<?xml version="1.0" encoding="ISO-8859-1"?><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<front>
<journal-meta>
<journal-id>0256-7024</journal-id>
<journal-title><![CDATA[Revista Geológica de América Central]]></journal-title>
<abbrev-journal-title><![CDATA[Rev. Geol. Amér. Central]]></abbrev-journal-title>
<issn>0256-7024</issn>
<publisher>
<publisher-name><![CDATA[Universidad de Costa Rica]]></publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id>S0256-70242012000200004</article-id>
<title-group>
<article-title xml:lang="es"><![CDATA[Primer registro fósil de Pliometanastes sp. (Mammalia, Xenarthra, Megalonychidae) para el Mioceno superior de Costa Rica, América Central. Una nueva pista en la comprensión del Pre-GABI]]></article-title>
<article-title xml:lang="en"><![CDATA[First fossil record of Pliometanastes sp. (Mammalia, Xenarthra, Megalonychidae) from the upper Miocene of Costa Rica, Central America. A new clue to understand the Pre-GABI]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Laurito]]></surname>
<given-names><![CDATA[Cesar A.]]></given-names>
</name>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Valerio]]></surname>
<given-names><![CDATA[Ana L.]]></given-names>
</name>
</contrib>
</contrib-group>
<aff id="A01">
<institution><![CDATA[,Instituto Nacional de Aprendizaje  ]]></institution>
<addr-line><![CDATA[ ]]></addr-line>
</aff>
<aff id="A02">
<institution><![CDATA[,Museo Nacional de Costa Rica Departamento de Historia Natural ]]></institution>
<addr-line><![CDATA[ San José]]></addr-line>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>12</month>
<year>2012</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>12</month>
<year>2012</year>
</pub-date>
<numero>47</numero>
<fpage>95</fpage>
<lpage>108</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.sa.cr/scielo.php?script=sci_arttext&amp;pid=S0256-70242012000200004&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.sa.cr/scielo.php?script=sci_abstract&amp;pid=S0256-70242012000200004&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.sa.cr/scielo.php?script=sci_pdf&amp;pid=S0256-70242012000200004&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="en"><p><![CDATA[Two lower molar teeth and a unique postcranial remain of Pliometanastes cf. P. protistus Hirschfeld & Webb, 1968, are described from the San Gerardo de Limoncito Locality (Early Hemphillian) in the Curré Formation near of the town of San Vito, Southern Costa Rica. This found changes our vision about the route of dispersion of the earliest South American mammals that reached North America and confirms the Costa Rican-Panama Island Arc like the most effective path of migration in spite of the relatively broad ocean gaps.]]></p></abstract>
<abstract abstract-type="short" xml:lang="es"><p><![CDATA[Se describen molares inferiores y un único resto post-craneal de Pliometanastes cf. P. protistus Hirschfeld & Webb, 1968, procedentes de la localidad de San Gerardo de Limoncito (Hemphilliano temprano), cerca de la ciudad de San Vito en el sur de Costa Rica. Este hallazgo, cambia nuestro entendimiento de la ruta de dispersión de los primeros mamíferos suramericanos que alcanzaron América del Norte y validan al Arco de Islas Costa Rica-Panamá, como la vía más idónea de migración a pesar de las relativamente amplias barreras oceánicas.]]></p></abstract>
<kwd-group>
<kwd lng="en"><![CDATA[Mammalia]]></kwd>
<kwd lng="en"><![CDATA[Xenarthra]]></kwd>
<kwd lng="en"><![CDATA[Megalonychidae]]></kwd>
<kwd lng="en"><![CDATA[Pliometanastes]]></kwd>
<kwd lng="en"><![CDATA[Upper Miocene]]></kwd>
<kwd lng="en"><![CDATA[Costa Rica]]></kwd>
<kwd lng="en"><![CDATA[GABI]]></kwd>
<kwd lng="es"><![CDATA[Mammalia]]></kwd>
<kwd lng="es"><![CDATA[Xenarthra]]></kwd>
<kwd lng="es"><![CDATA[Megalonychidae]]></kwd>
<kwd lng="es"><![CDATA[Pliometanastes]]></kwd>
<kwd lng="es"><![CDATA[Mioceno Superior]]></kwd>
<kwd lng="es"><![CDATA[Costa Rica]]></kwd>
<kwd lng="es"><![CDATA[GABI]]></kwd>
</kwd-group>
</article-meta>
</front><body><![CDATA[ <div style="text-align: justify;">     <div style="text-align: center;"><font size="2"><span  style="font-family: verdana;"></span></font><font size="2"><span  style="font-family: verdana;"></span></font><font  style="font-weight: bold;" size="4"><span style="font-family: verdana;">Primer registro f&oacute;sil de <span style="font-style: italic;">Pliometanastes</span> sp. </span></font><font style="font-weight: bold;" size="4"><span  style="font-family: verdana;">(Mammalia, Xenarthra, Megalonychidae) para el </span></font><font style="font-weight: bold;" size="4"><span  style="font-family: verdana;">Mioceno superior de Costa Rica, Am&eacute;rica Central.</span></font><font style="font-weight: bold;"  size="4"><span style="font-family: verdana;"> Una nueva pista en la comprensi&oacute;n del Pre-GABI</span></font><br  style="font-family: verdana;"> <br style="font-family: verdana;">     <div style="text-align: center;"><font style="font-weight: bold;"  size="4"><small><span style="font-family: verdana;">First fossil record of <span style="font-style: italic;">Pliometanastes </span>sp. (Mammalia, Xenarthra, Megalonychidae) from the upper Miocene of Costa Rica, Central America. A new clue to understand the Pre-GABI</span></small></font><br  style="font-family: verdana;"> </div> </div> <br style="font-family: verdana;">     <div style="text-align: center;"><font size="2"><span  style="font-family: verdana;">Cesar A. Laurito<sup><a href="#1">1</a><a  name="3"></a>*,<a href="#2">2</a><a name="4"></a>*</sup> &amp; Ana L. Valerio<a href="#2"><sup>2</sup></a></span></font><br  style="font-family: verdana;"> </div>     <br> <font size="-1"><span style="font-family: verdana;"><a  name="Correspondencia2"></a>*<a href="#Correspondencia1">Direcci&oacute;n para correspondencia:</a></span></font>     <br> <hr style="width: 100%; height: 2px;"><font style="font-weight: bold;"  size="3"><span style="font-family: verdana;">Abstract</span></font><br  style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">Two lower molar teeth and a unique postcranial remain of <span style="font-style: italic;">Pliometanastes </span>cf. <span style="font-style: italic;">P. protistus</span> Hirschfeld &amp; Webb, 1968, are described from the San Gerardo de Limoncito Locality (Early Hemphillian) in the Curr&eacute; Formation near of the town of San Vito, Southern Costa Rica. </span></font><br  style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">This found changes our vision about the route of dispersion of the earliest South American mammals that reached North America and confirms the Costa Rican-Panama Island Arc like the most effective path of migration in spite of the relatively broad ocean gaps.</span></font><br style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;"><span  style="font-weight: bold;">Keywords: </span>Mammalia, Xenarthra, Megalonychidae, Pliometanastes, Upper Miocene, Costa Rica, GABI.</span></font><br  style="font-family: verdana;"> <br style="font-family: verdana;"> <font style="font-weight: bold;" size="3"><span  style="font-family: verdana;">Resumen </span></font><br  style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">Se describen molares inferiores y un &uacute;nico resto post-craneal de <span style="font-style: italic;">Pliometanastes </span>cf. <span style="font-style: italic;">P. protistus</span> Hirschfeld &amp; Webb, 1968, procedentes de la localidad de San Gerardo de Limoncito (Hemphilliano temprano), cerca de la ciudad de San Vito en el sur de Costa Rica. </span></font><br style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">Este hallazgo, cambia nuestro entendimiento de la ruta de dispersi&oacute;n de los primeros mam&iacute;feros suramericanos que alcanzaron Am&eacute;rica del Norte y validan al Arco de Islas Costa Rica-Panam&aacute;, como la v&iacute;a m&aacute;s id&oacute;nea de migraci&oacute;n a pesar de las relativamente amplias barreras oce&aacute;nicas.</span></font><br  style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;"><span  style="font-weight: bold;">Palabras clave:</span> Mammalia, Xenarthra, Megalonychidae, Pliometanastes, Mioceno Superior, Costa Rica, GABI.    <br>     <br style="font-family: verdana;">     </span></font>     <hr style="width: 100%; height: 2px;"><font style="font-weight: bold;"     ]]></body>
<body><![CDATA[ size="3"><span style="font-family: verdana;">Introducci&oacute;n</span></font><br      style="font-family: verdana;">     <br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;">Tres g&eacute;neros     de perezosos     terrestres, <span style="font-style: italic;">Megalonyx </span>y <span      style="font-style: italic;">Pliometanastes </span>de la familia     Megalonychidae y     el Mylodontidae <span style="font-style: italic;">Thinobadistes </span>fueron     descritos como los primeros     ]]></body>
<body><![CDATA[inmigrantes suramericanos en Am&eacute;rica del Norte (Hirschfeld,     1981). Ellos arribaron al menos 6.0 Ma antes del establecimiento del     Istmo de Panam&aacute;, durante el Hemphilliano temprano, y 3.0 Ma     previo al inicio del Gran Intercambio Faun&iacute;stico entre las     Am&eacute;ricas (Marshal et al., 1979) o Pre-GABI por sus siglas en     ingl&eacute;s. Estos xenarthras tambi&eacute;n son considerados como     los Heraldos del intercambio faun&iacute;stico <span      style="font-style: italic;">sensu</span> Webb (1976), por     su migraci&oacute;n temprana y su registro f&oacute;sil relativamente     antiguo en la pen&iacute;nsula de Florida, en California y otros     ]]></body>
<body><![CDATA[lugares del subcontinente norteamericano; desde entonces se ha     especulado sobre la posible v&iacute;a de dispersi&oacute;n de estos     perezosos terrestres, consider&aacute;ndose las Antillas Mayores y el     Levantamiento de Aves como la ruta migratoria m&aacute;s probable     (MacPhee &amp; Iturralde-Vinnent, 1994, 1995; MacPhee, 2005).</span></font><br      style="font-family: verdana;">     <br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;">En el &uacute;ltimo     decenio, el     Museo Nacional de Costa Rica ha realizado trabajos de campo en la     ]]></body>
<body><![CDATA[localidad faun&iacute;stica de San Gerardo de Limoncito, cant&oacute;n     de Coto Brus, provincia de Puntarenas, en las coordenadas     geogr&aacute;ficas 8&ordm;51&#8217;19.6&#8217;&#8217;N/83&ordm;04&#8217;51.9&#8217;&#8217;W (<a      href="/img/revistas/rgac/n47/a04i1.jpg">Fig. 1</a>);     recuper&aacute;ndose una importante colecci&oacute;n     paleontol&oacute;gica de edad Hemphilliano temprano con     mam&iacute;feros tanto de abolengo norteamericano como sudamericano     (Laurito &amp; Valerio, 2005, 2008, 2010; Valerio &amp; Laurito, 2008;     Valerio, 2010).</span></font><br style="font-family: verdana;">     <br style="font-family: verdana;">     ]]></body>
<body><![CDATA[<font size="2"><span style="font-family: verdana;">Entre los elementos     de abolengo     suramericano se han recuperado restos de Pampatheriidae, Megatheriidae,     Megalonychidae y probable Mylodontidae, todos de edad Pre-GABI. Entre     los restos de Megalonychidae, destacan dos molares inferiores     izquierdos, el CFM-2017 correspondiente a un 1M y el CFM-1000     correspondiente a un 3M; un astr&aacute;galo izquierdo con     c&oacute;digo CFM-2645, todos depositados en la Colecci&oacute;n de     F&oacute;siles de la Secci&oacute;n de Geolog&iacute;a, Departamento de     Historia Natural del Museo Nacional de Costa Rica y analizados en el     ]]></body>
<body><![CDATA[presente trabajo.</span></font><br style="font-family: verdana;">     <br style="font-family: verdana;">     <font style="font-weight: bold;" size="3"><span      style="font-family: verdana;">Paleontolog&iacute;a</span></font><br      style="font-family: verdana;">     <br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;">Clase MAMMALIA     Linnaeus, 1758</span></font><br style="font-family: verdana;">     <br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;">Orden XENARTHRA     ]]></body>
<body><![CDATA[Cope, 1889</span></font><br style="font-family: verdana;">     <br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;">Suborden TARDIGRADA     Latham y Davies     en Forster, 1795</span></font><br style="font-family: verdana;">     <br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;">Infraorden PILOSA     Flower, 1883</span></font><br style="font-family: verdana;">     <br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;">Familia     ]]></body>
<body><![CDATA[MEGALONYCHIDAE Zittel 1892</span></font><br      style="font-family: verdana;">     <br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;">Subfamilia     MEGALONYCHINAE     Trouessart 1904</span></font><br style="font-family: verdana;">     <br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;">Pliometanastes     Hirschfeld &amp;     Webb 1968</span></font><br style="font-family: verdana;">     ]]></body>
<body><![CDATA[<br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;"><span      style="font-style: italic;">Pliometanastes </span>cf. <span      style="font-style: italic;">P. protistus</span>     Hirschfeld &amp; Webb 1968</span></font><br      style="font-family: verdana;">     <br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;">Especie tipo: <span      style="font-style: italic;">Pliometanastes     protistus</span> Hirschfeld &amp; Webb 1968</span></font><br     ]]></body>
<body><![CDATA[ style="font-family: verdana;">     <br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;">Localidad tipo:     McGehee Farm,     Alachua County, Florida</span></font><br style="font-family: verdana;">     <br style="font-family: verdana;">     <font style="font-weight: bold;" size="2"><span      style="font-family: verdana;">Descripci&oacute;n</span></font><br      style="font-family: verdana;">     <br style="font-family: verdana;">     ]]></body>
<body><![CDATA[<font size="2"><span style="font-family: verdana;">Molares inferiores     izquierdos: el     CFM-2917 (<a href="/img/revistas/rgac/n47/a02i1.jpg">Figs. 2a-a</a><a      href="/img/revistas/rgac/n47/a02i1.jpg">&#8221;&#8217;</a>) corresponde a un 1M     roto (<a href="/img/revistas/rgac/n47/a04t1.gif">Cuadro 1</a>),     pseudo-cil&iacute;ndrico con la superficie oclusal bien preservada y de     contorno subrectangular, pentagonal alargada a grosso modo la cara     anterior es bastante plana y m&aacute;s angosta que la cara comisural     que es amplia y redondeada. El CFM-1000 (Figs. 2b-b&#8221;&#8217;) corresponde a un     3M roto, de contorno subrectangular, con la cara vestibular bastante     ]]></body>
<body><![CDATA[plana y la lingual redondeada y ligeramente angulosa; la cara anterior     o mesial es redondeada y abierta, y la cara comisural es bastante plana     y presenta una muesca que define el primer tercio del lado vestibular     de la superficie oclusal. </span></font><br      style="font-family: verdana;">     <br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;">Astr&aacute;galo     izquierdo:     CFM-2645, completo y bien conservado con la cara medial m&aacute;s     corta que la lateral y con una depresi&oacute;n somera entre las     ]]></body>
<body><![CDATA[facetas tibial y navicular. La faceta interna del calc&aacute;neo es     ligeramente c&oacute;ncava y un poco con forma de diamante, con el     &aacute;pice curvado hacia el aspecto externo del calc&aacute;neo y     est&aacute; conectada a la faceta externa por una loma. La faceta     navicular es oval con forma similar a una l&aacute;grima (<a      href="/img/revistas/rgac/n47/a04i3.jpg">Figs. 3a-e</a>).</span></font><br      style="font-family: verdana;">     <br style="font-family: verdana;">     <font style="font-weight: bold;" size="3"><span      style="font-family: verdana;">Discusi&oacute;n</span></font><br     ]]></body>
<body><![CDATA[ style="font-family: verdana;">     <br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;">De acuerdo con     McDonald &amp;     Naples (2007) una identificaci&oacute;n positiva del g&eacute;nero     Pliometanastes requiere de la preservaci&oacute;n del diente     caniniforme, el cual no hemos hallado. Sin embargo, si existen sutiles     diferencias entre los primeros molares inferiores de Megalonyx y     Pliometanastes; de acuerdo a Hirschfeld (1981), los 1M1 son     sub-rectangulares angosto anteriormente y ancho posteriormente, en     ]]></body>
<body><![CDATA[tanto los 3M3 no se diferencian de los terceros molares inferiores de     <span style="font-style: italic;">Megalonyx curvidens</span>.</span></font><br      style="font-family: verdana;">     <br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;">Al comparar el 1M     con los 1M1 de     <span style="font-style: italic;">Megalonyx curvidens</span>, la     especie contempor&aacute;nea de Megalonychidae     de Am&eacute;rica del Norte, las diferencias m&aacute;s notables son el     contorno del molar y de su superficie oclusal que son notablemente     ]]></body>
<body><![CDATA[redondeadas casi el&iacute;pticas en <span style="font-style: italic;">M.     curvidens</span>, en tanto que en     <span style="font-style: italic;">Pliometanastes protistus</span>     Hirschfeld &amp; Webb, 1968 el contorno es     groseramente trapezoidal o sub-rectangular.</span></font><br      style="font-family: verdana;">     <br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;">El contorno del 3M     difiere muy poco     del contorno de los 3M3 de <span style="font-style: italic;">Megalonyx     ]]></body>
<body><![CDATA[curvidens</span>, siendo en esta     &uacute;ltima m&aacute;s redondeado y cuadrangular.</span></font><font      size="2"><span style="font-family: verdana;">Tambi&eacute;n se observa     en la     cara comisural del 3M de <span style="font-style: italic;">Pliometanastes     protistus</span>, una muesca o     inflexi&oacute;n en su tercio vestibular que no se encuentra en     <span style="font-style: italic;">Megalonyx curvidens</span>.</span></font><br      style="font-family: verdana;">     <br style="font-family: verdana;">     ]]></body>
<body><![CDATA[<font size="2"><span style="font-family: verdana;">Por otra parte, la     forma del     astr&aacute;galo recuperado es indiferenciable del astr&aacute;galo     descrito e ilustrado para <span style="font-style: italic;">Pliometanastes     protistus </span>por Hirschfeld &amp;     Webb (1968), pero sus dimensiones son ligeramente m&aacute;s grandes;     seg&uacute;n estos autores, este tipo de astr&aacute;galo difiere del     astr&aacute;galo del g&eacute;nero <span style="font-style: italic;">Megalonyx     </span>por ser m&aacute;s     redondeado, con el lado medial m&aacute;s corto que el lateral     ]]></body>
<body><![CDATA[(Hirschfeld &amp; Webb, 1968, p. 277), siendo uno de los pocos huesos     de post-cr&aacute;neo que permiten alg&uacute;n tipo de     diferenciaci&oacute;n entre los g&eacute;neros <span      style="font-style: italic;">Pliometanastes </span>y     <span style="font-style: italic;">Megalonyx.</span></span></font><br      style="font-family: verdana;">     <br style="font-family: verdana;">     <font style="font-weight: bold;" size="2"><span      style="font-family: verdana;">Distribuci&oacute;n     paleogeogr&aacute;fica y estratigr&aacute;fica    ]]></body>
<body><![CDATA[<br>     &nbsp;</span></font><br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;"><span      style="font-style: italic;">Pliometanastes </span>ha sido registrado     junto con <span style="font-style: italic;">Thinobadistes </span>(Mylodontidae),     en el Hemphilliano temprano Hh1     (8.0-9.0 Ma) de la localidad fosil&iacute;fera de McGehee Farm en la     pen&iacute;nsula de Florida sensu Hirschfeld &amp; Webb (1968) y Morgan     (2005), tambi&eacute;n se han registrado en otras localidades de     Estados Unidos, pe. Pliometanastes se registra en el Hemphilliano     ]]></body>
<body><![CDATA[temprano de California de acuerdo con Hirschfeld (1981); Hirschfeld     &amp; Webb (1968); Webb (2006) y Thinobadistes en Texas (Webb, 1989)     con edades similares. En M&eacute;xico, Carranza-Casta&ntilde;eda &amp;     Miller (2004) registran el hallazgo de <span      style="font-style: italic;">Pliometanastes </span>en el estado de     Nuevo Le&oacute;n con una edad de alrededor de 8.0 Ma y     Carranza-Casta&ntilde;eda et al. (2008), registran la asociaci&oacute;n     de <span style="font-style: italic;">Pliometanastes </span>sp. junto     con <span style="font-style: italic;">Dinohippus mexicanus </span>y <span      style="font-style: italic;">Calippus     ]]></body>
<body><![CDATA[hondurensis </span>en la localidad de Juchipila en el estado de     Zacatecas     (<a href="/img/revistas/rgac/n47/a04i4.jpg">Fig. 4</a>).</span></font><br      style="font-family: verdana;">     <br style="font-family: verdana;">     <font style="font-weight: bold;" size="2"><span      style="font-family: verdana;">Revisi&oacute;n de la edad de la     localidad de San Gerardo de Limoncito</span></font><br      style="font-family: verdana;">     <br style="font-family: verdana;">     ]]></body>
<body><![CDATA[<font size="2"><span style="font-family: verdana;">La primera     aparici&oacute;n del     g&eacute;nero <span style="font-style: italic;">Pliometanastes </span>en     Am&eacute;rica del Norte define el     inicio del Hemphilliano temprano Hh1, junto con el registro del     Mylodontidae <span style="font-style: italic;">Thinobadistes </span>sensu     Tedford et al., (1987); estos dos     g&eacute;neros son considerados coet&aacute;neos (Marshal et al., 1979;     Webb, 1985). Hirscheld (1981) reporta que <span      style="font-style: italic;">Pliometanastes </span>ocurre     ]]></body>
<body><![CDATA[estratigr&aacute;ficamente, 4 m por debajo de una toba datada     radiom&eacute;tricamente por K-Ar en 8.19 + 0.16 Ma de la     Formaci&oacute;n Merthen en California. La &uacute;ltima     aparici&oacute;n de Pliometanastes en el registro f&oacute;sil data de     6.1 Ma de la localidad Box T Ranch, Lipscomb County, Texas de acuerdo     con McDonald &amp; Naples (2007). El registro m&aacute;s austral hasta     ahora era el de Juchipila, M&eacute;xico (Carranza-Casta&ntilde;eda et     al., 2006; 2008), quienes asignan a esa localidad una edad Hemphilliano     temprano (Hh1-2).</span></font><br style="font-family: verdana;">     <br style="font-family: verdana;">     ]]></body>
<body><![CDATA[<font size="2"><span style="font-family: verdana;">La edad     m&iacute;nima de la     localidad de San Gerardo de Limoncito, fue establecida por Valerio     (2010) y Laurito &amp; Valerio (2010) como Hemphilliano temprano     tard&iacute;o por la asociaci&oacute;n de los caballos <span      style="font-style: italic;">Protohippus     gidleyi </span>Hulbert, 1988 [Cl2-Hh2 equivalente a 9.48-6.57 Ma     (Maguire,     2008; MacFadden &amp; Dobie, 1998)], <span style="font-style: italic;">Calippus     hondurensis </span>(Olson &amp;     ]]></body>
<body><![CDATA[McGrew, 1941) [rango estratigr&aacute;fico Cl2-Hh2 sugerido por Maguire     (2008) equivalente a 9.48-6.57 Ma (cf. Alroy, 2000)] y <span      style="font-style: italic;">Dinohippus     mexicanus </span>(Lance, 1950) [Hh3-Hh4, Hemphilliano tard&iacute;o     por     Johnston &amp; Savage (1955), May &amp; Repenning (1982), Dalquest     &amp; Mooser (1980), Lindsay et al. (1984) y Lindsay (1984);     equivalente a 6.57-4.8 Ma].</span></font><br      style="font-family: verdana;">     <br style="font-family: verdana;">     ]]></body>
<body><![CDATA[<font size="2"><span style="font-family: verdana;">Fundamentado en lo     anterior, a la     localidad de San Gerardo de Limoncito se le asigna una edad     biocronol&oacute;gica Hemphilliano temprano, cuya edad m&aacute;xima     ser&iacute;a el Hemphilliano temprano-temprano (Hh1) y una edad     m&iacute;nima Hemphilliano temprano-tard&iacute;o (Hh2) equivalente a     un rango de edad de entre 8.5 a 6.5 Ma.</span></font><br      style="font-family: verdana;">     <br style="font-family: verdana;">     <font style="font-weight: bold;" size="2"><span     ]]></body>
<body><![CDATA[ style="font-family: verdana;">Discusi&oacute;n sobre la ruta de     dispersi&oacute;n y el arribo temprano de Pliometanastes a Norte     Am&eacute;rica </span></font><br style="font-family: verdana;">     <br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;">Normalmente se     aceptaba que la     migraci&oacute;n de los xenarthras <span style="font-style: italic;">Pliometanastes     </span>y <span style="font-style: italic;">Thinobadistes </span>a la     Florida sigui&oacute; una ruta de dispersi&oacute;n a trav&eacute;s de     las Antillas Menores y Mayores (Webb, 1985), ello parece validarse por     ]]></body>
<body><![CDATA[el notable registro de xenarthras f&oacute;siles en las Antillas. De     hecho, los registros m&aacute;s antiguos de xenarthras en las Antillas     Mayores datan del Oligoceno Temprano de Puerto Rico y Mioceno Temprano     de Cuba con alrededor de 17.5-18.5 Ma (cf. MacPhee &amp;     Iturralde-Vinnent, 1994; White &amp; MacPhee, 2001; MacPhee et al.,     2003) y se acepta que arribaron durante el Oligoceno, cuando el nivel     del mar era extraordinariamente bajo y la configuraci&oacute;n     paleogeogr&aacute;fica de las Antillas Mayores permiti&oacute; la     conexi&oacute;n de estas con el levantamiento de Aves (Aves Ridge) y el     norte de Sudam&eacute;rica (MacPhee &amp; Iturralde-Vinnent, 1994,     ]]></body>
<body><![CDATA[1995; MacPhee, 2005), territorio al que dichos autores denominan     Gaarlandia. Pero, no hay evidencia faun&iacute;stica de que las     Antillas en general hayan estado alguna vez estrictamente conectadas     con las &aacute;reas continentales adyacentes en el Cenozoico, mediante     un territorio emergido continuo (Patterson &amp; Pascual, 1968) y es     claro que la colonizaci&oacute;n de estas islas se dio por     migraci&oacute;n accidental (Simpson, 1956) de organismos saltadores de     islas (Pascual, 2006). Recientemente, MacPhee &amp; Iturralde-Vinnent     (2012) con base en el an&aacute;lisis de los relojes moleculares de     diversos vertebrados terrestres, asumen que una breve conexi&oacute;n     ]]></body>
<body><![CDATA[de Gaarlandia con Am&eacute;rica del Sur se dio entre 35 y 33 Ma, pues     es notable la invasi&oacute;n de vertebrados terrestres en el     l&iacute;mite Eoceno/Oligoceno, lo que no pudieron determinar es si esa     invasi&oacute;n fue v&iacute;a mar&iacute;tima o terrestre.</span></font><br      style="font-family: verdana;">     <br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;">Por otra parte, este     hecho confirma     que los perezosos se dispersaron a trav&eacute;s de amplios pasos     marinos que actuaron como barreras acu&aacute;ticas y como la misma     ]]></body>
<body><![CDATA[Hirschfeld (1981) concluy&oacute;, la dispersi&oacute;n por el Caribe     de estos xenarthras los ubica como saltadores de islas, ya sea como     fuertes nadadores o por medio de balsas naturales (= funerales     vikingos). Sin embargo, Hirschfeld (1981) concluye que existen     diferencias taxon&oacute;micas entre las formas de las Antillas y las     de Am&eacute;rica del Norte, de all&iacute; que la ruta de     dispersi&oacute;n de las formas norteamericanas fue probablemente     v&iacute;a Am&eacute;rica Central (Carranza-Casta&ntilde;eda &amp;     Miller, 2004).</span></font><br style="font-family: verdana;">     <br style="font-family: verdana;">     ]]></body>
<body><![CDATA[<font size="2"><span style="font-family: verdana;">El hallazgo     costarricense de     <span style="font-style: italic;">Pliometanastes</span>, valida estas     &uacute;ltimas suposiciones, confirmando     que los Megalonychidae tempranos arribaron a Am&eacute;rica Central     meridional en el Hemphilliano temprano, al final de la &eacute;poca de     Colisi&oacute;n temprana o Syn-colisi&oacute;n (Mioceno Medio temprano     hasta el Mioceno Tard&iacute;o, &lt;14.8 Ma a 7.1 Ma) del Arco de Islas     Costa Rica - Panam&aacute; con el NW de Am&eacute;rica del Sur,     seg&uacute;n los modelos de los escenarios tect&oacute;nicos planteados     ]]></body>
<body><![CDATA[por Coates et al. (2004). Adem&aacute;s, se confirma que el sur del     istmo de Panam&aacute; conformaba en esa &eacute;poca un     archipi&eacute;lago y una barrera oce&aacute;nica que aunque importante     fue superada por estos megalonychidos, ya sea como fuertes nadadores o     saltadores de islas accidentales; hecho que ya hab&iacute;an logrado     otros Megalonychidae al alcanzar las Antillas Mayores en el Oligoceno     Temprano (MacPhee &amp; Iturralde- Vinnent, 1995). </span></font><br      style="font-family: verdana;">     <br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;">Adem&aacute;s, es     ]]></body>
<body><![CDATA[claro que no hay     evidencia de arribo de xenarthras en Am&eacute;rica Central de previo     al Hemphilliano temprano tard&iacute;o (Laurito &amp; Valerio, 2012) y     las localidades faun&iacute;sticas m&aacute;s meridionales y antiguas     del Istmo como las de la Formaci&oacute;n Cucaracha en Panam&aacute; no     muestran evidencia de elementos de abolengo suramericano a pesar de su     cercan&iacute;a paleogeogr&aacute;fica con dicho continente (MacFadden     et al., 2012).</span></font><br style="font-family: verdana;">     <br style="font-family: verdana;">     <font style="font-weight: bold;" size="2"><span     ]]></body>
<body><![CDATA[ style="font-family: verdana;">&iquest;D&oacute;nde se     diferenci&oacute; el g&eacute;nero <span style="font-style: italic;">Pliometanastes</span>?     y     &iquest;cu&aacute;l fue el ancestro suramericano que dio origen al     g&eacute;nero <span style="font-style: italic;">Pliometanastes</span>?</span></font><br      style="font-family: verdana;">     <br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;"><span      style="font-style: italic;">Pliometanastes </span>se caracteriza por     una amplia distribuci&oacute;n en el Hemphilliano temprano de     ]]></body>
<body><![CDATA[Am&eacute;rica del Norte y se acepta que dio origen al g&eacute;nero     <span style="font-style: italic;">Megalonyx </span>(McDonald, 2005;     McDonald &amp; Naples, 2007), a pesar de que     <span style="font-style: italic;">Megalonyx </span>hab&iacute;a sido     considerado como un inmigrante temprano de     Am&eacute;rica del Sur (Hirschfeld, 1981), ahora se acepta que es     end&eacute;mico de Am&eacute;rica del Norte (Morgan, 2005), su registro     m&aacute;s antiguo proviene de la fauna de Lemoyne en Nebraska y data     de 6.7 Ma (Leite, 1990). El an&aacute;lisis clad&iacute;stico de Gaudin     (2004), sugiere que <span style="font-style: italic;">Megalonyx </span>es     ]]></body>
<body><![CDATA[el grupo hermano (&#8220;sister group&#8221;) de     <span style="font-style: italic;">Pliometanastes </span>y &eacute;ste     el grupo hermano de <span style="font-style: italic;">Pliomorphus</span>,     que se     supone es el g&eacute;nero basal del grupo corona de todos los     Megalonychidae de las Indias Orientales (sensu Gaudin, 2004),     adem&aacute;s confirma al g&eacute;nero <span      style="font-style: italic;">Pliomorphus </span>como ancestral con     respecto a <span style="font-style: italic;">Pliometanastes</span>,     todo ello es acorde con lo concluido por     ]]></body>
<body><![CDATA[Hirschfeld &amp; Webb (1968).</span></font><br      style="font-family: verdana;">     <br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;">De momento se asume     que     Pliometanastes migr&oacute; de Am&eacute;rica del Sur, sin embargo este     g&eacute;nero no ha sido registrado en ese subcontinente y una nueva     posibilidad es que este se haya diferenciado tempranamente en las islas     del archipi&eacute;lago que conformaban el sur de Am&eacute;rica     Central, a partir de un Megalonychidae ancestral durante el     ]]></body>
<body><![CDATA[Hemphilliano temprano.</span></font><br style="font-family: verdana;">     <br style="font-family: verdana;">     <font style="font-weight: bold;" size="3"><span      style="font-family: verdana;">Conclusiones</span></font><br      style="font-family: verdana;">     <br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;">El Megalonychidae <span      style="font-style: italic;">Pliometanastes </span>se     describe por primera vez en Am&eacute;rica Central, este hallazgo     representa el registro m&aacute;s austral del g&eacute;nero en     ]]></body>
<body><![CDATA[Am&eacute;rica del Norte y ampl&iacute;a el rango de edad de la fauna     de la localidad de San Gerardo de Limoncito correspondiente al tope de     la Formaci&oacute;n Curr&eacute;.</span></font><br      style="font-family: verdana;">     <br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;">Este registro valida     la     suposici&oacute;n previa de que los Megalonychidae y en especial     <span style="font-style: italic;">Pliometanastes</span>, ingresaron     v&iacute;a el Istmo de Panam&aacute; casi     ]]></body>
<body><![CDATA[6.0 Ma antes del cierre efectivo del mismo y la instauraci&oacute;n del     corredor biol&oacute;gico interamericano. Pero no verifica el sitio de     evoluci&oacute;n y aparici&oacute;n del g&eacute;nero <span      style="font-style: italic;">Pliometanastes</span>,     quedando la posibilidad de que el mismo se haya diferenciado en el sur     de Am&eacute;rica Central a partir de un Megalonychidae ancestral     proveniente de Am&eacute;rica del Sur.</span></font><br      style="font-family: verdana;">     <br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;">El modo de     ]]></body>
<body><![CDATA[dispersi&oacute;n es muy     probable que se diera por el arribo accidental de estos perezosos     terrestres, a la porci&oacute;n m&aacute;s meridional del     archipi&eacute;lago del Arco de Islas Costa Rica-Panam&aacute;, durante     el Mioceno Superior.</span></font><br style="font-family: verdana;">     <br style="font-family: verdana;">     <font size="2"><span style="font-family: verdana;">El arribo de este y     otros     Xenarthras al sur de Am&eacute;rica Central, como es el caso de los     Pampatheriidae, Mylodontidae y Megatheriidae, confirma una vez     ]]></body>
<body><![CDATA[m&aacute;s la gran capacidad de estos mam&iacute;feros terrestres de     superar grandes pasos marinos, ya sea como fuertes nadadores o     afortunados sobrevivientes de balsas o funerales vikingos, que     r&aacute;pidamente se adaptaron a las condiciones clim&aacute;ticas de     estas j&oacute;venes tierras donde originaron especies nuevas y mejor     adaptadas.    <br> <br style="font-family: verdana;"> </span></font><font style="font-weight: bold;" size="3"><span  style="font-family: verdana;">Agradecimientos</span></font><br  style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">Al Dr. Greg McDonald del National Park Service at the Hagerman Fossil Beds, Idaho, U.S. Department of the Interior, qui&eacute;n nos suministr&oacute; importante material comparativo y bibliogr&aacute;fico y al Dr. Gabriel Gonz&aacute;lez Barba, Universidad Aut&oacute;noma de Baja California Sur, M&eacute;xico, por la revisi&oacute;n del texto y sus acertadas observaciones.     <br> <br style="font-family: verdana;"> </span></font> <hr style="width: 100%; height: 2px;">    <!-- ref --><br> <font style="font-weight: bold;" size="3"><span  style="font-family: verdana;">Referencias bibliogr&aacute;ficas</span></font><br style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">ALROY, J., 2000: New methods for quantifying macroevolutionary patterns and processes.- Paleobiol. 26(4): 707&#8211;733.    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=982887&pid=S0256-7024201200020000400001&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --></span></font><br style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">CARRANZA-CASTA&Ntilde;EDA, O. &amp; MILLER, W., 2004: Late Tertiary Terrestrial Mammals from Central Mexico and their relationship to South American Inmigrants.- Rev. Brasileira Paleont. 7(2): 249-261.    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=982888&pid=S0256-7024201200020000400002&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --></span></font><br style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">CARRANZA-CASTA&Ntilde;EDA, O., ARANDA, J., AGUIRRE, G., &amp; NIETO, J., 2006: Estratigraf&iacute;a del Terciario Tard&iacute;o en la cuenca de Juchipila-Jalpa, Estado de Zacatecas y sus implicaciones para el Gran Intercambio de Faunas entre las Am&eacute;ricas.- Geos, 26(1): 132.    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=982889&pid=S0256-7024201200020000400003&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --></span></font><br  style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">CARRANZA-CASTA&Ntilde;EDA, O., WANG, X., ARANDA, J.J., TZENG, J., TRONCOSO, H. &amp; CERVANTES, J., 2008: Mastofauna del Terciario Tard&iacute;o de la Formaci&oacute;n Juchipila, Estado de Zacatecas y su correlaci&oacute;n bioestratigr&aacute;fica con las faunas del centro de M&eacute;xico.- Geos, 28(2): 191.    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=982890&pid=S0256-7024201200020000400004&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --></span></font><br style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">COATES, A.G., COLLINS, L.S., AUBRY, M. and BERGGREN, W.A., 2004: The Geology of the Darien, Panama, and the late Miocene-Pliocene collision of the Panama arc with northwestern South America.- Geol. Soc. Amer. 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J. G., 2004: Phylogenetic relationships among sloths (Mammalia, Xenarthra, Tardigrada): the craniodental evidence.-Zoological J. Linnean Soc. 140: 255&#8211;305.    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=982893&pid=S0256-7024201200020000400007&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --></span></font><br style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">HIRSCHFELD, S.E., 1981: <span style="font-style: italic;">Pliometanastes protistus </span>(Edentata, Megalonychidae) from Knight&#8217;s Ferry, California, with discussions of early Hemphillian megalonychids.-PaleoBios, 36: 1&#8211;16.    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=982894&pid=S0256-7024201200020000400008&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --></span></font><br  style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">HIRSCHFELD, S.E. &amp; WEBB, S.D., 1968: PIio-Pleistocene megalonychid sloths of North America.- Bull. Florida State Mus. Biol. Sci. 12(5): 213-296.    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=982895&pid=S0256-7024201200020000400009&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --></span></font><br  style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">HULBERT, R.C., 1988: Calippus and Protohippus (Mammalia, Perissodactyla, Equidae) from the Miocene (Barstovian-Early Hemphillian) of the Gulf Coastal Plain.-Bull. Florida State Mus. Biol. 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Gard. 93: 245&#8211;257.    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=982937&pid=S0256-7024201200020000400050&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --></span></font><br style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">WHITE, J., &amp; MACPHEE, R.D.E., 2001: The sloths of the West Indies: a systematic and phylogenetic review.- En: WOODS, C.A. &amp; SERGILE, F.E. (eds): Biogeography of the West Indies: Patterns and Perspectives [2&ordf; ed.].- CRC Press. Boca Rat&oacute;n, Florida: 201-236.    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=982938&pid=S0256-7024201200020000400051&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><br>     <br> <a name="Correspondencia1"></a><a href="#Correspondencia2">*</a>Correspondencia:</span></font><font  size="2"><span style="font-family: verdana;"> Cesar A. Laurito: </span></font><font  size="2"><span style="font-family: verdana;">Instituto Nacional de Aprendizaje.&nbsp; </span></font><font size="2"><span  style="font-family: verdana;"></span></font><font size="2"><span  style="font-family: verdana;">Departamento de Historia Natural, Museo Nacional de Costa Rica.</span></font><font size="2"><span  style="font-family: verdana;">cesarlaurito@ice.co.cr</span></font>    <br> <font size="2"><span style="font-family: verdana;">Ana L. Valerio: </span></font><font size="2"><span  style="font-family: verdana;"></span></font><font size="2"><span  style="font-family: verdana;">Departamento de Historia Natural, Museo Nacional de Costa Rica. </span></font><font size="2"><span  style="font-family: verdana;">Apdo. 749-1000, San Jos&eacute;    <br> </span></font><font size="2"><span style="font-family: verdana;"><a  name="1"></a><a href="#3">1</a> Instituto Nacional de Aprendizaje</span></font><br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;"><a name="2"></a><a  href="#4">2</a> Departamento de Historia Natural, Museo Nacional de Costa Rica. </span></font><br  style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">Apdo. 749-1000, San Jos&eacute;. </span></font><font size="2"><span  style="font-family: verdana;">cesarlaurito@ice.co.cr</span></font>    <br> <span style="font-family: verdana;"></span> <hr style="width: 100%; height: 2px;"><span  style="font-family: verdana;"></span>     <div style="text-align: center;"><font style="font-weight: bold;"  size="-1"><span style="font-family: verdana;">Recibido: 21/03/2012 ; aceptado: 17/12/2012</span></font></div> </div>      ]]></body><back>
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