Unable to find any PTR-records for the specified domain/ip :(
Log
+000
Resolving PTR record of '54.239.16.0'
+101
ERRNo PTR record availible DNS server 'pdns4.ultradns.org' raised an NotExistentDomain error, while beeing queried for PTR-records on domain '0.16.239.54.in-addr.arpa'.