Was southern Central America an archipelago or a peninsula in the middle Miocene? A test using land-mammal body size

Phylogeography of the Pygmy Rain Frog (Pristimantis ridens) across the lowland wet forests of isthmian Central America

“…This fossilized mammal community suggests that central Panama was the terminus of a longpeninsula stretching south and eastward (Whitmore and Stewart, 1965;Kirby and MacFadden, 2005). Clearly, this landmass supported northern elements of the modern-day frog fauna during the Miocene (Savage, 1982;Crawford and Smith, 2005;Crawford et al, 2007), and it may have received anuran colonists from South America, such as P. ridens and the túngara frog (Weigt et al, 2005), by the Late Miocene.…”

History of upwelling in the Tropical Eastern Pacific and the paleogeography of the Isthmus of Panama

“…Although a Late Pliocene date for final closure is now well constrained and strongly supported by several lines of independent evidence, the form, elevation and degree of subaerial emergence of the southern tip of Central America after it collided with South America approximately 24 Ma (Farris et al, 2011) remains unresolved (Kirby and MacFadden, 2005;Retallack and Kirby, 2007;Schmidt, 2007;Molnar, 2008). Uplift rates based on paleobathymetries of marine sediments from across the Isthmus suggest that the majority of the volcanic arc was submerged up until very recently with bathyal sediments of latest Miocene age present in the Caribbean and Pacific of western Panama, the Caribbean of central Panama and eastern Panama (Coates et al, 1992;Collins, 1992Collins, , 1993Collins, , 1996Coates, 1999;Coates et al, 2000Coates et al, , 2003Coates et al, , 2004Coates et al, , 2005.…”

“…Strong similarities between Pacific and Caribbean Mio-Pliocene biota (Chaisson and Ravelo, 2000;O'Dea et al, 2007b) and near-identical environmental conditions on either side of the Isthmus (Keigwin, 1978(Keigwin, , 1982Keller et al, 1989;Haug and Tiedemann, 1998;Haug et al, 2001) in the Early Pliocene imply the CAS was maintained in some form until the mid-Pliocene. Nevertheless, well-studied and extensive lacustrine sediments, shallow water reefs and mangroves, plus a continental-like mammal fauna in the Canal Zone of Panama demonstrate the presence of substantial subaerial land(s) in the middle Miocene (Whitmore and Stewart, 1965;Kirby and MacFadden, 2005;Johnson and Kirby, 2006;Retallack and Kirby, 2007;Kirby et al, 2008). Accordingly, Coates and Obando (1996) proposed a semi-submerged archipelago of islands from the Miocene up to final closure.…”

“…Accordingly, Coates and Obando (1996) proposed a semi-submerged archipelago of islands from the Miocene up to final closure. Subsequently however, Kirby and MacFadden (2005) demonstrated that mammals in Panama in the middle Miocene were no smaller than coeval conspecifics from mainland North America, thus strongly implying free gene flow amongst them. As such, rather than an archipelago the proto-Isthmus must have been an entirely subaerial peninsula unconnected to south America until final closure, a conclusion supported by geological evidence (Montes et al, 2012).…”

First Central American record of Anthracotheriidae (Mammalia, Bothriodontinae) from the early Miocene of Panama

“…1) between A. meridionale and similarly aged A. fricki suggest that the two species occupied two separate ecosystems during the earliest Miocene. A. acridens fron the Toledo Bend L. F. and A. meridionale occupied a distinctive biogeographic area connecting the Gulf Coast with southern Central America (Albright, 1998(Albright, , 1999Kirby and MacFadden, 2005), whereas A. fricki was restricted to more temperate and open habitats in the northern and central Great Plains (Strömberg, 2002(Strömberg, , 2006. We also note that there is a remarkable difference in the dimensions of the molars in the later forms of Arretotherium.…”