Gallolestes pachymandibularis, LILLEGRAVEN, 1976

Archibald, J. David & Averianov, Alexander, 2012, Phylogenetic analysis, taxonomic revision, and dental ontogeny of the Cretaceous Zhelestidae (Mammalia: Eutheria), Zoological Journal of the Linnean Society 164 (2), pp. 361-426 : 405

GALLOLESTES PACHYMANDIBULARIS LILLEGRAVEN, 1976 .

(See Appendix 4 for synonymies, referred illustrations, and referred specimens.)

Holotype: LACM 42633 , right dentary with fragmented p4, dp5, and m1-3.

Type locality and horizon: LACM locality 3302, Baja California del Norte, Mexico. ‘ El Gallo Formation’, Late Cretaceous (late Campanian) .

Revised diagnosis: About 40% larger than G. agujaensis in dental measurements.

Description: See Lillegraven (1976: 438–440) and Clemens (1980: 2–3).

Measurements: See Lillegraven (1976: tab. 1).

Comments: We follow Butler (1977, 1990) in the interpretation of the last premolar on the holotype of G. pachymandibularis as a milk tooth, dp5, contra our previous claim that this tooth is a molariform p5 (Archibald & Averianov, 2001; see also discussion in Lillegraven, 1976; Clemens, 1980; Nesov et al., 1998; Kielan-Jaworowska, Cifelli & Luo, 2004). The deciduous nature of this tooth was rejected on the ground that ‘the roots are well formed, very unusual for a deciduous tooth that was soon destined to be shed’ (Archibald & Averianov, 2001: 543). The roots of this tooth, however, actually are formed as well as in some dp5s of zhelestids from Dzharakuduk having the same state of wear. The smaller size relative to m1 and the much heavier wear strongly argue that this is a milk tooth. As was pointed out by Clemens (1980), retention of the last deciduous premolar until the m3 has erupted is quite unusual. In the Asiatic Zhelestinae dp5 is replaced when m3 is not fully erupted (see the next section). A similar delay in replacement of dp5 was noted for the zalambdalestid Barunlestes by Butler (1990).