by Neal Immega
The Houston Museum of Natural Science Triceratops skull was purchased from Black Hills Institute who dug it up on a ranch in South Dakota. Skulls of dinosaurs are rare because by definition, dinosaurs are upright land reptiles that lived during the Mesozoic Era, the time between about 65 and 230 million years ago. It takes a special situation to get skeletons preserved, like having parts of the carcass washed into a river and rapidly buried. Marine animals like the Mosasaur are much more commonly preserved.
Triceratops was likely a herd animal. There is a ceratopsian bonebed in Alberta that has been interpreted as a herd of over a thousand animals, killed while trying to cross a flooded river. This is similar to a modern occurrence in Alaska, where 162,000 caribou were killed trying to cross a flooded Arctic river. The Canadian bonebed contains immature as well as adult bones, implying that the ceratopsians stayed with their young. There are also lots of shed and broken carnivore teeth among the bones – someone had lunch.
Skull Bones: The head usually comes off when the carcass gets washed into a river because the head/neck attachment is not strong. There is an additional difficulty that you can see in our specimen: a reptile skull is made up of many separate pieces that are only held together by muscles and tendons -- the whole skull can come apart into a dozen pieces. This is quite different from mammal skulls where all the bones in the head are fused soon after birth. In dinosaurs, the jaw moves up and down and the whole head moves during the chewing process. Like all dinosaurs, Triceratops has small brain, about the size of the littlest joint on your thumb.
Horns: This animal is called a Triceratops (“three horned face”) because of the three horns, two above the eyes and one on the nose. Another member of the family has horns that also come off the frill in back and is called Pentaceratops. The most primitive member, Paraceratops, has no horns. What you are seeing on our specimen are the horn cores, the bony support. In life, these cores were covered with a hard layer not unlike a modern cow horn. With this, the horns were 18” longer that the cores you see now and were truly formidable weapons. T. rex fossils are found in the same places as Triceratops and likely the horns were a defense against a big predator because no one can survive getting a stab wound in the gut. The picture in front of the skull shows Triceratops making a defensive ring around their young, but there is no evidence that that happened. Triceratops skulls have been found with holes in them that are the right size to have been made by another Triceratops horn, possibly the result of a fight for dominance. It has also been suggested that the horns may have been used to uproot or topple vegetation.
Beak: A Triceratops jaw has a beak in front and teeth
in back, a considerable difference from modern animals. The beak would have a
hard covering like the horns, making it like a parrot beak. In the hall, the
duck bill dinosaur, Hadrosaur (by the T. rex) has the same arrangement of a
beak and teeth. The beak may give us a clue to what the Triceratops ate. One of
the speculations is that Triceratops ate cycads, like the modern version called
a Sago Palm. As you know, a cycad is defended by the very sharp leaves that
surround the starchy central trunk. A Triceratops may have used his beak to nip
off the leaves before eating the trunk. The problem with this theory is that
cycads are quite poisonous and the triceratops would have had to evolve the
ability to process those poisons. This is not impossible when you consider that
nothing eats a milkweed plant but a monarch caterpillar.
Teeth: Notice that the Triceratops has individual lower teeth that are beveled at a 60-degree angle by rubbing on the upper teeth – they are self-sharpening.. These teeth act like scissors to cut vegetation. Mature teeth are replaced by new ones growing from below. Triceratops is considered to be a herbivore because the teeth are suitable for chopping vegetation into small pieces that can be digested. Animals that eat low-grade food with lots of cellulose have to be big to have a long enough gut to give the protozoa time enough to process the cellulose. An elephant can digest a tree branch but a human cannot. Another feature of a herbivore is that they usually have a cheek to chew food into. When a human eats a carrot by chewing it into his cheek and then chewing it back again. Try it, and see how you chew things. The teeth are recessed from the side of the jaw to have lots of space for a cheek. You can even see the holes that the nerves make when they pass through the jaw to control the cheek muscles. Humans use their cheek muscles to push the food back through the teeth for a second pass of chewing.
Shield: Notice that the skull is huge, much larger than any other dinosaur in the hall. The back part of the skull is called the shield or frill and one might think that it would protect the neck and upper spine. If you could get behind the skull, you would see that the shield is less than an inch thick and that would be no protection from a T. rex attack. The Pentaceratops (5 horned Ceratopsian) in the Noble Museum in Oklahoma has the largest skull of any dinosaur. Likely the shield is used in a threat display, like a Kodiak bear standing on his hind legs when meeting a possible rival or a peacock spreading his tail feathers to impress the peahens. The shield also served as an attachment for powerful jaw muscles.
Nose: The holes in the skull for the nostrils are huge. This might mean that the Triceratops needed lots of air, at least occasionally. Now, can you think of any modern reptile that has such big nostrils? Even a 10-foot komodo dragon (a lizard) has only 1-inch nostrils. This implies that a Triceratops is a much more vigorous animal that a modern reptile. This brings up the “warm blooded dinosaur” controversy. A komodo dragon has to warm up in the morning before he can move and he can only sprint for 50 feet before he uses up the sugar stored in his muscles. A modern reptile does not have the circulatory system to deliver sugar to its muscles fast enough to run miles. Air consumption must be related to sugar consumption in the muscles, which suggests that Triceratops could run like a mammal. There is a lot of controversy, though, about whether those short, well-muscled legs were posed like a mammal’s for running or sprawled out like those of a crocodile. I vote for “runner”.
If you are thinking that one of these would look good in your living room, then you should know that you probably cannot trade your brand-new, fully-outfitted luxury car for one. Even a replica skull costs about $6,000.