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Embryonic growth rates of marsupials with a note on monotremes
Author(s) -
ROSE R. W.
Publication year - 1989
Publication title -
journal of zoology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.915
H-Index - 96
eISSN - 1469-7998
pISSN - 0952-8369
DOI - 10.1111/j.1469-7998.1989.tb02521.x
Subject(s) - marsupial , monotreme , biology , platypus , ontogeny , evolution of mammals , embryonic stem cell , zoology , altricial , evolutionary biology , anatomy , endocrinology , genetics , taxonomy (biology) , systematics , gene
Earlier workers suggest that marsupial embryonic growth rates are slower than those of many eutherians and that there is little correlation between marsupial gestation lengths and their weight at birth. Previously, this latter observation has been explained as being due to the considerable variability in duration of the initial slow phase of marsupial embryonic growth. The latter phase of pregnancy has always been regarded as rapid and highly uniform in all marsupials. However, this review shows that there can be considerable variation in growth rate during this ‘fast’ phase and also that marsupials have similar rates of embryonic growth to most eutherians. Development within the monotreme egg may proceed at a similar rate to intra‐uterine growth in therian mammals.