First record of supernumerary teeth in Glyptodontidae (Mammalia, Xenarthra, Cingulata)

GONZALEZ-RUIZ, L.; CIANCIO, M.R; MARTIN, G.; ZURITA, A. E

JOURNAL OF VERTEBRATE PALEONTOLOGY

SOC VERTEBRATE PALEONTOLOGY

Lugar: Lawrence; Año: 2015 p. 1 - 6

0272-4634

The Glyptodontidae (Cingulata) (late Eocene?early Holocene) (Scillato-Yané, 1977; Carlini and Scillato-Yané, 1999) comprise a clade of armored herbivorous xenarthrans and, like the rest of Xenarthra, have a particular and distinct dentition from other mammals; they are characterized by being homodont, monophyodont and euhypsodont (Gillette and Ray, 1981). The molariform teeth of gliptodonts lacks enamel (like most xenarthrans) and are structurally composed of a central axis (with or without branches of osteodentine), surrounded by a matrix of orthodentine and an external layer of orthodentine hardened by minerals (Ferigolo, 1985; McDonald, 2003; Vizcaíno, 2009; Kalthoff, 2011). Glyptodonts have eight trilobed and triprismatic molariform teeth in each hemimaxilla and eight in each dentary (Mf 8/mf 8), none of them located in the premaxillary bone. In some taxa, the first two or three have a simpler morphology (i.e., not trilobed) and they are called incisiforms though without implying homologies (Ameghino, 1889; Scott, 1903; Hoffstetter, 1958; Paula Couto, 1979; Gillette and Ray, 1981; Pujos and De Iuliis, 2007). A remarkable reduction in the number of teeth (n=32), relative to the typical eutherian (n=54) and placental (n=44) dental formulas, occurs in Glyptodontidae (Gillete and Ray, 1981; Ji et al., 2002; O´Leary et al., 2013). Despite ongoing work, tooth homologies for this group (i.e., Xenarthra) could not be established yet. This is because the most basal forms have a particular and distinct dentition and their teeth do not correspond with, or show a known homology to, the typical dental classification used for mammals (i.e., incisors, canines, premolars and molars) (McAfee and Naples, 2012; Ciancio et al., 2012). The dentition of Xenarthra is unique among mammals and does not retain the tribosphenic condition (Gillette and Ray 1981; Engelmann, 1985; Fariña, 1985; Fariña and Vizcaíno, 2001; McDonald, 2003; Vizcaíno, 2009). In this contribution we describe the first case of supernumerary teeth for a glyptodont (Glyptodontidae, Xenarthra) and discuss possible explanations for its occurrence.