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Table 1 Variations in the trophoblast comprising the interhemal area of the chorioallantoic placenta.

From: Comparative aspects of trophoblast development and placentation

Placental Type

Trophoblast Component

Examples

Hemomonochorial

Syncytial trophoblast, villous

Armadillo; higher primates

 

Syncytial trophoblast, labyrinthine

Most hystricomorph rodents (e.g. guinea pig, capybara); sciuromorph rodents (squirrels)

 

Cellular trophoblast

Hyraxes; spiny tenrecs (e.g Echinops); mollosid bats (late gestation); some myomorph rodents (Zapus, Jaculus)

Hemodichorial

Syncytial (maternal facing) and cellular trophoblast

Lagomorphs; vespertilionid bats

Hemotrichorial

Cellular trophoblast (maternal facing) and two layers of syncytial trophoblast

Most myomorph rodents (e.g. rat, mouse)

Endotheliochorial

Syncytial trophoblast (fenestrated)

Sloths; shrews (insectivores)

 

Syncytial trophoblast (nonfenestrated)

Carnivores and pinnipeds

 

Cellular trophoblast

Elephants; some sciuromorph rodents (Dipodomys, Microdipodops); some bats (Natalus, Saccopteryx)

Epitheliochorial

Cellular trophoblast only

Lower primates; pangolin; some artiodactyls (e.g. pig)

 

Cellular trophoblast with trophoblastic girdle cells

Equids (perissodactyls, e.g. horse)

Synepitheliochorial

Cellular trophoblast; fusion of binucleate trophoblastic cells with uterine epithelium

Ruminants (artiodactyls, e.g. sheep, cow)