A cenozoic dinosaur what-if

This is book material.

But keep a few things in mind:
1) Many dinosaurs just plain weren't very bright. Mammals would outcompete a lot of them due to that alone.
2) Evolutionary pressures work, even on isolated species. You only need to do 2 things in the evolutionary arms race: live long enough to reproduce, and then do so successfully. Large reptilian species would either have to evolve better intelligence, etc. to compete (see #1). So, they would most likely not remain unchanged.
3) As for their reactions, see #1 and #2. They would either evolve to compete better, or go extinct.

Keep in mind, Chixclub is only one part of dinosaur extinction.

I see. Thanks for your answer. You know:i've heard,through time that the reason why dinosaurs last for almost two hundred milions of years was because they were very succesful. And I also heard that they were pretty much better than mammals,in this. But i wasn't so sure about. Damn:i can't really stop imagine a sauropod interact with a gonphotherium. Or a theropod having to deal with a saber tooth tiger. And yeah:this can surely be some very good book material,ahahah! I should really write some. Let's see if someone want to give his/her answer on this.

It sounds like you are speculating about a combat scenario between the mammals of N. America and the "Dinosaurs" of S. America, suddenly clashing with each other in Panama and wondering which would "win".

Putting aside for a moment the fact that "Dinosaurs" is a very broad grouping of a range of very different animals which would make it hard to estimate a direct conflict, just in a general I feel that environments have more to do with species success/failures than interactions between species (or Classes). So I suspect that instead of an exciting gladiatorial combat between Classes, it would actually be more like a very slow interaction throttled by the environments, allowing for new things to evolve in the middle.

Over eons one Class might decimate the other, or press it into obscurity, but I think it's more likely they would simply coexist like birds and mammals of today.

There are examples of large reptiles alive today, crocs and large lizards, that are essentially unchanged from their ancestors who lived with dinosaurs. You can read up on them if you are still interested. Also, apex predators usually don't routinely fight each other, too much risk, too little reward.

well, thi i an interesting topic because several subclasses of reptiles and mammals were able to evolve during the mesozoic. The "What if" could also work in reverse . If enough, say theropods lived and were not the giants that we actually were thinking about, we could have several new orders of little dinos that became more like "Avemammalia"(beaked mammals) or maybe water dwelling things like some forms of descendents of pleisiosaurs. But evidence of a major unconformity marked by the iridium zone of the K/N line.

As Jes says, this would be a great big neat book tale. We should team write it eh? (we need some Canadian help 0n this.Send a snowplow to Ehbeth and Set).
Ill elect myself in charge of naming the new species . We need a timeline

That...would be amazing! I really have no words to describe your suggestion! It's a really great idea!

Okay, I've got Word open.

I have only one question,at this point:from what we start,exactly? You know:i would never expect to see you so interested to this what-if to this point. You really caught me unprepared

Depends on how fictitious you want to go. Do you want a what-if scenario with science? Or more of a fight on the isthmus?

Did you ever see the "Walking With" series,especially the Mesozoic and Cenozoic ones? I think we could use a similar approach. They would really fit with this what-if concept,as inspiration.

could you contruct a brief outline and we will follow it K?

Ok. This is what i come up with:
1)Our mesozoic survivors most be only and strictly from South America
2)The book will be divided in seven sectioms,each one from every cenozoic period:paleocene,eocene,oligocene,miocene,pliocene,pleistocene and holocene
3)The first four of this chapter will be concentrated only on south america,since our non-avian dinosaurs and eventually other cretacean reptiles descendants won't go outside the continent and will stay almost exclusively in there. Is in the fifth one that we will concentrate also on North America,with the isthmus of Panama formation. The others two chapters will be concentrated also in Africa and Europe,with the ice age. It will be you to decide if it should be better divide or not this sections in various chapters.
4)For all the book's sections a narrator will describe,in a scientific but enough understandable and charismatic way the environment,the animals and also what will come after the period he describe(he have to attire the reader's interest,you know). Almost exactly like in the "Walking With" series. Also,if you want...we can also add some illustrations,to better describe this things and some "behind the scenes" chapters.
5)We won't describe only non-avian dinosaurs:we almost exclusively will,in the first four chapters because of the fact that,since they will be limited only to the south america they on't affect too much the rest of the world,that,so will be almost identical to our's. But we will describe at least partially other animals class,that existed also in our world,like sabertooth tigers or ancient proboscideans because they will interact with our alternative dinosaurs and probably will take different ways:it can be entirely possible that animals like mammoth will not exist or exist aniway,but in a very different way. We will have to describe,in short the different consequences that some survived south american non-avian dinosaurs will create,in the rest of the world.

And...that's all,for the moment. I hope that could be enough,for you,to define at least partially the new book's scheme

Doctor Who has touched on this. The Silurians and Sea Devils were both intelligent biped 'dinosaurs' who sheltered underground to avoid the collision with the moon. They were to be revived once the collision was over, but it never happened because the moon became the moon.

Obviously this is very different from your concept but you might want to check some of it out.

It is very different indeed. But yeah:why not.