Seems that mountd dissector is not a dedicated dissector. It seems that it is part of the portmap dissector:
```c

extern FUNC_DECODER(dissector_mountd);

RPC_DISSECTOR Available_RPC_Dissectors[] = {
   {100005,  1, "mountd", dissector_mountd },
   {100005,  2, "mountd", dissector_mountd },
   {100005,  3, "mountd", dissector_mountd },
   {     0,  0, "", NULL }
};

```
But still I don't really understand how they with each other.