Get taxonomy parent using child slug (from merged taxonomies)

Since in most cases I would need to now the ‘taxonomy’, one work around I found (actually, pointe by @Howdy_McGee) was to pass the slug of the term and it’s parent to the value, and then split-string.

Here is my final code:

foreach ($tax_categorias as $tax_categoria) {
    echo '<option value=". $tax_categoria->slug .".'. $tax_categoria->taxonomy .'' . $selected . '>' . $tax_categoria->name . '</option>';
}
$ads_cat = $_GET['ads_filt_categorias'];
$list($ads_filt_categorias,$ads_categorias) = explode('.', $ads_cat);