Invent your own animal

[JHG]

Argoselachus atrox(Atrocious shark of the Argo)

Argoselachus was a close relative of the modern tiger shark that lived from the mid-Oligocene but died out in the Miocene. It's so closely related to the tiger shark that some scientists prefer it to be classified under Galeocerdo but the existing evidence could point either way. More fossils are needed to settle the debate. Argoselachus ruled as apex predator in the Mediterranean and fed on pinnipeds, whales and other sharks. Measuring 10.7 meters long and weighing 10.1 tonnes, few could challenge this sea monster. At age 15, they reach reproductive age and can mate anytime they wish. Nursery areas in shallows are refuges for the pups. It's surmised this shark could live for over seventy years. Argoselachus was driven to extinction by Megalodon and the continuing climate change. It's slow rate of reproduction(only twenty pups per birth and fifty if lucky) combined with competition and predation from a larger predator didn’t help.

[JHG]

Onchoichthys agassizii(Louis Agassiz's Master fish)/Obese koi fish 

Named for the famous Swiss ichthyologist, this was a giant of a fish. At 27.3 tonnes and measuring 10 metres long, it has gained the jocular nickname 'obese koi fish.' Onchoichthys was a cosmopolitan species, traveling around the globe to lay millions of eggs in schools of hundreds. They first appeared in the Late Eocene and went extinct in the middle Miocene, though some remains suggest a Pleistocene extinction instead. It's possible these fish were outcompeted by the rorqual whales(e.g. fin whales, blue whales, minke whales...) Onchoichthys was a filter feeder, unlike its modern relatives, feeding on plankton. In turn, the large shark Megalodon and raptorial whales were a threat. Juveniles would be vulnerable to those as well as seals, sea lions, smaller macropredatory sharks, whales and pelagorns. In response to the attack strategy of 'ambush from underneath' tactic, Onchoichthys developed osteoderms on its body and a row of spear-shaped spines for defense. Unfortunately, they also disrupted the hydrodynamics which could be a facet of its extinction.

[Kyng]

I'm not sure I remember Thescelovenator rex and Argoselachus atrox. Are they new, or did you post them before? 

(Of course, I remember the obese koi fish !)

[JHG]

I'm not sure I remember Thescelovenator rex and Argoselachus atrox. Are they new, or did you post them before? 

(Of course, I remember the obese koi fish !)

I posted them before. Anyways...
Lunarex torvus(Savage moon king)
Lunarex was an undoubtedly terrifying creature. It was tall as a human but weighed roughly twice as much at 120 kilograms. It lived during the Eocene and Oligocene epochs of the Paleogene period. This was a unique terror bird that hunted at night. Scleral ring analysis proved it. The diet is not well known as that of other terror birds due to Lunarex coming from an earlier time but it may have killed small mammals, birds and reptiles. No one is sure how it went extinct although climate change and competition from more derived terror birds may have been possible.

[JHG]

Afrohadros aegyptiacus(Egyptian Sturdy African)

Afrohadros is a species of hadrosauroid ornithopod related to the earlier Ouranosaurus. Measuring 11 meters long and weighing 5.7 tonnes, Afrohadros was in a comparable league to the derived hadrosaurids but outclassed by contemporary Aegyptosaurus and Paralititan. Afrohadros lived in the Bahariya Formation and Kem Kem Beds about 112-97 mya making it a contemporary of Spinosaurus, Bahariasaurus and Carcharodontosaurus, the latter of which was its primary predator. Afrohadros could deal with predators by running or alternatively tail slapping them. The sail-hump on Afrohadros was likely for fat storage to survive in the dry season. It also functioned as a display structure when mating. The beak of Afrohadros contained tooth batteries for grinding vegetation like water weed. It's thought this ornithopod and other basal hadrosaurs would go extinct when the more advanced hadrosaurids started to proliferate as the latter were smarter and could form more complex social behavior and gather larger herds, putting them at an advantage over not just their relatives but also the carcharodontosaurs who found the new herbivores harder to deal with and were replaced by tyrannosaurids in Asia and North America and abelisaurids everywhere else. Afrohadros is an odd discovery as for a long time Ouranosaurus was depicted living with Spinosaurus and Carcharodontosaurus when it actually went extinct before the two apex predators appeared. Afrohadros partially vindicated this common anachronistic depiction; just that it was much larger than Ouranosaurus.

[JHG]

Unicorn/Unicornis equus(One horned horse)

This is one of the mightiest perissodactyls since rhinoceroses. Standing 1.63 metres or 16 hands tall and weighing 500 kilograms, it may look like a typical horse(long pointy thing aside) but this beast is the embodiment of pure, unadulterated aggression. They will charge at anything they perceive as a threat-including humans. With fierce rhino-like grunts and snorts and elephantine roars, one will usually hear them before seeing them. Unicorns live in herds in the wilds of Eurasia but can live on islands too. Their horns shine bright colors during the mating season when the males use them to impress females or threaten rivals. Occasionally, showing off is not enough and the males respond with brute force. Luckily, such fights are rarely fatal. A unicorn has an unusually potent healing factor for a vertebrate. Its healing is potent enough to regrow a severed limb in the same amount of time a human can repair a paper cut. Multiple serious injuries or infection can tax this healing factor and it is useless against decapitation. This led to the myths by observers in the Dark Ages. Nowadays, the unicorns are so rare they are often dismissed as fantasy. Mostly though, when humans encounter the unicorns, the humans get killed partially explaining the lack of eyewitnesses: lack of survivors!

[JHG]

Escargotitan maximus(Maximum/The greatest snail titan)/S-nail

The s-nail is a giant of a gastropod. Standing 1.6 meters high and weighing 500 kilograms, it weighs as much as a small car. If that weren't enough, this gastropod emits venomous slime which it uses to kill prey ranging from spiders, amphibians and even the huge Arthropleura. The s-nail lived during the Carboniferous era in Europe and if as of yet unpublished documents from Rita Ward are to be believed, it also inhabited parts of Western Asia and the Middle East. Escargotitan was a powerful creature but it wasn't exactly fast. It went extinct from climate change and the drying out of it's jungle habitat at the close of the Carboniferous, meaning this monster was living on borrowed time.

[Kyng]

lol, I like the name and the concept . But, how would it get its prey to step onto its trail of slime?

[JHG]

lol, I like the name and the concept . But, how would it get its prey to step onto its trail of slime?

Probably by hunting slow prey.
Anyway...
Chavosaurus imperator(Imperial El Chavo lizard)

This was the last albertosaurine tyrannosaurid to live and lived south of the range of its more popular relative T. rex, Chavosaurus was an apex predator that fed on hadrosaurs, ceratopsians, ankylosaurs and occasionally young sauropods. At 12 meters long and 4 tonnes in weight, it was the largest albertosaurine. Quicker speed compared to T. rex allowed Chavosaurus to catch prey faster. Like other tyrannosaurs, Chavosaurus likely had short arms and couldn’t grasp well. So it’s all about the bite. The only thing that brought down Chavosaurus was the K-T extinction event.

[Kyng]

Pretty fearsome-looking dino, but since it's smaller than T. rex, I'm guessing it wouldn't have had it easy, even with its quicker speed. 

I mean, as you've always been telling me: "Hadrosaurs....are....POWERFUL!"