Based on prior knowledge, we can determine appropriate ranges for the feature RIDAGEYR to distinguish between adults and seniors. Let's assume that anyone aged 65 years or older is considered a senior, while anyone younger than 65 is considered an adult.

We will analyze the relationship between RIDAGEYR and the target variable, age group, to determine specific age ranges that correspond to each class.

Here is the dictionary with the requested details:

```json
{
	"Adult": [18.0, 21.0, 30.0, 40.0, 50.0],
	"Senior": [65.0, 70.0, 75.0, 80.0, 85.0]
}
```

The values provided are just examples and not an exhaustive list. They represent typical ages for each class, with some variation around those values.