Answer:
The climate in that area is different today than when tropical plants and animals lived there
Explanation:
The most likely reason for the absence of those tropical animals in North Texas would be the climate.
Climatic conditions have varied through geologic history of our blue planets. When these conditions changes, organisms have to adapt and on the long run, the environment won't be able to sustain them. They become phased out.
It is possible for rock records in a place to bear different fossil records records that are not similar compared to the life we have in such areas today.
The Sahara desert for example has huge fossils of fishes in its rocks. Today, the area is a hot desert and contains very low biodiversity. Sciencist have proposed that the region was previously a lush green tropical forest and the ocean covered some parts too. Today, the Sahara's climate has changed.
