On Jan. 5, scientists came upon a rare discovery -- they found the bodies of two conjoined gray whale calves floating in Laguna Ojo de Liebre in the Mexican state of Baja California, which opens up to the Pacific Ocean.

According to National Geographic and several other reports, the conjoined twins, who sadly didn't make it and are believed to be "miscarried due to their disability," are also known as Siamese twins. They measured about seven to ten feet (two to three meters) in length, which is shorter than the usual 12- to 16-foot (3.6- to 4.8-meter) length of full-term gray whale calves.

The conjoined gray whale calves weighed nearly half a ton and were linked at the mid-section, Sky News reports. They had two full heads and tail fins, according to Benito Bermudez, a marine biologist and regional manager at the National Natural Protected Areas Commission.

How old were the they?

Jim Dines, collections manager of mammals at the Natural History Museum of Los Angeles County in California, told National Geographic that gray whale gestation lasts for 13.5 months; therefore, the conjoined twins were probably between 8.5 and 10.5 months of age when they were born.

Dines points out "that those ages are only estimates based on the lengths of single fetuses."

"In the case of twins, the mother has to provide nourishment for two growing fetuses and that may result in two slightly smaller fetuses rather than one normal-sized one," he explained. "These were pretty sizeable. There's a fair chance the mother was trying to deliver them and couldn't."

How rare is this discovery?

"It's not unheard of in large whales to have Siamese twins," Michael Moore, a veterinarian who specializes in forensic analysis of marine mammal deaths, at the Woods Hole Oceanographic Institution in Massachusetts told National Geographic.

"A search through the scientific literature comes up with occurrences of conjoined twins in minke, sei, and humpback whales," he added.

"[But] because of their reproductive biology, whales and dolphins almost always have a single baby," said the Natural History Museum's Dines.

According to Fox News Latino, "gray whales are currently in the midst of their yearly 6,000-mile migration from their home waters up near the Arctic Circle and make stops in the waters off Mexico's Baja California peninsula. They generally give birth during their southbound journey or in lagoons, where they nurse their calves before making the journey north to the Bering and Chukchi seas.

"The Pacific gray whale population numbers about 21,000, according to the National Oceanic and Atmospheric Administration (NOAA)."

Watch the video that captured what scientists believe to be the first ever conjoined grey whale twins.