For 40 thousand years, a massive basin lay motionless at the bottom of a flooded cave. It was 3 meters in diameter and weighing 36 kg. It once belonged to a giant terrestrial sloth the size of an elephant who lived in ancient America with a saber-toothed tiger and a woolly mammoth. About how to get a giant sloth, said the University of San Diego.
Once a poor giant animal fell into a network of caves in the form of a maze until it fell into a hole. Today, this pit is known as Hoyo Negro – The Black Hole. Sloth flew about 30 meters and died. Before this giant animal was discovered there – an extinct species of bear, saber-toothed feline, other gigantic sloths and Naya – a young woman who lived 13,000 years ago.
In November 2019, a group of researchers went in search of the pelvis of a giant terrestrial sloth with the help of a carefully planned expedition. Rising sea levels flooded the cave system at the end of the last ice age, which made the search for a basin impossible for all but the most experienced divers. During the expedition, the team had to work along international lines and combine their skills in paleontology, three-dimensional modeling, engineering, and virtual reality in order to safely get this fragment of history into the light.
Cave divers discovered the remains of a giant ground sloth during their initial dives in Hoyo Negro in 2007. Under the guidance of the National Institute of Anthropology and History of Mexico (INAH) and the expert guidance of James Chatter and Blaine Schubert, paleontologists specializing in late ice age species, divers took all the sloth bones, with the exception of several vertebrae, arm, and pelvis. After the discovery of the pelvis, it turned out that the sloth was a completely new kind.
Scientists called the giant terrestrial sloth Nohochichak xibalbahkah, which in Mayan means “the Great claw that lives in the underworld.” While he lived, he was 5 meters high and weighed a little less than a ton. His pelvis was the last major bone missing in the skeleton, and a key component in restoring its resemblance to other species.
It took a whole year to pick up a basin from a cave. Using QI SunCAVE’s high-performance virtual reality device, they planned a route for divers through the cave system in Hoyo Negro. From the diving platform, divers almost in total darkness descended into a narrow corridor and walked 60 meters to the edge of the black hole. The pelvis lay 30 meters below their position and was upside down.
Bone size was an additional problem. The team had to design a support frame that was strong enough to protect its load, but not so bulky that it could scratch the walls of the tunnel. Using images from a previous dive, engineers from QI Prototyping Lab, QI Drone Lab, and East Tennessee State University recreated the pelvis as a three-dimensional digital model that they could rotate and study in detail. Now they could identify weak points in the bone and design a framework that would cover every part of the pelvis.
Then, a few days before the dive, the researchers had to abandon their plan. The frame they created was too expensive for production, and its size made it impossible to create it on a 3D printer.
A team of engineers needed a material that would be easy to maneuver underwater, and fiberglass, the material used to create surfboards. The creator of the surfboards decided that the engineers were crazy – if someone called someone and said that he needed a surfboard to get the basin of a giant sloth who had been lying underwater for 40,000 years, he would definitely twist his finger at the temple, one of the engineers shared.
“The giant ground lazy basin is the largest fossil ever extracted from Hoyo Negro, and the underwater part of the restoration went exactly as planned and as we rehearsed”Brett Butler, QI Prototyping Lab Engineer
The team used their designed cradle to connect the basin to the cable and pulley system and lifted it 9 meters from the diving platform through the mouth of the cave.
Taz is now in the National Museum of Anthropology of Mexico. Information from the fossil will contribute to INAH’s broader mission to document, study, and preserve the paleontological history of Mexico.