[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Addendum (Re: LATE SURVIVING CYNODONT)
Today I found something in the 5 June issue of Nature, which is an
interesting addendum to the monotreme question/answer:
Investigation of mitochondrial DNA sequences of the platypus and an
Australian kangaroo species (Macropus robustus or wallaroo), strongly
supports the position of the platypus on the marsupial lineage, or
in cladistic terms: platypus and the marsupials shear a more recent
common ancestor than each with placental mammals. If I understand
correctly, this means Theria has to be redefined, as in the light of
the current evidence, Theria (Marsupialia and Placentalia) is
This also suggests that the view of monotremes as being
'primitive' as reflecting the ancestral state and not having
developed the 'advanced' features of the other mammals
should give way to the vision that considers the characteristics of the
Australian mammals as adaptations to specific environments that have
been existing in Australia, for example harsh conditions with periods
of prolonged drought.
There goes another 'living fossil'....
Penny and Hasegawa: Molecular systematics: The platypus put in its
place (News and Views), Nature 387, p549 (1997).
Janke et al. J. Mol. Evol 42, 153-159 (1997).
Janke et al. Proc. Natl. Acad. Sci USA 94, 1276-1281 (1997).