What are the Characteristics of Prototheria?

The characteristics of Prototheria are given below:

1) External ear is absent.

2) They are united by having, for at least some period of their life cycle, a notochord, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail.

4) Cephalochordates have a notochord and a nerve cord and a very simple circulatory system.

5) Attempts to work out the evolutionary relationships of the chordates have produced several hypotheses.

6) All of the earliest chordate fossils have been found in the Early Cambrian Changing fauna, and include two species that are regarded as fish.

7) There is famous shale called Middle Cambrian Burgess Shale of British Columbia, which has yielded pikaia fossils.

8) The segmental arrangement of the mooneyes facilitates the lateral movements used during swimming.

9) Corpous callosum is absent.

10) Testes are abdominal.

11) Egg lying mammals, placenta is absent.