The key difference between thallophyta and pteridophyta is that the thallophyta is a group of non-mobile organisms that possess a thallus-like undifferentiated body while the pteridophyta is a group of vascular plants that possess a plant body differentiated into true stem, roots, and leaves.
Thallophyta and pteridophyta are two groups of organisms. Thallophyta comprises non-mobile organisms that do not possess a differentiated plant body. They have a simple thallus-like body. Furthermore, they don’t have vascular tissue. They are mostly found in aquatic environments. On the other hand, pteridophyta comprises of plants that have differentiated complex plant bodies. They are vascular plants and possess true leaves, stem, and roots. These plants are mostly terrestrial and seen in damp and shady places.