Problem overloading assignment operator in template class - c++

Question

Using the MS command line C++ compiler, version as indicated in the output below, compiling the following fails with the compiler report as included:
// File: shared_memory.h
template <class Contents>
class SharedMemory {
public:
...
operator Contents& () {
...
}
...
SharedMemory &operator= (Contents &contents) { // [EDIT] CONST REMOVED AT PARAMETER
...
}
...
};
// File: shared_memory_test.cpp
class SharedAnimals: public SharedMemory <Animals> {
...
using SharedMemory <Animals>::operator=; // [EDIT] HAD TO BE ADDED
...
}; // This is line 67 in the original code
int main (int argc, char** argv) {
...
Animals animals (kind);
...
sharedAnimals = animals; // This is line 93 in the original code
...
}
// Compiler reports:
shared_memory_test.cpp
C:\Program Files (x86)\Microsoft Visual Studio\2017\BuildTools\VC\Tools\MSVC\14.16.27023\include\xlocale(319): warning C4530: C++ exception handler used, but unwind semantics are not enabled. Specify /EHsc
shared_memory_test.cpp(93): error C2679: binary '=': no operator found which takes a right-hand operand of type 'Animals' (or there is no acceptable conversion)
shared_memory_test.cpp(67): note: could be 'SharedAnimals &SharedAnimals::operator =(SharedAnimals &&)'
shared_memory_test.cpp(67): note: or 'SharedAnimals &SharedAnimals::operator =(const SharedAnimals &)'
shared_memory_test.cpp(93): note: while trying to match the argument list '(SharedAnimals, Animals)'
Can anyone give me a hint on what I am doing wrong?
[EDIT]
Indeed the answer at Assignment operator inheritance provided by user1810087 solved the problem.
While the answer is already there, the context of this question, namely using a template class, led me to believe that the error was connected to that, and did not look for questions relating to "assignment operator inheritance".
Since I may not be the only one running into this, I suggest this question be maintained.