Bekhorot 17: True Simultaneity (or Not)

If a ewe gives birth to animal that looks like a goat, or vice versa, but also looks a little like its mother... Rabbi Meir says it is subject to the laws of first-born, but the majority view of the sages say no, the owner is exempt. Plus, when lambs are exempt from the first fleece. Also, a new mishnah! When a female sheep gives birth to twin male lambs - and their heads emerge at exactly the same time. Who gets which of the lambs? Does the first-born status kick in, and for which animal? Plus, can such things happen truly simultaneously?