ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

The Vicious and Terrifying Reptiles that ruled over the world before Humans

Updated on August 10, 2021
RidaeFatima021 profile image

Space enthusiast and an aspiring astrobiologist who works hard to write amazing and captivating content for the viewers.


Reptiles belong to the phylum Chordata and kingdom Animalia. They are the cold blooded vertebrates having dry skin surrounded by epidermal scales. Reptiles are tetrapods that lack the ability to maintain a constant internal body temperature. They have internal and external fertilization. Some reptiles lay eggs and some produce offspring through internal fertilization.

Paleozoic era started about 544 million years ago and ended in about 245 million years ago. Throughout the Paleozoic era there have been some great and remarkable events of evolution including the evolution of reptiles and some other allied animals such as fishes, insects. The development of the invertebrate groups also took place in this era.

The start of the Paleozoic era, was marked by the diverse explosion of life form. The great mass extinction event in the end of the Permian period put an end to the Paleozoic era and 95% of the marine life and 70% of the terrestrial life was completely wiped out. The world was divided into several continents during the paleozoic era. Although, they were all merged together forming one big supercontinent, Pangea.


By the end of the Paleozoic era, terrestrial life included fishes, arthropods, amphibians, and reptiles.


Anapsids are the most primitive subclass of the reptiles present in the Paleozoic era and the ancestral stock from which the diapsids and synapsids had evolved. Anapsids are classified on the temporal holes present in their skulls. They have no temporal fenestrae (holes) in their skulls. However, their descendants the diapsids had two temporal fenestrae and synapsids had only one temporal fenestrae.

Sign of Diapsid and Synapsid Evolution from Anapsids


About 252 million years ago, when the era was Mesozoic, the reptiles were ruling the entire world. That’s why the Mesozoic era is also known as “the age of the ruling reptiles”. This era started and ended in two great mass extinction. The first mass extinction was in the end of the Paleogene era, the era before the Mesozoic. Throughout the Mesozoic era the temperature of the earth remained warm and humid, there were no polar ice caps. This climate was suitable and ideal for the reptiles and this is one of the major reason why they evolved in the best possible way throughout the Mesozoic era and eventually gave rise to huge reptiles weighing approximately 200 tons.


The Ruling Reptiles
The Ruling Reptiles


Later on in the first period of Mesozoic era, the Triassic period, Diapsids evolved into archosaurs and lepidosaurs further having four temporal fenestrae in their skulls. This evolution took place in the start of the next era, the Mesozoic era. Archosaurs are the predecessors of the pseudosuchians and the dinosaurs. The lepidosaurs are the predecessors of snakesand lizards.

Pseudosuchians had strong hind limbs that’s why they were able to stand on two legs and run fast however, they had unsteady breathing which lead to their extinction in the Triassic-Jurassic extinction event. Only one lineage was able to survive which was prone to live in the swamps and it resembles the modern day alligators. If they had strong breathing physiology, they could have dominated the Jurassic age instead of Dinosaurs.

Dinosaurs evolved from the Archosaurs as well and they were the most dominant branch of the Archosaurs, and became dominant terrestrial reptiles after Triassic – Jurassic Extinction. They were the highly intelligent reptiles of the Mesozoic era and the first noted dinosaur was the eoraptor which was an omnivore.

Artistic diagram of Triassic Period
Artistic diagram of Triassic Period


The number of dinosaurs increased exponentially in the Jurassic period. In fact, the earth was ruled by them for over 160 million years. The temperature was slightly warmer, both for the aquatic and terrestrial life, which was the ideal climate for them. Pangea started to split in two smaller continents, Gondwana and Laurasia. Two groups of Dinosaurs emerge as dominant in the Jurassic period, grass eating herbivore lineage of the omnivore eoraptor, the sauropods and flesh eating terrifying carnivore lineage of the eoraptor, the theropods. However, by the end of the Mesozoic era all these dominating reptiles were gone and once they were gone the mammals had a chance to take over the world, which is what happened in the Cenozoic era.

Ruling Period of Reptiles
Ruling Period of Reptiles


Therapsids were the Evolved form of Synapsids, most of them died out in the end of Triassic period. They had four-footed locomotion and they gave rise to mammal like reptiles and mammals having one temporal opening in their skull like mammals of today, including humans. That is a major proof of human evolution from Therapsids.

Artistic diagram of Thrapsids
Artistic diagram of Thrapsids


Ichthyosaurs (fish lizard) had evolved from unidentified reptilian group. They were the first land reptiles to become fully aquatic. They evolved a ‘fish’ shaped body from a four footed animal.

Artistic diagram of Ichthyosaurs
Artistic diagram of Ichthyosaurs


Pterosaurs (Winged lizard) had also evolved from Archosaurs. They are closely related to Dinosaurs. They had evolved the power of flight at the end of Triassic and survived the extinction. The current bird lineages are successors of Pterosaurs. The first bird was the archaeopteryx.


After the Mesozoic era ended the world was left with no dinosaurs. However, the few that were left behind evolved into today's reptiles such as Alligators, crocodiles, Iguana, turtles, and many other reptiles. Some birds have evolutionary history starting from reptiles also. On the other hand Molecular genetics studies also show mammalian evolution from reptiles. The aquatic dinosaurs of that time also managed to evolved into the present day sharks and whale.

Evolution of Birds

Birds Evolution from Dinosaurs
Birds Evolution from Dinosaurs

This website uses cookies

As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

Show Details
HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
LoginThis is necessary to sign in to the HubPages Service.
Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
AkismetThis is used to detect comment spam. (Privacy Policy)
HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
MavenThis supports the Maven widget and search functionality. (Privacy Policy)
Google AdSenseThis is an ad network. (Privacy Policy)
Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
Index ExchangeThis is an ad network. (Privacy Policy)
SovrnThis is an ad network. (Privacy Policy)
Facebook AdsThis is an ad network. (Privacy Policy)
Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
AppNexusThis is an ad network. (Privacy Policy)
OpenxThis is an ad network. (Privacy Policy)
Rubicon ProjectThis is an ad network. (Privacy Policy)
TripleLiftThis is an ad network. (Privacy Policy)
Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)
ClickscoThis is a data management platform studying reader behavior (Privacy Policy)