ptr.133.19.16.81.static.yourvserver.net has no NS records.
NS records for this zone are defined at yourvserver.net.
NS records for this zone are defined at yourvserver.net.
Question and response
Question
dig ptr.133.19.16.81.static.yourvserver.net. NS
Answer
The response has no answer records.
Authority
yourvserver.net. 7200 SOA root-dns.netcup.net. dnsadmin.netcup.net. 2026010900 28800 7200 1209600 7200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0