Pennsylvanian Epoch

The age of coal swamps

The Pennsylvanian (323-299 Ma) is in the Carboniferous Period, occurring after the Mississippian and before the Permian Period.

The Epoch begins with carbon dioxide levels around 700 ppm, and ends with ~350 ppm
Oxygen levels at the start of the Epoch are the highest recorded in Earth's history at around 33%
Significant glaciation marks the beginning of this time with a sea-level drop
There was an ice age with a climate much like today: ice at the poles, with wet tropics near the equator, and temperate regions in between
Most of Pangaea was formed but fragments on the edges of the plates continued colliding and merging
- The formation of the supercontinent of Pangea was completed by the early Triassic
- This was also a time of mountain building as all of the continents came together

Flora

Swamps had an emergent layer of tree clubmosses, such as Sigillaria and Lepidodendron
- Tree-sized clubmosses will diminish dramatically at the end of the Pennsylvanian
- The modern herbaceous clubmosses, including Lycopodiales and Selaginellales, appear during the Pennsylvanian
- Some of the earliest evidence of plant epiphytes occurs in the Pennsylvanian with fern epiphytes and Selaginella-like plants (Mamay 1952; Rothwell 1991; Psenicka & Oplustil 2013)
Marattialean tree ferns, like Psaronius, will replace these scale trees in some swampy areas
- Zygopteridalean ferns are still on the landscape
Noeggerathians, a cryptic group of progymnosperms, or Cordaites, an ancestral group of conifer-like plants are also dominant in some ecosystems
Sphenophyllophytes in the understory, such as Sphenophyllum
Origin of the Cordaites, Voltziales, Cycads, Callistophytales, Peltaspermales, and Vojnovskyales
- Glaciation and freezing temperatures probably affected forest distribution
- "Repeated freezing likely influenced freeze- and drought-tolerance evolution in lineages like the coniferophytes..." (Matthaeus et al. 2021)

Fungi

All modern classes of fungi were present by this time, although they were not efficient at decomposing the lignin and cellulose of the trees of this time
Fungal epiphytes of Pennsylvanian age growing on Cordaites leaves or tree fern pinnules (Krings et al. 2010, 2011)

Fauna

First insects with folded wings (~320 Ma) and complete metamorphosis (~310 Ma)
Carboniferous amphibians were diverse and common by the Pennsylvanian, more so than they are today
- Some Carboniferous amphibians were aquatic and lived in rivers (Loxomma, Eogyrinus, Proterogyrinus); others may have been semi-aquatic (Ophiderpeton, Amphibamus, Hyloplesion) or terrestrial (Dendrerpeton, Tuditanus, Anthracosaurus)
During this time appears: Hylonomus, the earliest sauropsid reptile, Petrolacosaurus, the first diapsid reptile, and Archaeothyris the earliest known synapsid