Conjoined grey whale calves could be world's first ever documented find

Experts said that while other species have been found to have conjoined twins, the find is 'without any precedent' among grey whales

A pair of conjoined gray whale calves have been found dead off the coast of Mexico, in what scientists believe could be the first discovery of its kind.

The 4m - (13ft-) long conjoined whales were dead when they were found in the Ojo de Liebre lagoon

Joined at the waist, the creatures weighed nearly half a tonne and measured around 4 metres (13ft) long. Experts said it would have been virtually impossible for the twin whales to have survived - at around half the length of an average gray whale, they would likely have been born prematurely.

The animals were discovered in the Ojo de Liebre lagoon, which opens onto the Pacific Ocean and is one of a number of prominent breeding sanctuaries used by gray whales on the Baja California peninsula.

The find was verified after a visit on Monday by the National Natural Protected Areas Commission (CONANP). Marine biologist Benito Bermudez, CONANP's regional manager, told the AFP the discovery was "exceptionally rare, without any precedent" to his knowledge.

While examples of conjoined twins have occurred in other whale species such as fin, sei and minke, it is thought there are no previously published discoveries of the phenomenon in gray whales.

Alisa Schulman-Janiger, a researcher with the American Cetacean Society, said there were concerns that with the twins severely underdeveloped, the birth or possibly stillbirth might also have killed the mother. A video of the discovery of the animals was uploaded to YouTube and images were posted to the Facebook group with the translated statement: "Unfortunately, the specimen died. [Its] survival was very difficult."

The carcass of the whales has been taken away for further study by a government agency.

Every year hundreds of gray whales migrate around 6,000 miles from the Bering Sea to the warmer waters of Mexico's west coast. Most have calves during the last week of December and the first two weeks of January, and nurse for a number of weeks before making the long return journey north.

- The Independent