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Description
Only two more to go.

This is the duckbills' vitriolic travel companion. The replacement for the Pachyrhinosaurus, a more basal eucentrosaur that might even be its direct ancestor, or at least closely related to its ancestor. The Pachyrhinosaurus in March of the Dinosaurs is one of the more accurate creatures overall (along with the Edmontonia ), but it's still plagued by some outdated tropes common with depictions of the "thick-nose lizard" throughout the 1980s-2000s. Thankfully, they at least didn't put a keratinous horn on its boss , which sounds like a no-brainer but given some of the documentary's other flaws (freshwater Prognathodon, bipedal pterosaurs , tyrannosaurids with pennaceous feathers ), I could totally see them going down this route, especially since the notion of Pachyrhinosaurus sporting a keratinous horn (while always controversial and dubious) wasn't truly slain until a 2009 study on its skull anatomy fully discredited it by highlighting how its boss is nothing like the corresponding structure in a rhinoceros skull.

Pachyrhinosaurus is one of the best-known ceratopsids, alongside Triceratops, Styracosaurus and Centrosaurus, and part of the reason is because we have found a lot of specimens, including bonebeds preserving entire herds consisting of variously aged individuals, the same being true for other centrosaurines, but also due to its novel, if not obverse appearance for a ceratopsid. Pachyrhinosaurus canadensis was named by Charles Sternberg back in 1950, based on two skulls found in the lower Horseshoe Canyon Formation of Alberta, dating to the early Maastrichtian (72-70 mya), with additional material subsequently being recovered from the Scabby Butte locality of the contemporary St. Mary River Formation, located on the Alberta and Montana border, which shares other fauna with Horseshoe Canyon, like Albertosaurus and Edmontonia. As you can imagine, this ceratopsid was quite the landmark find at the time, as it lacked the one feature that got its family its name.

Later on, during the 1980s, we started finding Pachyrhinosaurus fossils at two other localities, one being the famous Pipestone Creek bonebed located further north in Alberta, part of the Wapiti Formation (a total of 3,500 bones and 14 skulls) and a 1987 expedition to what would later be called the Prince Creek Formation in northern Alaska, discovered even more fossil material of Pachyrhinosaurus, the northernmost occurrence of these animals and ceratopsians period (recently joined by indeterminate leptoceratopsids). For the record, both Wapiti and Prince Creek also have fossils of Edmontosaurus, with the type species (E. regalis) originating from the lower Horseshoe Canyon (and also being found at Wapiti), so it and Pachyrhinosaurus usually come in pairs. The fact that both genera were found in Alaska, northern Alberta and southern Alberta inspired the narrative that these animals traveled great distances (over 3,000 km) as part of an annual, transcontinental migration, further than any living land herbivore, other than maybe the caribou (recorded covering up to 5,000 km), which was first suggested for polar duckbills by paleontologist Nicholas Hotton in 1980, dubbed the "Happy Wanderers" theory.

This idea was very much a product of the Dinosaur Renaissance , when we were gradually moving away from the image of dinosaurs as cold-blooded, sluggish reptiles incapable of surviving outside of tropical climes, with finds from Prince Creek and Dinosaur Cove providing the hard evidence, but workers still struggled to imagine these animals, especially larger taxa, toughing it through polar winters, with months of no sunlight, so the migration theory was tempting. However, it was never a very robust idea, and the vast distribution of both Edmontosaurus and Pachyrhinosaurus (as workers pointed out as far back in the 90s) could have been just that, a wide geographic distribution, not unlike with (historically) extant large herbivores in North America such as moose, elk, and bison. By the mid 2000s, workers already expressed doubts about the "Happy Wanderers" theory based on various lines of evidence , but the dramatic narrative persisted in media.

However, for Pachyrhinosaurus specifically, this theory started to crumble apart from 2008 onward, when the Wapiti fossils were described as a second species, P. lakustai, and it was shown that it was geologically older, having lived during the tail end of the Campanian (73-72 mya), while the Alaskan species was named as P. perotorum in 2012 (a year after March of the Dinosaurs aired) and it was recognized as the geologically youngest species, having lived during the mid Maastrichtian (70-68 mya), thus representing the final known occurrence of Pachyrhinosaurus and centrosaurines as a whole. Coincidently, the upper Horseshoe Canyon dates to the mid Maastrichtian as well, but by that point, the local Pachyrhinosaurus were seemingly fully replaced by chasmosaurines such as Eotriceratops and Regaliceratops (the latter known from the upper St. Mary River). The picture that emerges is not one of an intrepid migrant (which was shaky to begin with) but rather the rise and fall of a once successful ceratopsid genus, with its final stronghold seemingly being the Arctic.

Furthermore, while many portrayals of the polar Pachyrhinosaurus (including March of the Dinosaurs and Walking with Dinosaurs 3D) show it with a unicorn-like horn located just behind the eyes, this feature is only known in the basal P. lakustai, not the later P. canadensis and P. perotorum, thus ultimately making many media portrayals chimeric ones (like slapping a lion's mane on a tiger). As I have changed the date to the upper Campanian, 76 million years ago, I naturally had to go with a different centrosaurine. While there is no shortage of Campanian centrosaurs in Laramidia, picking one was not as easy as you might think, since a lot of the known taxa did not live at the same time and in fact, seem to represent very rapid evolutionary turnovers (with many species lasting just half a million years or so), with Pachyrhinosaurus being the final evolution of the centrosaurine lineage, with its ancestors gradually morphing their nasal horns into a thick boss.

Because so many taxa have been named from Late Cretaceous Laramidia, we have a pretty good idea of how these eucentrosaurs evolved, and my replacement for Pachyrhinosaurus is one of the earliest forms, next to Coronosaurus brinkmani, which was previously considered an older species of Centrosaurus. The type species of the centrosaurines, Centrosaurus apertus, is known from numerous specimens found in the lower Dinosaur Park, before being replaced or evolving into Styracosaurus albertensis in the upper layers (basically C. apertus but with much, much larger parietal spikes), including the Hilda mega-bonebed (another mass mortality event similar to Pipestone Creek), and it very much embodies the classic centrosaurine bauplan; a large nasal horn, tiny brow horns and a (comparatively) smaller frill, while the related chasmosaurines went in the exact opposite direction, with larger frills, ever-large brow horns, and tiny nasal horns.

Besides being living at the right time, Centrosaurus was also chosen because we have potential evidence of its presence in Montana as well. The Two Medicine Formation has a lot of faunal overlap with Dinosaur Park and also a large collection of (mostly unique) centrosaur genera, who also happen to represent probable intermediary forms leading from Centrosaurus to Pachyrhinosaurus (Styracosaurus ovatus, Stellasaurus, Einiosaurus, and Achelousaurus), but all of these guys come from the upper Two Medicine, closer to 75-74 mya. In most other cases, this would be an acceptable time gap but with upper Campanian Laramidia, the fossil record is far too rich to let that slide.

The other major fossil site in Montana, the Judith River Formation (where many other species in my revised take come from) offers older ceratopsids, fitting the circa 76 mya mark, but none of them are known from Alberta too. There is, however, the now dubious Monoclonius crassus, known from fragmentary material likely stemming from juvenile animals, thus they are not particularly diagnostic. As you may know, Monoclonius and Centrosaurus had a long and convoluted taxonomic history, but as Centrosaurus is known from much more complete material, it won out as the valid name, even though Monoclonius was named first. The Monoclonius material, in turn, could represent possible direct evidence of Centrosaurus in Montana, hence why they could be shown traveling between Alberta and Montana along with the Brachylophosaurus, outside of pure speculation.

Anatomical Reference: www.deviantart.com/randomdinos…

Description
Only two more to go.

This is the duckbills' vitriolic travel companion. The replacement for the Pachyrhinosaurus, a more basal eucentrosaur that might even be its direct ancestor, or at least closely related to its ancestor. The Pachyrhinosaurus in March of the Dinosaurs is one of the more accurate creatures overall (along with the Edmontonia ), but it's still plagued by some outdated tropes common with depictions of the "thick-nose lizard" throughout the 1980s-2000s. Thankfully, they at least didn't put a keratinous horn on its boss , which sounds like a no-brainer but given some of the documentary's other flaws (freshwater Prognathodon, bipedal pterosaurs , tyrannosaurids with pennaceous feathers ), I could totally see them going down this route, especially since the notion of Pachyrhinosaurus sporting a keratinous horn (while always controversial and dubious) wasn't truly slain until a 2009 study on its skull anatomy fully discredited it by highlighting how its boss is nothing like the corresponding structure in a rhinoceros skull.

Pachyrhinosaurus is one of the best-known ceratopsids, alongside Triceratops, Styracosaurus and Centrosaurus, and part of the reason is because we have found a lot of specimens, including bonebeds preserving entire herds consisting of variously aged individuals, the same being true for other centrosaurines, but also due to its novel, if not obverse appearance for a ceratopsid. Pachyrhinosaurus canadensis was named by Charles Sternberg back in 1950, based on two skulls found in the lower Horseshoe Canyon Formation of Alberta, dating to the early Maastrichtian (72-70 mya), with additional material subsequently being recovered from the Scabby Butte locality of the contemporary St. Mary River Formation, located on the Alberta and Montana border, which shares other fauna with Horseshoe Canyon, like Albertosaurus and Edmontonia. As you can imagine, this ceratopsid was quite the landmark find at the time, as it lacked the one feature that got its family its name.

Later on, during the 1980s, we started finding Pachyrhinosaurus fossils at two other localities, one being the famous Pipestone Creek bonebed located further north in Alberta, part of the Wapiti Formation (a total of 3,500 bones and 14 skulls) and a 1987 expedition to what would later be called the Prince Creek Formation in northern Alaska, discovered even more fossil material of Pachyrhinosaurus, the northernmost occurrence of these animals and ceratopsians period (recently joined by indeterminate leptoceratopsids). For the record, both Wapiti and Prince Creek also have fossils of Edmontosaurus, with the type species (E. regalis) originating from the lower Horseshoe Canyon (and also being found at Wapiti), so it and Pachyrhinosaurus usually come in pairs. The fact that both genera were found in Alaska, northern Alberta and southern Alberta inspired the narrative that these animals traveled great distances (over 3,000 km) as part of an annual, transcontinental migration, further than any living land herbivore, other than maybe the caribou (recorded covering up to 5,000 km), which was first suggested for polar duckbills by paleontologist Nicholas Hotton in 1980, dubbed the "Happy Wanderers" theory.

This idea was very much a product of the Dinosaur Renaissance , when we were gradually moving away from the image of dinosaurs as cold-blooded, sluggish reptiles incapable of surviving outside of tropical climes, with finds from Prince Creek and Dinosaur Cove providing the hard evidence, but workers still struggled to imagine these animals, especially larger taxa, toughing it through polar winters, with months of no sunlight, so the migration theory was tempting. However, it was never a very robust idea, and the vast distribution of both Edmontosaurus and Pachyrhinosaurus (as workers pointed out as far back in the 90s) could have been just that, a wide geographic distribution, not unlike with (historically) extant large herbivores in North America such as moose, elk, and bison. By the mid 2000s, workers already expressed doubts about the "Happy Wanderers" theory based on various lines of evidence , but the dramatic narrative persisted in media.

However, for Pachyrhinosaurus specifically, this theory started to crumble apart from 2008 onward, when the Wapiti fossils were described as a second species, P. lakustai, and it was shown that it was geologically older, having lived during the tail end of the Campanian (73-72 mya), while the Alaskan species was named as P. perotorum in 2012 (a year after March of the Dinosaurs aired) and it was recognized as the geologically youngest species, having lived during the mid Maastrichtian (70-68 mya), thus representing the final known occurrence of Pachyrhinosaurus and centrosaurines as a whole. Coincidently, the upper Horseshoe Canyon dates to the mid Maastrichtian as well, but by that point, the local Pachyrhinosaurus were seemingly fully replaced by chasmosaurines such as Eotriceratops and Regaliceratops (the latter known from the upper St. Mary River). The picture that emerges is not one of an intrepid migrant (which was shaky to begin with) but rather the rise and fall of a once successful ceratopsid genus, with its final stronghold seemingly being the Arctic.

Furthermore, while many portrayals of the polar Pachyrhinosaurus (including March of the Dinosaurs and Walking with Dinosaurs 3D) show it with a unicorn-like horn located just behind the eyes, this feature is only known in the basal P. lakustai, not the later P. canadensis and P. perotorum, thus ultimately making many media portrayals chimeric ones (like slapping a lion's mane on a tiger). As I have changed the date to the upper Campanian, 76 million years ago, I naturally had to go with a different centrosaurine. While there is no shortage of Campanian centrosaurs in Laramidia, picking one was not as easy as you might think, since a lot of the known taxa did not live at the same time and in fact, seem to represent very rapid evolutionary turnovers (with many species lasting just half a million years or so), with Pachyrhinosaurus being the final evolution of the centrosaurine lineage, with its ancestors gradually morphing their nasal horns into a thick boss.

Because so many taxa have been named from Late Cretaceous Laramidia, we have a pretty good idea of how these eucentrosaurs evolved, and my replacement for Pachyrhinosaurus is one of the earliest forms, next to Coronosaurus brinkmani, which was previously considered an older species of Centrosaurus. The type species of the centrosaurines, Centrosaurus apertus, is known from numerous specimens found in the lower Dinosaur Park, before being replaced or evolving into Styracosaurus albertensis in the upper layers (basically C. apertus but with much, much larger parietal spikes), including the Hilda mega-bonebed (another mass mortality event similar to Pipestone Creek), and it very much embodies the classic centrosaurine bauplan; a large nasal horn, tiny brow horns and a (comparatively) smaller frill, while the related chasmosaurines went in the exact opposite direction, with larger frills, ever-large brow horns, and tiny nasal horns.

Besides being living at the right time, Centrosaurus was also chosen because we have potential evidence of its presence in Montana as well. The Two Medicine Formation has a lot of faunal overlap with Dinosaur Park and also a large collection of (mostly unique) centrosaur genera, who also happen to represent probable intermediary forms leading from Centrosaurus to Pachyrhinosaurus (Styracosaurus ovatus, Stellasaurus, Einiosaurus, and Achelousaurus), but all of these guys come from the upper Two Medicine, closer to 75-74 mya. In most other cases, this would be an acceptable time gap but with upper Campanian Laramidia, the fossil record is far too rich to let that slide.

The other major fossil site in Montana, the Judith River Formation (where many other species in my revised take come from) offers older ceratopsids, fitting the circa 76 mya mark, but none of them are known from Alberta too. There is, however, the now dubious Monoclonius crassus, known from fragmentary material likely stemming from juvenile animals, thus they are not particularly diagnostic. As you may know, Monoclonius and Centrosaurus had a long and convoluted taxonomic history, but as Centrosaurus is known from much more complete material, it won out as the valid name, even though Monoclonius was named first. The Monoclonius material, in turn, could represent possible direct evidence of Centrosaurus in Montana, hence why they could be shown traveling between Alberta and Montana along with the Brachylophosaurus, outside of pure speculation.

Anatomical Reference: www.deviantart.com/randomdinos…