Monday, 30 September 2013

Marine Reptiles in Alberta

You may have noticed that there was no blog post last week. Sorry about that! That is because the writer of this blog (me - Liz) was busy last week starting a PhD at the University of Southampton in the United Kingdom. I was so busy last week I just didn't have a chance to write! But now we're back!

Although we've talked in passing about extinct marine reptiles in the past, it has never been in detail, which is why I decided that this week we would talk a bit about the sea creatures often found in Alberta. In order to talk about the marine reptile fossils found in Alberta, I think it's important to explain some of geological history of the region.

In the mid to Late Cretaceous, a large water body called the Western Interior Seaway ran through North America, connecting the Arctic Ocean to the Gulf of Mexico. This large seaway lasted for about 100 million years, and caused nearly the entire province of Alberta to be underwater. This large seaway allowed for many large and small marine animals to invade, including sharks, fish, and of course, large marine reptiles. 
Image of modern North America in the mid-Late Cretaceous, covered in seaways
Although there are many groups of marine animal fossils that have been found in Alberta, we are going to focus on the two groups of marine reptiles that have appeared. The first group is the plesiosaurs. Plesiosauroids are the long-necked marine reptiles in the group Plesiosauria. They differ from their close relatives, the pliosauroids, by (generally) having very long necks and small heads, while pliosauroids (generally) have short necks and large heads. As of 2012, nearly 30 plesiosaurid specimens had been found in western Canada, with just over half of them coming from Alberta [1]. Although not all are identifiable to genus or species, most of them are either from the family Elasmosauridae, which includes the plesiosauroids with the longest necks of all, or the Polycotylidae, which have shorter necks and closely resemble pliosaurs. Elasmosaurids from Alberta include Albertonectes (found near Lethbridge) and Wapuskanectes which was found in a Syncrude mine near Fort McMurray. Because the oil sands are marine deposits, it's quite common for marine fossils to be found in these mines. Trinacromerum (from Dinosaur Provincial Park) and Nichollsaura (also from near Fort McMurray) are some of the polycotylids found in Alberta. Plesiosaurs are also found in Saskatchewan, Manitoba, and occasionally in BC.
Artists impression of Albertonectes by Smokeybjb
Trinacromerum by Nobu Tamura
The second group of marine reptiles found in Alberta is the mosasaurs. Mosasaurs lived only in the Late Cretaceous, and were the dominant marine predators during this time. They were strong swimmers, and even better predators, reaching lengths from 3-18 m and having double-hinged jaws much like modern snakes, allowing them to open their mouths wide and swallow prey. Prognathodon, a rare, large-jawed mosasaur has been identified by a few specimens in Alberta, including one nearly complete specimen from near Lethbridge [2]. These were found by the Korite International, an ammolite mining company, while mining for ammolite. Another possible specimen was discovered in 2012 in a mine as well. Another mosasaur, Plioplatecarpus, which has proportionally larger eyes than other mosasaurs, was identified from an incomplete specimen found in southern Alberta.
Artists impression of Prognathodon
Plesiosaurs and mosasaurs are just two of the groups of marine fossil animals that have been found so far in Alberta. Other groups include fishes, sharks, and possibly pliosaurs as well. I hope this has given an insight into the non-terrestrial fossils that can be found in Alberta, and the kinds of marine reptiles often found!

1. Kubo, T., et al. 2012. Albertonectes vanderveldei, a new elasmosaur (Reptilia, Sauropterygia) from the Upper Cretaceous of Alberta. Journal of Vertebrate Paleontology 32: 557-572.
2. Konishi, T., et al. 2011. New exceptional specimens of Prognathodon overtoni (Squamata, Mosasauridae) from the Upper Campanian of Alberta, Canada, and the systematics and ecology of the genus. Journal of Vertebrate Paleontology 31: 1026-1046.

No comments:

Post a Comment