Albertonectes Was an Extreme Elasmosaur

Giraffes, with their beautifully elongated necks, have only seven cervical vertebrae. So do you, and, for that matter, most mammals. (Sloths and manatees are among the few oddballs that differ.) Short or long, mammal necks are typically supported by just seven bones. But other creatures played by different anatomical rules. The fantastic sauropod dinosaurs – such as the familiar Diplodocus and what may have been the largest terrestrial animal ever, Amphicoelias – had a higher number of intricately modified neck vertebrae. One of my favorite dinosaurs, Apatosaurus, had 15 neck vertebrae.

Other prehistoric creatures racked on even more bones. And paleontologists may have just identified the animal with the highest cervical vertebra count of all time. In the latest issue of the Journal of Vertebrate Paleontology, researchers Tai Kubo, Mark Mitchell, and Donald Henderson describe a new elasmosaur from the roughly 70-million-year-old rock of Alberta, Canada’s Bearpaw Formation. They have named the quad-paddled, long-necked marine reptile Albertonectes vanderveldei, and, while the creature’s skull went missing, the rest of the plesiosaur is represented by a nearly complete skeleton that stretched about 37 feet long in life.

Most of that length was neck. Even though the Albertonectes specimen – designated TMP 2007.011.0001 – folded up on itself prior to fossilization, it is immediately clear that this animal had a wonderfully long neck. When reconstructed, Albertonectes had 76 cervical vertebrae that stretched about 23 feet from the back of the skull to the neck’s base. This barely edges out the nearest competition for cervical count – the more famous Elasmosaurus had 71 neck vertebrae. And Albertonectes has also just become the longest elasmosaur we know of. While some of the big-headed, short-necked pliosaurs attained larger sizes – such as the still-unnamed Predator X – Albertonectes sets the new limit for the longest of the long-necked plesiosaurs.

Why did Albertonectes have such an extreme neck? Paleontologists have been puzzling over the natural history of long-necked plesiosaurs for over a century, but the lifestyles of these marine reptiles remains frustratingly obscured by the depth of time between us and them. One thing seems certain, though – these animals were not the snake-necked predators I so often saw in paleo books as a kid. Quite the contrary. Albertonectes and closely related forms probably had relatively stiff necks, and the jumbled nature of TMP 2007.011.0001 throws support to this interpretation.

When the decaying body of the Albertonectes hit the sea floor, Kubo and co-authors propose, the front portion of the neck buckled under the weight of the rest of the plesiosaur’s body. Rather than coiling neatly, though, the animal’s stiff neck broke into different segments. This arrangement, coupled with the lack of flexibility seen between each neck vertebra, means that these marine reptiles were not rapidly whipping their necks around after fish and squid. Even though they were among the first magnificent monsters to be uncovered by 19th century paleontologists, plesiosaurs remain some of the most puzzling fossil creatures we have ever encountered.

References:

Kubo, T., Mitchell, M., & Henderson, D. (2012). Albertonectes vanderveldei , a new elasmosaur (Reptilia, Sauropterygia) from the Upper Cretaceous of Alberta
Journal of Vertebrate Paleontology, 32 (3), 557-572 DOI: 10.1080/02724634.2012.658124