Pan-Erthaic Era (地合代, Chigōdai)

The Pan-Erthaic Era marks the time in which all the major cratons of Erthas were fully assembled into a single, unified supercontinent known as Pan-Erthas. Spanning from approximately 330 to 300 million years ago, this era represents one of the most ecologically dense and evolutionarily formative periods in Erthas's geological history. It is traditionally the second Era in the Paleohistoric Age.  

Geography

Pan-Erthas stretched from the polar regions to the equator, encompassing a vast array of climates and ecosystems. All known cratons—including Thädh, Shinshin, Kōbō, Chichū, Gohyō, Zhamo, Tōsai, and many others—were bound together into a continuous landmass. The interior of the continent was largely arid due to the lack of inland seas, while coastal lowlands, river basins, and swamp forests flourished in equatorial zones.  

Climate

The Pan-Erthaic climate was warm, humid, and oxygen-rich. High atmospheric oxygen (~30%) led to the proliferation of large-bodied arthropods and dense vegetation, especially in tropical and subtropical belts.  

Flora

Plant life was dominated by non-flowering vascular plants:

• Swamp forests filled with towering lycopsids (*Lepidodendron*, *Sigillaria*) and giant horsetails (*Calamites*).
• Tree ferns and seed ferns flourished in subtropical uplands and drier valleys.
• Early gymnosperms (conifers and cycads) emerged, especially in temperate zones.
• Peat-forming wetlands began forming the massive coal beds still mined in later ages.

 

Fauna

Animal life experienced explosive diversity:

• Arthropods: Gigantic insects and millipedes thrived, including dragonflies with meter-wide wingspans and multi-meter-long myriapods.
• Amphibians: Dominant vertebrates in most ecosystems, ranging from small burrowers to apex aquatic predators.
• Early Synapsids: Pelycosaurs like *Dimetrodon* emerged as top terrestrial predators in tropical and subtropical biomes.
• Sauropsids: Early diapsids (reptilian ancestors) coexisted with synapsids in drier upland environments.
• Marine Life: Coastal waters were rich with ammonoids, trilobites (in decline), early sharks, and reef-building invertebrates like crinoids and brachiopods.

 

Evolved Lifeforms During the Pan-Erthaic Era

 

Flora

• Lycopodiales — Dominant vascular spore plants; includes massive Lepidodendron-type trees in swamp forests.
• Isoetales — Small, quillwort-like relatives of lycopsids; may have existed in quiet freshwater zones.
• Equisetales — Giant horsetails (e.g. Calamites widespread along floodplains and rivers.
• Marattiales — Large tree ferns; part of understory and mid-canopy vegetation in tropical forests.
• Filicales — True ferns; widespread in low canopy and disturbed ground.
• Peltaspermales — Seed ferns; early gymnosperm-like seed-bearing plants forming upland woodlands.
• Cordaitales — Primitive gymnosperms with long strap-like leaves; ancestral to conifers.
• Cycadophyta — Early cycads beginning to appear in upland and seasonal zones.
• Ginkgophyta — Earliest ginkgo-like plants likely in scattered subtropical pockets (rare at this point).

 

Fauna

• Odonatoptera — Dragonflies and their giant relatives (Meganeura apex aerial insect predators.
• Palaeodictyoptera — Ancient, beaked-winged insects; now declining but still present in wetlands.
• Arthropleuridea — Giant millipede-like myriapods, some over 2 meters long.
• Trigonotarbida — Spider-like arachnids (not true spiders), some dominant ground-dwellers.
• Xiphosura — Horseshoe crabs; widespread in marine shorelines.
• Temnospondyli — Dominant amphibian group; ranged from small insectivores to crocodile-sized predators.
• Lepospondyli — Smaller, more specialized amphibians; some evolved burrowing or aquatic traits.
• Pelycosauria — Early synapsid "mammal-like reptiles" including Dimetrodon and Edaphosaurus.
• Captorhinida — Primitive anapsid reptiles; generalist insectivores and omnivores.
• Araeoscelidia — Early diapsid reptiles; precursors to archosaurs and lepidosaurs.
• Acanthodii — “Spiny sharks”; still present in freshwater ecosystems but fading.
• Chondrichthyes — Sharks, rays, and relatives; present in coastal seas and reefs.
• Actinopterygii — Ray-finned fishes; growing in diversity in marine and freshwater habitats.
• Placodermi — Armored fishes in terminal decline; last remnants in brackish zones.
• Ammonoidea — Ammonites; common marine predators with spiral shells.

 

Major Evolutionary Developments

• First true seed-bearing plants become dominant in drier upland regions.
• Synapsids split clearly from other amniotes — laying the foundation for mammalian ancestry.
• Reptiles (Sauropsida) begin to differentiate from early amphibians.
• Flight and aerial predation established in large insects (Odonatoptera).

   

Craton Climate Map

The cratons of Pan-Erthas occupied the following climate zones:

• Tropical: thadh, Kiin, jinshi, boukou, teishin, gohyou, teigo, zhamo, heiyuu, Boshu, Shinshin, shinshi, kyoushi, Chishi, koubou, chichuu, tousai, shinchuu, shinyuu, shinbou, konchuu, lomba, ndali, Chishu, kyougai
• Subtropical: chuuin, jinchuu, boshi
• Temperate: teigai

 

Legacy

The Pan-Erthaic Era laid the groundwork for all later terrestrial ecosystems. The rise of seed-bearing plants, advanced amphibians, and the first amniotes (synapsids and sauropsids) would drive the evolutionary engines of future ages. As the Era closed, rifting began to fracture Pan-Erthas—ushering in the next great phase of continental and biological change.