Upper Pennsylvanian

System (period)		Series	Stage (age)	Lower boundary, Ma
Permian		Cisuralian	Asselian	298.9±0.15
Carboniferous	Pennsylvanian	Upper	Gzhelian	303.7±0.1
			Kasimovian	307.0±0.1
		Middle	Moscovian	315.2±0.2
		Lower	Bashkirian	323.2±0.4
	Mississippian	Upper	Serpukhovian	330.9±0.2
		Middle	Visean	346.7±0.4
		Lower	Tournaisian	358.9±0.4
Devonian		Upper	Famennian	older
Subdivisions and "golden spikes" according to IUGS as of September 2023

The Upper Pennsylvanian is a third and upper series of the Pennsylvanian subsystem, corresponding to the Late Pennsylvanian epoch of the Pennsylvanian period (or subperiod) within the Carboniferous. It started after the Middle Pennsylvanian epoch (which corresponds to the Moscovian age) at 307.0 ± 0.1 Ma (million years ago) and lasted until 298.9 ± 0.15 Ma, when the Asselian age of the Cisuralian epoch began (IUGS 2023). The oldest sphenacodontoids are known from this series.

In Eastern European stratigraphic chart, the Upper Pennsylvanian corresponds to the Upper Carboniferous series.

Definition

As of 2024, there is still no GSSP for the Upper Pennsylvanian series and the Kasimovian stage. Candidates are sections in Southern Urals (Russia) and Nashui (South China) with the first appearance of the conodont species Diplognathodus ellesmerensis as a marker of the lower boundary.

Subdivisions

The Upper Pennsylvanian, unlike other Carboniferous series, divided into two stages: Kasimovian and Gzhelian. In geochronology, both correspond to the same ages.

Paleogeography

Almost the entire landmass formed a single supercontinent Pangaea. Only East Asia was not part of a supercontinent at that time. The Karoo Ice Age continued, with ice covering land in the southern hemisphere and leaving glacial deposits that can be found today in South America, southern Africa, Australia and Antarctica. The territory of Eastern Europe was partially covered by the sea.

Climate

The climatic conditions at this time were very diverse: from swamps overgrown with lush vegetation to arid and icy deserts. In the equatorial region of Pangaea there were wide river deltas and swamps, on the banks of which grew jungles of primitive plants, barely visible in the foggy evaporations. The southern part of the supercontinent was covered with glaciers, making it almost impossible for life to exist there.

Late Pennsylvanian life

Flora and fungi

The streams and creeks were crowded with thickets of giant horsetails. On mudflats and sandy islands, giant trees 30-50 m high grew, in which it was difficult to recognize the relatives of modern small club mosses. Their straight trunks followed the sunlight upward through the green gloom, spreading branches at the very top. Herbaceous and tree ferns, whose relatives survive in what is now New Zealand, grew in damp places. On the hills surrounding the swamps there were groves of primitive gymnosperm trees. Some of them by this time probably populated the outskirts of the deserts.

In addition to plants, fungi evolved on land, although their fossils are much less common. In those days, most likely, molds capable of processing huge amounts of dead vegetation did not yet exist. As a result, all this plant biomass decayed over time and turned into coal. Coal basins from this era have been found in North America, Europe and Asia.

Fauna

Many echinoderms lived in the seas at this time, and lots of brachiopods could be found on the seabed. Brachiopods differ from similar bivalves in the position of their shell valves: upper and lower, while in bivalves they are right and left. Late Mississippian brachiopod genera include Punctospirifer, Neospirifer , Crurithyris and Enteletes. Gastropods like Anomphalus, Straparollus and Pseudozygopleura lived on reefs consisting of anthozoan corals. Ammonites, such as Prouddenites, Gonioloboceras, Subkargalites and Glaphyrites, hunted in the water column. There were few trilobites at that time; rare members as Brachymetopus, Ditomopyge and Pseudophillipsia, were fast-moving bottom detritus eaters. Rare eurypterids like Hibbertopterus lived in estuaries and bays. The seas were inhabited by numerous cartilaginous fish similar to sharks. Stethacanthus, Denaea and Glikmanius are known from the Upper Pennsylvanian of Nebraska, USA.

The dense, humid forests were home to a variety of terrestrial arthropods, including centipedes (Arthropleura), scorpions (Feistmantelia, Eoscorpius), and trigonotarbids (Aenigmatarbus). Insects were already among the most numerous arthropods. From the Late Pennsylvanian, such groups as Geraridae (Gerarus), Caloneurodea (Caloneura, Sthenarocera), Grylloblattodea (Protoperla, Palaeocixius, Stenoneurites) and Orthoptera (Oedischia) are known. Various cockroach-like insects (Dictyomylacris, Amorphoblatta, Miaroblatta, Asemoblatta), plant-eating palaeodictyopterans (Breyeria, Megaplitoides, Compsoneura) and griffinflies (Meganeura, Meganeurula) were found in the Upper Pennsylvanian (Gzhelian) of France.

Ophiacodon

Bony fishes like Elonichthys, Paramblypterus and Bourbonnella lived in the Late Pennsylvanian rivers. The swamps overgrown with lush vegetation were home to many amphibians like Isodectes, Eryops, Iberospondylus and Megamolgophis. At that time, many small reptiles and synapsids already lived on land. From the Upper Pennsylvanian of Illinois and probably New Mexico, the earliest sphenacodontoid specimens are known. This animals were direct ancestors of later therapsids and, therefore, the mammals. Among other synapsids, the first large land predators like Ophiacodon already existed. Their prey were herbivorous Edaphosaurus with variable processes on their dorsal vertebrae.