When Did Spinosaurus Go Extinct?

The Spinosaurus was one of the largest and most fearsome predators to ever walk the Earth. With its massive sail-like fin and crocodile-like jaws, this giant theropod dominated the river systems of North Africa during the Cretaceous period.

But exactly when did this iconic dinosaur meet its demise and disappear from the fossil record?

If you’re short on time, here’s a quick answer to your question: Spinosaurus likely went extinct around 97 million years ago near the end of the middle Cretaceous period.

In this article, we’ll take an in-depth look at the timeline of Spinosaurus, from its origins to its eventual extinction. We’ll explore key fossil discoveries that have shaped our understanding of this prehistoric predator and examine the climatic and ecological factors that may have led to its demise.

Whether you’re a dinosaur enthusiast or just curious about this apex predator, read on to uncover the mystery of when Spinosaurus went extinct!

The Discovery and Description of Spinosaurus

Early Spinosaurus Fossils

The first known Spinosaurus fossils were discovered in Egypt in 1912 by German paleontologist Ernst Stromer. These included vertebrae, ribs, and hindlimb bones. Stromer classified the fossils as a new species, which he named Spinosaurus aegyptiacus.

Unfortunately, these original Spinosaurus fossils were destroyed during an Allied bombing raid over Munich in World War II.

Additional Spinosaurus fossils were later found in Algeria in the 1950s and Morocco in the 1970s. These allowed scientists to better understand the unique physical characteristics of Spinosaurus, but many questions remained about its size, behavior, and extinction.

The 1912 Discovery in Egypt

In 1912, Ernst Stromer led a fossil hunting expedition in Egypt’s Bahariya Oasis. His team discovered remarkable dinosaur fossils, including bones that Stromer realized represented a previously unknown species.

Vertebrae showed tall neural spines up to 5 feet long, leading Stromer to name the dinosaur Spinosaurus, meaning “spine lizard.”

Stromer brought the Spinosaurus fossils back to Germany and began studying them. He published his findings in 1915, amazed by the giant vertebrae and distinct adaptations like crocodile-like jaws and conical teeth.

Tragically, Allied bombing during WWII destroyed the fossils before much research could be done.

Defining Characteristics and Classification

Spinosaurus belongs to the dinosaur group known as theropods – bipedal mostly meat-eating dinosaurs. It has historically been classified as part of the family Spinosauridae, which includes similar large predators like Baryonyx and Suchomimus.

Some experts argue Spinosaurus was not a typical theropod, given adaptations like crocodile jaws and conical teeth suited for catching fish. Debate continues today over the behavior and extinction of this iconic giant predator.

Dating the Age of Spinosaurus

Geological Context of Fossil Sites

Spinosaurus fossils have been discovered in the Cretaceous rock layers of North Africa, primarily in Egypt and Morocco. These geological formations, like the Bahariya Formation in Egypt, are dated to the Cenomanian stage of the Late Cretaceous, around 99 to 93 million years ago.

The fossils were encased in sedimentary rock layers along with ammonites, bivalves, and other marine creatures. This indicates that the Spinosaurs lived in coastal swamp environments adjacent to the ancient Tethys Seaway.

The creatures were buried in sediments from river deltas that washed their remains out to sea.

Faunal Comparisons and Biostratigraphy

Spinosaurus remains have been found alongside fossils of other Cretaceous dinosaurs and animals. These include the giant crocodilian Sarcosuchus, sawfish, coelacanths, and an early version of modern pike fish.

Studying the other fossils provides clues about Spinosaurus’ place in the Cretaceous ecosystem and food chain.

Comparisons to global finds and evolutionary trends in related species like Baryonyx help paleontologists refine the biostratigraphic position and evolutionary relationships of Spinosaurus. This information supports placement in the mid-Cretaceous around 100-95 million years ago.

Radiometric Dating of Surrounding Rock

In addition to relative dating methods, radiometric dating techniques directly date the Cretaceous rock layers where Spinosaurus was found. Methods like uranium-lead and argon-argon dating are applied to volcanic ash and minerals in the associated sedimentary rocks.

At the Kem Kem Beds in Morocco, radiometric dating consistently provides age estimates of about 95 to 100 million years for the geological strata containing Spinosaurus. This matches well with biostratigraphic data and confirms a mid-Cretaceous age for these predators.

Climatic Changes in the Late Cretaceous Period

The Breakup of Gondwana

During the Late Cretaceous period between 100-66 million years ago, the supercontinent Gondwana was breaking apart. This initiated significant climatic changes across the globe. As the landmasses drifted apart, ocean currents were altered leading to regional cooling and aridification.

Antarctica became isolated over the South Pole resulting in a cold polar climate. Australia separated from Antarctica around 80 million years ago moving northward into warmer latitudes. Africa pulled away from South America opening the South Atlantic Ocean gateway.

Overall, the breakup of Gondwana caused global cooling and increasing aridity which impacted terrestrial ecosystems.

A Transition to Arid Environments

The Late Cretaceous was characterized by a transition from humid conditions to more arid environments in many regions. Several factors contributed to this drying trend. As mentioned, the breakup of Gondwana altered ocean currents leading to regional cooling and reduced precipitation.

In addition, the expansion of shallow epeiric seas inland created major arid zones in continental interiors. Marine transgressions occurred in modern-day Europe, Russia, northern Africa, and North America.

Though spinosaurus and other dinosaurs were adapted to semi-aquatic environments, these vast arid expanses likely caused food shortages and loss of habitat. Uplift of mountain ranges such as the Rocky Mountains created rain shadow effects further reducing moisture in certain areas.

The global cooling coupled with marine transgressions and rain shadow effects created ideal conditions for deserts and arid ecosystems to expand by the Late Cretaceous.

Ecological Pressures and Competition

The Rise of Giant Carcharodontosaurids

Around 95 million years ago in the mid-Cretaceous period, giant carcharodontosaurids like Carcharodontosaurus and Giganotosaurus rose to dominance as apex predators in the ecosystems of North Africa and South America respectively (for reference check this article).

These huge theropods likely outcompeted and replaced spinosaurids like Spinosaurus as top predators.

For example, Carcharodontosaurus is estimated to have weighed up to 8 tons, while the largest Spinosaurus specimens weighed 6-7 tons. The robust jaws and serrated conical teeth of carcharodontosaurids were well-suited to tackling large prey and ripping off flesh, giving them an edge over the more elongated crocodile-like jaws and conical teeth of spinosaurids that were adapted for catching fish.

These giant carcharodontosaurids probably also had higher metabolisms and activity levels compared to the more sluggish spinosaurids. So in a head-to-head battle, the quick and agile carcharodontosaurids likely dominated the slower spinosaurids, forcing them into smaller niche roles and eventually leading to their extinction.

Changes in Prey Availability and Behavior

As sea levels rose during the mid-Cretaceous, the environment of North Africa changed from forests and coastal plains to being more aquatic. Spinosaurids like Spinosaurus were well-adapted to these semi-aquatic ecosystems teeming with large fish and other marine life.

However, by the late Cretaceous around 85 million years ago, falling sea levels led to the retreat of these productive shallow aquatic habitats. This reduced food availability from fish significantly for spinosaurids.

Other contemporaneous theropods like carcharodontosaurids were more generalized hypercarnivores, able to switch between hunting terrestrial plant-eaters and aquatic prey.

The loss of preferred spinosaurid prey sources like fish and marine reptiles likely led to fierce competition and further ecological pressure. Their specialized jaws and teeth made it difficult for them to catch more evasive terrestrial prey compared to other large theropods.

These changes in environmental conditions and the dominance of carcharodontosaurids probably led to Spinosaurus and related spinosaurids dying out by the early late Cretaceous.

Theories on the Extinction of Spinosaurus

Climatic Drying and Loss of Habitat

The predominant theory is that Spinosaurus became extinct due to major climatic changes in what is now North Africa, which led to the loss of its riverine habitat. Around 100-93 million years ago, the region was lush and wet, perfect for a massive aquatic predator like Spinosaurus.

However, the climate gradually became drier and more arid. Rivers and floodplains dried up, eliminating the habitat Spinosaurus depended on.

With the loss of rivers and coastal habitat, Spinosaurus populations would have declined catastrophically. The species was highly specialized for a semiaquatic lifestyle. It lacked many adaptations seen in purely terrestrial theropods.

Stranded in shrinking oases, Spinosaurus would have been outcompeted by more adaptable predators.

Competition from Other Predators

Some paleontologists theorize that increased competition from other predator species, especially Carcharodontosaurus, may have contributed to Spinosaurus’ extinction. Spinosaurus and Carcharodontosaurus lived in the same North African river ecosystems during the mid-Cretaceous.

Both were apex predators, growing to enormous sizes.

As climate change reduced resources, competition between these mega-predators would have intensified. With a more generalized body plan, Carcharodontosaurus may have been better adapted to survival in drier conditions.

There is some fossil evidence of injuries that may have resulted from fights between the huge creatures.

If climate change stressed Spinosaurus populations, conflict with Carcharodontosaurus could have been, literally, the killing blow. Outcompeted for prey and territory, Spinosaurus would have slowly died out.

Combination of Factors

The most likely scenario is that Spinosaurus’ extinction resulted from a combination of climate change, habitat loss, competition with other predators, and other factors like disease or environmental toxins. We see similar patterns driving modern extinctions.

No single threat wiped out Spinosaurus overnight. Rather, multiple forces created a “”perfect storm”” of environmental pressure. Its specialized adaptations became liabilities under shifting conditions. The species passed through an evolutionary bottleneck from which it did not recover.

Ultimately, Spinosaurus disappeared forever around 97 million – 93 million years ago. But discovering more fossils from that crucial period could shed light on why this bizarre, semiaquatic predator died out, even as related dinosaurs like Suchomimus survived a bit longer.

Conclusion

The extinction of Spinosaurus remains an intriguing mystery in paleontology. By synthesizing clues from geology, climatology, and comparative anatomy, scientists have pieced together a narrative of decline as forests receded, competitor dinosaurs arose, and prey became scarce in the dinosaur’s North African haunts.

While an exact extinction date is difficult to pinpoint, most evidence indicates Spinosaurus likely perished around 97 million years ago, 10 million years before the catastrophic asteroid impact ended the Age of Dinosaurs.

The story of Spinosaurus teaches us that even the mightiest kings of the prehistoric world were vulnerable to sudden changes in climate and ecological pressures. As we enter our own age of rapid environmental change, the fossil record reminds us how dramatically shifting habitats and competition can ripple through ecosystems.

While many details remain unclear, each new Spinosaurus fossil discovery brings us closer to understanding the life and demise of the spined reptile that once reigned over Cretaceous North Africa.