Dinosaurs of the Ice Age

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Around the boundary of the Jurassic and Cretaceous periods, about 145 mya, was a time during the age of dinosaurs when the world actually started to cool down due to a minor glaciation. However, what if there wasn't any volcanic activity after the glaciation? How much more severe would the world get? What groups would go extinct if this happened? What groups would evolve? Would the non-avian dinosaurs survive the K-T mass extinction in this alternate timeline?

History

Early Cretaceous (145-120 MYA)

The split for this alternate timeline happens at about 140 MYA, after the Berriasian age ended and the Valanginian age began. However, in this timeline, there are none of these volcanic eruptions. This causes the world's temperature to quickly drop and causes dinosaur groups such as the stegosaurs and most other armored dinosaurs to go extinct as they couldn't adapt very well to the cooling climate. Sauropods also had a hard time with the cooling climate, and most groups such as the diplodocids and brachiosaurs went completely extinct, with only the titanosaurs surviving by the skin of their teeth. The theropods lost some groups as well: the colder climates caused the extinction of the spinosaurs, the majority of abelisaurs, and most carnosaurs; while the coelurosaurs easily survived, with most species having evolved primitive insulating feathers. The dinosaurs weren't the only group hit hard; the rhamphorhynchs and temnospondyls, already on the decline, also went extinct.

Some other groups fared better. The mammals, crocodilians, and birds easily survived; the mammals with endothermy and fur; the birds with endothermy and feathers; and the crocodiles with a conservative metabolism and low bodily needs. The ornithopods suffered some losses, but generally did well as flowers and fruits evolved around this time.

In the oceans, life was also hit hard. Ichthyosaurs and Thalattosuchia went extinct by this time. Long-necked plesiosaurs and pliosaurs went on the decline due to the cold oceans while the short-necked plesiosaurs fared better. However, on the land the colder, drier climates caused some ferns to evolve into grass-like forms with much smaller leaves. Ankylosaurs, therizinosaurs and ceratopsians nearly went extinct because they were designed for eating leaves and not these grass-like ferns. Titanosaurs and ornithopods fared better with this new food source since the could evolve teeth designed to chew this tough plant matter.

Mid-Late Cretaceous (120-66 MYA)

By the mid Cretaceous, about 90 MYA, life was starting to recover to these colder climates. The dominant predators in the north were the carnosaurs and dromaeosaurs since the tyrannosaurs were less plentiful due to competition from the larger carnosaurs. In the south, the carnosaurs and abelisaurs ruled. Like in our home timeline, the titanosaurs are the dominant herbivores in the south while ornithopods are dominant in the north. However, the titanosaurs in this alternate timeline are smaller due to the colder climates.

By the end of the Cretaceous, around 66 MYA, the dinosaurs were thriving. While in our timeline they had gone extinct by this time due to a meteor strike, the cooling trend of the Early Cretaceous in this alternate timeline causes the K-Pg mass extinction to be much less severe and the majority of non-avian dinosaurs survived because of that. However, ankylosaurs nearly went extinct due to the spread of fern prairies, and were down to just several species by the end of this period. Pliosaurs also went extinct by this time due to competition from short-necked plesiosaurs.

Paleogene (66-23 MYA)

Since the K-Pg mass extinction was much less severe in this timeline, the majority of dinosaurs were able to survive. However, the cooling trend of the Cretaceous was put to a halt by the Paleocene-Eocene thermal maximum. The titanosaurs and other large dinosaurs started to shrink in size due to the expansion of forests. The therizinosaurs, ankylosaurs and ceratopsians started to recover during this time since there were more leaves to eat.

At the end of the Eocene however, the fern prairies once again started to spread, allowing some dinosaurs to grow large again. The therizinosaurs, ankylosaurs and ceratopsians started to once again decline, but they mostly stayed diverse in the tropical zones. The carnosaurs started to decline during the Oligocene due to the decline of their sauropod prey.

Neogene (23-2 MYA)

Ceratopsians and therizinosaurs migrated from Asia to Africa and brought serious competition for the African titanosaurs and they nearly went extinct. The Isthmus of Panama also allowed tyrannosaurs, therizinosaurs and dromaeosaurs to migrate to South America during the Pliocene. The tyrannosaurs also drove the abelisaurs to extinction in India and South America. By this time, the dromaeosaurs had spread to every continent except Antarctica. One group of dromaeosaurs in Africa grew to large sizes and became the tyrant raptors, they also outcompeted the carnosaurs into extinction in that continent. The tyrant raptors were part a new subgroup of dromaeosaurs called Gigaraptors. They get their name because of the large claws on their front hands.

Quaternary (2 MYA-Present Day)

When the Pleistocene arrived, the ceratopsians and therizinosaurs went extinct in most of the northern hemisphere due to the decline of forests. The dromaeosaurs continued to diversify, the smaller ornithomimids and mikrosaurs also became more diverse during this time. Ankylosaurs also went extinct everywhere except on a few islands where competition is scarce.

Present Day

In the end, the age of mammals would never come in this alternate timeline. Most mammal groups from our home timeline, including humans, would never evolve. Eutherian mammals would get no larger than cougars while metatherians and monotremes would be much more diverse than in our home timeline. Most ceratopsians would also stay small since the niches were already held by larger dinosaurs. Almost all modern bird groups failed to evolve since pterosaurs were still ruling the skies. However, birds would still be very diverse. Mosasaurs, oviraptorosaurs, pachycephalosaurs and grass never evolved. The lack of volcanic activity after the Tithonian-Berriasian glaciation in this alternate timeline completely changed the course of evolution.

1,000 years from Present Day

Many years after Present Day, climate change began due by a massive supervolcano named yellowstone erupting. It caused acid rain around the world mainly in North America. But in Africa the Gigaraptornae were starting to die out due by competition with tyrannosaurs. They moved to South Africa to prevent their species to go extinct. But in the South Titanosaurs were bigger than ever same goes for ceratopsians. so they evolved to hunt in bigger gangs than their ancestors. Around that time still no humans but a 25 foot tall ape named Kong maximus evolved around this time. But they need to evolve into humans but not during this period because dinosaurs ruled. Mammals ruled South Africa but it was short lived. The new apex predators named Gigamegaraptor evolved and was able to nearly wipe out the Kong's out. But one was so large that many never attacked him. Gigamegaraptor is nicknamed the big one. If Kongs falls the Gigamegaraptor comes up. But even if the gigaraptornae attacked in packs the ape will still handle them. But then the mammals were gone forever only the small ones remain. But somehow the spinosaurs rose up again and started invading South Africa. Giga-raptors to decline and only one species remain in Africa and many now lived in Asia.

32 million years from present day

Dinosaurs outcompeted almost all large mammals on Earth. During this time a bigger Supervolcano erupted killing off almost all Gigaraptornae but all Gigaraptornae in Africa are gone not by the volcano erupt but it weakened them but Tyrannosauroidea and carnosaurs started taking over and destroyed them completely. All large mammals both land and aquatic are wiped out once again dinosaurs defeated our ancestors and maybe will outcompete mammals to extinction. After the eruption half of all life on earth are gone forever.

Tyrannosauroidea: 1%

Gigaraptornae: 1%

Mammals: 104%

Therizinosauria: 1%

Carnosaurs: 1%

Abelisauroidea:1%

Ceratopsians: 1%

Ankylosaurs: 1%

Orinthomimosauria: 1%

Aves: 104%

Titanosauria: 1%

Hadsaurs: 1%

Pterosaurs: 3%

Spinosaurs: 1%

Non Avian and Dinosaur Reptiles ( Lizards Snakes Crocodilees and Many Others) 100%

Amphibians (Frogs Salamanders Caecilians And Many Others) 100%

40 million years to 10 Million years

10 Million Years to 1 Milion Years Present

Since the Gigaraptornae is nearly wiped out they become smaller than a albertosaurus and about the size of ceratosaurus. Tyrannosaurs become as large as a spinosaurus but a bit smaller. Around this time ceratopsians moved to South America some South American titanosaurs migrated to North America once again like alamosaurus back 70 million years ago. The ones that stayed in South America now have some serious competition with ceratopsians. With tyrannosaurs, carnosaurs, abelisaurs, and spinosaur living in the same place they all compete for food. The around 700 years after ceratopsians came to South America, they started to have horns not above their eyes or have one above their nose they have it were the jaws are. Some ceratopsians have tusks made of bone which made a new family called Jugaloceratopsians. At this time small islands were the ankylosaurs lived felt an earthquake so powerful that all the islands begun to sink. Each island falls into the water about 3 inches every year. The carnosaurs, the Tyrannosaurs, titanosaurs and ankylosaurs left the islands. The islands sink so they all migrated to northern Asia, Africa, and Europe causing serious competition with mainly giga-raptors which finally decline. All the giga-raptors try to keep control but ended up being smaller, they stand about 7 feet tall and now reach length of 15 feet long and weighing 200 pounds. In Africa, ceratopsians and Therizinosaurs were smaller about the size of triceratops instead of spinosaurus. Around this time climate change rage across South America and North America. Jugaloceratopsians were still doing fine but snakes became larger about as long as titanoboa. But not as heavy as titanoboa. Jugaloceratopsians begun to decline from the competition with ankylosaurs. Hadsaurs also begun to decline due to competition with not ankylosaurs but Jugaloceratopsians. Hadsaurs started to have thumb spikes about as long as megaraptor and carries bacteria so if the attack survives the stab they will not last long. Cruncher Beasts tyrannosaurs started moving down to the whole North America. Some even moved down to Mexico, Central America, and even South America. This caused serious competition with false carnosaurs. But somehow they both started coexisting with each other without either one going extinct. They rarely breed with each other causing false carnosaurs to decline. Jugaloceratopsians now have to face new more advanced and powerful predators.

50 million years from present day

Jugaloceratopsians started migrating north due with larger predators and more powerful predators. The breeding of false carnosaurs and Cruncher beasts evolved a animal similar to Tyrannosaurus rex in fact the new species name is Tyrannosaurus rex ultimatum. Like Tyrannosaurus rex, they had bone crushing jaws and had a mouth filled with bacteria.

Suggestions

If anyone wants to give suggestions for animals for this project, please leave them here.

add terror bird like descendant of Prehistoric Flightless Birds

Add Modern Birds Like Descendant Of Prehistoric Birds

And Mammals Will Evolves Later

Reptiles and Amphibian Will Evolve Later Agian

Invertebrates Will Evolve Later Agian

Some Non-Avian Dinosaur Died out at Pleistocene and 5 New Eras

50 million yrs: In Australia perhaps because of the high degree of variation in climate and rain fall, dinosaurs begin to decline and are mostly out competed by a group of mammals known as the Rodetheres, and a group of terrestrial fish descended from a mudskipper like species and this group has 3 legs. And perhaps a pigeon like bird begins to out compete most pterosaurs in Australia because the pterosaurs chicks and eggs are being destroyed by the Rodethere groups as they become more common with fewer predators . And in Tasmania, monotremes are out competing most surviving dinosaurs in Tasmania (that are bigger than a meter in length) because of this monotremes carry their eggs around in a pouch and bury them under ground.

Dinosaurs of the Ice Age
Sauropsida	Archosauria	Theropoda	Abelisauroidea • Aves • Dromaeosauridae • Gigaraptornae (Dinosaurs of the Ice Age) • Ornithomimosauria • Therizinosauria • Tyrannosauroidea
		Sauropoda	Titanosauria
		Ornithischia	Ankylosauria • Ceratopsia • Ornithopoda
		Pterosauria	Pterodactyloidea
		Crocodylomorpha
	Lepidosauromorpha	Plesiosauria • Squamata
Mammalia	Eutheria • Metatheria • Monotremata