A South American sebecid from the Miocene of Hispaniola documents the presence of apex predators in early West Indies ecosystems

Abstract

The absence of terrestrial apex predators on oceanic islands led to the evolution of endemic secondary apex predators like birds, snakes and crocodiles, and loss of defence mechanisms among species. These patterns are well documented in modern and Quaternary terrestrial communities of the West Indies, suggesting that biodiversity there assembled similarly through overwater dispersal. Here, we describe fossils of a terrestrial apex predator, a sebecid crocodyliform with South American origins from the late Neogene of Hispaniola that challenge this scenario. These fossils, along with other putative sebecid specimens from Cuba and Puerto Rico, show that deep-time Caribbean ecosystems more closely resembled coeval localities in South America than those of today. We argue that Plio-Pleistocene extinction of apex predators in the West Indies resulted in mesopredator release and other evolutionary patterns traditionally observed on oceanic islands. Adaptations to a terrestrial lifestyle documented for sebecids and the chronology of West Indian fossils strongly suggest that they reached the islands in the Eocene-Oligocene through transient land connections with South America or island hopping. Furthermore, sebecids persisted in the West Indies for at least five million years after their extinction in South America, preserving the last populations of notosuchians yet recovered from the fossil record.

Keywords: Caribbean; Sebecus; biodiversity museum; extinction; palaeobiogeography.

Figure 1.

(a) Generalized relationship of crocodilians that independently evolved ziphodont dentition and the general anatomy of nuchal and caudal vertebrae in Notosuchia and Eusuchia. (b,c) Comparison of (b) caudal (MNHNSD FOS 23.1324) and (c) nuchal (MNHNSD FOS 23.1323) vertebrae of Sebecus sp. from the late Miocene–early Pliocene of Dominican Republic (scale bar = 15 mm). (d,e) Sebecid teeth from the (d) early Miocene of Cuba (MNHNCu P3115; scale bar = 10 mm) and (e) late Miocene–early Pliocene of Dominican Republic (MNHNSD FOS 23.1325; scale bar = 15 mm).

Figure 2.

Maps of South America and the Caribbean region during the (a) Palaeogene, (b) Neogene and (c) late Quaternary show the generalized distribution of Sebecidae in circles. The silhouettes correspond to the terrestrial apex predator groups present in the region during each period, with native South American predators (Sebecidae, Madtsoiidae, Phorusrhacidae, Sparassodonta) in blue, late Cenozoic invasive predators (Canidae, Felidae, Ursidae) in red and endemic secondary terrestrial predators in the West Indies (Strigiformes, Accipitridae, Crocodylus) in green. Localities of Sebecidae based on electronic supplementary material, table S2.