We all know about the different dinosaurs that had roamed the Earth billions of years before we were even born. From the Tyrannosaurus Rex to the Triceratops to the pterodactyls, we have always been left in awe of their beastly attributes and ways of life. Most of us would have been very thankful that they were not born to live alongside these mighty beasts. However, there are dinosaurs whose characteristics, mainly their mouths, are still evident until now. These are the hadrosaurs of the duck-billed dinosaurs, which roamed parts of North America back then.
What are hadrosaurs? Hadrosaurs are known as the duck-billed dinosaurs of North America. These were herbivores, which ate leaves and vegetation unlike their more carnivorous counterparts, and they also laid eggs. They are very well-known for their duck-billed beaks, which they use for eating.
This article will discuss the hadrosaurs discovered in North America, from the New England states to Canada. We will also discuss the Parasaurolophus, another hadrosaur species discovered in northern Montana, known for its nesting colonies. Lastly, we will also discuss the anatomy of a hadrosaur, focusing more on its teeth and mouth.
What Hadrosaurs Lived In North America And Where Have Fossils Been Found?
Dr. Caspar Wistar discovered the first dinosaur fossil in the United States in 1787, when he discovered a thigh bone in Gloucester County, New Jersey. It has since been lost, but more fossils were later found in the area.
Not only did New Jersey was the place where the first dinosaur fossils have been found, but also the first hadrosaurs fossils were found here as well.
William Parker Foulke discovered the first nearly-complete dinosaur skeleton. Foulke had heard about a discovery made by workers in a Cretaceous marl (a crumbly type of soil) pit on the John E. Hopkins farm in Haddonfield, New Jersey, in 1838.
In 1858, Foulke became aware of the discovery and recognized its significance. Unfortunately, workers had already removed some of the bones.
Hadrosaurus fouki (meaning “Foulke’s big lizard”) was discovered and named by US anatomist Joseph Leidy.
It was a dinosaur with a duckbill, but it is now a doubtful genus because there is so little fossil information. The Philadelphia Academy of Natural Sciences is home to the “Haddonfield Hadrosaurus.”
Ferdinand Vandeveer Hayden and Joseph Leidy’s Discoveries
Several years later, Ferdinand Vandeveer Hayden discovered the very first dinosaur fossils from North America. It was seen during one of Hayden’s expeditions near the Judith River from 1854 to 1856.
Joseph Leidy obtained these specimens in 1856. Two of the several species named among the specimens were Trachodon mirabilis of the Judith River Formation and Thespesius occidentalis of the Great Lignite Formation.
Around the same time, geologist William Parker Foulke in Philadelphia, on the other side of the continent, was informed of numerous large bones accidentally discovered by farmer John E. Hopkins some twenty years earlier.
In 1858, Foulke obtained permission to investigate the now-disappearing fossils, and these specimens were also given to Leidy. They were described the same year as Hadrosaurus foulkii, providing a slightly better picture of a hadrosaur’s form.
In a paper published in 1865, Leidy added to the description. Leidy briefly suggested in his 1858 work that the animal was likely amphibious. This school of thought about hadrosaurs would come to dominate for over a century to come.
Further discoveries from the East included “Hadrosaurus minor” and “Ornithotarsus immanis,” and Edward Drinker Cope led an expedition to the Judith River Formation, where Trachodon was discovered.
Following the discovery of the fragments, he named seven new species in two genera and assigned material to Hadrosaurus.
YouTube Video About Hadrosaurs
Cope had studied hadrosaur jaws and concluded that the teeth were fragile and could have been dislodged incredibly easily. As a result, he hypothesized that the animals must have primarily fed on soft water plants.
He presented this hypothesis to the Philadelphia Academy in 1883, and it would be very influential on future research. (Source)
Ostrom’s Challenge To The Hadrosaurs Being Semi-Aquatic Dinosaurs
Twenty years later, in 1964, another seminal work, this time by John H. Ostrom, would be published. It called into question the belief that hadrosaurs were semi-aquatic animals, which had been held since Leidy’s work in the 1850s.
This novel approach was supported by evidence of the environment and climate in which they lived, coexisting flora and fauna, physical anatomy, and preserved stomach context from mummies.
Based on the data, Ostrom concluded that the idea that hadrosaurs were adapted for aquatic life was extremely lacking in evidence and instead proposed that they were capable terrestrial animals that browsed on plants such as conifers.
He was still unsure about the purpose of the paddle-like hand Osborn had described, as well as their long, paddle-like tails. As a result, he agreed with the theory that hadrosaurs would have sought refuge from predators in the water.
Unique Hadrosaur Dinosaurs Found in North America
Starting with the Parasaurolophus, let’s examine some of the well-known Hadrosaurs from North America.
The Crested Parasaurolophus
Parasaurolophus is a hadrosaurid, a group of Cretaceous dinosaurs known for their bizarre head adornments. This genus is known for its large, elaborate cranial crest, which forms a long curved tube projecting upwards and back from the skull at its largest.
The Chinese Charonosaurus, which may have been its closest relative, had a similar skull and possibly a similar crest.
Scientists have debated the crest’s functions, but the consensus is that they include visual recognition of both species and sex, acoustic resonance, and thermoregulation. It is one of the rarer duckbills, with only a few good specimens known.
The Discovery Of Maiasaura In Northern Montana
The late 1970s discovery of Maiasaura revealed the first evidence for parental care in dinosaurs. Thousands of Maiasaura bones have been discovered together in northern Montana. Maisaura is known from the fossils of eggs, babies, juveniles, and adults, and it is Montana’s state fossil.
The first Maiasaura fossils were discovered in 1978. In 1979, the genus was named. The term refers to discovering nests containing eggs, embryos, and young animals in a nesting colony.
It was the first time such evidence for a dinosaur was obtained, demonstrating that Maiasaura fed its young while they were in the nest. Hundreds of Maiasaura bones have been discovered.
Maiasaura stood about 9 meters (30 feet) tall. Adults walked on all fours, while young animals walked on their hind legs. Maiasaura was most likely a close relative of Brachylophosaurus.
Edmontosaurus: The Guardians Of The Great White North
Aside from the discoveries in Montana and New Jersey, dinosaurs were also discovered to be living on the northern border between the United States and Canada.
Edmontosaurus is a perfect example of the Canadian dinosaurs discovered by paleontologists. Edmontosaurus included some of the largest hadrosaurid species, reaching lengths of up to 12 meters (39 feet) and weighing around 4.0 metric tons (4.4 short tons).
Evidence for an even larger maximum size of 15 m (49 ft) and weighing 9.07 metric tons (10.00 short tons) for Edmontosaurus annectens exists in the form of two fossilized specimens housed at the Museum of the Rockies. Several well-preserved specimens are known, including bones and extensive skin impressions and possibly gut contents in some cases. (Source)
It is classified as a genus of saurolophine (or hadrosaurus) hadrosaurid, a group of hadrosaurids with smaller solid crests or fleshy combs rather than large, hollow crests.
The first Edmontosaurus fossils were discovered in the Horseshoe Canyon Formation, formerly known as the lower Edmonton Formation, in southern Alberta (named after Edmonton, the capital city).
Edmontosaurus was found all over western North America. The distribution of Edmontosaurus fossils suggests that it preferred coastal plains and coasts. It was a herbivore that could move on two and four legs. Edmontosaurus has lived in groups and may have been migratory, based on evidence from several bone beds.
Researchers have studied its paleobiology in-depth, including its brain, how it may have fed, and injuries and pathologies, such as evidence for tyrannosaur attacks on a few edmontosaur specimens.
Crests, Skulls, Teeth, and Body – Anatomy of Hadrosaurs
The General Description Of A Hadrosaur
Hadrosaurs were strong-built dinosaurs, measuring about 30 feet from head to tail and weighing between three and four tons. It most likely spent its time crouched on all fours, munching on the low-lying vegetation of its late Cretaceous habitat in North America.
When startled by hungry tyrannosaurs, Hadrosaurus, like other duck-billed dinosaurs, would have been capable of rearing up on its two hind legs and fleeing, which must have been a stressful experience for any smaller dinosaurs lurking nearby.
This dinosaur almost certainly lived in small herds, with females laying 15 to 20 large eggs at a time in circular patterns, and adults may have provided some parental care. However, keep in mind that the “bill” of Hadrosaurus and other dinosaurs was not flat and yellow like a duck’s, but it did bear a passing resemblance. (Source)
Browsers Or Grazers: How Hadrosaurs Eat With Their Teeth
Hadrosaurids were large herbivores that lived on land. Paleontologists disagree about whether hadrosaurid dinosaurs were grazers who ate vegetation close to the ground or browsers who ate higher-growing leaves and twigs.
Preserved stomach content findings suggest they were browsers, whereas other studies on jaw movements suggest they were grazers. A hadrosaur’s mouth contained hundreds of tiny teeth packed into dental batteries. These teeth were replaced regularly with new teeth.
Hadrosaur beaks were shaped and adapted to cut vegetation, either by stripping or cropping leaves. Hadrosaurs are thought to have had cheeks to keep food in their mouths. Researchers have long suspected that their unusual mouth mechanics contributed to their evolutionary success.
Scientists have been unable to determine how the hadrosaurs broke down and ate their food because they lacked the complex flexible lower jaw joint found in modern mammals.
It would have been impossible to form a complete understanding of the Late Cretaceous ecosystems and how they were affected during the Cretaceous–Paleogene extinction event 66 million years ago without this understanding.
It has also remained unknown what hadrosaurids ate. It has never been proven definitively whether hadrosaurs were grazers who ate vegetation close to the ground, like modern-day sheep or cows, or browsers who ate higher-growing leaves and twigs, like deer or giraffes.
Duck-billed dinosaurs have always fascinated a lot of paleontologists and other people with their unusual appearance. Also, North America is not the usual continent where we can find dinosaurs in general.
Still, it is astounding how these dinosaurs lived in these places with practices different from their more popular carnivorous counterparts. It is a living testament that not all dinosaurs relished at the sight of raw meat.
There are species such as the hadrosaurs who enjoy a more vegetarian and docile lifestyle than others.
● I’ve written a whole article about hadrosaurs including the different types and the ones with distinctive head crests which gives a broader perspective on these duck-billed dinosaurs.
● If you are interested in reading more about dinosaur teeth, including hadrosaurs and why scientists speculate hadrosaurs did not feast on hard vegetation, I wrote an article just about this topic.