Statherian Period

What happened during this time?

Geological

• The super-continent Columbia formed during this period.

• Continents of Ur, Nena, and Atlantica drifted together, they expanded through accretion and formed a huge supercontinent

Biological

• This period starts a time called the "Boring Billion," stretching 1.8-0.8 Ga (Holland, 2006; Roberts, 2013; Young, 2013; Liu et al., 2019) 

  • Characterized by a supposed lack of significant geological or evolutionary changes, although this is debatable

• Diversification of unicellular organisms

• Oldest direct evidence of thylakoid membranes in a cyanobacterium, Navifusa majensis (Demoulin et al., 2023), found in Australia

• Appearance of possible early eukaryote (Grypania spiralis) around 2.1 Ga (Grey and Williams 1990; Han and Runnegar 1992; Kumar 1995), with the youngest occurrence of Grypania is in the Ediacaran Period (900 Ma)

  • The organism has a coiled, filamentous appearance; possibly green, Chlorophyceae algae, although some of the earlier fossils may be large bacteria

Shuiyousphaeridium macroreticulatum

• • Acritarch from northern China, dating back to 1.85–1.70 Ga, with large sizes (~250 μm)

  • Spherical shape with a net-like surface that bears elongated structures on the exterior (Yan & Liu, 1993; Butterfield, 2015).

  • The organism’s size, ornamentations, and multi-layered wall structure confirm its identity as a eukaryote. 

  • The fossilization of Shuiyousphaeridium may be good enough to preserve what appears to be the nucleus of this organism. If interpreted correctly, this feature would be the “smoking gun,” the diagnostic feature to indicate a eukaryote. 

  • Among microfossils in the Paleoproterozoic, this taxon is considered one of the “oldest widely accepted eukaryotic fossils” (Carlisle et al., 2021, p. 6). 

Tappania plana

• • Possible eukaryote fossil, Tappania plana, from 1,630 Ma in Northern China (Javaux et al., 2001; Javaux et al., 2003; Nagovitsin, 2009; Adam et al., 2017), and 1,430 Ma of the Wynniatt Formation, Victoria Island, northwestern Canada (Javaux et al., 2001; see also Javaux et al., 2003)

  • Structurally complex microfossils with irregularly branching and bulbous protrusions; morphology suggests the presence of a cytoskeleton: a character unique to eukaryotes

  • Analysis of Tappania morphology shows it to have been an actively growing, benthic, multicellular organism capable of substantial differentiation (Butterfield 2005)

  • Most notably, its septate, branching, and filamentous processes were capable of secondary fusion, a synapomorphy of the "higher fungi" 

  • Combined with phylogenetic, taphonomic and functional morphologic evidence, such "hyphal fusion" identifies Tappania reliably, if not conclusively, as a fungus, probably a sister group to the "higher fungi," but more derived than the zygomycetes.

Valeria lophostriata

• • Acritarch from northern China, dating to 1.68 Ga, and northern Australia, dating to 1.65 Ga (Yan & Liu, 1993; Li et al., 1995; Wan et al., 2003)

  • Spherical acritarch with a corduroy-like cell wall easily distinguished by its concentric pattern

  • Valeria has the features of a eukaryote (Javaux et al., 2004)

• Early eukaryotic acritarchs are found in northern Australia, fossilized in "marginal marine environments such as tidal flats and back-barrier lagoonal settings" (Reidman et al., 2023)

• This site shows significant morphological disparity, particularly in vesicle construction. The high levels of eukaryotic species richness and morphological disparity for this age suggest that the eukaryotic clade has a much deeper history.