Wegener's theory was supported by evidence of varying nature. Among the paleontological evidence, Cynognathus fossils were important to theory because: a) they were found on lands now separated by a wide ocean.
Before answering the question, let us firts review sometheoretical framework,
The tectonic plates theory explains the movement of the different plates based on the crust movements.The continental drift theory explains how these movements have been taking place for millions of years.
Alfred Wegener proposed for the first time the idea of continental drift.
He thought that continents were once all together in one big continent named Pangea, and with time, they split and separated into many pieces.
Although Wegener’s theory was criticized, the geologist Du Toit published in 1937 a list of 10 pieces of evidence that would support the theory of tectonic plates and continental drift.
The list includes Gondwana glaciation evidence, lithological and structural evidence, plates fitting together, and paleontological evidence.
Paleontological evidence
Plant and animal fossils distribution suggests the existence of a big unique continent. When reconstructing the supercontinent, the areas where these fossils were found get together in the same supercontinental region. Glossopteris (fern) impressions are widely distributed in determined areas of Africa, South America, India, and Australia. Terrestrial vertebrate fossils also support the theory. The presence of Triassic tetrapods in all continents suggests terrestrial corridors between landmasses.
⇒ Lystrosaurus ⇒ Triassic reptile ⇒ Found in Africa, India, and Antarctica
⇒ Mesosaurus ⇒ Triassic reptile ⇒ Found in South America and Africa
⇒ Cygnonathus ⇒ Triassic reptile ⇒ Found in South America and Africa
Finding Cynognathus fossils in South America and Africa suggests that these two continents were once together, and these animals used to live in the same region.
With time, these continents diverged and got separated by the ocean. The region where Cynognathus used to live got divided. Some of the fossils remained in South America and some others in Africa.
The correct option is a) they were found on lands now separated by a wide ocean.
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