Allothere earth notes
Not sure if this will become a full blown Speculative Evolution project but I couldn’t hold it anymore:
- Earth mostly identical to ours except instead of therian mammals allotherians survived and displaced them (basically already happening in the early Paleocene; damn you PETM!). Meridiolestidans, monotremes and zealandatheres are also present.
- Gondwanatheres were already dominant across the southern continents, and extend into the northern continents during the Paleocene/Eocene. Indian sudamericids and adalatheriids colonise Asia, with adalatheriids probably making it into Europe and North America, as do ferugliotheriids from South America (an abstract claims there’s a ferugliotheriid in the Campanian of Mexico). In Africa a clade derived from Galulatherium (Galulatheriidae?) goes full Afrotheria. They are the dominant megafaunal herbivores of the Paleogene in most continents aside from North America and Europe (where taeniolabidids rule) and South America, Australia and Antarctica (where they co-exist with mesungulatids). Ferugliotheriids are largely pwned by the spread of grasslands in the Oligocene and Miocene, being restricted to island habitats like the Caribbean and Macaronesia, while galulatheriids die out altogether, but sudamericids and adalatheriids attain a near-cosmopolitan rule as grazing herbivores, the former more akin to ground sloths and the latter more akin to perissodactyls.
- Kogaionids follow a similar initial trajectory as in our world, spreading throught Europe but being largely displaced by other groups like ptilodontids and djadochtatherids. However, they survive in two major places: Afro-Arabia and Turkey (see Anatoliadelphys for the state of the “Turkey Island” in the Eocene). Here, they experience a mild period of success from small insectivores to carnivores to otter and bat like forms, but are gradually displaced by successive waves of other groups. Now they can still be found in mainland Africa if you know where to look, but their kingdom is Madagascar, where they occupy both insectivore and carnivorous roles.
- Like in our world Taeniolabidoids are among the first large mammals in the northern hemisphere. Taeniolabidids disperse across North America and Europe where they are the largest land mammals; at least two genera are found in South America and Asia but they are otherwise largely displaced by gondwanatheres in these regions. Some species take to the water and become sirenian/desmostylian analogues; these are the only ones to survive after the cooling of the Oligocene, where forest biomes gave way to grassland. Lambdopsalids remained relatively small due to the influx of gondwanatheres in Asia and djadochtatherids cramming their style, but by the mid-Eocene they managed to produce cursorial forms similar to early horses and artiodactyls and when the plains open they quickly diversify in a manner similar to that of ruminants, gaining an edge over djadochtatherids at first due to their teeth being better suited for grass. In the present day they are in all continents except Ocenia and Antarctica, ranging from gopher-like forms to gracile horse-like ones. Some use their tarsal spurs like antlers, having them grow more complex and branched.
- Ptilodontids are easily one of the most diverse multituberculate clades, having spread across the canopy biomes during the Paleogene, occupying all manner of niches from seed specialists to frugivores to marten or cat-like carnivores. Some have even taken into the air and developed powered flight, while others moved to the ground to become shrew analogues and others to the water to become otter analogues. A great number of clades disappeared during the Oligocene/Miocene transition and latter during the Pliocene, but they still remain one of the most speciose multituberculate lineages and are found in all continents except Antarctica.
- Djadochtatherids are not quite as morphologically diverse as ptilodontids, but they are the most speciose clade. During the Paleogene they mostly stuck to small omnivorous niches akin to those of elephant shrews and galagos as other groups diversified around them, but the expansion of grasslands in the Neogene lead to an explosion of diversity, quickly catching up with lambdopsalids and gondwanatheres in grazing speciations. Now they range from small mouse-like granivores to arboreal squirrel and sifaka analogues to hare and kangaroo like grazers, the largest forms having become bipedal runners like the theropods dinosaurs of old. Some also moved into aquatic niches, filling roles similar to those of seals, while others have acquired powered flight. Like ptilodontids they are found in all continents, though in their case including Antarctica.