kenney sez-I believe there are the main species among dinosauria and alot of mixxed breeding.there was continental shift,a multitude of volcanic activity and not to mention Islands popping up and disapearing,land bridges came and went.so i have a theory/idea that dinosaurs found themselves broke off from the main herds and come mateing time reacted accordingly.for example;I believe that ceratopsians were probably the most prevailiant w/this.monoclonius,triceratops,chasmeosaur,styracosaurus i believe they were all mateing and breeding so that here we keep finding all these new variations and its actually just a new blend,not a new species.several different theropods like a daspletosaurus female finds a t-rex male and recently volcanic activity trapped a variety of dinosaurs in a valley or whatever scenario your imagination can come up with i say they found the species compatable enuff to breed."life finds a way" and all that.this is my idea,not my fact…so I want to see what everyone else has to say???_—-KENNEY(ksdinoboy95@gmail.com)

mmm.... interesting but its pretty hard for different species to mate... for example nowadays , boars and pigs do mate,and wild and domestic gooses too.. but i find unlikely for diferent species of ceratopsians to mate successfully

interspecies mating is a possibility, successfully? i guess we may never know. horses and donkeys make a mule, but a mule cant reproduce. environmental changes also weigh on behavior, and evolution makes sure the animal adapts accordingly, if the animal can it will change drastically. the frills on ceratopsians could be different due to genetic mutation, weather and environment could influence this, theres no real way to tell, look at dogs though, multiple species of dog mate together when secluded like in a breeding house, seclusion could provoke this, in the animal kingdom, the urge to mate and further the species, sex, is the most powerful urge of all. its one of the roots to life, mating, making sure theres a new generation. its almost hard wired in the very genes that make life up. ya know? theres a ton of evidence for both sides the fence, i think studying todays life more closely we can make a better educated guess, but will e ever know for sure?

I believe I agree with Kenny as far as the situation of environmental obstructions closing off habitats and confining species, affecting both inter or infra, into a partially or totally closed system. Ecologically speaking, species related closely enough are prone to at least attempt to inter-mate, successful or not. Such situations would definitely cause one to take a second glance at the wide array of ceratopsian frill displays. Granted, things like mutations and abnormal defects will always show up in the fossil record whether we recognize them or not. And then there is the subject of inbreeding in completely closed systems. Very interesting topics. When you see two ceratopsians so similar in appearance, one wonders if one is looking at the same species with bad abnormalities, or two different species all together.

Of course without seeing Dinos in the wild there is no way to know but I would think that interbreeding was at least rare. Modern species that are similar in appearance still don't get together much. Some probably did it more than others, like some have mentioned the ceratopsians and I think the different varieties of Tyrannosaurids may have been more likely.Today things like the shape and size of antlers and other appendages makes a difference among members of particular species and I think it was probably the same in the Dino world.