#proterozoic

Dickinsonia for reference: (all pictures are scientific artistic reconstructions based on fossilized imprints)

Dickinsonia in his natural habitat surrounded by his Ediacaran friends (they’re having a game night and the Charnias are winning)

Here is one of the weird fossils I've been working on since getting back to Belgium. It's about 60 microns long, or 0.06 millimetres and 1.4 billion years old and no one in the lab has seen anything like it before. The texture is not just a surface pattern, the light areas are pits, the dark areas are raised tubes. There are multiple layers of tissue and structures that look like pore that could open and close. These features indicate the fossil is probably from a eukaryotic organism - those with complex nucleated cells. I don't think this level of detail has ever been preserved in a fossil this old before. Additionally, you normally need to look at rocks less than a billion years old to find fossils with this level of complexity.

1. Soil-forming bacteria lead to clay-mineral formation, enhanced chemical weathering, and burial of organic carbon, leading to oxygenation, softer sediments, increased productivity, and a more favorable environment for larger life forms on land, leading to more soil formation and marine burrowing by animals. This loop begins 800 Mya and expands to the latest Neoproterozoic eon approximately 600 Mya.

2. Microbenthic predation leads to evolution of zooplankton, suspension feeding, and larger phytoplankton, leading to transfer of organic carbon to sediments, leading to increased seafloor productivity and predation. This loop begins in the latest Neoproterozoic eon.

3. Predation on the seafloor leads to burrowing by animals, bioturbation, increased productivity, and more intense predation. This loop begins in the latest Neoproterozoic eon and expands stepwise throughout the Phanerozoic eon.

4. Predation on the seafloor leads to evolution of rock-boring animals, creating holes as habitats for predators. This loop begins in the Cambrian period and expands stepwise throughout the Phanerozoic eon, especially from the Late Triassic onward.

5. Predation on the seafloor leads to evolution of secondary shell dwellers and expansion of shell-bearing prey resources, leading to more predation. This loop begins in the Cambrian, expanding in the Late Mesozoic era.

6. Pelagic predation leads to evolution of vertically migrating plankton, resulting in biotic vertical mixing of nutrients, higher-water-column productivity, and more pelagic predation. The timing is not well constrained. This mechanism was proposed by Kunze et al. (2006) and Katija & Dabiri (2009).

7. Herbivory leads to higher photosynthetic capacity on land, leading to an enhanced hydrological cycle, greater terrestrial runoff, higher productivity on land and in sea, and higher herbivory. This loop begins in the mid-Cretaceous, about 100 Mya.

8. Predation leads to small species seeking refuge on or in the bodies of well-defended species, leading to numerous mutualisms.

Even among primarily sedentary suspension-feeders, species that passively intercept food-laden currents (especially cnidarians and echinoderms) have been replaced on most unconsolidated sea bottoms by animals that actively pump water through a filter. Low-energy brachiopods, which dominated most Paleozoic and Early Mesozoic suspension-feeding guilds, gave way to bivalves whose metabolic rates are 3 to 10 times higher [EN: this is disputed].

Transitions from low-energy to more forceful modes of predation and herbivory have been documented in many groups. Marine gastropods that drill at the valve margins or force their way between the valves of bivalve prey have appeared only in the past 80 million years... Although shell crushing is known from the Early Cambrian onward... it is increasingly common in the mid-Paleozoic and especially from the Late Cretaceous to the Recent. This increase is reflected in the evolution of ever more resistant shell defenses... On most large land masses, particularly from the Cretaceous onward, plant eaters that break up pieces before swallowing, including several groups of dinosaurs and most herbivorous mammals, have supplanted herbivores that ingested their food without oral preparation.

In land plants, ancient groups such as bryophytes and ferns employ passive means of opening and closing stomata, the pores through which gas exchange occurs; in seed plants, in contrast, these functions are metabolically controlled, permitting better response to environmental variation and greater photosynthetic use of water... Angiosperms [flower plants] (especially in the eudicot clade) of the past 100 million years have evolved photosynthetic capacities that are three to four times higher than those of more ancient plants...

Intense predation on the seafloor beginning shortly before the Cambrian caused some animals to seek refuge in the plankton, on land, and in sediments. Burrowing, swimming, flying, deposit feeding (sediment ingesting), rock boring, animal-assisted pollination and propagule dispersal, agriculture, plant-animal symbioses, secondary shell dwelling, herbivory, long-distance migration, and social organization are some of the new ways of making a living that animals of multiple clades evolved during the Phanerozoic. Meanwhile, other modes of life became extinct or were limited to a few environments. Unattached sedentary animals living on soft sediment surfaces were common in the Paleozoic but are rare today. The same is true for large, shell-bearing swimming animals; large, terrestrial, molting arthropods; and marine animals that protected themselves by rolling up into a passive ball. The over- all effect was the expansion of macroscopic life into parts of the biosphere that were previously occupied only by microbes.