अध्य्-एकायनम्

अभिप्रायान्तरम्

एकायनशाखा कठस्यैवोपशाखासीद् इत्यनिमेषः - द्वयोर् अपि काश्मीरमूलत्वात्।
मानसतरङ्गिणीकृतो ऽभिप्रायः पृथग् रक्षितः।

Source: RavilochanaH

There is no record of an ekayana shakha in sukla yajur Veda. Rather pAncharAtra texts talk abt kanva shakha only. Otoh a pancaratra sruti and pancaratra upanishad are quoted by kashmira shaiva acharyas like utpala. My presumption is that just as taittiriya shakha has vaikhanasa branch with its own mantrapatha, pancaratrins must have been of kanva shakha with some mantrapatha/sruti of their own.

The primary pAncharAtra guys have to be of kanva shakha following katyayana sutra. Should also belong to one of the five gotras - bhAradvaja, kaushika, maunjayana, aupagayana and another one. Jayakhya makes it clear that kanva shakha of SYV is what pAncharAtra is affiliated with. And ekayana is naturally a school of that shakha.

Ekayana/pancaratra sruti and upanishad have been quoted in Kashmir texts prior to yamunas time. Which makes me think that they had a pAncharAtra mantrapatha - similar to the vaikhanasa one.

Desikan quotes a katyayana upanishad as evidence for urdhvapundra. This upanishad is also published by adyar library. Said publication also has a sudarshanopanishad which has been quoted as well by Desikan.