Interacial union (at the beginning)

[Bruton the Iguanodon]

did u notice at Littlefoots birth there were all sorts of critters gathered there. What the hell I thought all kinds kept to their own...we find that out later...

[DarkHououmon]

I think the whole "everyone keeps to their own kind" bit may have been mostly for dinosaurs. And even some of the dinosaurs are generally more accepting. Flyers may never had had the aggressive type of racism displayed by threehorns (the most I recall seeing is Pterano thinking his kind is better than everyone else's but he wasn't hostile about it). And swimmers may generally be more accepting, as Ducky's mom adopted Spike right away without needing pressuring from anyone else to make that decision.

[jansenov]

I agree with DarkHououmon. But I would also add some tidbits.

I think Litlefoot's mother was refering to the culture she was a part of - the leafeaters. Everybody sticks to their species, but the herds still live together and share the same food and water. They speak the same language. On the other hand, the critters you speak of and the sharpteeth are not a part of this culture and Littlefoot's mum may not have been thinking about them when she said that. She never mentioned the sharpteeth, after all. The sharptooth way of live is incompatible with that of the leafeaters, and many of the critters who appeared at Littlefoot's birth are probably too primitive to speak and have notions of speciesm (with the exception of pterosaurs, who appear to be a tolerant bunch throughout the whole movie).

[Bruton the Iguanodon]

Yeah, I guess i kinda knew that anyways...just kinda had to get it out. Littlefoot even chases a hopper (frog) at one point; that would qualify as the primitive kind, right? And unless you're a swimmer like Mo, the grasshoppers in LBT 11.