This tradition has been narrated on the authority of Sufyan with the addition from Abd ar-Razzaq (one of the narrators) explaining the meaning of shikal as a bone whose right back foot and left front foot or left back foot and right front foot are white.
عَنْ سُفْيَانَ بِهَذَا الإِسْنَادِ مِثْلَهُ وَزَادَ فِي حَدِيثِ عَبْدِ الرَّزَّاقِ وَالشِّكَالُ أَنْ يَكُونَ الْفَرَسُ فِي رِجْلِهِ الْيُمْنَى بَيَاضٌ وَفِي يَدِهِ الْيُسْرَى أَوْ فِي يَدِهِ الْيُمْنَى وَرِجْلِهِ الْيُسْرَى