Spinosaurus waded into the water to ambush fish of any size

The lifestyle and hunting strategies of Spinosaurus aegyptiacus, a colossal Cretaceous-era dinosaur with a distinctive sail-like spine, have long been subjects of intense scientific debate. 

Was this massive predator, one of the largest to ever exist and notably adapted to aquatic environments, a deep-sea hunter or did it prefer to catch its prey in shallower waters near the shore? 

Hunting habits of Spinosaurus aegyptiacus

A recent study led by a team of paleontologists at the University of Chicago, examining the bone density of this enigmatic dinosaur, delves into this question, providing new insights into the debate.

Shoreline predator 

The discussion around the aquatic habits of Spinosaurus reignited with the publication of a near-complete specimen in 2014, described in the journal Science by a UChicago-led team as possibly a shoreline predator. 

Underwater predator 

On the contrary, a 2020 Nature study proposed, based on the discovery of tall-spined tail bones, that Spinosaurus might have swum like an eel to pursue prey underwater. 

Further support for this underwater hunting theory came in 2022, suggesting Spinosaurus used its dense bones as ballast for diving, similar to a penguin’s strategy.

Critical new assessment 

However, the University of Chicago team, including senior author Paul Sereno and first author Nathan Myhrvold, Founder and CEO of Intellectual Ventures, revisited these claims in their latest work, by critically assessing the methodology used in prior studies to determine bone density and its implications for the dinosaur’s lifestyle.

“We had made the thin sections of these species that were used for bone density calculations, and so we thought we would start by trying to replicate their measurements. But we encountered many factors that generated a range of values – enough to undermine the conclusions,” explained Sereno. 

This reflects the complexity of accurately interpreting bone density in relation to aquatic capabilities, especially given the variances in modern and extinct species’ bone compositions.

Limitations of the statistical method 

Moreover, the study scrutinized the statistical method employed in the 2022 study – phylogenetic flexible discriminant analysis (pFDA) – to classify Spinosaurus’s behavior. Myhrvold pointed out the limitations of this approach: 

“Unfortunately, that technique does not work properly unless you have lots of data, you make apples-to-apples comparisons, and you check that the data meet certain statistical prerequisites. None of those requirements were met in that earlier study, so the results just didn’t hold up under reexamination.”

Spinosaurus aegyptiacus was a semi-aquatic hunter

The team’s findings not only challenge previous interpretations but also underscore the importance of applying rigorous, consistent criteria in statistical analyses. 

The research suggests that Spinosaurus, despite its massive size and aquatic adaptations, was likely a semi-aquatic predator that hunted in waters where it could remain grounded, ambushing fish with its powerful jaws and claws while avoiding deep or open water hunting.

“We think Spinosaurus, one of the largest predatory animals ever to have evolved, needed extra bone strength to support its weight on its relatively short hind limbs,” explained Sereno

“Spinosaurus was able to wade into waterways more than six feet deep without floating, where it could ambush fish of any size with its claws and jaws – but all while keeping its toes firmly anchored in the mud.”

Broader implications 

This research, published in the journal PLoS ONE, sheds light on the complex nature of paleontological inquiry, where new evidence and methodologies can significantly alter our understanding of prehistoric life. 

It also highlights the need for cautious interpretation of statistical analyses and the value of considering multiple lines of evidence when reconstructing the behaviors and lifestyles of ancient creatures.

More about Spinosaurus aegyptiacus 

Spinosaurus is one of the most intriguing and distinctive dinosaurs known to science, primarily due to its unique features and adaptations. Here are some key points about Spinosaurus:

Name and discovery

The name “Spinosaurus” means “spine lizard,” a reference to its most noticeable feature: the long, prominent spines extending from its vertebrae. 

These spines could grow over 1.5 meters (5 feet) tall. Spinosaurus fossils were first discovered in Egypt in 1912 by German paleontologist Ernst Stromer, but many original fossils were destroyed during World War II, making subsequent research challenging.

Physical characteristics

Spinosaurus is believed to have been one of the largest carnivorous dinosaurs, with estimates suggesting it could reach lengths of over 15 meters (49 feet) and weigh up to 20 tons. 

Its distinctive spines, forming a “sail” on its back, might have been used for display, thermoregulation, or other functions still debated among scientists.

Aquatic lifestyle of Spinosaurus aegyptiacus

Spinosaurus is notable for its aquatic adaptations, a rarity among dinosaurs. It had a crocodile-like skull with conical teeth perfect for catching fish, and its nostrils were located high on its skull, allowing it to breathe while partially submerged. 

Recent studies suggest it had paddle-like feet and a tail adapted for swimming, indicating it likely spent a lot of time in the water, hunting aquatic prey.

Diet and habitat

Its diet likely consisted mainly of fish, making it one of the few known semi-aquatic, piscivorous dinosaurs. 

Spinosaurus lived in what is now North Africa during the Cretaceous period, approximately 112 to 97 million years ago, in environments ranging from mangroves to river deltas, teeming with life, including various fish, sharks, and other aquatic and semi-aquatic creatures.

Spinosaurus remains a subject of active research and debate, symbolizing the ever-evolving understanding of dinosaur biology and ecology. 

Its unique adaptations make it a standout among dinosaurs, highlighting the diverse ways in which these ancient creatures could thrive in their environments.

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