santhAnak kuravar are the gurus who gave to this world the philosophy of shaiva sidhdhantha.They are in two classifications.

agach chandhAnak kuravar

They are four in number. They are not the normal human beings but the ones who live in the Holy Mount kailash (deva paramparai). The Prime Guru of this tradition is the Supreme guru dakshiNAmUrthi. These four gurus are:

1. thirun^an^dhi dhEvar
2. sanath kumArar
3. sathya nyAna dharshinigaL
4. paranychOdhi munivar

Adhi guru shrI dakshiNamUrthi is the guru for thirun^an^dhi dhEvar. thirun^an^dhi dhEvar is the guru of sanath kumArar and so on.

puRach candAnak kuravargaL

சந்தானாசாரியர் புராண சங்கிரகம்
 

They are also four in number. This tradition starts with the last in the agachchandhAnak kuravar - paranychOdhi munivar as the root. The four generations of disciples in this tradition are:

Meykandar (More detailed one) மெய்கண்டார் வரலாறு  ஸ்ரீமெய்கண்டதேவர் நான்மணிமாலை

Arul Nandhi shivam  அருணந்தி சிவாச்சாரியார் வரலாறு

Marainyana Sambandhar  மறைஞான சம்பந்தர் வரலாறு

Umapathi Shivachchariyar

paranychOdhi munivar was the guru of meykaNDAr. The four mentioned above lived in this earth (bUdha paramparai) in thamiz land and gave answers to much difficult philosophical questions in the form of shaiva sidhdhanthic explanations. Further disciples of this tradition established the mutts at thiruvAvaDuthuRai and dharumapuram (namachchivAya mUrthikaL and gurunyAna chamban^dhar respectively). Since this tradition starts from Lord dakshiNAmUrthi at Holy mount kailash, the two mutts get the titlekayilAya paramparai. The philosophic texts composed by the san^thAna kuravar are called santhAna n^UlgaL(1). (A few of them are composed by others who are not part of this four). These fourteen are regarded as the sAththiram (basis, scriptures) texts.

See Also: 
1. Meykanda Noolkal or Chanthaana Noolkal

2.  சந்தானசாரிய புராண சங்கிரகம்

3.  சமயாசாரியர் சந்தானாசாரியர் சரித்திர சங்கிரகம்