Contemporary images of 13th century Saracen mounted-crossbowmen are rare but they do exist.
An image of an Ayyubid mounted-crossbowman on a Glass Water-Flask, Syria, 1250-60 (http://www.warfare.altervista.org/13/Ayyubids_on_a_Glass_Flask-crossbow.htm). The trigger mechanism can be seen.
(http://forums.totalwar.org/vb/attachment.php?attachmentid=17202&d=1452304792)
Other illustrations of Ayyubids on a Glass Water-Flask, British Museum 1869,0120.3 (http://www.warfare.altervista.org/13/Ayyubids_on_a_Glass_Flask-1250-60.htm)
Another illustration from the Levant is The base of the Freer Canteen, with friezes of Christian or Muslim horsemen including two mounted-crossbowmen. (http://www.warfare.altervista.org/13/Freer_Canteen-Base.htm)
(http://forums.totalwar.org/vb/attachment.php?attachmentid=17203&d=1452304805)
From a later period is Mamluk mounted crossbow & bow shooting (http://www.warfare.altervista.org/15/Arabe2824-82r.htm) in Kitsab al-makhzun jami` al-funun by ibn akhî hizâm - A Mamluk manual of military practice and horsemanship, Egypt or Syria, 1470 (http://www.warfare.altervista.org/15/Arabe2824-Kitab_al-makhzun-1470.htm)
Druzhina
Illustrations of Egyptian and Syrian Costume & Soldiers (http://www.warfare.altervista.org/Egypt.htm)
Beautiful D
8)
Cheers - Phil
As you say, very rare. Another good find.