Woodburne, M.O.; Cione, A.L.; and Tonni, E.P., 2006, Central American provincialism and the 73 Great American Biotic Interchange, in Carranza-Castañeda, Óscar, and Lindsay, E.H., eds., Ad- vances in late Tertiary vertebrate paleontology in Mexico and the Great American Biotic In- terchange: Universidad Nacional Autónoma de México, Instituto de Geología and Centro de Geociencias, Publicación Especial 4, p. 73–101. CENTRAL AMERICAN PROVINCIALISM AND THE GREAT AMERICAN BIOTIC INTERCHANGE Michael O. Woodburne1,* Alberto L. Cione2,**, and Eduardo P. Tonni2,*** ABSTRACT The age and phyletic context of mammals that dispersed between North and South America during the past 9 m.y. is summarized. The presence of a Central American province of cladogenesis and faunal differentiation is explored. One apparent aspect of such a province is to delay dispersals of some taxa northward from Mexico into the continental United States, largely during the Blancan. Examples are recognized among the various xenar- thrans, and cervid artiodactyls. Whereas the concept of a Central American province has been mentioned in past investigations it is upgraded here. Paratoceras (protoceratid artio- dactyl) and rhynchotheriine proboscideans provide perhaps the most compelling examples of Central American cladogenesis (late Arikareean to early Barstovian and Hemphillian to Rancholabrean, respectively), but this category includes Hemphillian sigmodontine rodents, and perhaps a variety of carnivores and ungulates from Honduras in the medial Miocene, as well as peccaries and equids from Mexico. For South America, Mexican canids and hy- drochoerid rodents may have had an earlier development in Mexico. Remarkably, the first South American immigrants to Mexico (after the Miocene heralds; the xenarthrans Plaina and Glossotherium) apparently dispersed northward at the same time as the first Holarctic taxa dispersed to South America (sigmodontine rodents and the tayassuid artiodactyls). The main (Phase One) Great American Biotic Interchange (GABI) bipolar episode transpired from about 2.7–1.8 Ma, with laggards lasting until about 1.0 Ma. A later phase occurred from about 0.8 Ma to virtually modern times and resulted in mainly southern enrichment. Key words: Great American Biotic Interchange, vertebrate paleontology, dispersal, provinciality. RESUMEN Se presenta en forma sucinta la edad y el contexto filético de los mamíferos que se dispersaron entre América del Norte y del Sur durante los pasados nueve millones de años. Se explora la posible presencia de una provincia Centroamericana de cladogénesis y diferenciación faunística. Un aspecto relevante de tal provincia es el retardo en la dispersión de algunos taxones hacia el norte, de México a los Estados Unidos de América, principalmente durante el Blancano; como ejemplos de ello se tiene a los diversos xenartros y los artiodáctilos cérvidos. El concepto de una provincia Centroamericana de tales características ya ha sido tratado en investigaciones pasadas; en el presente estudio, dicho concepto es afinado. 1Department of Geology, Museum of Northern Arizona, 3101 N. Fort Valley Rd., Flagstaff, AZ 86001 *E-mail address: [email protected] 2Departamento Científico Paleontología Vertebrados, Museo de La Plata, 1900 La Plata, Argentina **E-mail address: [email protected] ***E-mail address: [email protected] CARRANZA-CASTAÑEDA, ÓSCAR, AND LINDSAY, E.H. EDS., ADVANCES IN LATE TERTIARY VERTEBRATE PALEONTOLOGY IN MEXICO 2006 74 WOODBURNE, CIONE AND TONNI Quizá los dos ejemplos más convincentes de cladogénesis en América Central sean el de Paratoceras (artiodáctilo protocerátido del Arikareeano tardío al Barstoviano temprano) y el de los proboscídeos ryncotherinos (Henfiliano a Rancholabreano); adicionalmente, esta categoría incluye roedores sigmodontinos del Henfiliano y, quizá, una diversidad de carnívoros y ungulados de Honduras en el Mioceno medio, así como de pecaríes y équidos de México. Para América del Sur, los cánidos y los roedores hidrocoéridos pueden haber tenido un desarrollo más temprano en México. Es notorio que los primeros inmigrantes sudamericanos a México (después de los precursores del Mioceno: los xenartros Plaina y Glossotherium) se dispersaron hacia el norte, a la vez que los primeros taxones holárticos se dispersaron a Sudamérica (roedores sigmodontinos y artiodáctilos tayasuidos). El episodio bipolar principal (Fase Uno) del Gran Intercambio Biótico Americano (GABI, por sus siglas en inglés) transcurrió durante el intervalo 2.7–1.8 Ma, con rezago que subsistió hasta hace cerca de 1.0 Ma. Una fase posterior ocurrió hace aproximadamente 0.8 Ma, en tiempos virtualmente modernos, y tuvo como resultado un enriquecimiento principalmente meridional. Key words: Gran Intercambio Biótico Americano, paleontología de vertebrados, dispersión, provincialismo. INTRODUCTION (procyonids, gomphotheres) reached South America by 7–9 Ma (Table 1) well in advance of 2.7–2.5 Ma Studies of land mammal dispersal between North and (e.g., Campbell et al., 2000; Carranza-Castañeda and South America usually focus on the Great American Miller, 2004; Morgan, 2005), at least in part coinci- Interchange or Great American Biotic Interchange dent with the earliest immigration of ground sloths (GABI) which began about 2.7 Ma and lasted into vir- (Pliometanastes, Thinobadistes) to North America (ca. tually modern times. The dispersal episodes are popu- 8–9 Ma; Hirschfeld, 1981; Webb 1985; Morgan, 2005). lated by suites of animals that display taxonomic facies After procyonids, the first North American taxa are which differ not only geographically, but temporally. sigmodontine rodents in Montehermosan beds perhaps The GABI events are summarized here before moving at 5–6 Ma. For many years, a classical view that pre- on to a discussion of faunal provinciality, evolution, vailed among workers maintained that representatives and dispersal with which participants in the GABI must of two families of North American origin occurred in have been associated. Chapadmalalan beds of southern South America and The Great American Biotic Interchange reflects eight in post Chapadmalalan-pre-Ensenadan beds (the the end of the Cenozoic isolation of South America with “Uquían”; see Marshall et al., 1984; Webb, 1985). respect to the land mammals and birds of that region in However, a new emphasis on biostratigraphical stud- contrast to those of Central and North America (Marshall ies demonstrated that the first occurrences of different et al., 1979). This episode witnessed land mammal dis- species of North American families in the south are persals across the newly established Isthmus of Panama, distributed in beds that encompass more than 4 mil- and resulted in faunas of both areas being enriched by lion years (one in the Chapadmalalan, one in the lower taxa from the other. In South America, North American Marplatan, two in the middle Marplatan, one in the up- mammalian immigrants included tayassuids, rodents, per Marplatan and four in the Ensenadan [Tonni et al., canids, gomphotheriids, camelids, cervids, felids, and 1992; Cione and Tonni, 1995, 2001, 2005]). In addi- ursids, although not all at the same time. For North tion there are other species of five families of North America, newcomers were largely edentates, but also American origin in very recent beds or with no fossil included rodents and marsupials. record at all (Webb, 1985; Cione and Tonni, 1995). It is well known that these dispersals took place More recently, Carranza-Castañeda and Miller at different times in the past 9 m.y. and that certain taxa (2004) and Flynn and others (2005) showed that UNIVERSIDAD NACIONAL AUTÓNOMA DE MÉXICO, INSTITUTO DE GEOLOGÍA AND CENTRO DE GEOCIENCIAS PUBLICACIÓN ESPECIAL 4 CENTRAL AMERICAN PROVINCIALISM AND THE GREAT AMERICAN BIOTIC INTERCHANGE 75 Neotropical immigrants to North America, Glossotherium TECTONIC/GEOLOGIC BACKGROUND and Plaina, were present in the vicinity of Guanajuato, central Mexico, by 4.6–4.8 Ma, and that Glossotherium Coates and others (2004) indicate that the Panamanian reached the USA somewhat later (3.0 Ma, Table 1), but region was progressively uplifted from about 12 to at still prior to the beginning of the late Blancan and the least 4.8 Ma, with concomitant disruption of formerly GABI. According to Tonni and others (1992) and Cione confluent marine depositional environments and fau- and Tonni (1995), Plaina occurs between 3.3 and 5.0 nas, and reflected in the overland dispersals across the Ma in the Chapadmalalan SALMA (South American Panamanian region at 8–9 Ma. Continued tectonic ac- Land Mammal Age) of Argentina. Whether this reflects tivity raised the region still more, coincident with the an evolutionary role for Central America and south- mammalian dispersals at ca. 4.8 Ma and subsequent- ward dispersal cannot be solved at present (and the ge- ly (GABI), after a brief episode of eustatic sea level nus seemingly does not occur in the USA in any case). rise that breached the peninsula at 6–7 Ma. According Megalonyx also is known from the early Blancan sites at to Haug and Tiedemann (1998) and Haug and others Guanajuato but rather than being designated as an immi- (2001) the Panamanian isthmus was a firm barrier to grant at Guanajuato by Carranza-Castañeda and Miller Caribbean-Pacific circulation from 4.7–4.2 Ma, and (2004) and Flynn and others (2005), Megalonyx is con- Hoernle and others (2002) show how the Caribbean sidered as an endemic North American descendant of plate presented an overland dispersal