Saurolophus

About Saurolophus

Features of Saurolophus: The Secret of the Crest

Saurolophus is a large herbivorous dinosaur that prospered during the Late Cretaceous period of the Mesozoic era (about 71.5 to 66 million years ago). It is a dinosaur whose fossils have been discovered from multiple continents, specifically modern-day North America and Asia, making it an important presence that proves the large-scale migration of fauna through the "Bering Isthmus," which was connected by land at the time.

Its most prominent feature is a rod-like crest protruding obliquely upward and backward from the skull at an angle of about 45 degrees. In the past, this crest was thought to be a "solid projection completely filled with bone." However, recent analysis of its internal structure has revealed that only the tip of the bone is solid, and there is a hollow space where it connects to the skull.

In 2015, a mass fossil of newly hatched juveniles was discovered along with eggshells in the Gobi Desert of Mongolia. Surprisingly, these juveniles lacked the characteristic crest. This suggested that the crest was an organ that developed postnatally as they grew.

Regarding the role of this crest, theories have been proposed that it functioned as a radiator to humidify inhaled air and lower body temperature, as well as an organ to support an "inflatable skin flap" thought to be located near the nostrils. It is believed that, like modern seals, they inflated a giant soft-tissue sac (nasal balloon) for visual appeal or used resonance to produce vocalizations and communicate with their peers.

Skin Impressions and Color Patterns

Hadrosaurids are known for well-preserved skin impression fossils, and Saurolophus also has well-preserved skin traces left behind. Recent research has demonstrated that species of Saurolophus can be clearly identified not only by hard skeletons but also by soft tissues (scale shape and arrangement patterns) alone, bringing a new perspective to dinosaur research.

These body surface patterns are thought to have functioned as camouflage adapted to their respective habitats (forests, open environments, etc.).

Walking and Ecology of Saurolophus

Saurolophus was a "facultative biped," selectively using bipedal and quadrupedal walking depending on the situation. It is speculated that they walked on four legs during normal movement or when eating low-lying plants near the ground, and stood up on two legs when eating leaves at heights of up to 4 meters, or when accelerating rapidly to escape from powerful predators like tyrannosaurids.

Also, analysis of a bony ring called the "sclerotic ring" in their orbits (eye sockets) reveals that they were "cathemeral," repeating short cycles of activity and rest day and night. To maintain their massive bodies reaching up to 11 tons, they needed to make full use of their dental batteries (an assembly of hundreds of teeth) to continuously eat enormous amounts of plants day and night.

Fossil Discovery

The first fossil of Saurolophus was discovered in Alberta, Canada. It was found by Barnum Brown of the American Museum of Natural History in 1911 and described as Saurolophus osborni the following year in 1912. Subsequently, many Saurolophus angustirostris were discovered in Mongolia, Asia, making it one of the most successful ornithopods in Asia.