Seeds and Those That Eat Them

275 million years PE, the now-warm Serinaustra is experiencing a boom in plant diversity, as grasses, sunflower trees and clovers grow to great new heights over the formerly glaciated landmass. Though Serinaustra does have grazers in the form of seraphs, sealumps, and some other birds, these animals are far more selective feeders than the northern thorngrazer herds, and so here trees and forests have already begun to appear. Ramblerooters are growing bigger and taller, becoming short-lived trees with lightweight wood which live just a couple decades, but in that time may reach over 50 feet high. Puffgrass, and some other grass families, form vast flood plains and upland meadows. Other clovers, not closely related to ramblerooters, fill in the margins as shrubs and undergrowth. 

Serinaustra is a refuge for plants in more ways than one. For not only does it lack thorngrazers to eat the grown plants, but it has no endemic molodonts at all, of any kind. Molodonts, as the most effective seed predators ever to evolve, functionally destroy large seeds and can consume many at one time by pulverizing them in their mortar-and-pestle jaws. Throughout the early Ultimocene, this led many trees to forgo seeds altogether, instead growing small plantlets directly on their branches as the modern sunflower ant trees do, while others evolved very small seeds produced in such numbers that it was impossible for the animals to crush them all even if they ate the whole cluster. A land without these predators for just 5 million years has been enough for many groups of plants to appear once again with large, well-protected seeds. Big seeds have many advantages; they provide the seedling with a hearty supply of energy with which to begin its growth, and they can last a very long time before they sprout. 

This is the combined strategy of the sawleaf starsedge, a long-lived, superficially palm like puffgrass with sharply serrated leaves to discourage grazers, grows in vast colonies along floodplains. It has lost the small, fuzzy wind-blown seeds its ancestors evolved to cope with grazing animals, and now produces grows huge nuts as big as plums and born in clusters of up to twenty in the heart of its crown, which are adapted to disperse in short-lived seasonal floods. Buoyant, they detach from their stems and float perhaps miles away, coming to rest when the waters recede again in higher areas that will remain dry just long enough for them to take root. Fueled by their big seed, they rapidly grow and establish so that by the time the plains flood again they will not be swept away. 

Another plant that relies on water dispersal for its seeds is beautygrass, an erroneously named family of clover which closely resemble rushes but have no relation to true grasses whatsoever. Short-lived plants that may live just one or two years, they are wispy, non-woody herbs that form thick clonal stands along rivers and can grow to some 15 feet high, with long willow-like leaflets arranged in groups of three. Immature beautygrass is nearly indistinguishable from true grass at a distance, except for that its leaves do not wrap around its stems but simply emerge from nodes every few inches, but all confusion of identity is lost when the plants flower after their first year. Their blossoms are large and beautiful in shades of purple and pink, born in panicles up to six inches across from the axils of each leaf and attract insect and metamorph bird pollinators. Six weeks after blooming, the flowers have given way to large spiked seed pods 3-4 inches across that each hold 3-5 beans about as big as nickels. The pod is hollow and full of air, and when dry the seeds rattle within like maracas. The stems die after blooming, and dip down from the riverbank into the water where they detach and float away. The pod rots away in the water, and with luck the individual seeds float far away and come to rest downstream along a new stretch of damp sediment deposited by the river. Without any competitors the seeds quickly put down taproots and colonize the new patch of land. Within a couple years they will flower too and then die out, their spot taken over by longer-lived plants in the natural successive process, for beautygrass can only survive in new and vacant patches of land along the water before other competitors show up.

Another advantage of large seeds is that they can be hidden within a nutritious fruit, so as to attract animals to disperse them. This is case for both the antbean and the butterfly apple, two different sorts of clovers which use very different transporters to do the job. Tiny, prostrate antbeans grow on high slopes above the high water line and may only grow to a few inches in height. They bear small pink pea-like blossoms and later grow rows of kidney bean-sized rock-hard seeds with just a small patch of edible flesh along their stems, known as an elaiosome. This structure is rich in edible oil, and it attracts ants which collect the seed and transport it below ground to their nest - which will also be situated in a dry, upland location. 

On the other end of the size spectrum, the butterfly apple is a spindly ramblerooter tree and its genus was one of the first tall, woody plants to evolve on the thawed continent 4 million years ago. Butterfly apples are named for their showy flowers, which are formed by four petals that collectively take the shape of a butterfly's open wings and attract small pollinating birds and large insects, and for the later resulting fruit which is about the size of a peach and very sweet. Large animals like trunkos and foxtrotters seek these fruits out and eat them with gusto, spreading the single pit-like seeds contained within wherever they go. The seed itself is edible too, but so hard that few animals have ever made any effort to crack it.

But that is now beginning to change. Even without molodonts, there are some birds that are beginning to evolve the necessary jaw structure to crack even very large seeds. Yet for now, these birds are not finch-like or parrot-like flyers. They are not even large, flightless bipedal birds like trunkos. No, Serinaustra's first significant seed predators are burdles.

And even as they become smaller, they are destined for far bigger things.

Murds are a new and coming genus of burrowing burdle descendants that have already adopted several distinctive changes from their ancestors which reached the southern continent 5 million years ago. They are smaller, about as big as groundhogs, and their beaks are no longer hooked or serrated but instead huge and built to pulverize hard foods. The body scales are smaller, except on the arms where they are still prominent, and they are more active, using the warmth of the tropical climate to forage day and night with a similar energy level to endothermic animals without the associated metabolic costs. 

Murds have evolved from a population of burrowing burdles that was heavily omnivorous, eating whatever it came across. Though they are still not above eating insects or the odd dead animal, most of their food is now fruits and seeds - and with a beak already quite large and strong to begin with, once used to break bones and eat animal prey, they were one of the best-suited animals to start feeding on seeds as well when the climate thawed. Sturdy and strong, they can push over tall plants to reach the seeds born at their canopies, and with sturdy arms and hooked claws, they can even climb up the lanky trees to reach seeds out of reach to other land animals. Some four species of murds exist now, all quite similar except for markings, and they are very widespread over the continent. Able to access food resources very little else yet can, their numbers are high and they are preyed upon by many mesopredators in turn - a striking reversal of role for an animal once an intimidating hunter in its own right. 

Murds have existed in their current forms for less than a million years, but some plants have already begun to evolve counter-measures. The seeds of some starsedges are getting bigger, to outsize the mouths of the burdles... but the burdles' beaks are growing larger too. Some antbeans have evolved to synthesize bitter chemicals in their seeds as a deterrent to predation, which they advertise with bright markings upon them. As murds continue to eat them, these chemicals may eventually become poisons. Evolutionary arms races are simply par for the course in the story of life upon Serina, and there may never be a clear winner; each organism, predator and prey, will simply change the other over time, becoming more unique and evermore intertwined. No matter what, the new seed-eater burdles seem set to last a long time, even as their larger relatives begin now to die out, faced with competition from other predator guilds able to grow bigger, run faster, or think smarter. For some the hothouse age will be a time where animals reach their biggest-ever sizes; for burdles, however, it will pay to lay low.