| Friday, February 04, 2005
| HIPPOS CLOSEST KIN ARE A WHALE OF A SURPRISE
|Wallowing in Africa's rivers by day and grazing
on their shores by night, hippopotamus have surprised
a long scientific debate about just how they fit into
the mammalian family tree.
Some scientist have argued that hippos are most closely
related to peccaries and wild pigs. More recent DNA
analysis suggested a closer kinship with modern whales;
but that left a troubling 40 million year gap between the
oldest known ancestors of whales (55 million years ago)
and the earliest hippos (15 million years ago).
Now, paleontologists say they have examined the bones and
teeth of 10 living species of hippos, whales and pigs,
and 22 of their fossil ancestors, and have found evidence
that the hippos closest kin is the WHALES.
Jean-Renaud Boisserie of Unviersity of California's Human
Evolution Research Center at Berkeley and colleagues in
France and Chad found similarlrities between hippos and
the most hippolike members of a diverse animal group called
ANTHRACOTHERES. This extinct family also included piglike
and camelike members, all of them gone for at least
2.5 million years.
"The ANTHRACOTERES are part of a very old family".
Boisserrie said. They first appear in the fossil record
45 million to 50 million uyears ago. "That allowed us to
make a link with the oldest whales -- semiaquatic animals
that appear in South Asia 55 million to 60 million years ago.
The 40 million year gap was largely eliminated. But it remains
unclear precisely what sort of critter that last common ancestor
of whales and early ANTHRACOTHERES might have been.
Because hippos and many ANTHRACOTHERES were semiaquatic,
Boisserie surmised that the common ancestor provably was
If so, the hippos closest ANTHRACOTHERES ancestors apparently
evolved to exploit a riverine environment like that in Africa
and a sister lineage -- leading to whales---evolved to live in oceans,
(abstracted from BALTIMORESUN/TRIBUNE by Frank D. Roylance
|posted by infraternam meam @ 3:52 AM