Pleistocene insular Proboscidea of the Eastern Mediterranean: A review and update Athanassios Athanassiou a, * , Alexandra A.E. van der Geer b, c , George A. Lyras c a Ministry of Culture, Ephorate of PalaeoanthropologyeSpeleology, Ardittou 34B, 11636 Athens, Greece b Naturalis Biodiversity Center, P.O. Box 9517, 2300 RA Leiden, the Netherlands c National and Kapodistrian University of Athens, Department of Geology and Geoenvironment, Panepistimioupolis, 15784 Athens, Greece article info Article history: Received 24 February 2019 Received in revised form 8 May 2019 Accepted 26 June 2019 Keywords: Dwarf elephants Elephantidae Europe Mediterranean Insularity Quaternary Palaeontology Palaeogeography abstract The Eastern Mediterranean islands, most of which belong to the Aegean archipelago, have a complex biogeographic history, which puts its stamp on their fauna and flora. A now extinct but most important faunal component, in terms of geographic spread and taxonomic diversity, are the elephants. The Eastern Mediterranean islands are particularly rich in Pleistocene endemic elephant localities, which preserve samples of extinct endemic populations. These were either descendants of the European straight-tusked elephant Palaeoloxodon antiquus or the Southern mammoth, Mammuthus meridionalis. Their presence, history and palaeobiogeography has been documented only for Cyprus, Crete, Kasos, Rhodes, Tilos, Kýthera, Naxos, and Delos. For six other islands only anecdotal references exist in the literature: K alymnos, Astyp alaia, Milos, S eriphos, Kýthnos and Paros. Here, we provide an update on previously published specimens and taxa, describe previously undescribed specimens that were relocated in museum collections, as well as recently excavated specimens, and put these in the context of island palaeobiogeography. We conclude that dwarf elephants, endemic to their palaeo-island, lived on the islands of palaeo-Cyclades, Astyp alaia, Crete, KasoseK arpathoseSaría, Tilos, Rhodes and Cyprus, whereas the elephants from Kephallenía, K alymnos and Kýthera are indistinguishable on the species level from mainland Palaeoloxodon antiquus. Elephant fossils of unresolved taxonomic status are reported from five present-day islands. The Eastern Mediterranean endemic elephants likely derived from separate and independent colonisation events from the mainland. No island supported more than one proboscidean species at any time. We found that isolation had no effect on the degree of dwarfism, but that there exists a threshold of about 6e10 km distance between the island and the mainland, below which no dwarfism evolved, likely as a result of genetic contact with the mainland population. We also found that although island area is correlated with the degree of dwarfism in elephants, other factors, such as the level of interspecific competition, may limit this degree. © 2019 Elsevier Ltd. All rights reserved. 1. Introduction The islands of the Mediterranean basin are highly diverse in terms of biodiversity due to a complex biogeographical and geological history, and comprise one of the 36 terrestrial biodi- versity hotspots worldwide (M edail and Myers, 2004). Most Med- iterranean islands are continental islands and became isolated by tectonic and glacio-eustatic processes, but there are also a few oceanic islands, that emerged de novo above the water (Whittaker and Fern andez-Palacios, 2007). Mediterranean islands thus constitute a prime example of evolutionary processes in isolation, amongst which the ‘island rule’ is the most widely known. Ac- cording to this rule, or trend, body size of island populations changes, adapting to the peculiar ecological conditions of the insular environment (Van Valen, 1973; Roth, 1992). The insular elephantid populations of the Mediterranean islands illustrate this rule perhaps better that any other endemic group, mainly because of the extreme size reduction observed in many of them (e.g., Caloi and Palombo, 1994; Palombo, 2004, 2007; van der Geer et al., 2010, 2016). Several factors, biotic as well as abiotic, influence the di- rection and the degree of body mass evolution on islands, including ancestral body mass, island area and isolation, and number and nature of ecologically relevant competitors and predators * Corresponding author. E-mail address: aathanas@geol.uoa.gr (A. Athanassiou). Contents lists available at ScienceDirect Quaternary Science Reviews journal homepage: www.elsevier.com/locate/quascirev https://doi.org/10.1016/j.quascirev.2019.06.028 0277-3791/© 2019 Elsevier Ltd. All rights reserved. Quaternary Science Reviews 218 (2019) 306e321