My last post was about a new bone that has just been excavated. I thought it was a bone that hadn't been seen before, hoping that it may be an elusive mandible or the missing inter-clavicle. The bad news is that it isn't a new bone - we have seen them before. The GOOD news is that this bone opens up a whole new world of wonder to contemplate.
The new bone is a chevron - one of the tail bones making up the spinal column of the tail. Together, the neural arch, centrum and chevron shape the tail into a vertically flattened oval, perfect for swimming. Chevrons are common in reptiles, and are even found in some mammals like whales, porpoises and manatees. We have already found several of them. In thalattosaurs they are a delicate Y-shaped bone generally 5-8 cm long in these animals such as Bernie or Miodontosaur Brevis.
Here is a picture of a Mosasaur tail, clearly showing the neural arches, centrums and chevrons (from top to bottom). This particular animal was about 6 Meters (20 feet). long. This one suffered injury during life that let to bone pathology. Picture courtesy of "Oceans of Kansas". Note that the chevron in the middle is about 7 cm from the tip to the notch - there will be a test later.
This is a picture of a copy of the most complete chevron found to-date from Bernie - it is about 5.5 cm long, a little over 2 inches. From the notch to the tip it is about 3.5 cm.
This new chevron is 11 cm from the tip to notch!
This is three times larger than the other centrums we have found. Scaling from the very complete Miodontosaurus Brevis from China, this would be an animal 10 meters long (33 feet). Scaling from the mosasaur above (remember the 7 cm chevron?) this would also be an animal about 10 meters long. In other words, a real GIANT!!!
Here is a picture of the actual bone, a copy of the normal -sized chevron, and the chevron enlarged 3.0 x to match the new centrum. [Aside, this is one of the benefits of 3D printers - I love 'em]. The match is pretty good all things considered.
There is the possibility that this bone is not from a Thalattosaur, although the slanted tip and grooved body are found on both bones. We will hold judgement on this until later. For now, just consider a 10m (33 foot) mama Thalattosaur looking over a whole colony of young animals only 1-3 meters long!
Sincerely, Greg Carr