Kasei Era (火星代, Kaseidai)

The Kasei Era — named Kaseidai（火星代）, the "Era of Fire and Stars" — spans the period between 90 and 60 million years ago and is marked by rapid diversification, tectonic transformation, and ultimately, planetary catastrophe. This epoch is divided by natural philosophers into two periods: the Gonankō Jidai（互南交時代）, 90–80 Mya, and the Kasei Shūketsu（火星終結）, 80–60 Mya.   During the Gonankō Jidai, the great placental divergence occurred. Two major mammalian lineages split on opposite sides of the world:

• Gonanotheres evolved on Archaeo-Gonan, giving rise to what would become the Afrotheres and Xenarthrans of later ages.
• Teikōtheres evolved on Archaeo-Teikō, eventually diversifying into the Laurasiatheres and Archontaglires.

These two placental foundations formed in isolation, separated by deepening oceans and continental drift, and were shaped by dramatically different environmental pressures.   By 70 Mya, Archaeo-Teikō itself had split into two daughter continents:

• Archaeo-Bōkō, home to the early Laurasiatheres: hoofed herbivores, insectivores, and large predatory forms.
• Archaeo-Teishin, where the Archontaglires emerged — small, clever, often arboreal creatures that would later give rise to rodents and primates.

  The final ten million years of the era — Kasei Shūketsu, the "Firestar Convergence" — were defined by violence. An asteroid impact, coupled with flood basalt eruptions, shook the biosphere. Vast swaths of flora and fauna perished. Tropical forests burned, coastal wetlands drowned in lava flows, and food chains collapsed. While many lineages were lost, both Gonanotheres and Teikōtheres endured, hiding in burrows, caves, and deep forests.  

Landmasses on the Eve of Destruction (60 Mya)

 

Archaeo-Bōkō

Climate: Subtropical

• Dominant Flora: Flowering trees (Magnoliaceae, Lauraceae), cycads, tropical ferns
• Fauna: Early hoofed Laurasiatheres, predatory mesonychids, insectivores, giant flightless birds

 

Archaeo-Teishin

Climate: Tropical

• Dominant Flora: Dense angiosperm jungles, strangler figs, bamboo-like grasses
• Fauna: Early archontaglires (rodentiforms, gliding proto-primates), arboreal insectivores, small theropod remnants

 

Archaeo-Gonan

Climate: Tropical

• Dominant Flora: Ancient gymnosperm forests, angiosperm pioneers near coasts
• Fauna: Burrowing gonanotheres (proto-tenrecs and hyrax kin), xenarthran ancestors, large crocodylomorphs

 

Archaeo-Ingai (Thadh, Kiin)

Climate: Polar

• Dominant Flora: Mosses, coniferous taiga, seasonal ginkgo groves
• Fauna: Small burrowing triconodonts, cold-tolerant monotremes, polar pterosaurs

 

Archaeo-Kouchuu (Kōbō)

Climate: Temperate

• Dominant Flora: Mixed conifer and early angiosperm forest
• Fauna: Tritylodont relicts, insectivores, euparkeriid descendants

 

Archaeo-Chichū

Climate: Subtropical

• Dominant Flora: Palm-like cycads, primitive broadleaf plants
• Fauna: Small rhynchocephalians, endemic lizards and invertebrates

 

Chishi

Climate: Subtropical

• Dominant Flora: Ginkgoes, podocarps, early flowering underbrush
• Fauna: Tritylodontids, early multituberculates, amphibians

 

Boshu

Climate: Tropical

• Dominant Flora: Cycads, ferns, mangrove-like gymnosperms
• Fauna: Archosaurian remnants, crocodylomorphs, burrowing synapsids

 

Shinshin

Climate: Subtropical

• Dominant Flora: Mixed forests, climbing flowering vines
• Fauna: Cynodont relicts, arboreal insectivores

 

Kyougai

Climate: Subtropical

• Dominant Flora: Thick cycads, podocarps
• Fauna: Tritylodontid specialists, endemic beetles, predatory therapsids

 

Archaeo-Tousai

Climate: Subtropical

• Dominant Flora: Coastal fern jungles, inland podocarp forests
• Fauna: Multituberculates, coelurosaurian remnants, small burrowers

 

Archaeo-Shinchuu

Climate: Temperate

• Dominant Flora: Conifer woodlands, early deciduous angiosperms
• Fauna: Insectivorous mammals, small feathered dinosaurs, amphibians

 

Archaeo-Heiyū

Climate: Temperate

• Dominant Flora: Ginkgo forests, seed ferns, ferns
• Fauna: Amphibamids, early monotremes, burrowing tritylodonts

 

Archaeo-Zhamo

Climate: Temperate

• Dominant Flora: Mixed coniferous forests
• Fauna: Cynodont relicts, early burrowing mammals

 

Archaeo-Lomba

Climate: Boreal

• Dominant Flora: Cold-tolerant conifers, mosses
• Fauna: Gliding mammaliaformes, small triconodonts

 

Archaeo-Chūin

Climate: Boreal

• Dominant Flora: Evergreen gymnosperms, ground-hugging ferns
• Fauna: Tritheledonts, frost-tolerant synapsids

 

Archaeo-Chishu

Climate: Polar

• Dominant Flora: Tundra mosses, stunted ginkgo stands
• Fauna: Polar amphibians, burrowing therapsids

 

Legacy

The Kasei Era represents both the branching of destiny and the fury of cataclysm. Its innovations and disasters alike paved the road toward modern faunal dominance. It is remembered in Elven lore as the "long sundering before awakening," where the twin roots of modern mammals took hold in ash and silence.