HOME | DD

Description
Three marine reptiles from the latest Campanian Bearpaw Formation (74-73 mya), which overlies the more famous Dinosaur Park Formation in Alberta, and there is debate about whether some of the dinosaurs found in uppermost strata in the latter formation actually come from the lower strata of Bearpaw (like some fossils of Lambeosaurus), and Bearpaw itself underlies the Horseshoe Canyon and St. Mary River Formation (lower Maastrichtian). The most notable finds from Bearpaw are actually some very complete skeletons of various marine reptiles, representing the three main types of marine reptiles from the Late Cretaceous.

Albertonectes vanderveldei (2012) is a type of elasmosaurid, known only from the well-preserved holotype (which lacks a skull), and closely related to the older Styxosaurus and Elasmosaurus from Niobrara/Pierre Shale and the later, Maastrichtian Hydrotherosaurus from the Moreno Formation of California. Albertonectes stands out for having an immensely long neck, even compared to other elasmosaurids, as the whole animal was about 11.5-12 meters long but the neck alone made up 7 meters (and with only one specimen, even larger one could have existed). These long-necked giants were piscivores, who used their long, interlocking teeth and moderately flexible necks to effectively snatch and swallow small fish.

Besides elasmosaurids, the other major group of Late Cretaceous plesiosaurs were the polycotylids, who replaced the ichthyosaurs after the latter vanished during the Turonian extinction. One of the best-known polycotylids is Dolichorhynchops, first erected with Dolichorhynchops osborni from the Smoky Hill Chalk of Niobrara, which reached 3-4.3 meters in length, later joined by D. herschelensis (2005), who is known from a single specimen from Bearpaw, and was about 2.5-3 meters long. Dolichorhynchops originally included two more species, but they have since been transferred to their own genera; Martinectes from Pierre Shale (who reached 5 meters) and the older, Turonian-aged Scalamagnus from Tropic Shale. Shaped like torpedos, polycotylids were likely faster and more agile than their elasmosaurid relatives and had long, thin jaws similar to gharials and river dolphins, for an obvious purpose (catching fish).

The main predators of both elasmosaurids and polycotylids were the mosasaurs, a highly diverse group of aquatic lizards (true squamates) related to varanids and snakes, who ranged in size from 3 to 13 meters in length and occupied various ecological niches in the oceans. Several different species are known from Bearpaw, all known from reasonably complete remains, but only small to mid-sized taxa have so far been found, the largest being Mosasaurus missouriensis (known from several specimens ) and Tylosaurus saskatchewanensis (known from only one ), both reaching around 9 meters.

The third large taxon, estimated at around 7-8 meters and known from several exceptionally preserved specimens is Brachysaurana overtoni (1897), a species with short and robust jaws, indicating that it was a macropredator that could chow down on almost everything. This species, along with many other mosasaurs of varying sizes who sport short skulls and robust teeth have often been lumped into Prognathodon, but this genus is likely a wastebin taxon, with the only species still confidently placed in it being the giant P. currii and P. giganteus (who reached 10 meters or more, and even they might be closer to Thalassotitan) and the small-sized P. solvayi (type species) and midsized P. lutugini (5 and 8 meters respectively), all four from the Late Campanian-Maastrichtian of Europe and/or the Middle East, with evidence of the genus from North America, Africa, and New Zealand being dubious and some have already been placed in separate genera.

Anatomical Reference: www.deviantart.com/crowncrocop…

Description
Three marine reptiles from the latest Campanian Bearpaw Formation (74-73 mya), which overlies the more famous Dinosaur Park Formation in Alberta, and there is debate about whether some of the dinosaurs found in uppermost strata in the latter formation actually come from the lower strata of Bearpaw (like some fossils of Lambeosaurus), and Bearpaw itself underlies the Horseshoe Canyon and St. Mary River Formation (lower Maastrichtian). The most notable finds from Bearpaw are actually some very complete skeletons of various marine reptiles, representing the three main types of marine reptiles from the Late Cretaceous.

Albertonectes vanderveldei (2012) is a type of elasmosaurid, known only from the well-preserved holotype (which lacks a skull), and closely related to the older Styxosaurus and Elasmosaurus from Niobrara/Pierre Shale and the later, Maastrichtian Hydrotherosaurus from the Moreno Formation of California. Albertonectes stands out for having an immensely long neck, even compared to other elasmosaurids, as the whole animal was about 11.5-12 meters long but the neck alone made up 7 meters (and with only one specimen, even larger one could have existed). These long-necked giants were piscivores, who used their long, interlocking teeth and moderately flexible necks to effectively snatch and swallow small fish.

Besides elasmosaurids, the other major group of Late Cretaceous plesiosaurs were the polycotylids, who replaced the ichthyosaurs after the latter vanished during the Turonian extinction. One of the best-known polycotylids is Dolichorhynchops, first erected with Dolichorhynchops osborni from the Smoky Hill Chalk of Niobrara, which reached 3-4.3 meters in length, later joined by D. herschelensis (2005), who is known from a single specimen from Bearpaw, and was about 2.5-3 meters long. Dolichorhynchops originally included two more species, but they have since been transferred to their own genera; Martinectes from Pierre Shale (who reached 5 meters) and the older, Turonian-aged Scalamagnus from Tropic Shale. Shaped like torpedos, polycotylids were likely faster and more agile than their elasmosaurid relatives and had long, thin jaws similar to gharials and river dolphins, for an obvious purpose (catching fish).

The main predators of both elasmosaurids and polycotylids were the mosasaurs, a highly diverse group of aquatic lizards (true squamates) related to varanids and snakes, who ranged in size from 3 to 13 meters in length and occupied various ecological niches in the oceans. Several different species are known from Bearpaw, all known from reasonably complete remains, but only small to mid-sized taxa have so far been found, the largest being Mosasaurus missouriensis (known from several specimens ) and Tylosaurus saskatchewanensis (known from only one ), both reaching around 9 meters.

The third large taxon, estimated at around 7-8 meters and known from several exceptionally preserved specimens is Brachysaurana overtoni (1897), a species with short and robust jaws, indicating that it was a macropredator that could chow down on almost everything. This species, along with many other mosasaurs of varying sizes who sport short skulls and robust teeth have often been lumped into Prognathodon, but this genus is likely a wastebin taxon, with the only species still confidently placed in it being the giant P. currii and P. giganteus (who reached 10 meters or more, and even they might be closer to Thalassotitan) and the small-sized P. solvayi (type species) and midsized P. lutugini (5 and 8 meters respectively), all four from the Late Campanian-Maastrichtian of Europe and/or the Middle East, with evidence of the genus from North America, Africa, and New Zealand being dubious and some have already been placed in separate genera.

Anatomical Reference: www.deviantart.com/crowncrocop…