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Fossils shed new light on land-walking whales
Source: Agencies |
February 5, 2009, Thursday
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FOSSILS from two early whales - a male and a rare pregnant female - have shed light on how these ancestors of modern whales made the leap from walking on land to ruling the sea.
The fetal remains, found with the 47.5-million-year-old pregnant female, were positioned head down, suggesting the creatures gave birth on land, while spending the rest of their time in water.
Initially, the tiny fetal teeth stumped University of Michigan paleontologist Philip Gingerich, whose team discovered the fossils in Pakistan in 2000 and 2004.
"When I first saw the small teeth in the field, I thought we were dealing with a small adult whale, but then we continued to expose the specimen and found ribs that seemed too large to go with those teeth," Gingerich said.
The fetal skeleton is the first specimen of the extinct whale group known as Archaeoceti, and the find represents a new species named Maiacetus inuus, a hybrid of the words for "mother whale" and Inuus, the name of a Roman fertility god.
The fetus was positioned head down like other land animals, allowing it to begin breathing right away. This suggests the group had not yet made the leap to giving birth in the water like modern whales, which are born tail first to allow them to start swimming right after birth.
The 2.59-meter male, which was collected in the same fossil beds as the female, is about 12 percent bigger and had fangs 20 percent larger than those of the female. Gingerich said these suggest the creatures spent a large portion of their time catching and eating fish. Both fossils had four flipper-like legs that could have supported their weight on land, suggesting they likely came on shore to mate, rest and give birth.
The fetal remains, found with the 47.5-million-year-old pregnant female, were positioned head down, suggesting the creatures gave birth on land, while spending the rest of their time in water.
Initially, the tiny fetal teeth stumped University of Michigan paleontologist Philip Gingerich, whose team discovered the fossils in Pakistan in 2000 and 2004.
"When I first saw the small teeth in the field, I thought we were dealing with a small adult whale, but then we continued to expose the specimen and found ribs that seemed too large to go with those teeth," Gingerich said.
The fetal skeleton is the first specimen of the extinct whale group known as Archaeoceti, and the find represents a new species named Maiacetus inuus, a hybrid of the words for "mother whale" and Inuus, the name of a Roman fertility god.
The fetus was positioned head down like other land animals, allowing it to begin breathing right away. This suggests the group had not yet made the leap to giving birth in the water like modern whales, which are born tail first to allow them to start swimming right after birth.
The 2.59-meter male, which was collected in the same fossil beds as the female, is about 12 percent bigger and had fangs 20 percent larger than those of the female. Gingerich said these suggest the creatures spent a large portion of their time catching and eating fish. Both fossils had four flipper-like legs that could have supported their weight on land, suggesting they likely came on shore to mate, rest and give birth.
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