The name "Proto-Tethys" has been used inconsistently for several concepts for a supposed predecessor of the Paleo-Tethys Ocean, a palaeocean that separated the margins of Gondwana, often referred to as peri-Gondwana, from various continents and Gondwana-derived continental fragments from Precambrian times and onwards.
In this model the Proto-Tethys separated the North China and Baltica continents from Gondwana.
[1] In the Early Ordovician 500-480 Ma, the Proto-Tethys was subducted under Cadomia as a result of the Chamrousse back-arc basin.
[5] The ocean formed when Pannotia disintegrated, Proto-Laurasia (Laurentia, Baltica, and Siberia) rifted away from a supercontinent that would become Gondwana.
In the late Devonian, the microcontinent of Kazakhstania collided with Siberia, shrinking the ocean even more.