Make sure your form mapping contains at least an entry for the DataViewList entity. The corresponding form will also be used for objects with an entity not defined in the form mapping (since all entities in the set derive from the DataViewList entity).
If there is no form defined for the DataViewList entity (Animals), and an object in the set has an entity other than the ones defined in the form mapping (Pets and WorkAnimals), the DataViewList just stops loading because there is no form to show (this behavior is also described in this post).
The DataViewList can be placed anywhere, because it does not depend on its context. I must agree that the documentation is not very clear on this point. Be careful though with nesting the DataViewList, or placing it in a TemplateGrid, for this may cause performance issues.
PS: the DataViewList will show descriptive warning and error messages in the console (navigate to index-console.html for debug mode).
Can you explain:
'Start'form has: Dataview (animals) with first row showing an attribute and second row containing the datalistview
It sounds like you have an dataview of a list of objects?! You can just add the dataviewlist as root widget (wrapped in a table) in the form to display a list of animals. You can use the widget in about the same situations as a template grid.
Note that 'list' stands for, a list of objects, not a list of formtypes (allthough that is true as well).