A step back in time

Anyone with even a passing interest in prehistoric animals will surely have, at some point in their life, either purchased or been given a small bag full of miniature curiosities. Coming in a wide array of colours, teeth showing menacingly, limbs tense seemingly ready to spring into action at any moment, this can only be a bag full of the most famous animals ever to walk the Earth. Except, what if it isn’t? What if there are some outliers amongst the diversity of teeth, claws, long necks, and tank-like armour? The truth is that in almost of all these bags, it was highly likely you would come across some prehistoric wonders not quite making it into the dinosaur threshold. This doesn’t make them any less impressive and their worlds any easier to comprehend. Still, surely, we deserve some accuracy when buying something even if they are toys designed to amaze young minds, and, in fairness that is something they certainly do. So, what was and was not a dinosaur? Let us take our own step back in time and revisit that bag of treasures unpacking them once more, secrets and all.

First out the bag is a truly bizarre sight. An animal that resembles a lizard with its walking style, boasts some seriously sharp teeth in its armoury, and, most eye-catchingly, a huge sail. Dimetrodon was an unusual animal in more ways than one. The variations in size in species of Dimetrodon is striking, with some being no larger than a dog, and others longer than a family-sized car with a sail over two meters high. The purpose of the sail itself has continued to cause debate amongst scientists with theories including helping to control body temperature by warming up in the sun, cooling down in the shade, and as a tool to impress a potential romantic interest. Currently, however, an agreement on the use of the sail has not been reached.

Image credit: Max Bellomio, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons

The question is, however, was Dimetrodon a dinosaur? The answer is no. They lived during the Permian period making them at least 35 million years older than the earliest dinosaurs. Despite appearances, it was not a reptile, instead, an ancient relative of the mammals. Their serrated knife-like teeth indeed were the first example of specialised teeth in the mammal lineage. In time, as their forest homes disappeared, Dimetrodon would be replaced by the so-called “mega herbivores” which became even closer to the mammals we recognise today.

Throughout time, every food chain has needed its share of predators to keep the balance of life in order. This basic principle is still present today, whether this be Lions in Africa, Polar Bears in the Arctic, or Sparrowhawks flying through your garden terrorising the resident songbirds. The time of the dinosaurs was no different in this regard and, if you were to reach the end of your bag of wonders and not pull out a replica super-predator you would be sorely disappointed. With such an array of meat-eating carnivores to hope for, it was a near certainty, but from all the choices available Tyrannosaurus Rex was surely top of everyone’s wish list.

Image credit: ScottRobertAnselmo, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons

The sight of this top predator would have been something to behold in life. Growing to almost thirteen meters in length including a one and a half meters skull containing over 50 teeth and weighing in at seven to eight tonnes, it’s unlikely a reputation has ever been more deserved. If you ever wondered if the King of the Dinosaurs was smart, they certainly were, and they had exceptional vision to match with eyes the size of grapefruits. Those small arms everyone laughs at in memes and cartoons? We now know they had strong elbow and shoulder muscles perfectly designed for holding victims close to them while thousands of pounds of bite force crushed through bone. They needed these incredible adaptations for good reason, it has been estimated as a teenager, Tyrannosaurus would have needed to eat five pounds of meat a day such was the rapid speed of its growth. The life of a top predator has never been easy and even Tyrannosaurus’s life at the top was a short one. Scientific research is yet to find a specimen aged over thirty years of age, clearly, this was a full-throttle approach to life all the way to the end for the King of the Dinosaurs.

Image credit: Fred Wierum, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons

The legendary appearance of the next dinosaur is well recognised. A member of the giant sauropod group of dinosaurs and reaching over twenty-four meters in length, Diplodocus was one of the longest dinosaurs ever to have lived. The eye-catching long tail in life would have acted as a counterbalance to their neck, preventing these giants from toppling over.  While older images have depicted Diplodocus as dragging its tail in a rather lethargic fashion, the lack of drag marks behind fossilised footprints suggests otherwise. This highlights one of the main differences between dinosaurs and other reptiles, while lizards and crocodiles walk in a sprawling fashion, dinosaurs were able to keep themselves upright.

There are just two replicas left now and one of them has flippers, a clear adaptation for life at sea. Dinosaurs would have ventured to the edge of and indeed into water at times, but no dinosaur was fully aquatic. This means mosasaurs were not dinosaurs but instead, marine lizards and they came in an incredible array of diversity ranging in size from just thirty centimetres to true monsters of the ocean at seventeen metres in length.  Their size wasn’t their only variation, their diets varied too, and their teeth reflected this. Some were specialised, designed for feeding on hard-shelled animals like ammonites while others targeted far larger prey and possessed enormous teeth to do so. 

Image credit: Loozrboy from Toronto, Canada, CC BY-SA 2.0 <https://creativecommons.org/licenses/by-sa/2.0>, via Wikimedia Commons

Mosasaurs were perfectly designed for life at sea, with a powerful tail and streamlined design helping them to reach startling speeds. Life as a young mosasaur probably wasn’t an easy one, there’s no evidence to suggest that juveniles lived in shelter close to the coast. Instead, they would have lived far from land, themselves vulnerable to larger predators like the one your model is possibly based on Tylosaurus. Tylosaurus grew up to over twelve meters and was a true monster capable of predating upon other mosasaurs, sharks, and seabirds and came equipped with a bony tip on the snout which would have been used to help stun large prey before the final assault. If Tyrannosaurus was the King of the Dinosaurs, Tylosaurus presents a strong case for being the ruler of the oceans.

Your final dive into your bag of treasures reveals perhaps the most bizarre creature of them all. Dragonesque in appearance, with a huge wingspan and a skull a meter in length accompanied with a strange looking crest, in flight Pteranodon would have been a truly magnificent sight. Despite being closely related to dinosaurs, Pteranodon is part of the flying group of reptiles known as pterosaurs. These creatures were hugely successful and soared the skies for almost the same amount of time as dinosaurs ruled the land. First emerging over two hundred million years ago, the first pterosaurs were small, often with a wingspan no more than a metre. However, some species had reached gigantic proportions by the end of their reign. Quetzalcoatlus would have stood eye to eye with a giraffe on the ground and came with an estimated three-metre wingspan, somehow taking to the skies to cover thousands of kilometres over the course of several days.

Image credit:Matt Martyniuk, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons

The head crests of pterosaurs came in a wide variety of sizes, shapes, and presumably colours too. There has long been debate about the purpose of the crest, ranging from aiding flying to controlling body temperature. The most widely accepted explanation currently is that the crests were used to impress potential mates, which is supported by the lack of head crests found in juvenile pterosaurs.

And there you have it, five wonderfully unique prehistoric animals. Some of them dinosaurs, some of them not, with an assortment of peculiar adaptations, the likes of which will probably never be seen again. So, while you may look at that bag of nostalgia with a slightly different perspective, it should not detract from the sheer wonder these animals continue to inspire in generations now and undoubtedly in future generations to come.

Further reading

Benton, M. J. (2021). Dinosaurs: New visions of a lost world. Thames & Hudson.

Brusatte, S., & Marshall, T. (2019). The rise and fall of the dinosaurs: A new history of their lost world. William Morrow, an imprint of HarperCollinsPublishers.

Castro, J., & Dutfield, S. (2022, October 13). Pterodactyl: Facts about pteranodon & other pterosaurs. LiveScience. https://www.livescience.com/24071-pterodactyl-pteranodon-flying-dinosaurs.html

Naish, D. (2023). Ancient sea reptiles: Plesiosaurs, ichthyosaurs, mosasaurs, and more. Smithsonian Books.

Norell, A.M. (2019). The World of Dinosaurs: The Definitive Visual Collection. André Deutsch.

Panciroli, E. (2022). The earth: A biography of life: The story of life on our planet through 47 Incredible creatures. Greenfinch.

Prothero, D. R. (2021). Story of the dinosaurs in 25 discoveries: Amazing fossils and the people who found them. Columbia University Press.