Interspecies Conflict/the biggest dinosaur after sauropods
1) 20t shantungosaurus vs 18t songhua river mammoth
2) 20t shantungosaurus vs 16t indricotherium
3) 20t shantungosaurus vs 10t tyrannosaurus rex
4) 20t shantungosaurus vs 7t acrocanthosaurus
5) 20t shantungosaurus vs 4x 600kg utahraptor
6) 20t shantungosaurus vs 30t apatosaurus
7) 20t shantungosaurus vs 2x 5t megatherium
1) 20t Shantungosaurus vs 18t Songhua river mammoth: Shantungosaurus was a huge hadrosaur with a large body and a long tail. It had the ability to walk upright or on all fours (and was likely the largest animal to ever walk on 2 legs), and was probably a good swimmer. Shantungosaurus had numerous tightly-packed teeth for crushing vegetation, and powerful legs that enabled it to run swifty. Fossils of this hadrosaur were found in close proximity to one another, suggesting this animal formed herds. The stiff tail of Shantungosaurus may have been used to swing at predators, but fast running, safety in numbers, and refuge in water were probably its primary avenues of protection/survival. The Songhua river mammoth (now known to be a Steppe mammoth of smaller size) was a massive pachyderm armed with long, curved tusks (more useful as impact weapons than stabbing weapons). In a battle between these 2, the Shantungosaurus will have difficulty shielding itself from the charges of the mammoth, and won't be able to generate offense more readily or effectively as the mammal will. It's unlikely that Shantungosaurus was skilled at fighting, and will be a bit outmatched by the mammoth. Edge to Songhua river mammoth.
2) 20t Shantungosaurus vs 16t Indricotherium: Indricotheriums (also known as Paraceratheriums) were likely the largest mammals ever to walk the earth. A full-grown one had nothing to fear due to its size, and probably didn't need to fight any animal of another species. A face-off between Shantungosaurus and Indricotherium would probably end up with the 2 animals staring at each other with no interest in any hostility. Assuming these 2 decided to engage, both would be ill-equipped to inflict any major damage to one another. Indricotherium might have delivered bites (like Indian rhinos of today will do), but no one is really sure. The Indricotherium would be harder to topple off its base in a collision of bodies, but there's no way to know if that action would even occur. With 2 animals that use means other than serious combat to defend themselves, it's hard to assign one as the favorite. I think the Indricotherium has the edge at parity, but the Shantungosaurus might have the edge with a 25% weight advantage. Probably a stalemate, though.
3) 20t Shantungosaurus vs 10t Tyrannosaurus rex: Tyrannosaurus was the most famous of theropods, and was a fearsome carnivore that likely struck fear into any herbivore it encountered. It had strong back legs, a thick-based tail, and a huge skull that sported extremely powerful jaws armed with dagger-like teeth. Shantungosaurus is twice as heavy in this scenario, and is the stronger dinosaur, but has no real way to employ its size/weight advantage as an effective means of combat against the Tyrannosaurus. It might be able to temporarily repel the theropod with a solid tail strike (if that's what it does), but will be in trouble against one that's determined to kill it. The jaws of the Tyrannosaurus will create large avulsions on the Shantungosaurus' body with each bite, and the herbivore will need to flee to keep from becoming dinner. It's certainly a possibility that Shantungosaurus can use its bulk to its advantage in certain situations (considering its size & speed), but it won't be favored in most encounters with a Tyrannosaurus if it stands its ground. Tyrannosaurus is practiced at tackling large animals (including dangerous ones like ceratopsians), and Shantungosaurus simply isn't a fighter. Edge to Tyrannosaurus-rex.
4) 20t Shantungosaurus vs 7t Acrocanthosaurus: Acrocanthosaurus was a carnivorous theropod that routinely preyed on sauropods that exceeded the size of the hadrosaur Shantungosaurus. With its powerful jaws and sharp teeth, Acrocanthosaurus would have been able to inflict serious wounds rather easily on the body of Shantungosaurus. This won't be a battle of 2 willing participants like most matchups; the Shantungosaurus will be looking to flee/escape. Even though Acrocanthosaurus is only slightly above 1/3 of Shantungosaurus' weight, its means of offense is much greater. The hadrosaur might be able to knock the theropod back with its tail for a short time, but will need to utilize its speed & elusiveness to ensure its survival. If surprised by Acrocanthosaurus, the Shantungosaurus will probably be powerful enough to pull away (and avoid fatal wounds) before the theropod can overcome it. Unlike a sauropod that won't be fast enough to escape if no water is nearby, the hadrosaur will use its powerful legs to run (some estimates of its speed approach 50kph) and create separation. I don't think Acrocanthosaurus will be able to easily overpower Shantungosaurus in a realistic situation (where the hadrosaur looks to escape), but will kill it if it unwisely chooses not to flee. Depends on how you look at it.
5) 20t Shantungosaurus vs 4x 600kg Utahraptor: Utahraptor was a uniquely-armed theropod (jaws/teeth, clawed forelimbs for grabbing, clawed hindlimbs for kicking & slashing) with good agility (stiff tail for making quick turns) and leaping ability. It is believed they hunted in groups, and were capable of using their numbers (and formidable weaponry) to overcome large prey items. Shantungosaurus had relatively tough hide and a muscular body, but no way to effectively repel a group of Utahraptors looking to dig into it. Once the Utahraptors leap upon the Shantungosaurus' body and cling to it, the hadrosaur won't be able to shake them off without great difficulty or use its tail to strike at them. Because the Shantungosaurus will weigh 30 times as much as each Utahraptor and have considerable bulk, it will take the theropods a long time to subdue it. The Shantungosaurus' only hope will be escape into water, perhaps breaking into a run to make them fall off, or an unwillingness to put forth the effort by the Utahraptors. The Utahraptors might not attempt this kill, but will have a decent chance to succeed (eventually) if they do. It's a lot like 4 Velociraptors (15kg) making the attempt to subdue an animal as large as a Grevy's zebra. Overall edge to Utahraptors.
6) 20t Shantungosaurus vs 30t Apatosaurus: Apatosaurus (formerly known as Brontosaurus) is likely the most famous of the sauropods, and one of the most recognizable dinosaurs. It has stout body, 4 pillar-like legs, a long neck, and a long tail. Apatosaurus likely used its tail to strike attackers (like Allosaurus). Even though Shantungosaurus is a faster, more mobile animal than Apatosaurus, it can't capitalize on these advantages because it has no real weaponry to utilize. Its swinging tail (assuming it did this at all) might be more than an annoyance to the larger Apatosaurus, but a solid swing from the sauropod's tail might have decent effect on the hadrosaur. With most (but not all) hostile herbivore encounters the large animal tends to get its way, and that will be the case here. Apatosaurus wins.
7) 20t Shantungosaurus vs 2x 5t Megatherium: Megatherium (giant sloth) was a huge mammal that could stand taller than a giraffe and intimidate other animals with its large size and long clawed forelimbs. Megatherium's body was also well-protected by tiny pieces of bone (osteoderms) that formed an armor much like chain mail underneath its furry hide. The drawback of this mammal in combat was its inability to move swiftly. In this matchup, the Megatheriums won't able to move laterally quickly enough for their claws to be true offensive weapons, but they can plant itself in one spot and offer a good defense with them. Realistically, any encounter between these parties will likely result in indifference, but the Shantungosaurus will be too large & fast for the Megatheriums to do much damage to if hostilities arise. The Shantungosaurus has the size & strength to bowl each Megatherium over if it decides to throw its weight around, but it probably won't do this without being injected with a magical dose of aggression. The hadrosaur might back away if it gets swiped at, but weighing 4 times as much as each Megatherium weighs heavily in its favor if it decides to push the issue. The Megatheriums are better protected and better armed for combat, but don't have much to offer the much larger (and more mobile) Shantungosaurus. Edge to Shantungosaurus.