Invalid use of template-name ‘Queue_el’ without an argument list

Hello i bet it is just a tiny thing but i can´t find an ansewer anywhere, so in my code i get this error:

queue.cpp:33:3: error: invalid use of template-name ‘Queue_el’ without an argument list
   Queue_el*<T> head<T>;
   ^
queue.cpp:34:3: error: invalid use of template-name ‘Queue_el’ without an argument list
   Queue_el*<T> tail<T>;
   ^
queue.cpp: In constructor ‘Queue<T>::Queue()’:
queue.cpp:37:13: error: ‘head’ was not declared in this scope
   Queue() { head=nullptr; tail=nullptr; }
         ^
queue.cpp:37:27: error: ‘tail’ was not declared in this scope
   Queue() { head=nullptr; tail=nullptr; }

Here is the Code:

using namespace std;

template<typename T>
class Queue;

template<typename T>
class Queue_el {
        private:
                T value;
                Queue_el* next; 
                Queue_el* prev;

        public:
                Queue_el() { value=0; next=nullptr; prev=nullptr; }
                Queue_el(T n) { value=n; next=nullptr; prev=nullptr; }

        friend class Queue<T>;
};
template<typename T>
class Queue {
        private:
                Queue_el*<T> head;
                Queue_el*<T> tail;

        public:
                Queue() { head=nullptr; tail=nullptr; }
                void push(T);
                int pop();
                bool empty() const;
                int size() const;
};

Now i don´t understand that because I wrote

Queue_el*<T> head;
Queue_el*<T> tail;

So the list should be there.