Primitive Forest

The first non-coastal terrestrial biome on TIRA 292b consisted of a massive xylophyte forest that spanned the planet's entire supercontinent. This forest covered the continent for roughly 100 million years before changes in climate and geography shrank and fragmented its range.

## Description

The primitive forest biome is characterized by being hot and wet year-round, though not to as extreme a degree as the tropical rainforests. Though the forest’s range has decreased considerably since its original formation, many environments with a similar climate and biota still persist in many areas.

Plant-wise, these regions are almost exclusively dominated by archexylophytes. However, the thinness of these forests still offers enough resources for ample growth of smaller plants like eucaulophytes and brachyphytes; a particularly notable clade of these brachyphytes are the fruiting and nectar-producing chromatophytes, which were brought by migrating opisthopterans and pleuropterans from the eastern rainforest.

In addition to those plants, these stretches of primitive forest also support a healthy diversity of animals. Most of the forests on both continents are home to various species of omnivorous archeplatydontines, basal pursuit-hunting archedromaeopods, basal ambush-hunting eudeinognathans, browsing archemegalobrachids, various clades of malacoformes, malacovorous eudesmostracids, carnivorous flying latopterans, arboreal ambush-hunting archelastospondylids, basal grazing euplacostracans, and, presumably, many species of arboreal malacovorous eudolichostracids, nectarivorous picopterans, frugivorous scandopods, basal flying pleuropterans, and possibly the larger platypterans.

Many primitive forests on the eastern continent may additionally be home to camptopods, which are more generalist relatives of the plains-dwelling leptopods. These forests are also inhabited by the durophagous malleognathans.

## History

The first xylophytes evolved roughly 4,122,000,000 years (4122ma) after the planet’s formation, and spread out all over the continent not long after. Though xylophytes were the dominant forms of plant life in the biome, many caulophytes were also present there; a notable clade of these plants evolved to survive exclusively on the bountiful amounts of organic matter building up on the forest floor, becoming the necrophytes.

The primitive biome began to truly take shape with the emergence of the fully-terrestrial lophostomes in 4170ma. These pioneering animals gradually diversified to fill a variety of different niches offered by the forest, giving rise to the small-bodied malacoformes, the browsing placostracans, the omnivorous desmostracans, and the carnivorous coleostracans.

The forest ecosystem experienced a significant restructure when the osteopods evolved, in 4190ma. These new contenders underwent an adaptive radiation of their own, becoming the omnivorous platydonts, the pursuit-hunting dromaeopods, the browsing megalobrachids, and the ambush-hunting deinognathans. The true endoskeletons and efficient breathing mechanisms of these osteopods allowed them to easily outcompete the large-bodied lophostomes for many ecological niches, forcing the lophostomes to adapt for different ones. The desmostracans, coleostracans, and placostracans survived by evolving into the exclusively malacovorous eudesmostracans, the arboreal ambush-hunting elastospondyls, and the grazing euplacostracans, respectively.

Up until this point, the continent-wide primitive forest had been supported by frequent hypercanes that regularly brought huge bouts of acid rain to as far as the center of the supercontinent. However, this soon began to change. The massive quantities of photo- and chemotrophs all over the planet, among other factors, had been gradually decreasing the proportions of carbon dioxide and hydrogen sulfide in the atmosphere. By 4220ma, the quantities of these gases had decreased enough to create a significant reduction in the potency of the planet’s greenhouse effect. This caused a global temperature drop, which resulted in the production of the reliable storm systems that fueled the growth of the forests grinding to a halt. This culminated in the transformation of the innermost parts of the forest into vast tracts of dry, open plains. The remaining regions of primitive forest could only persist in areas closer to the coasts and other sources of water, where rain was frequent enough to support dense groves of xylophytes.

Along with the reduction in range, some evolutionary developments in the primitive forest also occurred during this time. A lineage of gliding elastospondyls evolved into the flying opisthopterans; some of these animals further specialized for life in the dense forests, becoming the latopterans. Additionally, some ground-dwelling platydonts evolved for life on the open steppe, becoming the swift leptopods; more on them later.

Some caulophytes also adapted for life on the plains, becoming the smaller brachyphytes; these were the ancestors of the chromatophytes.

The primitive forest’s range yet again saw a significant decrease with the formation of the coastal mountain ranges in 4249ma. These massive walls of rock barred the oceanic weather systems from bringing water to much of the original forests, turning them into broad expanses of desert, tundra, and seasonal biomes.

The outcomes of the rising mountains weren’t all bad, however; while the mountains blocked moisture from reaching some areas, they concentrated it in others, giving rise to vast tropical rainforests. The one documented rainforest, which is the one that formed on the far eastern side of the supercontinent, came to be potentially responsible for many of the clades that now reside in several regions of primitive forest. Of these clades were surely the picopterans, which are nectarivorous opisthopterans, the pleuropterans, which are flying platydonts, and the chromatophytes, which are fruiting and nectar-producing brachyphytes that were primarily brought by those two flying clades. Though it hasn’t been directly confirmed, some other immigrants from the rainforest may have been the scansorial, frugivorous scandopods and the arboreal, malacovorous eudolichostracids, as they likely had to travel through many stretches of primitive forest in order to attain their “worldwide” status.

In 4300ma, the supercontinent finally broke apart. Much of what used to be dry continental interior became the new, wet coasts, allowing the middling primitive forests to spread and reclaim some of their past range. However, the separation of the landmasses was soon followed by an ice age, which resulted in a slight decrease in the forest’s range (some of those forests grew back during the interglacial period, though).

Later, on the newly-formed eastern continent, some of the leptopods mentioned before adapted for a life spent more in the forests, becoming the camptopods. Additionally, some of the naturally forest-dwelling deinognathans evolved a durophagous, or bone-eating lifestyle, becoming the malleognathans.