A pair of conjoined gray whale calves were discovered in a lagoon on Mexico's northwestern coast, the first such case documented in that region, the National Protected Natural Areas Commission, or Conanp, said.

The whales, which did not survive, were found Monday in Laguna Ojo de Liebre on the coast of the northwestern state of Baja California Sur.

"These were two newborn Siamese gray whales that were fused ventrally," biologist Benito Bermudez Almada, Conanp's regional director for the Baja California peninsula, told Efe Tuesday.

Gray whales arrive annually at this time of year at Baja California Sur's coastal lagoons to mate and give birth, he said. "On this occasion, we were surprised (Monday) to find two whales adrift that had recently died within the Laguna Ojo de Liebre."

The expert said conjoined twins are a rare phenomenon seen in different classes of animals, including reptiles, mammals and birds.

Bermudez said no previous such case had been recorded in Conanp's whale censuses dating back to 1985.

"That's what's interesting for research purposes; to see what type of information scholars can obtain ... that enriches the knowledge we have about this species," he added. EFE