Is This What Dinosaurs Looked Like?

As most five-year-olds can tell you, Spinosaurus has always ranked among the coolest dinosaurs, but despite its consistent standing, its anatomy and behaviour have been the subject of wild debate. The original discovery of Spinosaurus aegyptiacus pegged it as an upright Godzilla-esque creature supported by its hind legs and tail. No more than 30 years later, it was overhauled and became the longer, traditional dinosaur shape we all know and love. A few decades after that, its boxy jaws were swapped out for narrow fish-eating ones.

As years continued to go by, the namesake spines were given a new shape, the tail became thicker, the feet became webbed, and on and on it goes. With the recent discovery of a new species of Spinosaurus — Spinosaurus maribilis — the semi-aquatic predator finds itself up in the air yet again. This long line of changes begs the question: how much can we really learn from fossils?

Perhaps the largest change in palaeontology recently has been the revocation of “shrink-wrapping,” a practice in which skin is placed directly over bones, leaving little room for fat, muscle, and other organs. This problem created iconic mythologised creatures like Jurassic Park’s T. rex and led to pervasive misconceptions. In reality, animal silhouettes often bear little resemblance to their skeletons; just take a look at an elephant, pug, or hippo skull. Unfortunately, soft tissues are almost never fossilised, which means we often times have to guess at the distribution of muscle and fat based on skeletal shape, bone texture, and modern-day descendants.

Another big change came from the discovery of a feathered Sinosauropteryx in 1996. Prior to that, dinosaurs were associated much more strongly with their reptilian relatives rather than their avian offspring, leading to scaly, lizard-like depictions as seen in Jurassic Park.

Though this remains accurate for some larger dinosaurs like the long-necked Brontosaurus, the iconic Velociraptor should really be covered in mottled feathers and feature small wings instead of scabrous arms. This has been just one portion of a long and ongoing debate over skin in dinosaurs. Texture, colour, patterns, scales, and feathers are all hotly debated for most species, and almost all the iconic dinos are colored and textured based on guesswork alone.

Researchers have found preserved feathers for Yutyrannus – an ancestor of T. rex – but it lived nearly as far from the king of the dinosaurs as T. rex did from us, leaving 60 million years of speculation. In fact, melanosomes (pigment-storing organelles) have only been preserved for a handful of species, and do not give any indication of blues and greens that may have been present.

This being said, we can actually infer a lot about dinosaur behaviour through their bones and tissues. In Netflix’s recent The Dinosaurs series, Spinosaurus was shown with its open mouth submerged in the water, waiting for an unfortunate fish to swim between its jaws. Though it is speculation, scientists point to lots of evidence for this hunting style.

The most basic piece of the puzzle is the teeth; Spinosaurus had conical teeth instead of large banana-shaped ones like most predators, which means it specialised in eating fish. Additionally, the nostrils of Spinosaurus are positioned near the base of the snout instead of the tip, which would allow its mouth to be almost fully submerged for as long as it wants. Finally, some strange dimpling in the bones of Spinosaurus, along with large sinuses, indicates that it may have had a lot of specialised pressure-sensing structures, allowing it to acutely feel vibrations in the water – perfect for ambushing. It is mainly through this comparative anatomy that we can make assumptions about the body and behaviour of this megafauna.

Though our understanding of ancient animals continues to evolve, for most creatures, there is a clear convergence to one form or another. While Spinosaurus has been through many changes, it has always kept its namesake spines, and although T. rex may be feathered, it is still undoubtedly the king of the Cretaceous. As researchers unearth more and more fossils, their confidence and consensus only grows meaning today’s reconstructions are the most accurate and evidentiary they can be. 

Illustration by Isabelle Holloway