New thoughts on a swimming Spinosaurus

Earlier we looked at an illustration of Spinosaurus (Fig. 1) showing how the sail could have emerged from cooler waters into hotter atmospheres to regulate internal temperature through blood flow.

Figure 1. Aquatic Spinosaurus to scale with contemporary Early Cretaceous giant fish.

Figure 1. Aquatic Spinosaurus to scale with contemporary Early Cretaceous giant fish.

That illustration 
(Fig.1) showed Spinosaurus in waters shallow enough to barely touch the bottom with toes and fingers. Pretty conservative. Today, let’s go deeper (Fig. 2).

Figure 1. Spinosaurus in deeper waters. Graphic is from Henderson 2018 with water line as he indicates.

Figure 1. Spinosaurus in deeper waters. Graphic is from Henderson 2018 with water line as he indicates. Five images change every five seconds. More stability occurs when the skull and/or tail drops and by even partially allowing the sail to be filled with air. Maybe that’s why Spinosaurus has a sail!

Henderson 2018
brings his own doubt to the floating Spinosaurus hypothesis using computer models (Fig. 2) despite all other evidence, including stomach contents (fish) pointing to an aquatic niche. Henderson’s data indicated a lack of stability in water for his spinosaur models. Henderson’s computer models of pterosaurs have been infamous for their inaccuracy.(Several pterosaur workers also opined on this.)

This time morphological accuracy doesn’t seem to be the problem.
Instead his models appear to float a little too high out of the water, the model appears to be a little ‘stiff’ (flexibility and dynamism are present in all tetrapods), AND he assumes the spaces between the dorsal spines were solid, even if thin.

Here
(Fig. 2) alongside the underwater lounging croc, spinosaurs could have floated with greater stability by simply dropping the solid tail or by dropping the skull to search for fish… while floating. When diving, Spinosaurus could have filled the spaces between the tall dorsal ribs with air, or emptied them, precisely as necessary. Theropods are famous for being pneumatic.

So, perhaps the most important part
of the Spinosaurus sail is the space between the bones. And if soo, is that why Spinosaurus had a sail to begin with? Sometimes you just have to look at a problem from another point-of-view. Toss that idea around. See if it generates any further discussion…

Don’t hold your breath waiting for consensus on this one.
It takes about a hundred years for paleontologists to agree to anything.

References
Henderson D 2018. A buoyancy, balance and stability challenge to the hypothesis of a semi-aquatic Spinosaurus Stromer, 1915 (Dinosauria: Theropoda). PeerJ 6:e5409; DOI 10.7717/peerj.5409

2 thoughts on “New thoughts on a swimming Spinosaurus

  1. 1. How would giving the sail airsacs fix Spinosaurus floating too high out of the water? If anything, wouldn’t Bailey’s (1997?) idea that the base of the sail (where the spines are expanded) was really thick with muscles and the rest of the sail structured like withers give it enough mass on top to sink it a bit more?

    2. Spinosaurus likely didn’t have airsacs around the dorsal neural spines anyway. These would probably leave evidence like Mapusaurus’ laminae.

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