January 24, 2014 by Alexandra Jones
A study published earlier this month, co-authored by Drexel University associate professor of Biodiversity, Earth and Environmental Science Ted Daeschler, unveiled fossil evidence that lends support to the theory that vertebrates developed four strong, usable appendages while still living in the water.
In 2006, a group of scientists revealed the discovery of a fossil that marked the beginning of the transition of life from water to land. This fossil was called Tiktaalik roseae, commonly known as Tiktaalik (tic-TAH-lick). Newly examined Tiktaalik roseae materials have shown that the fossil’s hind limbs appear strong and robust. This discovery discredits a former theory of evolution called “front-wheel drive” that proposes that the front limbs evolved and the hind limbs remained weak until these ancient creatures made their transition to land.
The team that discovered this fossil included Daeschler, Neil Shubin, a professor at the University of Chicago, and the late Farish A. Jenkins Jr. of Harvard University.
The name Tiktaalik literally means “large freshwater fish” in Inuktitut, the native language of the indigenous Inuit people of Canada. The research team was stationed in the Canadian Arctic where the Inuit people live. When they found the fossil, they asked the local Inuit people for their input on the name.
“We sent a brief description of the fish over and said it was a kind of large freshwater fish,” Daeshler recalled. “They said, ‘Well, we call a large freshwater fish Tiktaalik.’”
According to Daeshler, Tiktaalik used advanced fins to travel through shallow waters and rarely ventured onto land. It is theorized that the fins were used for doing things like walking along the bottom of waterbeds and evading predators. These functional limbs are what make Tiktaalik the missing link between lobe-finned fish and tetrapods.
Daeschler explained where the fossil falls in the evolutionary line, “When Tiltaalik came along, it really gave us a sort of stepping stone that split the difference. … [Tiktaalik] was definitely finned and definitely had limbs as well. Really, it has given us a more robust framework for our understanding of that transition.”
The creature was approximately nine feet in length. With both scales and webbing, it appeared like a cross between a crocodile and a fish. Its body had both steady limbs, the beginnings of a mobile neck, and (what fascinated scientists most) a pelvis with a pivoting hip socket.
“The size of the pelvis is much larger than the lobe-finned fish and the hip socket in Tiktaalik is very unique,” Daeschler commented.
Tiktaalik hip sockets were large enough to support heavy limbs that extended under the creature’s body. These limbs appeared very similar to the limbs of many animals seen today.
“Every limbed animal goes back to an animal like Tiktallik,” Daeshler said.
In fact, Tikaalik is an ancestor to not only reptiles and amphibians, but all mammals, including humans.
The Academy of Natural Sciences of Drexel University is currently housing Tiktaalik’s fossil. Admission to the Academy of Natural Sciences is free for all Drexel DragonCard holders.