Visean

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 Visean is a second stage of the Mississippian subsystem and the Carboniferous system, corresponding to the Visean age of the Mississippian part of the Carboniferous period. It lasted from approximately 346.7 Ma to around 330.9 Ma (million years ago). It is preceded by the Tournaisian and is followed by the Serpukhovian. The oldest tetrapods are known from this stage.

Definition

The GSSP of the Visean stage was ratified in 2008. The lower boundary is fixed in the Pengchong Section, south China, and related to the first appearance of the benthic foraminifer Eoparastaffella simplex.

Visean life

Ecosystems continued to recover slowly from the Devonian extinctions. Along the coasts and in the open ocean, the bottom was inhabited by numerous brachiopods (Kitakamithyris, Unispirifer, Asyrinxia, Cleiothyridina), bivalves (Modiolus, Sanguinolites, Spirorbis, Pernopecten) and gastropods (Retispira, Ianthinopsis, Bellazona, Orthonychia). Pseudorthocerid (Pseudorthoceras, Cyrtothoracoceras), ammonoid (Bollandites, Neoglyphioceras) and nautilid (Knightoceras, Tylonautilus) cephalopods hunted in water column.

Woodwardopterus

Pulmonoscorpius

Arthropleura

Arthropods occupied a variety of ecological niches, although the abundance and taxonomic diversity of trilobites remained low. Palaeophillipsia, Australokaskia and Monodechenella are known from the Visean strata of Dungog Council Quarry in New South Wales, Australia. Kulmiella and Pseudospatulina were found in the Visean claystone of Dieken Formation in Germany. All these trilobites belong to the order Proetida. Eurypterids Woodwardopterus and Adelophthalmus are known from the marine sediments of Eskdale in Scotland. Their clode relatives, arachnids, have long settled on land. Scorpion genera of the Visean include Eoscorpius, Pseudarchaeoctonus, Gigantoscorpio and the huge Pulmonoscorpius. Brigantibunum, a member of the order Opiliones, is known from the East Kirkton Limestone Formation of Scotland. In those days, there were also archaic arachnids that left no descendants, such as trigonotarbids (Anthracomartus, Aphantomartus) and phalangiotarbids (Bornatarbus). Centipedes like Arthropleura and Euphoberia crawled in the dense forests. Fossils of insects of this age are unknown. It is assumed that before the appearance of wings, insects were quite rare. Ostracods, the shelled crustaceans, lived in water.

Goodrichthys

Ophiderpeton

Сhordates that were discovered in the Visean deposits, are mostly aquatic. Numerous conodonts lived in the shelf zone far from the coasts. Visean genera include Gnathodus, Lochriea, Polygnathus, Pseudopolygnathus and Apatognathus. The diversity of cartilaginous fishes increased. Various menaspiforms (Deltoptychius), chondrenchelyiforms (Chondrenchelys), petalodontiforms (Antliodus), hybodontiforms (Onychoselache), cochliodontiforms (Venustodus), ctenacanthiforms (Cladodus, Goodrichthys) and other members swam in the deep seas. The active evolution of bony fish continued. Holurus, Canobius, Paramesolepis, Rhadinichthys and several other marine fishes are grouped in the order of Palaeonisciformes, whose members were numerous in the late Paleozoic and Mesozoic. Eurynotiforms (Proteurynotus, Styracopterus, Cheirodopsis), tarrasiiforms (Tarassius), elonichthyiforms (Acrolepis, Elonichthys) and coelacanthiforms (Dumfregia) also lived in the ocean, as well as primitive tetrapodomorphs, such as Megalichthys and Strepsodus, a huge predator of the family Rhizodontidae. Among tetrapodomorphs, by this time specialized forms had appeared, such as the legless Ophiderpeton.

Crassigyrinus

Westlothiana

Stegocephalians, the closer relatives of true tetrapods, inhabited fresh waters. Some of them, like Crassigyrinus, had weak limbs and probably were fully aquatic. The oldest tetrapods are known from deposits of this age. Balanerpeton is one of the oldest temnospondyls, a large group of amphibians that existed nearly 200 million years. Small Westlothiana was close to amniotes, a group that includes modern reptiles, birds and mammals. Silvanerpeton was probably even closer to them. Both of these animals lived on land, although they could probably feed in the water as well. Casineria is also a tetrapod, but of uncertain taxonomy.

External links

• https://paleobiodb.org/classic/displayTimescale?interval=Visean