Haemoendothelial placenta takes place in

The correct option is rat and rabbit.

To understand why this is the correct answer, let us look at the classification of placentas based on the layers of tissue separating the maternal blood from the fetal blood (histological classification):

1. Epitheliochorial placenta: The maternal epithelium is in contact with the fetal chorion. This is found in pigs, goats, and cows.
2. Syndesmochorial placenta: The maternal uterine mucosa is eroded, and the chorion comes in contact with the maternal connective tissue. This occurs in ruminants like camels and deer.
3. Endotheliochorial placenta: The maternal epithelium and connective tissue are lost, and the chorion is in direct contact with the endothelial walls of maternal capillaries. This is found in carnivores (like dogs and cats).
4. Haemochorial placenta: Maternal blood vessels are eroded, allowing maternal blood to directly bathe the chorion. This is found in apes and humans.
5. Haemoendothelial placenta: The barriers are reduced to a minimum. The maternal tissue layers, as well as the fetal chorionic epithelium and fetal connective tissue layers, disappear. As a result, maternal blood is separated from fetal blood only by the thin endothelial wall of the fetal capillaries. This highly specialized type of placenta occurs in rodents and lagomorphs, specifically in animals like the rat and rabbit.