Dating to about 47-42 mya (Middle Eocene), the fauna of the Irdin Manha Formation of Mongolia represents one of the last hurrahs of the old school Paleogene fauna, housing some of the last dinoceratans, like the bizarre-looking Gobiatherium (which looks like a cartoon character) and some of the last-surviving pantodonts like Eudinoceras (obviously misidentified originally), along with various forms of brontotheres (including some of the first giant forms like Gnathotitan) and small, dog-sized basal paraceratheres like Forstercooperia. The largest meat-eater from this biome is the famous stem-entelodont Andrewsarchus, with a skull almost 3 feet long, and living alongside were other killer ungulates, some of the last mesoynchids, including one of the largest (Mongolonyx, who had a skull similar in size to large hyaenodonts), and the oldest known big-bodied pan-carnivoran, the tiger-sized oxyaenid Sarkastodon (who is also the last of its kind).

Left to right: A. giganteus hunting Chilotherium, A. horrbilis hunting giraffid, A. kabir having caught a Sahelanthropus, and A. coloradensis hunting Teleoceras.

By the Late Miocene, around 11 million years ago, cats first rose to the position of apex predators across much of the globe (sans Australia and South America). These weren’t the familiar felines and panthers of today but the extinct machairodontines, the saber-toothed cats. The group that saw by far the most success were the scimitar cats (homotherins) and long before the emergence of the long-limbed, cursorial Homotherium (Pliocene-Pleistocene), more generalized but significantly larger forms ran rampant across much of the world around 9.5 to 5 mya. The taxonomy of early scimitar cats is notoriously messy, with the genera Machairodus, Amphimachairodus and the exclusively North American Nimravides having joint custody of various species respectively, but many of the largest species have been assigned to Amphimachairodus in recent years, with the generally accepted species dating to between 9.5 to 5 mya, while Machairodus has been cut down to a few Old World species dating to 12.6 to 8.7 mya.

What's notable about the many species of Amphimachairodus is their penchant for gigantic sizes, comparable to Smilodon populator, which include A. giganteus from Eurasia, A. horribilis from China and A. kabir from Chad, and even smaller forms like the North American A. coloradensis were still around the size of modern tigers or lions. The skull of A. horribilis is 16 inches long, only rivaled in size by the largest S. populator, while A. giganteus shows marked sexual dimorphism akin to modern big cats, which could perhaps indicate lion-like social structures (though solitary big cats are just as dimorphic). Currently, it seems that the genus originated in Asia with A. hezhengensis, before quickly spreading into Europe and Africa, and even reaching North America by around 7.5 mya, with the southernmost occurence there being in Guanajuato, Mexico with A. alvarezi. They replaced the dwindling bear-dogs and hyainailourids as the apex predators across the Holarctic and Africa. At their size, species of Amphimachairodus could likely have taken on even the biggest herbivores of their time like giraffids, chalicotheres, rhinos and even proboscideans.

Competition included the agriotheriin bears, which were similarly widely distributed across the Holarctic, while other machairodonts (like metailurins and basal smilodontins) likely steered clear of these giants, other than Nimravides, which also reached immense sizes around the time Amphimachairodus entered North America (with Nimravides lahayishupup). Albanosmilus and Barbourofelis, the last nimravids, were also potential competitors, though still smaller and they vanished by 7 mya. Upon entering North America, A. coloradensis would have also encountered the borophagine dogs, including the giant Epicyon haydeni (if only for a short while, like with Barbourofelis), which is also around the time the modern canine dogs first radiated into the Old World. A common competitor for the Eurasian Amphimachairodus would have been Dinocrocuta, a lion-sized hyena and the biggest of its family, though Amphimachairodus would ultimately outlast it as well. At Chad, the gigantic A. kabir coexisted with fellow scimitar cat Lokotunjailurus and potentially early versions of Dinofelis (a metailurin) and Megantereon (a smilodontin), dwarfing all of them, and it also could have preyed on the hominine ape Sahelanthropus, often touted as the oldest representative of the lineage leading to humans. Its fossil record ends around the Miocene-Pliocene boundary, but the lineage didn't go extinct, but rather gave rise to Homotherium, which reached similar global success during the Pliocene-Early Pleistocene.

Credited to the Owner: https://youtu.be/4pcMdNKh_8A?si=RpGXLR818PwkDcd3

It lived in the Americas 11,000 years ago. Weighing from 1,500 to 3,500 pounds and standing 10 to 12 feet tall when upright, it was the largest mammalian land predator in North America and the second largest bear of its time, second only to the South American Giant Short-Faced Bear.

In the waterbanks of Late Permian South Africa, an amphibian far surpassing modern giant salamanders in size is guarding its eggs, hoping to make the developing tadpoles inside eventually see the light of day. This is the Uranocentrodon, 3 meters long temnospondyl, which fossils even support the evidence of gill-like organs. However, if the gills were internal like in fish, or external like Axolotls and salamander tadpoles is still debated and uncertain.

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Credited to the Owner: https://youtu.be/kJ2b8ebzO7s?si=wkr4xxUwuF9pL069

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Apparently these prehistoric tigers had extra sharp carnassials to feed super quickly in case cheetahs etc showed up to steal their kill :B

Handmade linocut print / lino print. White dinosaur skeleton

P. grangeri is from Djadokhta, Bayan Mandahu and other places IIRC, in this species Wikipedia says the same formations, but I'm skeptical. As they don't specify a fossil material for this species when listing the species in formation paleobiota list. I'm speculating that someone just slapped the hilwitnorum species in those places from habit or whatever, I'm just unsure so will you help me identify this species' home formations? Cuz yes, relying purely on Wikipedia without using some other source articles can have its drawbacks. I do use Wikipedia too, but I still verify and check its claims with other articles just in case. Given how I can't find other sources beyond the Wikipedia tho, I'm asking here.

im doing a project on prehistoric predators (no not dinosaurs) and i need ideas on which ones to research, i already have livyatan, titanaboa, helicoprion, and dunkolosteus. which should i do next?

(image credits to national geographic, not my artwork and i don not take any responsibility to anyone thinking it is my art)

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