The era of the dinosaurs was a remarkable one with a lot of fascinating creatures. One of them was the Polacanthus, a massive ankylosaurian dinosaur whose name roughly translates to “many thorns.” It was a fitting name, considering the fact that this dinosaur had spikes all over its body, including its sides and tail. Polacanthus was a robust herbivorous that lived in present-day England during the early Cretaceous period.
What Did a Polacanthus Look Like?
To say this robust dinosaur was heavily armored would be an understatement. It had a formidable appearance, thanks to the rows of spikes lined almost the entire length of its back. The part of its back where these prickly spikes were absent was covered with a bony plate that would have protected the hips from predators.
From the fossils, it is clear that this dinosaur was a medium-sized creature. It had an average length of 5m (16 ft) and would have weighed about 2 tonnes (4409 lb). Like all ankylosaurus dinosaurs, the Polacanthus had relatively long hindlimbs, about 5.5 cm in length.
What Did the Spikes of the Polacanthus Look Like?
Experts have been working for a long time to understand this dinosaur’s appearance better and come up with an accurate description of the armor on its body. Each of the spikes on its back had a triangular shape, with a broad base and a narrow tip.
It is agreed that the Polacanthus had a massive shield made from fused dermal bone covering its hip area. This shield was most not likely not connected to the dinosaur bone beneath. The sacral shield is a feature seen in many dinosaurs of the same family, such as Gastonia and Mymoorapelta. The shield was about 1 m (42.5 inches) wide and 0.9 m (35.4 inches) long.
The Polacanthus had four rows of large horizontal keel osteoderms on each side of its body, and smaller ossicles enclosed them. The armor spikes are often categorized into three types, A, B, and C, with different sizes. There are contradictory ideas about how these spikes were arranged. According to one theory, each row of the spike had at least 5 spikes. There were two main rows of spikes on the tail with up to 22 shorter ones.
Fossils of Polacanthus were first discovered on the Isle of Wight in 1865. The first finding, which was later named Polacanthus foxii, was found in the Upper Wessex formation. It was an incomplete skeleton with the head, anterior armor, forelimbs, and neck absent.
Using the recovered remains and comparison with more complete remains from close relatives like the Gastonia and Gargoyleosaurus, scientists were able to come up with a reasonably complete picture of how this dinosaur might have looked. Because only fossils from the rear half of this creature are more commonly preserved, a few anatomical features like its skull and other body parts are poorly known.
Habitat and Habits
Polacanthus lived about 130 to 125 million years ago in an area now in Western Europe. Other species of dinosaurs have been identified in this region of Sussex. This includes some less-known ones, such as the Horshamosaurus and Hylaeosaurus. These were spiked dinosaurs that lived in the Cretaceous.
They lived alongside the Neovenator, a ferocious predator. However, the floating armor of the Polacanthus would have prevented predators like this from biting through to their skin. They also had a row of spikes on their tail which might have served as a weapon against any attackers. Other dinosaur species that lived alongside Polacanthus around the same time include the Baryonyx, Hypsilophodon, and Iguanodon.
The presence of many herbivorous dinosaurs in the same region would have posed a bit of a problem for the Polacanthus. They would have faced stiff competition for food in the small area they occupied.
The lack of cranial fossils makes it difficult to tell conclusively what the Polacanthus’s diet was. However, we can make some extrapolations based on the body structure of this dinosaur. The general consensus is that the Polacanthus was a herbivore. It had a stout body that was relatively low to the ground. This body structure is characteristic of many low-browsing herbivorous dinosaurs such as the Ankylosaurus. This observation has led to the conclusion that this dinosaur foraged food on the forest floor. The environment where it lived had abundant conifer plants, which would have formed a significant part of its diet.
When Did the Polacanthus Become Extinct?
It is difficult to tell the exact period when the Polacanthus went extinct. The last fossils scientists could date confirm that this dinosaur was around until the Early Cretaceous, between 145 and 100.5 million years ago. This was about 40 million years before the mass extinction that wiped out the non-avian dinosaurs occurred at the end of the Cretaceous period. Experts think the Polacanthus could have lived till this time, in which case they died off along with other dinosaurs due to that extinction event. However, some other theories suggest they might have died off earlier. In this case, changes in the food supply due to drought, flood, or any other natural disaster might have contributed to the disappearance of this dinosaur species, as this would have disrupted their feeding habits.
Similar Animals to the Polacanthus
There were many spiked dinosaurs that were quite similar to the Polacanthus in terms of their appearance. Some lived around the same time, while others arrived on the scene later. Some of the most notable ones include:
- Ankylosaurus: This is a genus of armored dinosaurs that lived during the Cretaceous. This armored dinosaur also had spikes on its back like the Polacanthus. However, it had a club at the end of its tail, a feature absent in the Polacanthus.
- Horshamosaurus: this is a genus of herbivorous dinosaurs that lived in England during the Early Cretaceous period.
- Hoplitosaurus: This is a genus of armored dinosaurs closely related to the Polacanthus. It lived in North America during the Cretaceous period.
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- , Available here: https://en.wikipedia.org/wiki/Polacanthus
- , Available here: https://jurassicworld-evolution.fandom.com/wiki/Polacanthus
- , Available here: https://www.nhm.ac.uk/discover/dino-directory/polacanthus.html
- William Blows, Available here: https://www.researchgate.net/publication/284097769_The_armoured_dinosaur_Polacanthus_foxi_from_the_Lower_Cretaceous_of_the_Isle_of_Wight