossils you found.

Almost every feature of this dinosaur is remarkable, and most notably for its great girth and for its muscularity. The femur, the thigh bone, is over six feet tall. The humerus, the upper arm bone, is almost as tall as I am. The tailbones are gargantuan with huge muscle scars that show us that it essentially had this weaponized tail that was 30 feet long. This is an incredibly bulky, massively muscled tail. Everything about it bespeaks to its power. One of the really interesting aspects of this tail is that these chevron bones, the tail-wagging bones, stay big and are present right most of the way down the tail.

Lacovara with the femur of Dreadnoughtus
Lacovara with the femur of Dreadnoughtus

Its neck was 37 feet long. One vertebra in the neck is over a yard across…. They actually have ribs in the neck, to hold their throat open.

Another interesting feature of these big animals is they have all kinds of evolutionary adaptations for saving weight. They’re really, really big, but it saves energy if they have ways to lighten their body. And so their neck vertebrae have lots of air cavities inside it. In fact, there are air chambers not only that go through the lungs, but other pneumatic cavities that pervade these bones. Their neck is largely a tube of air. Their heads are small. You can’t afford to have a very big weight at the end of a 37-foot lever. So even though this animal is as big as a house, its head would be about as big as a horse’s head, made with more bones than your skull, thinner bones than your skull, in places, less well put together. And so these animals are almost never found with any skull material. We have a little bit of premaxilla for this dinosaur, and a single tooth, which is good for this class of dinosaurs.

Even going back into their body, they have lungs but they have numerous air bladders and air chambers that go through their back vertebrae into their ribs, into their hip, even into their tail a little bit. Any bone that doesn’t bear a lot of weight is very pneumatic.

And so they have lots of ways to save weight, but these are also ways of shedding heat. One of the major problems with having a really, really big body is that heat builds up inside of it. So if you look at modern animals, living animals, there’s a close correlation between body mass and body temperature, and you can see this positive correlation going up. If you plotted a 65-ton animal on that curve of living animals, it would be a temperature that would literally cook meat. We know this thing wasn’t cooking inside of its body, so it has all these extraordinary mechanisms to constantly get rid of heat. I don’t think it has to spend any calories at all to maintain its body temperature. But it has all these passive mechanisms to shed heat. So it’s the air cavities that go through the body. It’s also the really long neck and really long tail, and long legs, which give it a tremendous amount of surface area per volume, allowing it to shed heat efficiently to the environment. They’re remarkable creatures.

Bones of Dreadnoughtus schrani in Lacovara’s fossil lab at Drexel University. Scapula (shoulder blade) (standing against divider); Cervical (neck) vertebra (on pallet), surrounded by preserved neck tendons; Sternal (chest) plates (front of table); Dorsal (mid-back) vertebrae (Rear of table).
Bones of Dreadnoughtus schrani in Lacovara’s fossil lab at Drexel University. Scapula (shoulder blade) (standing against divider); Cervical (neck) vertebra (on pallet), surrounded by preserved neck tendons; Sternal (chest) plates (front of table); Dorsal (mid-back) vertebrae (Rear of table).

The metatarsals, or toe bones, are some of my favorite bones to show people, and I usually put them in people’s hands and let people feel the weight of them. They’re pretty heavy, maybe 30 pounds each. [We also found] a claw from the back foot of this dinosaur. Now if you’ve ever seen a cat’s claw come off, you know it has that little bony nub inside. That’s what [we found]. And so it would have the keratinous sheath, like fingernail material, that would come way out. [We are looking at] a huge animal, as big as a house with that weaponized tail, and then these giant claws. It’s not preying on animals, but it doesn’t want other animals to mess with it. It doesn’t want competitors for resources messing with it. And so it has a combination of defensive and offensive weaponry that is, I think, unparalleled.

This incredibly large and muscled individual would have feared nothing in its landscape.

This animal would not have had to worry about predators. It wouldn’t have to worry about other species of herbivores. It would have feared nothing. And as a result of that, that evokes, to me, this class of turn-of-the-last-century battleships called the dreadnoughts, which were huge, thickly clad and impervious. And as a result I’ve decided to name this dinosaur Dreadnoughtus or ‘fears nothing.’ I think it’s finally time the herbivores get their due for being the toughest creatures in an environment.

So Dreadnoughtus was about the size of a two-story house, and a vegetarian?

[People are] often surprised when I tell them it eats plants, but any ecologist would know right away that this animal would have to eat plants. You can only get this big if you eat plants. When you change feeding levels in an ecosystem, you leave behind 90 percent of the energy, so most of the calories in an ecosystem are in the plants. And in the herbivores, you can only transfer about ten percent of that to that level, and only about ten percent to the meat eating level. So if you want to be either really big or really numerous, you have to eat plants.

Artist's rendering of Dreadnoughtus in life. Credit: Mark A Klingler, Carnegie Museum of Natural History
Artist’s rendering of Dreadnoughtus in life. Credit: Mark A Klingler, Carnegie Museum of Natural History

Let me just add: Herbivores, plant eaters in general, I don’t think get their due for being fearsome creatures, but if you ask any expeditioner, if you ask anybody who goes on safari in Africa, what they’re afraid of, they’re not going to say lions or cheetahs. They’re going to say water buffalo, and hippos, and rhinos. Herbivores are nasty creatures, and they can sustain serious injury and motor right along. You can have a hippo with a broken leg that can feed just fine and can live a long, happy life. If you’re a cheetah and you break a toe, you’re probably going to starve to death. So I always say I would rather be locked in a room with a lion than with a water buffalo. And I definitely wouldn’t want to be locked in a room with [Dreadnoughtus]. I’m sure it was a nasty beast.

It would be hard to find a room big enough.

Yeah, it’d be a convention center, maybe.

How did Dreadnoughtus live?

Imagine this incredible lifelong obsession with eating. I mean, every day is about taking in enough calories to nourish this house-sized body and to grow very, very rapidly. There’s a premium on growth, there’s this evolutionary pressure to get big, so you’re not predated upon by the meat eaters. So I imagine their day consists largely of standing in one place. You have this 37-foot-long neck balanced by a 30-foot-long tail in the back. Without moving your legs, you have access to this giant feeding envelope of trees and fern leaves, and so you spend maybe an hour clearing out this patch that has thousands of calories in it. And then you take three steps over to the right and you spend the next hour or so clearing out that patch. And I think that’s essentially your day. Have sex every now and then, and you pretty much have the life and times of a big dinosaur like this.

There’s a good chance that they were migratory because of the amount of calories that they needed to take in. They probably had to follow the growth patterns of the plants. This particular dinosaur was found in southernmost Patagonia at about 77 million years ago, which was when it lived. But the Drake Passage between South America and Antarctica hadn’t opened up yet. So I suspect that this dinosaur was actually an Antarctic species, and that we found it in its northernmost range. The planet was warm enough in the late Cretaceous period that Antarctica was not glaciated. It was a pine forest, a boreal forest, and there were dinosaurs that lived there. We don’t really have access to that record because of the glacial cap that covers Antarctica today. And so the only fragments we get into that Antarctic fauna are things that we can find in southern Patagonia and things you can find in Australia, which was also attached at that point. So I wouldn’t be surprised if we found this dinosaur on its migration from Antarctica to Patagonia when it got caught in a flooding event on a river. A levee broke and it got spit out onto the flood plain with this big ball of soupy sediment that allowed it to be preserved.

How would Dreadnoughtus die?

A big animal like this dinosaur was probably also a long-lived animal. We don’t know for sure, but I wouldn’t be surprised at all if members of this species lived to be 100 or even more. You very rarely find a nearly complete dinosaur skeleton that doesn’t show signs of both injury and pathology. So we see arthritis in dinosaurs, we see bone cancer in dinosaurs, we see lots of fractures and healed breaks and developmental abnormalities. They had a hard life, like all animals tend to.

A dinosaur like this is going to be at great risk when they’re small. The size of eggs did not scale with adult size. This dinosaur, weighing 65 tons as an adult, would have hatched out of an egg that wasn’t much larger than an ostrich egg. And so you could have a herd of these dinosaurs running around on your kitchen table, that eventually grow to be the size of your house. So they probably have a very different lifestyle when they’re young, probably hiding in the fern forest, staying away from predators, eating all that they can so that they can gain the body mass necessary then to be invulnerable to predation.

Once they’re full size, then their major threats are pathological diseases and environmental. In the case of this [individual fossilized] dinosaur, it appears to have been killed in a geological disaster. It doesn’t matter how big you get, you always have to fear geology.

Read Part 2 of the interview to look back into the process of discovery and then forward into how paleontology is going high-tech and much more.

 

Note to news media: Additional resources, including available multimedia resources and other information about Dreadnoughtus schrani are available from the Dreadnoughtus resource page at https://newsblog.drexel.edu/dinosaur.

For news media interview requests for Kenneth Lacovara, contact Rachel Ewing, raewing@drexel.edu, 215.895.2614.