But there was one thing that did S. mirabilis different from S. egyptiacus. The word “mirabilis” in the name of the newly discovered Spinosaurus translates to “wonderful” in Latin. The most surprising find by Sereno’s team was a prominent plaque on the animal’s head, one of the largest ever found.
A scimitar crown
Instead of the jagged, sharp edge you see on it S. egyptiacus, S. mirabilis it had a blade-shaped, scimitar-like bone that curved up and back from its nose, reaching high above its eyes. This structure is made of solid bones, unlike the more porous, airy casques found in other modern birds. However, the bone itself was covered with fine longitudinal lines and deep grooves, indicating that the spinal cord was just a rudiment.
A newly discovered skull, along with a model of what its skull would have looked like in a living animal.
A newly discovered skull, along with a model of what its skull would have looked like in a living animal.
Credit: Chicago Fossil Lab
In life S. mirabilisthis plant would be covered and greatly expanded with a keratinous shell, like the strong growths formed by modern guinea fowls. When the scale reaches a fully grown adult, the spinal cord alone can measure about 40 centimeters in length; with its keratinous shell, it could easily exceed half a meter. For Sereno, the purpose of this “wonderful” scimitar crown was similar to the crests worn today by cranes and herons. “It was asymmetrical. It varies between individuals. So, I think it was only for display,” explained Sereno.
His team hypothesizes that visual signaling was the primary function of both cranial crests and the large trunk and tail sails that define spinosaurids. On crowded beaches and riverbanks, an elevated, brightly colored deck or sail can be a great way to broadcast your size, maturity, and genetics to competitors and potential mates without getting into an expensive fight.
However, when it comes to S. mirabilis, weighing more than 7 tons, they can argue. “Spinosaurus was very big. I think it could eat anything it wanted even though its vehicle was a fish,” said Sereno.
Crocodile jaw
The showpiece on its forehead on the side, i S. mirabilis it was a special killing machine. Its snout showed a low profile with parallel dorsal and ventral margins, ending in a mushroom-shaped extension at the tip. The upper and lower jaws allowed the teeth to fit together—there was a noticeable diastema, a gap in the upper tooth row, that accommodated the larger teeth of the lower jaw. I S. mirabilis the jaw structure appears to be similar to that of modern long-nosed crocodiles, adapted for snapping and capturing aquatic prey with a quick, trap-like closure. Surprisingly, S. mirabilis showed a relatively large gap between the teeth in the back part of its nose S. egyptiacus despite being almost identical.
