Albertosaurus

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Species: sarcophagus

Range: Late Cretaceous (Maastrichtian, 70-65 MYA) of Alberta, Canada

Size estimate: 25-30 ft length, 3 tons

Discovery: Henry F. Osborn, 1905

Classification: dinosauria, saurischia, therapoda, coelurosaura, tyrannosauridae

 

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True to Life?

 

Since no one has ever seen a living dinosaur, and the missing pieces of the fossil record withhold important clues to their appearance, no artistic representation of a dinosaur ever gets it 100% right. On top of that, new discoveries can change our ideas of extinct creatures drastically. So, how close does this sculpture come to what we know of the original animal?

Albertosaurus:

• Perhaps the most prominent feature of this sculpture, its ribs, tells more of a story about art history than about Albertosaurus. The 70s, 80s, and 90s experienced a paradigm shift in dinosaur science and paleoart later called “the Dinosaur Renaissance.” New evidence suggested dinosaurs reached higher levels of activity than most other reptiles, leading some researchers to champion the idea of dinosaurian warm-bloodedness. Artists in particular took to this idea, shifting their portrayals of dinosaurs to more dynamic, athletic poses. Many of them stated outright that their art reacted against dinosaur portrayals of the early 20th century which they said often depicted dinosaurs as fat, slow, and stupid. Some even said that they would intentionally err on the side of making dinosaurs look skinny if it helped them look more active, energetic, and less like the dinosaur art of yesteryear. One extreme and famous example shows the belly and lower hip bones of Tyrannosaurus as little more than skin-covered bone—so much so that the flap of skin covering the pubis (the hip bone shaped like an upside-down T ) and ischium (the rod that points backwards and down) appears to be backlit by sunlight, as if the skin could get that thin! Since muscles used for maneuvering the animal attached to those bones, a Tyrannnosaurus that skinny would not be capable of changing direction! This Albertosaurus sculpture embraces that Dinosaur Renaissance super-skinny aesthetic, which explains why its belly ribs are showing. Most, if not all theropods featured belly ribs, but their extreme thinness made them prone to rot or washing away in the currents that buried dinosaur fossils. Crocodiles have them, too. These belly ribs play an important role in reptilian abdominal muscle complexes, and would not jut from the skin in even an emaciated animal.

• We know Albertosaurus through many excellent specimens, some of which remained articulated and even preserved traces of soft tissue like skin as impressions in the rock. The skeleton of an older, close relative—some even consider it a species of Albertosaurus—called Gorgosaurus is featured on the northern wall of the Stewart Museum (look behind the trees) slightly larger than life size and depicted as it was fossilized. This sculpture therefore follows the skeletal anatomy fairly closely.

• Though skin patches found with Albertosaurus and other members of the tyrannosaurid family preserve areas only a foot or two square at largest, collectively they confirm a pebbly skin texture composed of very small scales, resembling a basketball in some places. Larger feature scales on this animal’s back are speculative for this species, but they have been found on other theropods, like Carnotaurus. The lumps around the eyes are based on rough areas of bone found on some relatives which suggest thick, horn-like skin grew there, though the pattern shown here is based on older information and not strictly accurate. It would have had prominent, sculptured eyebrows, extending even partly behind the eye, but they would not have looked like round, regular lumps.

• The birdlike scales covering the ankles and toes have not been found in tyrannosaurs, but a distant relative, the carcharodontosaur Concavenator (closer in relation to the Acrocanthosaurus behind you), preserved such a podotheca—the term roughly means “foot armor.” Fossils suggest that birds as a group had to re-acquire their podothecas after developing feathers. To do so, they delay feather development long enough for scales to form on the legs, then release the hormones for creating feathers. Exactly how Concavenator and presumably other scaly theropods would have developed their podothecas remains controversial, since theropod embryos are hard to come by and impossible to observe as they grew, but the results appear controlled by the same needs for extra protection around the ankles. The scalation on this sculpture’s toes is therefore loosely feasible.

• One defining characteristic of tyrannosaurs in particular sets them apart from most reptiles. Whereas reptiles tend to have jaws full of teeth all roughly the same size and shape, tyrannosaurs vary the shape and size of their teeth depending on their placement in the jaws. The ones in front trend smaller, narrower, and have a D-shaped cross section. Further back in the jaws, they become almost circular in cross section, taller, and proportionately stouter. This trend never matches the extent of the crazy variety of mammal teeth, but it still sets them apart from reptilian trends. Scientists call the condition of having a variety of tooth shapes in the same jaws “heterodonty.” The teeth in this sculpture don’t do tyrannosaur heterodonty much justice, unfortunately.