A deep groove extends from the dorsomedial margin of the flexor tubercle, terminating just posterior to the missing distal tip. At its inception, this groove is placed in the lower 1/3 of the dorso-ventral complex, a form maintained for 3/4 of the claw’s curvature. However, this placement rapidly migrates dorsally at the 3/4 point until it reaches the top 1/3 of the bone. The groove reaches its maximum width halfway through the claw’s total length. A similar groove can be found on the lateral side of the claw. However, this groove is much deeper, a feature that may also be in part due to erosion of the medial surface. The lateral groove differs substantially from the medial one in that it thins radically to a ‘crack-like’ form 3/4 of the way through the medial groove’s duration.
The flexor tubercle is large and robust, being subequal in width to the dorsal margin of the articular facet. Its form, whose posterior margin is placed anterior to the articular facet, is subtriangular in both posterior and ventral views. A deep, median ridge divides the articular facet, which is oval-shaped in posterior view. The ventral portion of this ridge is especially bulky, being twice as thick as the maximum width reached by the midline. The articular surface for the condyles of the penultimate phalanx is deeper on the medial side than its lateral counterpart. Given the overall proportions of the ungual and its articular surfaces, the phalanx to which it was connected in life was likely equally robust.