Cretaceous period- The last of dinosaurs ⋆ TheScientificRevelation (2023)

Namaste everyone. Welcome to another post on the “history of earth” series. Previously we had focused on the physical sides of the Cretaceous period like environment, geology, geography, and tectonic movements. In the recent post, Cretaceous period- The last of dinosaurs, we will go for the most advanced dinosaurs, marine reptiles, and flying reptile species. Cretaceous ended with another major mass extinction that wiped all the major mega reptiles in air, land, and water.

Cretaceous life

When we think about cretaceous life we imagine all kinds of mega reptiles dominating the earth. When the Cretaceous ended these amazing life forms ended too. Cretaceous is an important transition period from the Mesozoic life of reptiles to the Cenozoic life of mammals. In cretaceous periods all the dinosaurs, marine reptiles, and pterosaurs were in their apex and most advanced forms. Flowering plants had made their debut in the Early Cretaceous and became the dominant land flora till the end of the period. Both major mammal groups placental and marsupial originated in the Cretaceous period. Other animal groups like marine invertebrates and fishes developed forms with the end of the Cretaceous period.

Marine animals

The cretaceous marine realm is divided into two paleobiogeographic regions, the Tethyan and the boreal. You can think of Tethyan as tropical water and boreal as temperate waters. This division is based on rudist-dominated organic reef-like structures. Rudist were large and unusual bivalves that had dominated over corals and formed the Cretaceous waters. The few exceptions found outside the Tethyan had never made the reefs. These rudist reefs of the Cretaceous had formed the petroleum deposits of Mexico, Venezuela, and the middle east.

The other dominant Tethyan invertebrates were nerineid snails, calcareous algae, and large benthic foraminifera along with some ammonites and echinoids. on the other hand, belemnites were confined to colder boreal waters. Along with them bivalves exogyra and gryphaea and inoceramids were widespread invertebrates of the boreal region.

Marine diversity

As the cretaceous ended most plankton developed modern forms. Coccolithophores (extremely important for the modern marine food web) became so abundant that their carcasses had made the famous chalk deposits of the Cretaceous period. Along with coccolithophores, foraminiferans had also contributed to the Cretaceous chalk deposits. Some other notable animals were diatoms, radiolarians, and dinoflagellates. The most famous cretaceous and Mesozoic invertebrate was Ammonites. Countless species had swum the Mesozoic waters. Coiled forms were most abundant followed by other varied shapes. Ammonites were the food of many marine predators notably sharks and famous mosasaurs.

Mosasaurs were equivalent to modern killer whales, swift and lethal. Along with them long-necked Plesiosaurs and ichthyosaurs had ruled over the marine world. I have already detailed about Plesiosaurs and Ichthyosaurs in my previous post-Jurassicanimals. You can go and read it. Sharks and rays were widespread. Teleost (ray-finned) fishes were widespread back then too.

Terrestrial life

Although it wasn’t that significant, some minor extinctions happened at the end of the Jurassic period. This fossil record is incomplete and irregular at the early cretaceous. The late cretaceous fossil record is the best for Asia and North America. Although tyrannosaurs, triceratops, and Iguanodons were the most famed land animals, we have found fossils of other medium and small-sized herbivorous and carnivorous dinosaurs. Most stem mammals and mammal-like reptiles had long gone leaving the true mammals to live on. Both placental and marsupials have originated till the late cretaceous period.

Life in the air

Pterosaurs had dominated the air for all the Mesozoic era. Meanwhile, one specific pterosaur, Quetzalcoatlus, was the biggest thing to fly in the air. Birds developed from archaeopteryx and related forms.

Land plants

The lands plants were similar to the preceding Jurassic period except for the presence of angiosperms. Most gymnosperms had developed in Triassic and subsequent Jurassic. These cycads, ginkgoes, conifers, and ferns had retained their classic forms till now. On the other hand, the angiosperms that appeared in the early Cretaceous became the dominant flora. Figs, magnolias, poplars, willow, sycamores, and other herbaceous species first appeared in the fossil record. Insects had followed the suit and diversified to the modern levels.

The famous reptiles of the cretaceous period


Albertosaurus, close kin of Tyrannosaurus, had lived in North America and eastern Asia during the late Cretaceous period. It had reduced forelimbs, a large skull, and jaws but it was smaller than Tyrannosaurus. Albertosaurus was 9 meters long and its head was 3.5 meters high off the ground. Hands were similar to Tyrannosaurus with only 2 fingers. Its jaws had sharp and recurved teeth with a rounded shape. They were nearly perfect for puncturing the flesh. It was most possibly a scavenger too, like feeding on dead carcasses and protecting its kill from other small dinosaurs.


Dilong is known from fossils found in Liaoning province, China that dates back to 127 million years ago. It belongs to the Tyrannosaurus group and was one of its primitive members. This proves the theory that tyrannosaurids first originated in Asia and then migrated to North America. This also tells us that during early cretaceous times Asia and North America were joined together on various points. Dilong is also the first tyrannosaurs found with feathers. It was a small dinosaur with a body length of 1.6 meters and 5 kg of weight. It had longer forelimbs and three-fingered hands. Dilong had a skull very similar to later more advanced tyrannosaurus.

Shockingly enough, the anatomy of an adult Dilong resembles the juvenile of later tyrannosaurs. It had protofeathers that were 2 cm long, more like a coat of feathers. Dilong along with other feathered dinosaurs could not fly which explains that feathers might have developed for insulation.

Dominant herbaceous dinosaurs (hadrosaurus/ duck-billed)


This lineage of hadrosaurus lived in North America from 70 million to 66 million years. It was closely related to Edmontosaurus and Shantungosaurus, other dominant herbivores that lived in the northern hemisphere. Anatosaurus had an average length of 9-12 meters and was heavily built. It had a long skull and broad, flat beak much like a duck, hence the name. Similar to other groups of Hadrosaurs Anatosaurus didn’t have any teeth in beak which was rather covered with a sheath. It had many blunt teeth alongside the cheek. Anatosaurus also had extra teethes for the replacement of worn-out teeth. Fossil finds have suggested that it had leathery and rough skin. It might have fed on twigs, seeds, fruits, pine needles. They had flat, blunt, and hoof-like claws very similar to modern browsing animals. They lived in groups and didn’t have elaborate head crests on skulls.


Lambeosaurus had a hallow bone crest on the top of its skull, which was a noticeable feature. It lived in North America during the cretaceous period. Lambeosaurus belongs to the Lambeosaurinae family full of crest dinosaurs. The use of skull crest is not confirmed as there are different suggestions. It might have been used for sound formation or for better smell or perhaps it was just a display for species recognition. Along with the head crest, it also had a different pelvic bone configuration from other hadrosaurus.


Maiasura is another group of hadrosaur dinosaurs. Like its other two sister groups, Maiasaura dinosaurs were also browsing animals that lived in North America during the late Cretaceous period. Their fossils have been found in hundreds with both adults and juveniles in close proximity. This had led scientists to believe that perhaps Maiasura cared for their kids. Fossil finds also suggest that Maiasaura were migratory animals and returned to the same nesting site year after year. Research revealed that it would have taken 7-8 years for hatchlings to develop into adults.

Small carnivorous dinosaurs


dromaeosaur (family- Dromaeosauridae) lived in Asia and North America during the Cretaceous period. They were small to medium-sized carnivorous dinosaurs. They were agile, swift, lightly built, and possessed sharp claws. Dromaeosaurs were bipedal and the second toe of each foot had a sharp talon-like structure. This toe was always off ground and much larger in size. Their head was small and elongated, with sharp razor-like teeth. Their wrist had the same type of motion and flexibility as modern birds. It would have helped them seize the prey. Along with that, they had a very long and strong tail.

Scientists believe that Dromaesaur would have leaped on the prey and stuck both of the talon lags on the prey. At that time the tail would have acted as a counterbalance giving stability to the animal. Dromaeosaur brains were bigger in comparison to other dinosaurs that had allowed them to carry out such complex hunts. It had an average length of 1.8 meters and its prey were small and medium-sized herbivorous dinosaurs.


Deinonychus was a kind of Dromaeosaur dinosaur. It lived during the early Cretaceous period in western America. Deinonychus was bipedal and killed with sharp, 13 cm long talons. Its talons were on the second toe of both feet much like Dromaeosaurs. Similar to Dromaeosaurus it had a long and flexible tail used for balance. Deinonychus had inspired the Jurassic movie’s velociraptor. Deinonychus was 2.5 meters in length with 50 kg of weight. It had a bigger brain for carrying out complex tasks smoothly. Dromaeosaurs are closely related to Archaeopteryx and existing birds. They share a lot of similarities like flexible wrist and sharp talons.


Velociraptors like Deinonychus had sharp-clawed toes. It lived in central and eastern Asia during the late cretaceous period. It had similar adaptations to sister species. Sharp claw and strong tail that helped them maintain balance during a hunt. Velociraptor was the smallest among them with an estimated length of 1.8 meters and 45 kg weight. It had hunted small and medium-sized herbivores with its agile motion.

Armored dinosaurs


Nodosaurus belongs to the Ankylosauria group, the armored dinosaurs along with Ankylosaurus. Its fossils have been found in North America dating to 95 to 90 million years ago. Although Nodosaurus was the smallest, it was heavy with a height of 5.5. It had supported a small head and long tail. It had thick and knobby plates on its back for protection against predators. Its front legs were much smaller than hind legs consequently its back was arched. Nodosauridae were more primitive and they lived before the Ankylisaurids. Nodosaurus didn’t have a tail club like ankylosaurus and their head was not covered with bony plates/scutes.

Horned dinosaurs


The darlings of the Cretaceous were horned dinosaurs/ceratopsians that lived in Asia and North America. One of the earliest protoceratops originated in east Asia, specifically Mongolia and China. Although Protoceratops had evolved from the small bipedal dinosaur Psittacosaurus, they walked on four limbs. Hind limbs were more strongly developed than forelimbs . Due to this, it had arched back. Protoceratops was 1.8 meters long and weighed about 180 kg. Its skull like other ceratopsians was very large, almost ⅕ of the full body. The skull bones grew backward like a frill and the jaws were pointed into a beak. The fossils are abundant with all the growth stages.


The oldest member of the ceratopsian family is Psittacosaurus lived around 122 million to 100 million years ago in the early cretaceous. It was 2 meters long and mostly bipedal. Its skull was small and narrow and supported a primitive beak. Its upper jaw had developed into a beak that covered the lower jaw, hence the name. It’s still unclear but Psittacosaur might have evolved from ornithopods in the early Jurassic.


The showstopper of ceratopsians was Triceratops that lived in North America during the late cretaceous. It was 9 meters long and weighed up to 4-5 tons. Its skull was some of the largest, almost 2 meters long. Triceratops had two 1 meter longhorns above their eyes. Its back frills were completely made out of bones and its beaklike mouth was well suited for ripping the vegetation apart. Teeth were present alongside the cheeks for grinding and chewing the harsh vegetation. Hindlimbs were longer than forelimbs and feet ended in hooves. It was a browsing animal and have traveled in groups.


You might think the largest carnivorous dinosaur are Tyrannosaurs however this title belongs to Spinosaurus. This African dinosaur had a distinctive sail back created by a tall vertebral spine. Its skull was 1.75 meters long much like a crocodile with a body length of 14-18 meters. It had a whopping weight of 13-22 tons. It had straight and conical teeth much like our beloved crocs. That is to say, Its features suggest piscivory means consumption of fish. Spinosaur’s major diet was fish but It might have hunted juvenile plesiosaurs too. Its teeth marks have been found on plesiosaur fossils. Although spinosaurus lived mostly in estuaries and freshwater bodies, it was adapted to live in the ocean.

I Have written in my previous blog post-Cretaceous period- the conclusion about paleo continents. Cretaceous was a turbulent time when all tectonic plates were moving in random motion. Consequently, ocean water had continuously flooded the land. In this scenario, spinosaurus had to deal with marine reptiles. We are not sure about the use of sail however some estimate that it is either for lipid and salt storage or recognition of the species.


Wonderful marine reptile mosasaurs were the T-rex of oceans. It had competed with Plesiosaur and Ichthyosaurus for food and dominance. All these marine reptiles are secondary aquatic means descended from land ancestors. Its major diet was ammonites, cuttlefish, squid, and occasionally other predators. It had a monitor lizard-like head and numerous sharp teeth. Mosasaurus had paddle-like limbs suited for swimming. Its backbone had more than 100 vertebrae for smooth motion. Its lower jaw could slide open for eating the larger prey, a very advanced feature indeed.


These long-necked marine reptiles had shared the oceans with other marine reptiles. They had pan ocean distribution and they dominated during the late cretaceous period. It had a dominating neck, flat body, and relatively short tail. Plesiosaur would flip its limb to swim much like sea lions. It had swum near the school of fish, moving head side by side to feed upon them.

I have written about these 2 species in my previous blog post on Jurassic animals, Ichthyosaurus, and pterosaurs


  1. The biggest resource is obviously the book “Mesozoic era- the age of dinosaurs“. Give it a try, you will like it.
  2. I have been biased in this post and only written about reptiles. However, no worries, read this post to know more about some cool cretaceous animals that weren’t dinosaurs.

I can’t say much here as this is the end. In the next blog post, we will see the last major mass extinction. Until then Stay tuned and DO REVELATION.



What happened at the end of the Cretaceous Period? ›

At the end of the Cretaceous Period, 65 million years ago, an asteroid hit Earth in the Yucatan Peninsula, Mexico, forming what is today called the Chicxulub impact crater.

What is the end of the Cretaceous Period called? ›

The Cretaceous–Paleogene (K–Pg) extinction event, also known as the Cretaceous–Tertiary (K–T) extinction, was a sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago. The event caused the extinction of all non-avian dinosaurs.

What happened to the dinosaurs in the Cretaceous Period? ›

One day 66 million years ago, an asteroid the size of a mountain struck near the Yucatán Peninsula with an explosive force equivalent to 100 trillion tons of TNT. In that cataclysmic instant, the 165-million-year reign of the dinosaurs came to an end.

Was the Cretaceous Period the last? ›

Cretaceous Period, in geologic time, the last of the three periods of the Mesozoic Era. The Cretaceous began 145.0 million years ago and ended 66 million years ago; it followed the Jurassic Period and was succeeded by the Paleogene Period (the first of the two periods into which the Tertiary Period was divided).

What are 3 major events that happened during the Cretaceous Period? ›

Significant Cretaceous events
  • First Flowering Plants. Angiosperms (flowering plants) appeared in the fossil record more than 100 million years ago during the Cretaceous Period. ...
  • Rise of the Rocky Mountains. ...
  • Cretaceous Interior Seaway. ...
  • Mass Extinction.

What was the result of the end of dinosaurs? ›

Whatever the causes, the huge extinction that ended the age of the dinosaur left gaps in ecosystems around the world. These were subsequently filled by the only dinosaurs to survive - birds - and mammals, both of which went on to evolve rapidly.

Did dinosaurs go extinct at the end of the Cretaceous Period? ›

Dinosaurs went extinct about 65 million years ago (at the end of the Cretaceous Period), after living on Earth for about 165 million years.

Does the Bible say about dinosaurs? ›

There are later descriptions of creatures in the Bible that could be referring to dinosaurs. One example is the behemoth of Job 40:15-19. Even in fairly modern history there are reports of creatures which seem to fit the description of dinosaurs.

Did dinosaurs exist during the Cretaceous Period? ›

The 'Age of Dinosaurs' (the Mesozoic Era) included three consecutive geologic time periods (the Triassic, Jurassic, and Cretaceous Periods). Different dinosaur species lived during each of these three periods.

What evolved after the Cretaceous extinction? ›

All that changed with the end-Cretaceous extinction. Mammals survived and took over. The following Paleogene Period saw the evolution of everything from bats to whales.

What period was before dinosaurs? ›

The Earth existed for millions of years before the time of the dinosaurs. This time is known as the Paleozoic Era while the dinosaur time is known as the Mesozoic Era.

What is a fact about Cretaceous Period? ›

The Cretaceous Period started around 145.5 million years ago and ended around 65.5 million years ago. During this period, land on Earth was breaking up into separate continents the way it is today. Flowering plants appeared for the first time, and dinosaurs lived all over the Earth.

What is the summary of Cretaceous Period? ›

Cretaceous Period, Interval of geologic time from c. 145 million to 66 million years ago. During the Cretaceous the climate was warmer than today. In the seas, marine invertebrates flourished, and bony fishes evolved.

When did the Cretaceous Period start and end? ›

What are 5 living things from the Cretaceous Period? ›

But many groups of organisms, such as flowering plants, gastropods and pelecypods (snails and clams), amphibians, lizards and snakes, crocodilians, and mammals "sailed through" the Cretaceous-Tertiary boundary, with few or no apparent extinctions at all.

What survived the Cretaceous Period? ›

Birds: Birds are the only dinosaurs to survive the mass extinction event 65 million years ago. Frogs & Salamanders: These seemingly delicate amphibians survived the extinction that wiped out larger animals. Lizards: These reptiles, distant relatives of dinosaurs, survived the extinction.

What ended the dinosaur era? ›

Sixty-six million years ago, dinosaurs had the ultimate bad day. With a devastating asteroid impact, a reign that had lasted 180 million years was abruptly ended. Prof Paul Barrett, a dinosaur researcher at the Museum, explains what is thought to have happened the day the dinosaurs died.

Why didn't dinosaurs evolve again? ›

Other than birds, Dinosauria doesn't include any living creature. So for a dinosaur to re-evolve in the future, it would have to come from a bird.

How did humans survive the dinosaur extinction? ›

Answer and Explanation: Humans survived the mass extinction event that killed the dinosaurs simply by not being there. The extinction of the dinosaurs occurred around 65 million years ago but humans did not evolve until quite recently.

Did humans and dinosaurs live at the same time? ›

No! After the dinosaurs died out, nearly 65 million years passed before people appeared on Earth. However, small mammals (including shrew-sized primates) were alive at the time of the dinosaurs.

Do dinosaurs Ruled the Earth? ›

Dinosaurs were a successful group of animals that emerged between 240 million and 230 million years ago and came to rule the world until about 66 million years ago, when a giant asteroid slammed into Earth.

Do Christians believe in evolution? ›

Indeed, the pope recently reaffirmed the Roman Catholic Church's view that “evolution in nature is not inconsistent” with church teaching on creation, pushing the debate on human origins back into the news.

What was the last dinosaur alive? ›

Check out the last dinosaur that survived on planet Earth.

The Chenanisaurus barbaricus species is said to be one of the last ones to have survived on Earth before an asteroid strike wiped them all out about 66 million years ago.

Did evolution start over after dinosaurs? ›

When non-avian dinosaurs died out 66 million years ago, mammals persisted. But a new study shows that this group didn't go unchanged: in the first 10 million years following the mass extinction event, mammals bulked up, rather than evolving bigger brains, to adapt to the dramatic changes in the world around them.

What lived on Earth after dinosaurs? ›

A stepwise recovery. After an asteroid wiped out much of life on Earth, mammals—responding to changes in plants—grew in size and diversity surprisingly quickly. After about 700,000 years, legumes showed up; their fossil pea pods are North America's oldest discovered to date.

What was alive before dinosaurs? ›

Plant life consisted mostly of ferns, conifers and small shrubs. Animals included sharks, bony fish, arthropods, amphibians, reptiles and synapsids. The first true mammals would not appear until the next geological period, the Triassic.

Who came before the dinosaurs? ›

For approximately 120 million years—from the Carboniferous to the middle Triassic periods—terrestrial life was dominated by the pelycosaurs, archosaurs, and therapsids (the so-called "mammal-like reptiles") that preceded the dinosaurs.

What is older than a dinosaur? ›

Lobsters and other filter-feeding crustaceans first emerged millions of years before dinosaurs, and in fact the creatures we call horseshoe crabs (more closely related to spiders than modern crabs) appeared around 450 million years ago.

What caused the Cretaceous Period? ›

Asteroid impact, not volcanism, caused the end-Cretaceous dinosaur extinction.

How did the Cretaceous Period start? ›

Was the T Rex alive in the Cretaceous period? ›

T. rex lived at the very end of the Late Cretaceous, which was about 90 to 66 million years ago. How do we know?

What dinosaurs went extinct in the Cretaceous period? ›

North America was close to its current position and shape. The dinosaurs of the Early Cretaceous, before the Seaway, are a mix of Jurassic-like holdovers and newer forms. The long, low Diplodocus-like sauropods and the plated stegosaurs went extinct, while ankylosaurs and ornithopods diversified.

How did animals survive the Cretaceous extinction? ›

"It was the huge amount of thermal heat released by the meteor strike that was the main cause of theK/T extinction," Graham explains, adding that underground burrows and aquatic environments protected small mammals from the brief but drastic rise in temperature.

What major event happened in the Cretaceous period? ›

During this period, oceans formed as land shifted and broke out of one big supercontinent into smaller ones. Continents were on the move in the Cretaceous, busy remodeling the shape and tone of life on Earth.

Who was king of the dinosaurs? ›

As the king of dinosaurs, Tyrannosaurus rex was an apex predator — the largest strictly meat-eating land animal that is known to have ever existed. T. rex roamed across North America for over two million years until a huge asteroid hit the earth 66 million years ago.

What two dinosaurs died together? ›

It may have been a battle for the ages in ancient Montana. About 67 million years ago, two iconic dinosaurs, a Triceratops horridus and a Tyrannosaurus rex, died and were quickly buried together side by side in a single grave. And both of them bear battle scars.

Which is older Jurassic or Cretaceous Period? ›

From oldest to youngest: Triassic (251.902 to 201.4 million years ago) Jurassic (201.4 to 145 million years ago) Cretaceous (145 to 66 million years ago)

How many species go extinct at the end of the Cretaceous? ›

Cretaceous-Paleogene extinction - 66 million years ago

Some 76 percent of all species on the planet, including all nonavian dinosaurs, went extinct. Over a thousand dinosaur species once roamed the Earth.

What is the biggest dinosaur in the Cretaceous period? ›

Paleontologists suggest that Patagotitan mayorum, a giant herbivore that belongs to a group known as titanosaurs, weighed in at around 70 tons. The species lived in the forests of today's Patagonia about 100 to 95 million years ago, during the Late Cretaceous period, and is one of the largest dinosaurs ever discovered.

Why did crocodiles survive but not dinosaurs? ›

There are two main reasons. First, crocodiles can live for a very long time without food. Second, they lived in places that were the least affected when the asteroid hit Earth.

What are the key 2 facts of the Cretaceous Period? ›

The Cretaceous Period started around 145.5 million years ago and ended around 65.5 million years ago. During this period, land on Earth was breaking up into separate continents the way it is today. Flowering plants appeared for the first time, and dinosaurs lived all over the Earth.

What caused the Cretaceous event? ›

Asteroid impact, not volcanism, caused the end-Cretaceous dinosaur extinction.

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