IANIGLA   20881
INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
PALEOPROTEOMIC ANALYSIS OF THE RELATIONSHIPS OF QUATERNARY WEST INDIAN FOLIVORANS (PILOSA, XENARTHRA)
Autor/es:
MACPHEE, R.D.E.; PRESSLEE, S. ; FORASIEPI, A.M.; FERANEC, R.S.; COLLINS, M. ; SLATER, G.; BLOCH, J.I.
Lugar:
Calgary
Reunión:
Jornada; 77th ANNUAL MEETING SOCIETY OF VERTEBRATE PALEONTOLOGY; 2017
Resumen:
A diverse assemblage of folivorans (sloths) occupied several islands in the West Indies from at least as early as the Early Miocene until the middle Holocene. Although often viewed as monophyletic and megalonychid by relationship, other family-level dispositions as well as a diphyletic origin have been asserted for this group in the past, mostly on the basis of morphology. Attempts to test these arguments with paleogenomic information have had limited success: DNA does not survive well in hot, wet localities like caves?virtually the only contexts in which folivoran fossils occur in the West Indies. Collagen is also subject to degradation under such conditions, but degrades more slowly. We successfully recovered collagen Ia1 and/or Ia2 sequence information from Cuban and Hispaniolan specimens of species of Parocnus, Acratocnus, and Neocnus, as well as from mainland North and South American mylodontids (4 spp.), megatheriids (2 spp.), and megalonychids (1 sp.). Sequence results for extant Choloepus hoffmanni, Bradypus tridactylus, Cyclopes didactylus, and Dasypus novemcinctus, as well as extinct Glyptodon and Doedicurus spp., were also included to permit a robust Bayesian phylogenetic analysis that simultaneously sampled tree topologies and branching times. Divergence time calibrations were integrated using a model allowing fossil occurrences to be treated as distinct lineages rather than node age prior distributions. Most traditional groupings were recovered on the maximum clade credibility tree, with the following important exceptions: (1) extant Choloepus strongly grouped with mylodontids, while (2) the Acratocnus-Neocnus clade paired with megatheriids, to the exclusion of megalonychids in both cases. It is noteworthy that grouping 1 is supported by recent aDNA studies, while grouping 2 is consistent with some morphological studies that couple Acrotocnini/Neocnini with schismotheriine megatheriids (e.g., Hapalops). Although not all relevant West Indian and mainland taxa are represented in this preliminary analysis, the diphyly argument for extinct Caribbean sloths now seems unlikely, all taxa having seemingly diverged within Megatheriidae. Our mean estimate for the divergence time of the MRCA of the West Indian taxa vs. other megatheriids is 24.0 Ma, during the Oligo-Miocene transition. The empirical age of the oldest named insular taxon, Imagocnus zazae (Lagunitas Fm, Domo de Zaza, Cuba), is mid- Burdigalian (18.5-17.5 Ma) and thus in good temporal agreement with the divergence estimate.