BOND mariano
congresos y reuniones científicas
Critical analysis of the alleged characters used to link afrotherian mammals American native ungulates
La Plata
Jornada; XXIV Jornadas Argentinas de Mastozoología; 2011
Institución organizadora:
Facultad de Ciencias naturales y Museo de La Plata, UNLP
Critical analysis of the alleged characters used to link afrotherian mammals and SouthAmerican native ungulatesBond M.(1,2,3), Kramarz A.(2,4), Gelfo J.N.(1,2,3), López G.M.(1,3), Lorente M.(1,2) andReguero M.(1,2)(1) División Paleontología de Vertebrados, Museo de La Plata. (2) CONICET (Consejo Nacional deInvestigaciones Científicas y Técnicas). (3) Cátedra Paleontología de Vertebrados, Facultad de CienciasNaturales y Museo de La Plata, UNLP. (4) MACN. studies claimed that the South American native ungulates (SANU) grouped in the ordersLitopterna Notoungulata, Astrapotheria, Xenungulata and Pyrotheria, were related to afrotherianmammals based on the alleged shared occurrence of three characters: (1) late eruption ofpermanent dentition relative to jaw growth, (2) presence of a cotylar fossa in the astragalus and(3) more than 19 thoracolumbar vertebrae. Here we review the presence of these charactersamong SANU and assess their validity as synapomorphies to ally them with afrotherians. (1) Thedelayed dental eruption relative to jaw growth was confused with a delayed premolarreplacement, and there is no evidence of an afrotherian-like delayed eruption among SANU,except in few late diverging notoungulates. (2) The cotylar fossa is the anterior extension of themedial malleolar facet that deepens into a cup and receives the condylar articular surface of thetibial medial malleolus. Concavities on the medial side of the astragalus have been oftenconfused with this character. A true cotylar fossa is absent in all known Pyrotheria, Xenungulata,and Litopterna; it is present in the astragali presumably assigned to Didolodontidae?condylarths? and in late diverging astrapotheres and notoungulates, but not in their earliestforms. (3) The presence of more than 19 thoracolumbar vertebrae positively occurs inAstrapotherium and in some notoungulates and litopterns, but it is variably observed in theknown skeletons of ?Macrauchenia patachonica and ?Toxodon platensis. Other SANUinterpreted as having this feature (e.g. ?Protypotherium, ?Pachyrukhos) have no knowncomplete thoracolumbar series, and the occurrence of this condition was merely inferred. In sum,these characters were incorrectly identified in most SANU and, when present, they are highlyvariable and/or limited to the more derived lineages. We therefore conclude that these charactersare insufficient to support a phylogenetic relationship between SANU and Afrotheria.