-- I have an animal table describing species
create table myschema.animal (
   species varchar2(64) primary key,
   region varchar2(64)
);
-- and some tables extending the animal
create table myschema.animal_mammal (
   species varchar2(64), -- foreign key
   max_height number,
   quadrupedal number(1) default 1 -- 0 or 1
);
create table myschema.animal_bird (
   species varchar2(64), -- foreign key
   max_wingspan number,
   number_of_eggs number
);