March 4th

The Skeletal Aggregate Question

Yesterday, we talked about Spinosaurus. The skeleton on display in the traveling Spinosaurus exhibit from National Geographic is a model derived from casts of the original skeletal material located by the nomad and reclaimed for science by Nizar Ibrahim, along with fragments digitally scanned from various private collections, and reconstructions of the original Spinosaurus aegypticus bones that were bombed in World War II. Whatever was still missing after all that work was digitally reconstructed by using basic principles of anatomy and the skeletal structure of close spinosaur relatives like Suchomimus.

Spinosaurus reconstruction / Tyler Keillor
Spinosaurus reconstruction / Tyler Keillor

Some have questioned whether this amalgamation really amounts to an accurate picture of Spinosaurus. Especially when the skeleton championed by Nizar Ibrahim, Paul Sereno, Tyler Keillor, and others suggested a quadrupedal, semi-aquatic lifestyle for the largest (or at least, longest) dinosaurian predator.

Keillor and Ibrahim took to the blogosphere defending their reconstruction. They provided additional information about measurements, scanning techniques, and other considerations which helped to calm rampant skepticism from some quarters. Even with Sereno seemingly somewhat backtracking on just how aquatic Spinosaurus might have been in more recent addresses, this skeleton is our best representation of what this bizarre predator looked like 97 million years ago.

As always in paleontology, the real skeletal answers always rest with the next discovery. But because Spinosaurus is so rare, a few more generations may pass until the next semi-complete skeleton is unearthed. Until then, this is our best guess. And it’s not a wild guess. The lines of evidence used by the team are not haphazard. They are carefully drawn from what would link the skeletal elements together, what makes sense anatomically, and reasonable extrapolations from closely related species.

This kind of digital paleontology is new, but it’s a logical progression from historical extrapolation and analysis. Which we will discuss, right here, tomorrow.

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