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The late Cretaceous period—a quick hop back through 90 million years or so—is one of our planet's most fascinating epochs. Massive dinosaurs roamed a hot, humid world rich in carbon dioxide. Today we're here to compare the sizes of two of that world's most significant: the Spinosaurus and the Mosasaurus.
The average Spinosaurus was slightly larger than the average Mosasaurus in length and weight. Spinosaurus was about 55 feet (16.76 m) and 16 metric tons (16000 kg); Mosasaurus was about 50 feet (15.24 m) and 14 metric tons (14000 kg). Extreme sizes for both are around 60 feet (18.28 m).
Therefore, after careful examination of the largest specimens of each species (both near 60 feet or 18.28 meters), the data does not necessarily leave either monster with bragging rights. And as you are about to learn, Spinosaurus and Mosasaurus are two very different animals in terms of appearance and habitat. But first, let's take a quick look at why dinosaurs were so enormous in the first place.
Had you been alive at a time just before the great Chicxulub asteroid impact 66 million years ago, you would have stood in awe of the massive lizards that walked the earth (though not for very long, as many of these lizards were carnivores). But why were these things so gigantic?
Paleontologists theorize that many dinosaurs were huge because of hollow bones and enormous stomachs. Their massive size also likely made hunting more difficult for ferocious predators.
This answer is about the best that science can do. Attempts to unravel the mystery further have resulted in conflicting theories, along with a few puzzle pieces that don't quite fit together.
For instance, we must today cross off richer amounts of atmospheric oxygen as a catalyst for growth, as scientists now know that Earth's atmosphere actually contained less oxygen than it does at present.
Another theory as to why dinosaurs were so big—an overabundance of food—also fails to hold water, as there are plenty of dinosaurs recorded by science whose size easily compares to animals on the planet today.
What we do know is that the bones of many sauropods (long-necked, long-tailed plant-eaters that stood on four legs) did indeed contain pockets of air, reducing the weight of the beasts while maintaining enough strength to support large amounts of skin and muscle. These same sauropods were also equipped with stomachs big enough to store food over long periods of time.
As for being hunted by predators...yeah. Go ahead and try tackling a titanosaur as big as an office building. It's going to take a while, and most T-rexes likely preferred easier pickings.
Now let's learn a little more about the two dinos in question.
To answer this question, I'm going to keep our sites focused on averages rather than extremes.
The average-sized Spinosaurus is indeed bigger than the average-sized Mosasaurus, though not by much. When we do not consider averages, the margin tends to go back and forth in a kind of tug of war.
Spinosaurus average size: 50 to 60 feet (15.24 to 18.28 meters) long, about 16 metric tons (16000 kg) in weight.
Mosasaurus average size: 50 to 55 feet (15.24 to 16.76 meters) long, about 14 metric tons (14000 kg) in weight.
It's a close game. Neither one of these fierce creatures would make good encounter exhibits at SeaWorld.
Now, let’s take a closer look at each of these massive creatures in more detail.
It lived over 90 million years ago in what is today North Africa.
The Spinosaurus was not the type of creature to meet in a dark alley. It wasn't going to help carry bags or hold open doors. It didn't say pleaseor thank you.This thing was massive—a jaw-dropping 50 to 60 feet (15.24 to 18.28 meters) from head to tail. (By comparison, the average Tyrannosaurus rex managed about 35 feet/10.66 meters.)
As for what it looked like, think of a T-rex, but extend its pointy-toothed jaw about 6 feet (1.82 meters). Then, add a rigid, humped spine to its back about 10 feet (3.04 meters) high (making the beast almost 20 feet (6.09 meters) in total height).
Give it a tail 23 feet (7.01 meters) long, and now imagine this tail helping it to swim for aquatic hunting.
Finally, turn and run as fast as you can. Unless your name is Usain Bolt, you won't get far. That's because the Spinosaurus could hit 15 miles per hour (24.14 kph) on land, while most humans can only manage about six miles per hour (9.65 kph), and that’s for humans in excellentphysical shape.
The Spinosaurus was amphibious, yet spent most of its time near the water hunting large fish. It would stand in the shallows and snatch at prey using its long neck and jaws. Modern theory relates the Spinosaurus hunting style to that of storks and cranes.
This seems a rather mundane tactic for such a ferocious-looking predator. However, some paleontologists maintain the Spinosaurus hunted much the way crocodiles do today, which is to say, hunkered down under the surface. It struck fast and hard and showed no mercy. Now that's more like it!
Whichever method it employed, the giant, fin-like spine on its back served to scare away other dinosaurs interested in its fishing spot. The fin was also handy for attracting dates from the opposite sex.
Having said that, it was also something of a bane for the beast, as opponents could easily bite into it and produce a crippling effect (remember that the fin is literally part of this dinosaur's spine).
Whenever we think of dinosaurs, it isn't long until we think about their extinction. From here, the mind almost always leaps to the great Cretaceous–Paleogene extinction event that happened 66 million years ago.
The Spinosaurus did not live to witness this event (a fact for which it would likely be quite grateful). Instead, it was a drought that laid the beast low.
At around 5 million years into its lifespan, the climate of its primary habitat (North Africa) changed. The Spinosaurus liked to hunt in shallow water.
With the drought, much of its hunting ground dried up, leaving our poor Spinosaurus without fish to eat (and because it was so big, it consumed a lot of fish). Worse still, the beast proved itself inept at adaptation.
And thus spells the tale of the Spinosaurus. Due mainly to lack of food for nourishment of its gargantuan size, this magnificent form of life disappeared.
Now let's take a closer look at the Mosasaurus.
It was an aquatic predator from 80 million years ago. It called the Atlantic Ocean home, though artifacts have been found from the Netherlands all the way over to Missouri. In fact, remains of this dinosaur have shown up on every single continent in the world, including Antarctica.
Reconstructed skeletons have the Mosasaurus looking like a twisted nightmare from the mind of Tim Burton. To see it in person, one might first think of a whale; however, a closer look shows us an aquatic reptile that slithered through the water using a long back, even longer tail, and four huge fins.
The Mosasaurus' skull was just under six feet (1.82 meters) in length, choked with double rows of conical teeth that ripped prey to pieces. The pieces were then swallowed in scaly, bloody chunks.
So what did our enormous, cold-blooded terror of the deep like to eat? You might know the old joke about where elephants like to sit. The same punchline applies here.
The Mosasaurus dined on pretty much everything it could fit inside its jaws. This included sharks, turtles, unsuspecting birds who just wanted a quick coelacanth snack, and even smaller members of its own species. In short, the Mosasaurus was a real schoolyard bully. Better be ready to hand over your lunch money.
For a more visual display of these predators in action, see the video here:
If you happen to suffer from galeophobia—the fear of sharks—it is perhaps best that you skip this section. No, the Mosasaurus wasn't a shark, but it looked enough like one. Enough and well beyond when we consider its size.
The average Mosasaurus was 53 feet long and weighed just under 31,000 pounds (14,061.36 kg); extreme versions of the beast could reach up to 60 feet (18.28 meters) long and weigh in at closer to 40,000 pounds (18,143.69 kg).
Richard Dreyfuss was right: Everybody out of the water.
There was really no safe place to go swimming in the reign of the Mosasaurus. As mentioned, fossils and bones from these long-extinct creatures have been found all over the globe. One fossil specimen, found in North Dakota of all places, belonged to a Mosasaurus estimated to be 60 feet (18.28 meters) long.
Why North Dakota? Consider that much of North America was still underwater during the late Cretaceous period. It would have been entirely plausible for the Mosasaurus to swim up a now vanished channel to what is today The Peace Garden State.
The Mosasaurus lived until 66 million years ago. Around this time, an asteroid over three miles (4.82 km) in diameter came hurling from the depths of space. At first, it appeared as a new star in the sky.
Over a period of months, the star became more prominent, until suddenly the Earth's shadow fell across it, making it invisible.
But invisible or not, the asteroid arrived with a message of death. One day it appeared again (surprise!), this time bright enough to blind. It impacted near Chicxulub, Mexico, effectively eliminating 75% of all life on Earth.
Indeed, large creatures such as the Mosasaurus had no chance. With the planet suddenly cast under a blanket of scolding ash, its surface burst into flames.
These flames were fanned by 620 mile per hour (997.79 kph) winds around the impact area that soon swept the globe. The die-off of the dinosaurs was abrupt. They never knew what hit them.
Oh, what a question! I can only imagine what tickets would be worth to see such a bout. To wonder about it today, though, arrives stillborn at the mercy of multiple variables. We must also remember that the two creatures lived in different time periods; they could never have met.
The Mosasaurus could potentially beat the Spinosaurus in a fight, though factors such as environment and opponent size would come into play. The victories and defeats would likely be near even.
Here I shall venture onto the proverbial limb and say that the Mosasaurus would never lose one of these fights in deep water. Its aquatic abilities far exceeded those of the Spinosaurus, which spent most of its time walking on land.
Really though, to ask who would win in a fight between Mosasaurus and Spinosaurus is like asking what would triumph in a battle between fire and ice. Or the Yankees against the Red Sox.
Or the Celtics against the Knicks. It would be epic. It would be glorious. And in the end, nearly as monumental as the extinction events that made it impossible for us ever truly to know.
The Spinosaurus and Mosasaurus were two of the most gigantic dinosaurs of their time. Each shared a similar diet—fish—though lived in different worlds.
They were so close in size that we may as well call it a draw. The same goes for which one would win in a fight.
As for their fate? The Spinosaurus seems to have perished because it could not bring itself to adapt to a new kind of environment.
The Mosasaurus didn’t have the chance to adapt; the asteroid wiped it out. But it’s clear that, at least in part, their massive size proved their undoing.
