Chasmosauri were apparently Canadian, discovered in Alberta from 75-76 million years ago they don purely ornamental head gear attached with up to 24 spikes. They vary greatly between individuals causing controversy among once valid species and such as in the case of triceratops vs torosaurus, genus. Interestingly enough, a nearly complete juvenile specimen and as well as skin impressions were also found, perhaps belonging to chasmosaurus.
“Chasm lizards” shared their habitat with centrosaurs in the Campanian age where earth’s climate was warmer and dinosaur diversity exploded. They were larger than most buffaloes at 1-2 tons and 4-5 meters in length and traveled in herds in tens or hundreds as many individuals have been found deposited together in fossil sites.
Mapusaurus roseae means “red earth lizard” named after a dig sponsor, Rose Letwin, and for the rock strata color of the formation where its fossils were found. Although not the biggest theropod on record, these carcharodontosaurs (shark toothed reptiles) perhaps were tolerant enough of each other to hunt in fearsome packs, bringing down prey as immense as whales.
Several individuals of various ages were discovered in a rare and isolated bonebed, though, not inclusive of pack behavior a group would be able to take on gigantic residents such as a fully grown Argentinosaurus, about thirty-five meters and eighty tons of titanosaur. Their serrated teeth, unlike those of tyrannosaurs, would be perfectly suited for mob attacks on large prey where bones would be too big to crush but flesh could be easily sliced off in sizeable chunks. Any sauropod who could not fend off swarming Mapusaurusi would eventually succumb to a grizzly death either by blood loss or infection.
Mapusaurus exceeded lengths of 10 meters and three tons in weight, they were apex predators existing with smaller agile abelisaurs such as Skorpiovenator and Ilokelsia. They inhabited arid woodlands with seasonal rivers 95 mya in Late Cretaceous Argentina.