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Plesiosaur fossil
hints at live births
By Nadia Drake
The fossil of a pregnant plesiosaur who
died 78 million years ago indicates that
the ancient sea monsters were surprisingly like today’s marine mammals.
The aquatic, carnivorous reptiles
gave birth to live young, a team reports
August 12 in Science. And plesiosaurs
probably birthed just one plesio-baby at
a time — one very big baby, estimated to
be more than 40 percent of the mother’s
body length at birth. Putting so much
effort into a single offspring suggests
that, similar to modern marine mammals, plesiosaurs offered a bit of post-natal maternal care.
“If you’re going to put all your eggs in
one basket, then you’re going to want to
take care of that egg when it comes out,”
This enormous fossil of a pregnant plesiosaur contains the nearly complete mater-
nal skeleton of the extinct sea creature and roughly 65 percent of the fetus (box).
says paleobiologist F. Robin O’Keefe
of Marshall University in Huntington,
W.Va.
The fossil, an enormous Polycotylus
latippinus, was excavated in Kansas
nearly 25 years ago. Called “Poly” by the
team, the 4.7-meter-long creature was
carrying a fetus. O’Keefe verified that
the fetal bones were the same species
as Poly, and not the remains of an
animal she had ingested.
Wasps’ apparent altruism isn’t
Females’ gamble benefits their own reproductive success
By Susan Milius
Acts of apparent altruism in European
paper wasps can be explained by plain
old self-interest, a new study finds.
Polistes dominulus females can either
establish their own nests to raise young
or join other females for joint homemaking. In those joint nests, though, one
female does most of the egg-laying while
the others do most of the drudge work in
taking care of the top wasp’s young.
When a subordinate helps her sister,
her reproductive success includes an
indirect share of her sister’s brood. For-
going her own direct offspring counts as
a kind of altruism. But some 15 to 35 per-
cent of cofoundresses slaving away are
not closely related to the top wasp.
Polistes dominulus foundresses build
a nest. Serving under another queen
suits the wasps’ reproductive interests.
the conclusion that just because animals
help each other, they are behaving
altruistically,” says Raghavendra
Gadagkar of the Indian Institute of
Science in Bangalore.
