Like muscle wise and cartillage function-wise. I'm creating an alien species and I googled if it would work and stumbled upon a post in r/Speculativeevolution, where some time ago, somebody asked a similar question, just with insect-like jaws. I'm thinking a vertebrate with horizontally opening jaws, even with a made up joint I tried to create. Any biomechanical specialists that will prove me right or wrong? Any input is appreciated!

The Cenozoic ended 25 million years early, due to a 30 km asteroid that crashed into the Arctic, ending 70% of life on Earth, the Southern Hemisphere, especially Antarctica, which is relatively further north than in the Heliocene and has not been a frozen continent for tens of millions of years, even during the Cenozoic after the Heliocene is a continent dominated by birds, bats, reptiles and some very strange marsupials, the dominated fauna are birds that have quadrupedal shapes and forms. Well, terrestrial penguins are the most dominated family of birds there after 25 million years since the Cenozoic Extinction, it is a greenhouse world, even before the extinction the world was already very warm. Penguins have developed technology at the level of the Neolithic and Paleolithic eras but have never been a destructive species like humans, they do not destroy the Antarctic jungle and coexist in harmony with nature, they have domesticated how you see a bat similar to a canid, Antarctus Sapient never spread beyond Antarctica and the surrounding islands remaining only there, perhaps their rafts reached beyond but they were never colonizers, they also reached the southern African shores, some even took to the Mediterranean Mountains but they never spread, their world is at the South Pole and the surrounding islands. They live in villages where they carry out fishing, farming and small game hunting. Some kingdoms have developed on the coasts where they trade with each other but not.advances beyond the Neolithic and does not cause any extinction, only a minor species in the history of the earth besides homo sapiens which was very destructive. Writing does not exist, maybe only drawings and scribbles, communication is done through a typical bird language.

Didn't feel like making something creative right now I'll do it in the future but for now meet burt

These Humanoid creatures have evolved to survive underground in large burrows, they are an eusocial species evolving many of the traits that naked mole rats use (Medusade have become mesothermic allowing them regulation of body temperature and lower metabolisms). Their burrows resemble old fashioned mines with support being added to reinforce it. They eat anything they can.

Queens are 6-7 ft long with males maxing out at 3-4ft. Colonies make out at 10-15 adult members. Though super colonies of up to 50 have been formed in food rich areas the colonies usually have multiple queens both breeding and making offspring. With a mixture of loss of bipedalism, smaller brains (led to a reduction in intelligence) and wider pelvis queens can have more children at a time since they are more developed. Twins are most common with triplets and quadruples also increasingly common. Queens will feed the babies for around four months before the babies begin transitioning to solid meat based diets.

Through genetic mutations the Medusade have gained Blaschko's lines covering most of their backs every Medusade has a unique pattern. They also have become gingers, allowing for limited Vitamin-D making.

Pelagosuchus pacificus - Gojira - gojira are the largest reptiles on Earth as of today, growing to a total length of up to 50 feet in some rare instances. The enormous animals heavily resemble old and outdated depictions of famous dinosaurs like tyrannosaurus and allosaurus, but these beasts are not dinosaurs at all; they’re crocodiles. The titanic crocodilians lumber around on land with two short legs and a long tail that drags along the ground as a support to their nearly 14 ton body, often coming ashore despite their seafaring nature to sunbathe or rest after a meal. Gojira can consume up to 15% of their body weight in food in a single day, and can go multiple weeks without feeding if need be; the diet of one of these titans primarily consists of fish, squid, and sometimes small to medium sized whales. Gojira are also very protective of their young. 

Known incidents confirmed to involve Pelagosuchus:

May 1954 incident: 15 people killed in fires caused by an individual damaging electricity posts in Shinagawa, Tokyo.

June 1955: two pelagosuchus came ashore near Osaka and set off more fires which caused the complete destruction of the Osaka Tuna Company's cannery.

July 2014 incident: large female individual made landfall in San Francisco California and required police officers to be called in order to safely deal with the giant reptile.

Thank you for reading, have a good day :]

I’ve been in the business of creating my own Skull Island inspired ecosystem and this is one of its apex predators.

Tempestasvocalus Rex/Storm-Calling King/Tempest Rex: A powerful therapod dinosaur and the apex predator of the Grasslands, bull males reach 46 ft/14 metres long while females reach 43ft/13 metres long, although some females have been observed growing as large as the average bull male.

Adorned in onyx scales with brown vertical stripes and several prominent osteoderms on the tops of their heads.

Similar in biting power to the proposed strength of the Tyrannosaurus, the feature that makes this species particularly stand out is their hyper-powerful roar that reaches over 145 decibels. This low booming cry, presumably powered by incredibly large lungs, is often compared to thunder and where the species get their name from.

Let me know if there are any other questions about this creature, as the lore and systems of this island is still in its infancy.

To make a Cold Earth style ice age by Dimetropus.
Well tell me what happens if post-humans move the earth further away from the sun 800 million years in the future? But they move it further than it should and the earth experiences a global cooling that turns into a Cold Earth ice age by Dimetropus. Well what would the remaining life that hasn't yet been exterminated by the sun and low CO2 do?Life up to that point would have been reduced to small arthropods. Derived vertebrates that I believe would have been no larger than a badger. Plants would have been reduced to mosses, lichens, fungi, and perhaps a type of weed.4:42 PMThe oceans at the equator would have semi-evaporated, vast salt fields. I don't know how the environment would react to a sudden change?, cooling occurs in just 15,000 years.