''Maiacetus'' ("mother whale") is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of early

cetacea Cetacea (; , ) is an infraorder of aquatic mammals belonging to the order Artiodactyla that includes whales, dolphins and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively c ...

n from the Habib Rahi Formation of

Pakistan Pakistan, officially the Islamic Republic of Pakistan, is a country in South Asia. It is the List of countries and dependencies by population, fifth-most populous country, with a population of over 241.5 million, having the Islam by country# ...

Paleobiology

The genus contains a single species, ''Maiacetus inuus'', first described in 2009 on the basis of two specimens, including a specimen which has been interpreted as a pregnant female and her

fetus A fetus or foetus (; : fetuses, foetuses, rarely feti or foeti) is the unborn offspring of a viviparous animal that develops from an embryo. Following the embryonic development, embryonic stage, the fetal stage of development takes place. Pren ...

. This represents the first description of a fetal skeleton of an archaeocete. The position of the fetus (head-first) suggests that the animal gave birth on land."Earliest whales gave birth on land"
''

Science News ''Science News'' (''SN'') is an American monthly magazine devoted to articles about new scientific and technical developments, typically gleaned from recent scientific and technical journals. The periodical has been described as having a scop ...

'', 3 February 2009 Modern whales generally give birth tail first, while land mammals give birth head first. That the ''Maiacetus'' should give birth on land is not so implausible because this whale is semiaquatic or amphibious. ''Maiacetus'' represents the transition of land mammals back to the oceans where these animals were living on the land-sea interface and going back and forth."Ancient Whale Relative Gave Birth on Land"
, "

Science Friday ''Science Friday'' (known as ''SciFri'' for short) is a weekly call-in talk show that broadcasts each Friday on public radio stations, distributed by WNYC Studios, and carried on over 500 public radio stations. ''SciFri'' is hosted by science ...

", 6 February 2009 However,

Hans Thewissen Gerardus arie (Hans) Thewissen is a Dutch-American paleontologister known for his significant contributions to the field of whale evolution. Thewissen's fieldwork has led to the discovery of key fossils that have shed light on the transition of ...

, discoverer of ''

Ambulocetus ''Ambulocetus'' (Latin ''ambulare'' "to walk" + ''cetus'' "whale") is a genus of early Semiaquatic, amphibious cetacean from the Kuldana Formation in Pakistan, roughly 48 or 47 million years ago during the Early Eocene (Lutetian). It contains o ...

'', has questioned these conclusions, suggesting that the smaller skeleton could be a partially digested meal. Even if the small skeleton is a fetus, Thewissen writes that it may not have been preserved in its normal in-vivo position. Authors pointed out in the original article, however, that the fetal skull has no tooth marks. The hip bones were strong, suggesting that ''Maiacetus'' was able to walk on land; however, the short legs and flat digits would've made walking difficult. Looking at the flattened finger and toe bones, scientists have come to the conclusion that ''Maiacetus'' had webbed feet and was most likely amphibious. The teeth of the preserved fossils show similarity to the teeth of ''

Basilosaurus ''Basilosaurus'' (meaning "king lizard") is a genus of large, predatory, prehistoric archaeocete whale from the late Eocene, approximately 41.3 to 33.9 million years ago (mya). First described in 1834, it was the first archaeocete and prehisto ...

'', another genus of prehistoric cetaceans. The incisors are cone-like, linking ''Maiacetus'' to modern toothed whales and other extinct cetaceans. The middle ear bones are also similar to those of ''

'' and modern whales. This species is medium-sized with a skeleton in length and an estimated weight of . Males are slightly larger than females; of the two adult skeletons found, the one interpreted as male was about 12% larger than the one interpreted as female.

References

Protocetidae Fossil taxa described in 2009 Monotypic prehistoric cetacean genera Extinct mammals of Asia {{paleo-whale-stub

Paleobiology

See also

References