Planops martini, S UNGUAL, Hoffstetter, 1961

ILLUSTRATION OF PLANOPS MARTINI ’ S UNGUAL

PHALANX

In the original description of P. martini Hoffstetter, 1961 , the author mentions an ungual phalanx twice without figuring it. The first mention is in the description of the lot that corresponds to the holotype (‘trois phalanges dont une ungueale’; [three phalanges, including one ungual]; Hoffstetter, 1961: 61). The second mention of the ungual phalanx, in the description itself, is written in the conditional tense, denoting the hesitation of the author regarding the attribution ( Hoffstetter, 1961: 80). There, the author mentions the second digit of the manus. The description states that this phalanx is less compressed than in Hapalops , that the dorsal side is transversely rounded, the palmar side flattened, and that the ungual bears a weak proximodistal curvature. Since the publication of Hoffstetter (1961), the ungual phalanx of the second digit of the manus has been described in an additional nothrotheriid, Mionothropus ( De Iuliis et al., 2011) , and in Thalassocnus ( Amson et al., 2015a) . It has already been emphasized that the semicircular cross-section of the ungual process of the second digit of the manus is a distinctive traits of nothrotheriids [ McDonald & Muizon (2002), ch. 28; Muizon et al. (2003), ch. 30; De Iuliis et al. (2011), ch. 55] and of the early species of Thalassocnus , T. antiquus (the later species of the genus being characterized by a dorsopalmar flattening of this process; Amson et al., 2015a), as this cross-sectional shape is not found in other digits or taxa. As the ungual process of the ungual phalanx of the holotype of P. martini features this distinctive cross-sectional shape, and hence strongly resembles those of nothrotheriids and of T. antiquus , we can today confirm Hoffstetter’s (1961) tentative attribution. Given the systematic importance of this phalanx (see below), an illustration is included herein ( Fig. 9 View Figure 9 ).