My teacher told me my generic data mapper was not a data mapper and now I'm confused

I received an assignment to implement a small system using the data mapper pattern for the data tier. I did not want to do the repetitive task of writing every single mapper for every single entity and I was restricted to not use any libraries or frameworks to do the mapping, so I implemented a generic mapper using reflection to generate SQL scripts with the following interface (pseudocode-like):

Mapper {

    create (Class) {
        create table in database using Class as reference;
    }
    create (object) {
        insert object into database;
    }

    read (Class, filters...) {
        return a list of objects that match the class specification in the database using the provided filters;
    }

    update(object) {
        update row of the database that has object's primary key with the values in object;
    }

    delete(Class) {
        drop table in the database that has the Class specification;
    }

    delete(object) {
        remove row that has the object's primary key;
    }
}

I would then use Java annotations to specify primary keys and foreign keys as well as String size constraints inside the classes I wanted to use it with. Upon giving the completed assignment to my teacher he told me I had implemented an active record instead of a data mapper and now I'm confused as to whether that's correct or not. Is that really not a mapper? He didn't give me a reason, just said that I essentially implemented Hibernate and that it wasn't a mapper.