Laurentia remained almost static near the Equator throughout the early Palaeozoic, separated from Baltica by the up to 3,000 km (1,900 mi)-wide Iapetus Ocean.

In the Late Cambrian, the mid-ocean ridge in the Iapetus Ocean subducted beneath Gondwana which resulted in the opening of a series of large back-arc basins.
During the Ordovician, these basins evolved into a new ocean, the Rheic Ocean, which separated a series of terranes – Avalonia, Carolinia, and Armorica – from Gondwana.

Avalonia rifted from Gondwana in the Early Ordovician and collided with Baltica near the Ordovician–Silurian boundary (480–420 Mya).
Baltica-Avalonia was then rotated and pushed north towards Laurentia.
 The collision between these continents closed the Iapteus Ocean and formed Laurussia, also known as Euramerica or the Old Red Continent, which then covered 37,000,000 km² (14,000,000 sq mi) including several large Arctic continental blocks.

With the Caledonian orogeny completed Laurussia was delimited by:
The eastern margin were the Barents Shelf and Moscow Platform;
the western margin were the western shelves of Laurentia, later affected by the Antler orogeny;
the northern margin was the Innuitian-Lomonosov orogeny which marked the collision between Laurussia and the Arctic Craton;
and the southern margin was a Pacific-style active margin where the northward directed subduction of the ocean floor between Gondwana and Laurussia pushed continental fragments towards the latter.

During the Devonian (416-359 Mya) Laurussia rotated around Laurentia which remained static near the Equator.
 The Laurentian warm, shallow seas and on shelves a diverse assemblage of benthos evolved, including the largest trilobites exceeding 1 m (3 ft 3 in).
 The Old Red Sandstone Continent stretched across northern Laurentia and into Avalonia and Baltica but for most of the Devonian a narrow seaway formed a barrier where the North Atlantic would later open.
 Tetrapods evolved from fish in the Late Devonian, with the oldest known fossils from Greenland.
 Low sea-levels during the Early Devonian produced natural barriers in Laurussia which resulted in provincialism within the benthic fauna.
 In Laurentia the Transcontinental Arch divided brachiopods into two provinces, with one of them confined to a large embayment west of the Appalachians.
 By the Middle Devonian, these two provinces had been united into one and the closure of the Rheic Ocean finally united faunas across Laurussia.
 High plankton productivity from the Devonian-Carboniferous boundary resulted in anoxic events that left black shales in the basins of Laurentia.
Laurentia remained almost static near the Equator throughout the early Palaeozoic, separated from Baltica by the up to 3,000 km (1,900 mi)-wide Iapetus Ocean.
In the Late Cambrian, the mid-ocean ridge in the Iapetus Ocean subducted beneath Gondwana which resulted in the opening of a series of large back-arc basins. During the Ordovician, these basins evolved into a new ocean, the Rheic Ocean, which separated a series of terranes – Avalonia, Carolinia, and Armorica – from Gondwana.
Avalonia rifted from Gondwana in the Early Ordovician and collided with Baltica near the Ordovician–Silurian boundary (480–420 Mya). Baltica-Avalonia was then rotated and pushed north towards Laurentia.  The collision between these continents closed the Iapteus Ocean and formed Laurussia, also known as Euramerica or the Old Red Continent, which then covered 37,000,000 km² (14,000,000 sq mi) including several large Arctic continental blocks.
With the Caledonian orogeny completed Laurussia was delimited by:
The eastern margin were the Barents Shelf and Moscow Platform;
the western margin were the western shelves of Laurentia, later affected by the Antler orogeny;
the northern margin was the Innuitian-Lomonosov orogeny which marked the collision between Laurussia and the Arctic Craton;
and the southern margin was a Pacific-style active margin where the northward directed subduction of the ocean floor between Gondwana and Laurussia pushed continental fragments towards the latter.
During the Devonian (416-359 Mya) Laurussia rotated around Laurentia which remained static near the Equator.  The Laurentian warm, shallow seas and on shelves a diverse assemblage of benthos evolved, including the largest trilobites exceeding 1 m (3 ft 3 in).  The Old Red Sandstone Continent stretched across northern Laurentia and into Avalonia and Baltica but for most of the Devonian a narrow seaway formed a barrier where the North Atlantic would later open.  Tetrapods evolved from fish in the Late Devonian, with the oldest known fossils from Greenland.  Low sea-levels during the Early Devonian produced natural barriers in Laurussia which resulted in provincialism within the benthic fauna.  In Laurentia the Transcontinental Arch divided brachiopods into two provinces, with one of them confined to a large embayment west of the Appalachians.  By the Middle Devonian, these two provinces had been united into one and the closure of the Rheic Ocean finally united faunas across Laurussia.  High plankton productivity from the Devonian-Carboniferous boundary resulted in anoxic events that left black shales in the basins of Laurentia.
Laurasia