Cretaceous Period

The Cretaceous period is a geological period. This geological period lasted from about 145 to 66 million years ago. This period is counted as the third and final period of the Mesozoic Era. Also, this is the longest of all the geological periods among the entire Phanerozoic, this surpasses the Ediacaran and Cryogenian period as well in terms of size.

The name of this period is being derived from the Latin word ‘Creta’ meaning ‘Chalk’. As in this period, chalk was abundantly found in the latter half of this time. 

In this section, we will discuss in detail the Cretaceous Period. 

Cretaceous Period 

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The Cretaceous period experienced a relatively warmer climate which resulted in the high eustatic sea levels which created a number of shallow inland seas. The oceans and seas in that time were populated with marine reptiles which are now extinct, ammonites and also rudists. While on the inland surface the dinosaurs dominated.  

The world at that time was an ice-free place with the forests being extended towards the poles. In this time, groups of new mammals and birds originated. Flowering plants also appeared in this time which began to rapidly diversify in the region. These flowering plants became the dominant group of plants on the planet. This occurred by the end of the Cretaceous period, with the decline and extinction of the previously dominating gymnosperm groups.

The Cretaceous period ended with the Cretaceous-Paleogene. At this time a large mass of extinction took place. Many groups, including the non-avian dinosaurs, pterosaurs, and also large marine reptiles died out during this time. 

Cretaceous Dinosaurs 

In this time, Cretaceous Period, there lived types of dinosaurs who dominated the land surface. We will know about these Cretaceous Period Dinosaurs in this section:

First, the Afromimus means "Africa mimic". They are the genus of theropod dinosaurs. This originated from the early Cretaceous Elrhaz Formation of Niger. They are single-species organisms of the Niger. A. tenerensis is a name of such a species as named by Paul Sereno, whose parts of the right leg, vertebrae, and ribs found in the Tenere Desert. They were originally classified as an ornithomimosauria but later it was debated to be an abelisauroid.  

Next, we have Aegyptosaurus which means 'Egypt’s lizard'. This name was given for the country in which this species was discovered. This lizard is a genus of the sauropod dinosaur who is believed to live in Africa 95 million years ago. This was during the Late Cretaceous Period. Like the sauropods, this species had a long neck with a small skull. This animal's long tail acted as a counterweight to its body mass. 

Pictures of the types of Dinosaurs are attached below:

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Abelisaurus

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Achelousaurus

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Achillobator

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Aegyptosaurus

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Alamosaurus

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Albertaceratops

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Albertosaurus

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Alectrosaurus

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Alioramus

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Alvarezsaurus

Late Cretaceous 

The Late Cretaceous is the younger most between the two epochs into which the Cretaceous geological period is being divided. The late Cretaceous period is divided into geologic time scales. The rock strata which are from the epoch form the Upper Cretaceous series. As mentioned, the name ‘Cretaceous’ is named after the white limestone, chalk. Chalk was extensively found in northern parts of France and is seen in the white cliffs of southwestern England.  

About the climate of Late Cretaceous Period - The climate was quite warmer than the present climate, although during the beginning and the end of this period a cooling trend existed but in the end it adapted into a warmer type. The tropics only exited near the equatorial regions and the northern latitudes too experienced more seasonal type climatic conditions. 

Cretaceous Extinction 

The Cretaceous Paleogene abbreviated as the K-Pg extinction event was a sudden and massive extinction. Almost three-quarters of plants, animal species in this time, that is approximately 66 million years ago, became extinct. While, ectothermic species like the sea turtles, crocodilians and tetrapods weighing less than 25 kg survived. This marked the end of the Cretaceous period and the Mesozoic Period.  

Cretaceous Period Animals 

The dinosaurs were the dominant group of land animals, especially the “duck-billed” dinosaurs like the Shantungosaurus, and horned forms, like the Triceratops. Other giant marine reptiles like ichthyosaurs, mosasaurs, and the plesiosaurs were also common in the seas, also flying reptiles (like the pterosaurs) dominated the sky.

Herds of herbivorous ornithischians also lived during the Cretaceous, they were known as Iguanodon (they are a genus that includes duck-billed dinosaurs, known as the hadrosaurs), Ankylosaurus and the ceratopsians. Theropods, including Tyrannosaurus rex, also continued as apex predators till the end of the Cretaceous period.

Triassic Jurassic and Cretaceous 

The Mesozoic period was preceded by the Palaeozoic Period which is then succeeded by the Cenozoic which meant new life. This era is being subdivided into three periods:

• The Triassic 

• The Jurassic

• The Cretaceous

They are further subdivided into epochs and ages.  

Cretaceous Organisms

Ammonites, belemnites, and other molluscs, and the fish were being hunted by great "marine reptiles," and pterosaurs while the birds flapped and soared in the sky above. 

Yet the Cretaceous period saw the emergence of many lifeforms which continued to play key roles in the coming Cenozoic world.