Poll: Who wins?
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Pentaceratops sternbergii
1 100.00%
Stegosaurus stenops
0 0%
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Pentaceratops sternbergii v Stegosaurus stenops
Pentaceratops sternbergii
Pentaceratops ("five-horned face") is a genus of herbivorous ceratopsid dinosaur from the late Cretaceous Period of what is now North America.
Pentaceratops fossils were first discovered in 1921. The genus was named in 1923 when its type species Pentaceratops sternbergii was described. Pentaceratops lived around 76–73 million years ago, its remains having been mostly found in the Kirtland Formation in the San Juan Basin in New Mexico. About a dozen skulls and skeletons have been uncovered, so anatomical understanding of Pentasaurus is fairly complete. One exceptionally large specimen later became its own genus, Titanoceratops, due to its more derived morphology, similarities to Triceratops, and lack of unique characteristics shared with Pentaceratops. Pentaceratops was about 6 meters (20 feet) long, and has been estimated to have weighed around five tonnes. It had a short nose horn, two long brow horns, and long horns on the jugal bones. Its skull had a very long frill with triangular hornlets on the edge.

[Image: Pentaceratops_BW.jpg]

Stegosaurus stenops
Stegosaurus (/ˌstɛɡəˈsɔːrəs/), from Greek stegos (στέγος) which means roof and sauros (σαῦρος) which means lizard (Greek: Στεγόσαυρος), is a genus of herbivorous thyreophoran dinosaur. Fossils of this genus date to the Late Jurassic period, where they are found in Kimmeridgian to early Tithonian aged strata, between 155 and 150 million years ago, in the western United States and Portugal. Of the species that have been classified in the upper Morrison Formation of the western US, only three are universally recognized; S. stenops, S. ungulatus and S. sulcatus. The remains of over 80 individual animals of this genus have been found. Stegosaurus would have lived alongside dinosaurs such as Apatosaurus, Diplodocus, Brachiosaurus, Allosaurus, and Ceratosaurus; the latter two may have been predators of it. These were large, heavily built, herbivorous quadrupeds with rounded backs, short fore limbs, long hind limbs, and tails held high in the air. Due to their distinctive combination of broad, upright plates and tail tipped with spikes, Stegosaurus is one of the most recognizable kinds of dinosaurs. The function of this array of plates and spikes has been the subject of much speculation among scientists. Today, it is generally agreed that their spiked tails were most likely used for defense against predators, while their plates may have been used primarily for display, and secondarily for thermoregulatory functions. Stegosaurus had a relatively low brain-to-body mass ratio. It had a short neck and a small head, meaning it most likely ate low-lying bushes and shrubs.The quadrupedal Stegosaurus is one of the most easily identifiable dinosaur genera, due to the distinctive double row of kite-shaped plates rising vertically along the rounded back and the two pairs of long spikes extending horizontally near the end of the tail. Although large individuals could grow up to 9 m (29.5 ft) in length and 5.3–7 metric tons (5.8–7.7 short tons) in weight, the various species of Stegosaurus were dwarfed by contemporaries, the giant sauropods.

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The Pentaceratops wins easily as its armored head and horns will deal more damage to the stgosaurus than the letter could do to the former with its tail whip.
No one wins easily here. Not only have stegosaur tail muscles proven strong enough and their tail spikes proven durable enough to go through bone (1, 2, 3; this is an Allosaurus caudal with a puncture wound that fits a thagomizer spike), but the joints in a stegosaur tail were apparently not locking and were consequently flexible with muscle attachments down to the tail tip (for what it's worth, Bob Bakker compared it to a monkey's tail, which would explain how the tail spikes managed to hit the ventral surface of an Allosaurus), allowing for not just power, but precision on where the tail spikes hit (perchance a blow to the throat?).

As for how much damage those could cause, according to Mallison (2011) (first source I posted) "Prescribed motion models based on a CAD range of motion analysis of Kentrosaurus and motions observed in extant long-tailed reptiles give results consistent with those of models using torque values calculated from detailed CAD reconstruction of muscle cross sections and moment arms. Both indicate that the tail of Kentrosaurus was a dangerous weapon, capable of inflicting painful slashing injuries and debilitating penetrating trauma, even on large theropods, across a large portion of its motion range. Continuous rapid motion was at least sufficient for the spikes to slash open the integument or penetrate soft tissues and fracture ribs or facial bones, while aimed whiplash blows may have had sufficient energy to fracture sturdy longbones.".

Fracturing facial bones and even sturdy longbones is some pretty serious damage output. And that's for Kentrosaurus: imagine what the far larger Stegosaurus could do. I don't necessarily think the horns of Pentaceratops were any less damaging or lethal, but the precision with which stegosaurs could apparently land their blows coupled with the damage they were capable of means that this is no easy foe for the ceratopsid, as formidable as it is.
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[-] The following 3 users Like Ausar's post:
  • OldGreenVulture, Taipan, Verdugo
Nice info there, the stegosaurus spikes are stronger than excepted, however, there is nothing mentioning the spikes going through the tri horns frill although these spikes can do some damage to the face. The tri horn still has longer and thicker horns that can pierce deeper than the spikes.
Quote:Nice info there, the stegosaurus spikes are stronger than excepted, however, there is nothing mentioning the spikes going through the tri horns frill although these spikes can do some damage to the face.

The frill is not a vital region, nor are the horns (not to mention Stegosaurus would be unlikely to land the pointed tips of its tail spikes on a horn due to the amount of surface area a comparatively elongated horn has, as well as the tiny surface area the pointed spike tips had), so there would be no point in targeting those. The point is that the facial bones of even large animals could be damaged by stegosaur tail spikes, and the frill of Pentaceratops doesn't cover its face.

Quote:The tri horn still has longer and thicker horns that can pierce deeper than the spikes.

But that doesn't really matter. Horns are puncturing/impaling weapons. And while stegosaur tail spikes certainly punctured, the whole system functioned as a striking/swiping weapon. Comparing the two by the length of the sharp projections and how far they puncture is an apples to oranges comparison because they're used too differently; you're not going to judge a spiked mace because its spikes aren't super duper long and won't penetrate anywhere near as deeply as a spear. Of course, an exaggerated comparison (Stegosaurus' tail spikes would be far longer and thicker relative to the ceratopsian's horns than the spikes on a spiked mace would be relative to a spear, anyway), but one that gets the point across.
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Since Stegosaurus could puncture through bone, I think that it would win more often than not. If Pentaceratops would manage to gore Stegosaurus into the side, it would open itself for a counter-attack. After the first charge, ceratopsian's horns would not be hitting Stegosaurus with high speed, while Stegosaurus would continue hitting Pentaceratops as fast as it did the first time, so in a long fight Stegosaurus would win.
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