Jurassic Period Animals: More than Just Dinos

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DinoAs the Jurassic period dawned and Earth waved goodbye to the Triassic period and many of the dinosaurs which thrived during that time, it also ushered in a new time of animal life. A variety of events which occurred at the end of the Triassic period and during the Jurassic period gave rise to many more species of animals as well as much more diversity within the species. As the temperature rose and humidity increased the vegetation became much denser and much more able to sustain much more animal life. The Jurassic period became a time of population explosion and while the animals that roamed the Earth are perhaps a little less recognized than the monsters of the Cretaceous period, they were still animals the likes of which the Earth had never seen before.

Land of the Giants

Bird life and marine life aside the terrestrial life of the Jurassic period brought to life some of the largest and heaviest dinosaurs the planet has ever seen. Why did the dinosaurs become so large? Dinosaurs are believed to have evolved in to such huge creatures as a direct result of the explosion of plant life during the Jurassic period. As vegetation grew more populous there was more food to feed these growing beasts. The new climate of the planet Earth also became conducive to tree growth, as the tree’s continued to grow thicker and taller dinosaurs had to grow taller in order to feed from the tall and luscious vegetation.

Jurassic Period Mammalian Life

Aside from dinosaur life during the Jurassic period mammal life also began to make its appearance in the form of Therapsids with mammalian features. Previously reptilian creatures have, by the Jurassic period, begun to show signs of mammalian evolution including rat like teeth and suckling their young. During the Jurassic period, however, the terrain was ruled by the much more impressive dinosaur life and the mammal life seems to have had a lesser impact.

Archaeopteryx – The First Known Bird

As terrestrial life expanded so too did life in the skies. While the skies of the Jurassic period were reined by the giant flying reptiles known as the Pterosaurs, there was a new visitor to the skies – the first known bird. The first known bird of the skies, known to dinosaur lovers as Archaeopteryx, is thought to have descended from dinosaur life and evolved over the years to adapt to life in the skies. It is thought that this new comer to the Jurassic age as well as to the skies was the approximate size of a crow and resembled more of a small running dinosaur.

As life on the ground and life in the skies boomed, life in the seas during the Jurassic period also blew up. The sea life during this time was ruled in the most part by Ichthyosaurs whose diversity as a species really boomed during this period. Also found in the oceans during the Jurassic period were the Plesiosaurs, Pliosaurs and the newest marine crocodiles who also made their first appearance at this time. It is the Plesiosaurs and Ichthyosaurs that made the most impact on ocean life during this time as they multiplied in numbers and diversified as a species.

Among the most recognized and important terrestrial life during the Jurassic period include the Apatosaurus, the Brachiosaurus, the Diplodocus, the Megalosaurus, the Ornitholestes, and the Stegosaurus. Some of these dinosaurs listed above are important as being in existence only during the Jurassic period and some of these dinosaurs are important only as being the most recognized land dwelling creatures of their time.

Apatosaurus (Brontosaurus) and Brachiosaurus: The Largest Mammals to Walk the Earth

The Apatosaurus (formerly called the Brontosaurus) is one of the biggest mammals to ever walk on the face of the Earth. The Apatosaurus is known for its incredibly long neck and its long and whip-like tail as well as its small skull with nostrils towards the top of its head. The Apatosaurus measured up to 90 feet long and fossils have been located in Colorado, Oklahoma, Utah and Wyoming. The Brachiosaurus is also known for its tall head and long thick tail as well as the small head and nostrils at the top of their heads.

The Brachiosaurus and Diplodocus

The Brachiosaurus, similar to the Apatosaurus is one of the largest animals that ever walked the Earth and they lived in large herds which literally shook the Earth as they walked. Brachiosaurus fossils have been found in North America and Africa. The Diplodocus was known for its 26 foot long neck and its long whip-like tail; it also had a rather small head with nostrils on the top of their head. It is believed that the Diplodocus traveled in herds which migrated when food supplies ran low. Many Diplodocus fossils have been located in the Rocky Mountains in the Western United States. The Megalosaurus was a bipedal carnivorous dinosaur with long rear legs and short small arms with three-fingered hands that featured sharp claws. The Megalosaurus was the first dinosaur fossil that was ever discovered. Megalosaurus fossils have been found in England. The Ornitholestes is known for its long tail and its crested snout. The Ornitholestes was bipedal carnivore and its fossils have been found in both Wyoming and Utah in the United States. The Stegosaurus is one of the most recognized dinosaurs of the Jurassic period, known for the plates that ran up and down its back in two columns. The Stegosaurus also had four spikes at the end of its tail and a particularly tiny brain. Stegosaurus fossils have been found in Western North America, Western Europe, Southern India, China and Southern Africa.

Evolution of Mammals – The Missing Links

Among the most recognized and important mammals during the Jurassic period include the Castorocauda, the Fruitafossor, the Hadrocodium, the Megazostrodon and the Oligokyphus. Since very few Jurassic mammals are actually recognized by the average person these animals are all of paleontological importance. The animals listed below answer questions as to missing links between the evolution of mammals.

The Castorocauda, Complete With Hair!

The Castorocauda gets its name from the Greek for “beaver tail” and it is recognized for its beaver like tail. The Castorocauda weighed in at around one or two pounds and feasted on fish. The first Castorocauda fossil was located in China and came complete with hair!

Fruitafossor – The First Digging Mammal

The Fruitafossor is known by paleontologists as the first digging mammal to ever be discovered. The Fruitafossor dug with long front claws and looked similar to a mole. The Fruitafossor was only about 6 inches long and fed on insects with its long pointed snout.

The Hadrocodium and its Large Brain

The Hadrocodium measured in at only about 1 inch long and weighed about 2 grams. The Hadrocodium fed on insects but is well-known by paleontologists for its relatively large brain. This tiny mammal is believed to have been one of the transitionary mammals that occurred before true mammals appeared.

The Megazostrodon – Cross Between Rat and Opossum

The Megazostrodon is another transitionary mammal that occurred between Therapsids and true mammals that lived off insects in the woodlands of South Africa. The Megazostrodon resembles a rat and an opossum cross but weighed in at only 1 ounce and measured only around 4 inches long.

The Oligokyphus – an Extremely Mammal-Like Reptile

The Oligokyphus is recognized by paleontologists as being an extremely mammal-like reptile such as fur, rodent-like teeth and they also suckled their young like mammals do. The Oligokyphus was a widespread mammal and fossils have been found all across the northern hemisphere.

The Largest Birds to Ever Fly

Cearadactylus - Flying DinosaurAmong the most recognized and important animal life in the skies during the Jurassic period for a variety of reasons include the Archaeopteryx, Pterodactylus, Rhamphorhynchus, and the Dimorphodon. While some of these sky flying creatures are known simply by name alone, a few of them gained Paleontological importance from their sheer size or even their status as the first bird!

Achaeopteryx – First Prehistoric Creature with Feathers

The Archaeopteryx is known as the first creature in prehistory as having feathers. This first bird is known by paleontologists as resembling a small lizard with the exception of their feathers and their brain case. The Archaeopteryx was approximately the size of a crow.


The Dimorphodon is known for having a wingspan of around 3 feet and had deep and wide jaws rather than a long slender beak. The Dimorphodon lived during the early Jurassic period.


The Pterodactylus is known for having a wingspan of 2 ½ feet as well as their long and narrow jaws which contained sharp teeth. The Pterodactylus lived until the late Jurassic period. Pterodactylus fossils have been found throughout Europe and Africa.


The Rhamphorhynchus is known for having a wingspan of around 3 feet and had long and narrow jaws filled with sharp teeth which pointed outwards. The Rhamphorhynchus had a very long tail which ended in a kite shaped flap. The Rhamphorhynchus is a late Jurassic flying dinosaur.

Ocean Dwellers of the Jurassic Period

Among the most recognized and important life in the seas during the Jurassic period included:

While the actual shape is the only thing that people today recognize on these Jurassic ocean dwellers, there was a significant amount of distinction that developed between these creatures during the Jurassic period.

Cryptoclidus – Loch Ness Monster?

Loch Ness Monster or Cryptoclidus Dinosaur?The Cryptoclidus is known for resembling the common day renderings of the Loch Ness Monster with four huge flippers, a short tail and a longer, flexible neck. The Cryptoclidus had a long snout and curved sharp teeth which aided in catching small fish, shrimp and squid. Fossils of the Cryptoclidus have been located in England, France and South America.

Ichthyosaurus – Prehistoric Dolphin?

The Ichthyosaurus is known for looking very much like a modern day dolphin with a large tail and a dorsal fin. The Ichthyosaurus had a long pointed snout with teeth that it used for catching fish and some cephalopods. The Ichthyosaurus could swim up to 25 MPH and fossils have been found throughout England, Germany, Greenland and Alberta, Canada.

]The Liopleurodon – 49 Feet Long with 4 Flippers!

The Liopleurodon is known by paleontologists as the biggest plesiosaur, it had a short and pointed tail and four large flippers. The Liopleurodon had a short neck and a crocodile type mouth filled with sharp teeth and topped with nostrils. The Liopleurodon was a carnivore known for feasting on fish, ichthyosaurs and other plesiosaurs. Measuring in at nearly 49 feet long the Liopleurodon’s fossils have been found throughout England, France, Germany and Eastern Europe.


The Plesiosaurus is known for its four large paddle-like flippers and its short pointed tail. The front flippers of the Plesiosaurus were longer than the back and the head was small and filled with sharp teeth. The Plesiosaurus had many various species under their genus and thrived during the early Jurassic period. The Plesiosaurus measures in at nearly 7 ½ feet long and its fossils were found in England and Germany.

Terrestrial Dinosaurs

Of all of the animals that lived during the Jurassic period perhaps the most impressive were the terrestrial dinosaurs. The Jurassic period brought giant Sauropods that brought a whole new meaning to the term “large” and after the end of the Jurassic period the Earth would never again see beasts of such magnificent proportions. The giant Sauropods that herded across the Earth’s plains during the Jurassic period never made a footstep in to the Cretaceous period; however, they did leave behind a legacy of their own.

Prehistoric Animals Hit Their Peak in the Jurassic Period

In addition to the giant Sauropods the Jurassic period brought many new faces which would manage to evolve through the end of the Jurassic era and in to the Cretaceous period. Not to be overlooked by the much larger dinosaurs who really hit their peak during the Jurassic period, the very first bird in the history of the world also made quite an impression during the Jurassic era! The Archaeopteryx was the beginning of something entirely new, something that even the end of the Cretaceous period could not kill off. The emergence of the Archaeopteryx marked the beginning of feathered beasts and consequently it brought the beginning of birds, birds which would continue to evolve and progress through to modern day Earth.

Prehistoric Animals Leave Clues that Help Us Better Understand the Dinosaurs

To encapsulate all of the animals of the Jurassic period is nearly impossible but the creatures listed above encapsulate some of the most influential animals of the Jurassic period. From the largest beasts to ever set foot on the earth to the beginning of crocodiles and the emergence of feathered birds the Jurassic era brought changes the likes of which modern day Earth cannot deny. As the Jurassic period drew to a close many of the giant beasts of the era may have laid down to die but the fossils they left behind provide clues about prehistoric Earth that allow paleontologists to better understand the evolution and extinction of the dinosaurs.

Other Jurassic Period Mammals

The Jurassic period saw a number of other animals that thrived alongside the dinosaurs and reptiles that we are most familiar with. Below we will take a look at some of these lesser known creatures of the period.

Ambondro Mohabo

The Ambondro Mohabo is a mammal that thrived during the middle of the Jurassic period around 167 million years ago. The Ambondro Mohabo lived in what is now Madagascar and is only known from the remnants of its lower jaw, including three lower teeth: the last premolar and two molars. While not too much can be determined by such minute remains, researchers have been able to determine that the teeth are similar to those of marsupial and placental mammals. More recent discussion of these limited remains indicate that the Ambondro Mohabo may actually have been related to monotremes and belong in the Australosphenida clade. Researchers hope to recover more remains of Ambondro Mohabo in order to be able to build a better picture of what this creature actually looked like!


The Apiocrinites is a genus of crinoid that existed in the mid to late Jurassic period throughout Europe and Asia. Crinoids are marine creatures that compose the Crinoidea class. These animals were found in shallow and deep waters and attach to the sea bottom or rocks or corals. These creatures had a mouth that sits at the top of the animal and feeding arms surrounding it to capture and pull food to the mouth. Some Crinoids live their lives attached to the ocean floor or a solid surface; others are free-floating after adulthood begins. Crinoid species were particularly abundant in the Earth’s history and while they still exist today they exist in much fewer numbers.


The Castorocauda is a small semi-aquatic mammal that was found in the upper Jurassic period 154 million years ago. Physically this creature resembles a cross between an otter and a beaver of today. The remains of Castorocauda were found in lakebed sediment in the Daohugou Beds in Mongolia. One of the most amazing things about this mammal is the various specialized adaptations that it had developed. Some do not believe that the Castorocauda is not actually a mammal by definition, instead it is a member of the Docodonta order – a group of proto-mammals. One of the most well-preserved specimens of Castorocauda was found in the Liaoning province in China. This specimen had hair preserved which indicated that Docodonta order creatures in addition to mammals had advanced hair. The Castorocauda even had hair that included guard hair and under fur.

The tail of Castrocauda had scales and hair and was similar to that of an otter in terms of its purpose. It is also known that this water lover had webbed feet which allowed it to swim more efficiently. Skeletal indications point to great similarities between today’s otter and beaver skeletal structure as well. The size of its limbs suggests that Castorocauda was a digger and its teeth indicate that it fed on fish and insects. From recovered fossils researchers suggest that Castorocauda was around 1 to 2 pounds heavy and measured around 17 inches long. These measurements make Castorocauda the largest of all mammaliaform creatures in the Jurassic period. Overall these findings of Castorocauda are extremely important to scientists because they are able to indicate that mammals and mammal like creatures were capable of life in water before the dinosaurs died out.


Coelodiscus is a genus of the Euomphalidae gastropod family that existed in Europe from the low to mid Jurassic period. The shell of this gastropod is small but quite thick and it has a spire which protrudes outward. The whorls of the Coelodiscus are smooth and round and overlap each other.


The Dinnebitodon is an herbivorous cynodont that lived during the early Jurassic period. The Dinnebitodon has only been recovered in the Kayenta Formation of northeastern Arizona and is similar in appearance to the Kayentatherium. The biggest differences between these two cynodont’s is a difference in tooth structure. The Dinnebitodon was a small creature of approximately 3 inches long with three incisors on each side of the upper jaw, five post canine teeth on the upper jaw and possibly a sixth that would come through in adulthood. The second incisor of the Dinnebitodon was larger than the others and the post canine teeth were rounded. The habitat of the Dinnebitodon was similar to modern day Senegal and it lived on the ground feeding on seeds and nuts.


Eozostrodon began life in the late Triassic and lives through until the early Jurassic period. Eozostrodon is important because it was one of the earliest mammals noted, living some 210 million years ago. Not only was this one of the earliest mammals but Eozostrodon was also one of the largest early mammals measuring more than a meter long! Little is known about exactly how Eozostrodon should be classified. Eozostrodon was an egg layer like the monotremes of today and it had mammal like teeth. After hatching, the young Eozostrodon would feed from the mother’s milk until large enough to feed for themselves. This creature was likely an insectivore and looked much like the shrew of today. The Eozostrodon had a long snout, four legs, eight toes, a long hairy tail and claws on each of its paws.


Guimarotodon lived during the late Jurassic period and is believed to have been a member of the Multituberculata order. Animals in the Multituberculata order were rodent like in appearance and lived throughout history for some one hundred and twenty million years. These creatures only became extinct in the early Oligocene. There were at least 200 species of Multituberculata known to exist. The remains of Guimarotodon leiriensis were recovered in Guimarota, Portugal. The Guimarotodon fed on low growing vegetation and is classified by three specimens of lower jaw. Unfortunately, like Ambondro Mohabo, little else is known about Guimarotodon’s appearance other than the fact that as a Multituberculata it would have resembled a rodent.


The Juramaia thrived during the late middle Jurassic period and lived in Liaoning, China. The Juramaia species is known from a nearly complete specimen that was found in Liaoning that had an incomplete skull with full preserved dentition. Juramaia was important to scientific research of the Jurassic period because it was able to prove that placental mammals were around some 35 million years before it was previously though! The Juramaia resembles a cross between a rodent and a wild pig in appearance.


The Kayentatherium is a genus of tritylodontid cynodont from the early Jurassic period and is one of just three types of tritylodonts from the Kayenta Formation located in the state of Arizona. The skull of this creature was around 4 inches long and its jaws contain four very sharp incisors in addition to rear molars. The tail of the Kayentatherium was thick at the base and tapered but was considerably short. The Kayentatherium resembles a large rodent with four thick legs. This creature was a herbivore despite its four very large and quite sharp front teeth. The Kayentatherium is known from the type species Kayentatherium wellesi.

Megateuthis gigantea

The Megateuthis gigantean is the largest species of belemnite known. This 18 inch long cephalopod thrived during the Jurassic period and was found throughout Asia and Europe. Megateuthis gigantean is estimated to have measured ten feet long in total.


The Morganucodon began life in the late Triassic period and thrived until the early Jurassic period. The Morganucodon is classified as an early mammal and is known from a great many specimens that have been very well-preserved. Fossilized specimens of Moganucodon have been found in Wales, China, Europe and North America. Morganucodon is believed to have been a small and furry rodent like animal with a long tail and the overall appearance of a shrew. Researchers believe that this creature was nocturnal and lived in a burrow, feeding on insects and other small animals at night. It is also believed that this mammal had a short lifespan and it likely laid eggs.

Some controversy has surrounded the Morganucodon in terms of whether or not it was actually a mammal or whether it was a pre-mammal. The tooth and jaw structure of Morganucodon however seems to indicate that this was a mammal. The teeth of this creature are also important in determining that this creature was a mammal because they were replaced just once in its lifetime.


The Neithea is a genus of bivalve mollusk that existed between the early Jurassic period to the early Paleocene. This creature could be found worldwide. The two valves of this bivalve mollusk were two different shapes, the right valve being concave and the left being flatter. This unequal shape of the Neithea valves makes this mollusk an inequivalve. The shell of the Neithea had radiating ribs that alternated between stronger and weaker ribs.

Nephila Jurassica

The Nephila jurassica is a now extinct species of spider that lived during the middle Jurassic period. The Nephila jurassica was found only in the Jiulongshan formation of the Daohugou Beds in northeastern China. The family Nephilidae are known for the most commonly recognized golden silk orb-weaver spider. The Nephila jurassica has been identified by just one fossil, that of an adult female. This species is significant because it is the oldest known species of the Nephila genus which also makes the Nephila genus the longest lived modern genus of spider. The total body length of the Nephila jurassica was around .97 inches long and the front legs measure around 2.22 inches in length.


Nanolestes is another mammal from the Jurassic period of which little is actually known. Researchers do know that Nanolestes was a member of the Amphitheriida order. A new species of the Nanolestes genus was located in China by Thomas Martin, Alexander O. Averianoc and Hans-Ulrich Pfretzschner in 2010.


Pycnodonte were actually a genus of oyster. These bivalve mollusks are from the family Gryphaeidae and shells from these creatures have been found throughout the world’s marine systems. Most commonly the fossils of these creatures are found in shell beds of the Cretaceous period; however, they are also common to the Jurassic period.


The Triconodontidae lived in what is now Africa, North America, South America, Europe and Asia during the middle to late Cretaceous period. The Triconodontidae was a mammal or the Eutriconodonta order. The teeth of the Triconodontidae were what characterized Eutriconodonts with molar teeth defined by three cups on the crown. There is some question as to whether the Argentoconodon is a member of the Triconodontidae family; if this is the case then this would extend the history of the Triconodontidae to the early Jurassic period. The Triconodontidae represented large rodents in appearance with large rat like feet, furry pelts and long snouts with sharp incisor teeth that were most likely used for digging.


The Tritylodon is a genus of tritylodont of the cynodont therapsid group. The Tritylodon thrived in the early Jurassic period and may also possibly and lived in the late Triassic period; however, this is uncertain. The Tritylodon is significant because it shows some characteristics similar to the mammals that followed them. The Tritylodon had reptilian jawbones and a unique skull structure but a skeleton structure similar to that of mammals. Like other similar creatures, the Tritylodon resembles a large rodent and measures approximately a foot long. The legs of the Tritylodon were directly under the body of the creature rather than being splayed to the sides like earlier therapsid species. The Tritylodon were burrowing animals that likely used their large front incisors to dig in to the ground when burrowing as well as when digging for food. Tritylodon was a warm-blooded creature and was oviviparous. This Jurassic creature thrived in warm wet climates.


The Vampyronassa is a vampyromorph cephalopod that has been identified from twenty different fossils that were recovered from Ardeche, France. The Vampyronassa was similar to the modern vampire squid; however, it had much longer dorsal arms, an elongated mantle and a larger hyponome. The Vampyronassa was most common during the middle Jurassic period.

Lean More

Find out more about Jurassic period animals at the Smithsonian either in person at the National Museum of Natural History or online at their Department of Paleobiology.

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lame, sorry but you need pics of the dinos.

I’m doing a project for science class and this was very helpful for the organisms section! Keep it up!

I have been trying to find the prehistoric ancestor of the cow (bovine animals) that led up to the modern cow. Does anyone know of this creature?

This was very helpful for my homework, so thanks 🙂

I am so glad we could help! Hopefully your teacher learned a lot about these prehistoric creatures while grading your homework too!