mongodump does not fully expose the cursor interfaces.
But you can work around it, using the --query parameter.
First get the total number of documents of the collection
db.collection.count()
Let’s say there are 10000 documents and you want the last 1000.
To do so get the id of first document you want to dump.
db.collection.find().sort({_id:1}).skip(10000 - 1000).limit(1)
In this example the id was "50ad7bce1a3e927d690385ec".
Now you can feed mongodump with this information, to dump all documents a with higher or equal id.
$ mongodump -d 'your_database' -c 'your_collection' -q '{_id: {$gte: ObjectId("50ad7bce1a3e927d690385ec")}}'
UPDATE
The new parameters --limit and --skip were added to mongoexport will be probably available in the next version of the tool: https://github.com/mongodb/mongo/pull/307