diff --git a/python/obitools3/dms/taxo/taxo.pyx b/python/obitools3/dms/taxo/taxo.pyx
index 3cdd500..a5894f2 100644
--- a/python/obitools3/dms/taxo/taxo.pyx
+++ b/python/obitools3/dms/taxo/taxo.pyx
@@ -113,7 +113,7 @@ cdef class Taxonomy(OBIWrapper) :
             raise Exception("Not implemented")
 
 
-    cpdef Taxon get_taxon_by_taxid(self, int taxid):
+    cpdef Taxon get_taxon_by_taxid(self, int taxid):   # TODO check deleted taxon behavior (403122)
         cdef ecotx_t* taxon_p
         cdef object   taxon_capsule        
         taxon_p = obi_taxo_get_taxon_with_taxid(self.pointer(), taxid)
@@ -254,7 +254,10 @@ cdef class Taxonomy(OBIWrapper) :
            first ancestor to the root.
         """
         cdef Taxon taxon
-        taxon = self.get_taxon_by_taxid(taxid)
+        try:
+            taxon = self.get_taxon_by_taxid(taxid)
+        except:  # TODO error handling (related to deleted taxon thing)
+            raise StopIteration
         if taxon is not None:
             while taxon.parent.taxid != 1:   # TODO was 0 before? 
                 yield taxon
@@ -264,6 +267,10 @@ cdef class Taxonomy(OBIWrapper) :
             raise StopIteration
 
 
+    def is_ancestor(self, int ancestor_taxid, int taxid):
+        return ancestor_taxid in [x.taxid for x in self.parental_tree_iterator(taxid)]
+
+
     def last_common_taxon(self, *taxids):
         
         cdef list  t1