Tiuclaenus minutus Muizon & Marshall, 1987

Muizon, Christian de, Billet, Guillaume & Ladevèze, Sandrine, 2019, New remains of kollpaniine “ condylarths ” (Panameriungulata) from the early Palaeocene of Bolivia shed light on hypocone origins and molar proportions among ungulate-like placentals, Geodiversitas 41 (25), pp. 841-874 : 856

Tiuclaenus minutus Muizon & Marshall, 1987

DIAGNOSIS. — See Muizon & Cifelli (2000).

DESCRIPTION

A maxilla with M1-3 (MHNC 13879) is referred to Tiuclaenus minutus . It bears three almost unworn molars, and has been referred to this species essentially on the basis of its size ( Fig. 10A ). Tiuclaenus minutus is the smallest “condylarth” species of the Tiupampa fauna and the molars of the new specimen are even slightly smaller than those of MHNC 1240 described by Muizon & Cifelli (2000: fig. 7C). For example, the length of the molar row is 5.86 mm in MHNC 13879, while it is 6.74 mm on MHNC 1240, but such a size difference is likely related to individual variation. The size and proportions of the upper molar of this specimen depart from the other species of Tiuclaenus and from Pucanodus , which are distinctly larger (see Muizon & Cifelli 2000: tables 7-9). However, some slight morphological differences exist between the specimens referred to T. minutus , which differ in the larger size of the para- and metastyles, the para-and metacones more approximated, the more pronounced ectoflexus and labial cingulum. Nevertheless, in spite of these morphological differences we tentatively refer MHNC 13879 to T. minutus , considering that they could regarded as related to individual variation, an interpretation that could be revised when a larger sample of that species will be available.

Figures

FIG. 10. — A, Tiuclaenus minutus: partial right maxilla of with M1-3 (MHNC 13879), stereophotograph of occlusal view; B, Tiuclaenus robustus: partial right mandible with m2-3 (MHNC 13875), stereophotograph of occlusal view; C, the same in labial view. Scale bar: 5 mm.