congresos y reuniones científicas
DELAYED DENTAL ERUPTION IS NOT A SHARED CHARACTERISTIC OF AFROTHERIAN MAMMALS AND SOUTH AMERICAN NATIVE UNGULATES
KRAMARZ, A., GELFO, J.N., BOND, M., LÓPEZ, G.M., LORENTE, M. AND M. REGUERO
Congreso; IV Congreso de Paleontología de Vertebrados; 2011
Universidad Nacional de San Juan
DELAYED DENTAL ERUPTION IS NOT A SHARED CHARACTERISTIC OF AFROTHERIAN MAMMALS AND SOUTHAMERICAN NATIVE UNGULATESA. KRAMARZ1,2, J.N. GELFO2,3,4, M. BOND2,3,4, G.M. LÓPEZ3,4, M. LORENTE, 2,3 and M. REGUERO2,31MACN, Av. A. Gallardo 470, 1405 CABA, Argentina. email@example.com Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)3División Paleontología de Vertebrados, Museo de La Plata. Paseo del Bosque s/n, B1900FWA La Plata, Argentina4Cátedra Paleontología de Vertebrados, Facultad de Ciencias Naturales y Museo de La Plata, UNLP.In a recent paper, Agnolin and Chimento (2011) claimed that the endemic South American ?ungulates? Notoungulata, Astrapotheria, and possiblyPyrotheria, are closely related to Afrotheria by sharing a late replacement of deciduous cheek teeth. This statement was based on: (1) the usual occurrencewithin these groups of individuals with deciduous and permanent teeth; (2) the impossibility of discriminating adults or senile individuals ofthese groups (with permanent premolars erupted) from juveniles (with deciduous premolars), when using the length/width ratio of cheek teeth toevaluate the total size of an individual; and (3) the retention of at least dP1?dP3 in adult or senile specimens of Parastrapotherium Ameghino 1895.More recently, Billet and Martin (2011) demonstrated categorically that there is no delayed dental eruption relative to skull growth in notoungulates,except in a few late-diverging lineages. Herein we critically examine the presumed existence of delayed dental eruption in astrapotheres, pyrotheres andxenungulates and the assumptions on which this was based. In most eutherians the DP4/4 is usually replaced before the eruption of M3/3, thus thecoexistence of deciduous and permanent teeth (e.g. DP4/4 and M1/1) does not necessarily indicate that the permanent cheek teeth finished eruptingafter adult body size was reached. Among taxa where no juveniles are known, the eruption of P4/4 before the M3/3 can be inferred in adults whenP4/4 is more worn than M3/3). The ontogenetic stage of astrapotheres, pyrotheres and xenungulates cannot be inferred though length/width ratioof molars because they are brachydont and their size is defined before eruption. In the only known specimen of the pyrothere Griphodon peruvianusAnthony 1924 with dp4, m1 and encrypted p3-4, the mesial part of alveolus of m2 is as deep as the p4, suggesting that both teeth would have eruptedalmost simultaneously, before the m3. In Astrapotherium magnum Burmeister 1879 (the only astrapothere in which the complete ontogenetic seriesis known) the p4 also erupted before m3. The timing of dental eruption relative to jaw growth in this species indicates that specimens with less than90% adult jaw length have more than 60% of permanent cheek teeth, as seen in the YPM PU 15332, whereas afrotherian specimens of 95% adult jawlength have much less than 60% of permanent cheek teeth (Asher and Lehmann, 2008). In all known adult specimens of Parastrapotherium Ameghinothe cheek teeth formula is unmistakably P3-4/3-4, M1-3/1-3 (Kramarz and Bond, 2008), and in no known astrapothere are the deciduous premolarsretained in adult stages as was claimed by Agnolin and Chimento (2011). In the xenungulates Carodnia vieirai Paula Couto 1952 and Etayoa bacatensisVillaroel 1987, the P4/4 shows more wear than M3/3. Consequently, we conclude that there is no evidence of delayed dental replacement inastrapotheres, pyrotheres and xenungulates that could support afrotherian affinities for these mammals.Agnolin, F. and Chimento, N. 2011. Afrotherian affinities for endemic South American ?ungulates?. Mammalian Biology 76:101?108.Asher, R. and Lehmann, T. 2008. Dental eruption in afrotherian mammals. BMC Biology 6:1?11Billet, G. and Martin, T. 2011. No evidence for an afrotherian-like delayed dental eruption in South American notoungulates. Naturwissenschaften 98:509?517.Kramarz, A.G. and Bond, M. 2008. Revision of Parastrapotherium (Mammalia, Astrapotheria) and other Deseadan astrapotheres of Patagonia. Ameghiniana45: 537?551.