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Placentalia    
有胎盘类

有胎盘类

Placentalia \Plac`en*ta"li*a\, n. pl. [NL.] (Zool.)
A division of Mammalia including those that have a placenta,
or all the orders above the marsupials.
[1913 Webster]


Mammalia \Mam*ma"li*a\, n. pl. [NL., from L. mammalis. See
{Mammal}.] (Zool.)
The highest class of Vertebrata. The young are nourished for
a time by milk, or an analogous fluid, secreted by the
mammary glands of the mother.
[1913 Webster]

Note: Mammalia are divided into three subclasses;
[1913 Webster] I. {Placentalia}. This subclass embraces
all the higher orders, including man. In these the
fetus is attached to the uterus by a placenta.
[1913 Webster] II. {Marsupialia}. In these no placenta
is formed, and the young, which are born at an early
state of development, are carried for a time attached
to the teats, and usually protected by a marsupial
pouch. The opossum, kangaroo, wombat, and koala are
examples.
[1913 Webster] III. {Monotremata}. In this group, which
includes the genera {Echidna} and {Ornithorhynchus},
the female lays large eggs resembling those of a bird
or lizard, and the young, which are hatched like those
of birds, are nourished by a watery secretion from the
imperfectly developed mammae.
[1913 Webster]


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  • Placentalia - Wikipedia
    Placentalia represents the only living group within Eutheria, which contains all mammals that are more closely related to placentals than they are to marsupials
  • Placental Mammals - Definition, Examples, Characteristics, and Picture
    Placental mammals are warm-blooded vertebrates belonging to the infraclass Placentalia They are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia
  • Placentalia - New World Encyclopedia
    Placentalia is a term used in some taxonomic classification schemes for one of the three major branches of mammals that includes extant members, the others being Monotremata (montremes) and Marsupialia (marsupials)
  • Placental mammal | Characteristics Facts | Britannica
    Although some authorities consider the marsupials (cohort Marsupialia) to be placental mammals, these animals have a less-developed, less-efficient type of placenta that limits the gestation period
  • Placentalia
    Placentalia, also known as the crown group of Eutheria, represents the largest and most diverse clade within the class Mammalia, comprising approximately 6,400 extant species (as of 2025) organized into 19 orders [6]
  • Placental Mammals (Infraclass Placentalia) · iNaturalist
    Placentalia is one of the three extant subdivisions of the class of animals Mammalia; the other two are Monotremata and Marsupialia The placentals are partly distinguished from other mammals in that the fetus is carried in the uterus of its mother to a relatively late stage of development
  • Placental Mammals (Placentalia) - Know Your Mammals
    When we talk about the incredible diversity of mammals, one of the most fascinating and significant groups is the Placental Mammals (Placentalia) This group is characterized by a unique reproductive strategy that distinguishes them from other mammals such as marsupials and monotremes
  • Placentalia - Detailed Pedia
    Placentalia represents the only living group within Eutheria, which contains all mammals that are more closely related to placentals than they are to marsupials
  • Placentalia Definition and Examples - Biology Online Dictionary
    The Placentalia is a subdivision of mammal s characterized primarily by the fetus being carried in the uterus of the mother The fetus is nourished via a placenta until such time that the fetus is fully developed to be delivered at birth
  • Placental Mammals - Classification Characteristics
    The defining feature of placental mammals is the presence of a placenta, a specialized organ that forms during pregnancy within the mother's uterus This organ allows for the exchange of nutrients, oxygen, and waste products between the developing fetus and the mother's bloodstream





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