See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/289502778 Phylogeny of the Xenarthra – morphological reconstruction of evolutionary relationships among extant and fossil Xenarthrans Chapter · January 2008 CITATIONS READS 0 1,378 1 author: H. Gregory McDonald BLM - The Bureau of Land Management Lakewood Colorado (Retired) 171 PUBLICATIONS 4,363 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: ecology and evolution of Megalonyx View project Coprophilous Fungi View project All content following this page was uploaded by H. Gregory McDonald on 06 January 2016. The user has requested enhancement of the downloaded file. 3 Morphology-based investigations of the phylogenetic relationships among extant and fossil xenarthrans TIMOTHY J. GAUDIN AND H. GREGORY MCDONALD Resumen de la fauna eocena de Messel en Alemania. Virtual­ mente todas las reconstrucciones recientes de la filo­ En un grupo como el de los Xenarthra, en el que la di­ genia de los perezosos apoyan el origen difiletico de los versidad conocida de formas extinguidas excede por dos generos arboricolas vivientes, pero difieren en las mucho la de las vivientes, aquellos analisis morfologicos hipotesis de relaciones con diferentes taxones fosiles. que incorporen taxones fosiles aumentan su importan­ Un comprehensivo analisis reciente ubica a Bradypus cia al mejorar nuestra comprension de la filogenia. En como el taxon hermano de los restantes perezosos y este estudio se revisan las investigaciones morfologicas reune a Choloepus con los megaloniquidos extingui­ recientes sobre filogenia de los xenartros. Se resaltan dos. Este estudio corrobora la monofilia de las familias las areas de amplio consenso, induyendo la monofilia Nothrotheriidae, Megatheriidae, Megalonychidae y de Xenarthra, de cada uno de sus tres subgrupos prin­ Mylodontidae, apoya la alianza de notroteridos, mega­ cipales [Cingulata, Vermilingua, Phyllophaga (= Tardi­ teridos y megaloniquidos en un dado Megatheriodea grada 0 Folivora)] y de los Pilosa [Vermilingua + Phy­ y, dentro de este ultimo grupo, reune a notroteridos Hophaga]. Tambien se revisan los estudios recientes de y megateridos en un dado Hamado Megatheria. Las las relaciones supraordinales del grupo, asi como los relaciones entre estas familias de perezosos, particu­ amilisis filogeneticos dentro de los Cingulata, Vermi­ larmente Mylodontidae y Megalonychidae, asi como lingua y PhyHophaga. Las afinidades de Xenarthra con la taxonomia alfa de todos los xenartros, requieren de otros grupos de mamiferos placentarios aun gene ran nuevos estudios. controversias y requieren de mas investigaciones. Den­ tro de los Cingulata aun son poco comprendidas la ta­ Resumo xonomia y la filogenia de los gliptodontes y se requie­ ren mas estudios, aunque los analisis recientes prove en Em urn grupo como 0 dos Xenarthra, em que a diversi­ nueva informacion sobre la sistematica de este grupo. dade conhecida de formas extintas excede com muito a Un estudio dadistico confirma hipotesis filogeneticas vivente, os estudos morfologicos que incorporam tax­ previas sobre las relaciones entre armadillos extingui­ ons fosseis aumentam sua importancia, ao melhorar dos y vivientes, pampaterios y gliptodontes, induyendo nossa compreensao da filogenia. Nesse estudo, revisam­ la monofilia de los eufractinos vivientes y un dado que se os estudos morfologicos recentes sobre a filogenia reune a gliptodontes y pampaterios y la posicion basal dos xenartros. Resaltam-se as areas de amplo consenso, de los dasipodinos dentro de los Cingulata. Sin em­ induindo 0 monofiletismo de Xenarthra, de urn de seus bargo, no sostiene la monofilia de los armadillos como tres sub-grupos [Cingulata, Vermilingua, Phyllophaga un todo 0 de los tolipeutinos, eutatinos y eufractinos. (= Tardigrada ou Folivora) e dos Pilosa [Vermilingua + Con respecto a los Vermilingua, las relaciones entre los Phyllophaga]. Tambem, revisam-se os estudos recentes miembros indiscutidos del grupo no produce contro­ das relayoes supra-ordinarias do grupo, assim como as versias, pero existe un gran desacuerdo sobre la ubi­ analises filogeneticas dentro dos Cingulata, Vermilin­ cacion de Eurotamandua, el presunto oso hormiguero gua e Phyllophaga. As afinidades de Xenarthra como 24 Phylogenetic relationships among extant and fossil xenarthrans 25 ""'--- , _, ,~x <; '~~,,_~.'-.: . '.~ ~ PHYLLOPHAGA CINGULATA VERMILINGUA (= TARDIGRADA) Figure 3.1. Cladogram depicting the relation­ ship among the three suborders of Xenarthra: Cingulata, Vermilingua, and Phyllophaga (= Tardigrada or Folivora). The alliance of anteat­ PILOSA ers and sloths in a monophyletic Pilosa to the exclusion of armored xenarthrans has been supported by a wide variety of subsequent mor­ phological and molecular studies (see Introduc­ tion). Animals depicted across the top, from left to right: Doedicurus (Pleistocene, SA), Chaeto­ phractus (hairy armadillo), Myrmecophaga (giant anteater), Choloepus (two-toed sloth), Megath­ erium (pleistocene, SA). Modified from Gaudin (2003). Abbreviations: SA = South America. outros grupos de mamiferos placentarios ainda geram ultimo grupo, reune os notroteriideos e megateriideos controversias e requerem mais estudos. Urn estudo em urn dado chamado Megatheria. As relac;:6es entre dadistico confirma hip6teses filogeneticas previas sobre estas familias de preguic;:as, particularmente Mylodon­ as relac;:6es entre tatus extintos e viventes, pampaterios tidae e Megalonychidae, assim como a taxonomia alfa e gliptodontes, induindo 0 monofiletismo dos eufracti­ de todos os xenartros, requer novos estudos. nos viventes, e urn dado que reune os gliptodontes e pampaterios, e a posic;:ao basal dos dasipodinos dentro Introduction dos Cingulata. Apesar disso, nao sustenta 0 monofile­ tismo dos tatus como urn to do, ou dos tolipeutinos, eu­ Historically, the roots of systematic analysis in biol­ tatinos e eufractinos. Com respeito aos Vermilingua, as ogy lie in comparative studies of organismal morphol­ relac;:6es entre os membros indiscutiveis do grupo nao ogy. Linnaeus (1758) based his great Systema Naturae produz controversias, mas existe urn grande desacordo on similarities in overall form among the organisms sobre a posic;:ao de Eurotamandua, 0 presumido taman­ he surveyed. The systematists and taxonomists of the dua da fauna eocenica de Messel na Alemanha. Virtual­ eighteenth and nineteenth centuries who constructed mente todas as reconstruc;:6es recentes da filogenia das much of the basic taxonomy of living and extinct xen­ preguic;:as ap6iam uma origem difiletica dos dois gene­ arthrans did so on the basis of morphology (much ros de preguic;:as arboricolas viventes, contudo diferem of this early literature is reviewed in Hoffstetter 1958, sobre as hipoteticas relac;:6es com diferentes taxons f6s­ 1982; Glass 1985; Wetzel 1985a). Individual species and seis. Uma analise recente posiciona Bradypus como 0 higher-level taxa have been recognized using external taxon-irmao das preguic;:as rest antes e reune Choloepus morphological or skeletal characteristics, be they living com os megaloniquideos extintos. Esse estudo cor­ (Wetzel 1985a) or extinct (Hoffstetter 1958). The various rob ora 0 monofiletismo das familias Nothrotheriidae, groupings and sub groupings within Xenarthra were Megatheriidae, Megalonychidae e Mylodontidae, ap6ia established largely on the basis of skeletal and dental a alianc;:a de notroteriideos, megateriideos e megalo­ traits (appendix 3.1, figure 3.1): the Cingulata, the ar­ niquideos em urn dado Megatherioidea e, dentro deste mored xenarthrans, which bear a carapace formed by 26 T. J. Gaudin and H. G. McDonald a mosaic of dermal ossifications and epidermal scales, should continue to playa vital role in improving our can be divided into armadillos, with their peglike teeth, knowledge of the phylogenetic history ofXenarthra. and pampatheres, with enlarged bilobate teeth, both of Recent advances in the study of xenarthran phylog­ which have imbricating osteoderms that allow flexibil­ eny utilizing both morphological and molecular in­ ity in the carapace, and the glyptodonts, with their very vestigations have been reviewed by Garcia (2003) and peculiar trilobate teeth and immobile carapaces; the Gaudin (2003). In addition, a separate chapter (Delsuc Vermilingua or anteaters, which have tubular, edentu­ and Douzery this volume) treats recent developments lous skulls; and the Phyllophaga (= Tardigrada or Foliv­ in the use of mitochondrial and nuclear gene sequences ora), including the living tree sloths and extinct ground to examine relationships of extant xenarthrans. There­ sloths, which share a hypselodont herbivorous denti­ fore, in this chapter we will focus on morphology-based tion and a characteristic reduced dental formula with investigations of phylogeny that have been published a maximum of five upper and four lower teeth in each subsequent to Gaudin (2003), while also considering half of the jaw (Gaudin 1999a). Armadillos, anteaters, pertinent earlier studies that have laid the groundwork and sloths were originally placed in different groups by for our current understanding of the phylogeny of the Linnaeus, with armadillos assigned to his Bestiae along group. We will follow the basic outline of Gaudin's with pigs, some insectivores, and opossums, whereas (2003) review. First, we will consider issues related to anteaters and sloths were allocated to Bruta along with the supraordinal relationships