Imagine a crocodile sculpted with the grace and agility of a greyhound—this was the sebecid, a formidable predator that once stalked prehistoric landscapes. Growing up to 20 feet in length, sebecids dominated ecosystems in South America during the Miocene epoch, long after the mass extinction that erased the era of non-avian dinosaurs. For decades, paleontologists believed that these terrestrial crocodilians had vanished from the face of the Earth approximately 11 million years ago, retreating into oblivion as ecosystems evolved without their formidable presence. However, a groundbreaking discovery from the Caribbean’s fossil record challenges this long-held assumption, reshaping our understanding of both sebecid persistence and the ancient biogeography of the West Indies.
The story begins with a series of enigmatic fossilized teeth, initially uncovered in the islands of the Caribbean three decades ago. These teeth, dating back roughly 18 million years and found in Cuba, exhibited tapered shapes and pronounced serrations, features specialized for a carnivorous lifestyle well-adapted to tearing flesh. Such characteristics immediately suggested these belonged to apex predators, yet the geographic location confounded researchers. Large terrestrial carnivores of that magnitude were thought to be absent from these island ecosystems. The enigma deepened when an even older tooth, approximately 29 million years old, surfaced in Puerto Rico. Unable to assign these to a specific genus or family conclusively, the scientific community left the question unresolved, pondering over unnamed predators lurking in the ancient Caribbean.
In early 2023, this mystery entered a new chapter when a research team excavated a fossil site in the Dominican Republic. Alongside one tooth reminiscent of those previously found, the team unearthed two vertebrae, a rare and invaluable addition that provided key anatomical insight. Despite the fragmentary nature of the find, the team led by graduate student Lazaro Viñola Lopez at the University of Florida confirmed that these fossils belonged to a sebecid crocodilian, dramatically extending the known temporal range of these animals and illustrating their survival in the Caribbean over five million years after their apparent extinction on the mainland. This revelation suggests the Caribbean islands served as a refugium, a sanctuary where these apex predators persisted beyond their continental extinction.
Sebecids represent the last surviving lineage of the Notosuchia, an extinct clade of crocodyliforms with evolutionary roots tracing back to the dinosaur age. Unlike their modern, semi-aquatic crocodilian relatives, sebecids were adapted entirely to terrestrial life. Their morphological traits—long limbs built for running, deep snouts, and serrated teeth—evoke images of a terrestrial predator that filled ecological niches comparable to those of carnivorous dinosaurs before them. This unique adaptation allowed them to become apex predators in South America’s Cenozoic ecosystems, a role they held for millions of years following the demise of the dinosaurs some 66 million years ago.
The mass extinction event at the Cretaceous-Paleogene boundary nearly obliterated notosuchians, yet sebecids endured and thrived. Their remarkable survival and subsequent radiation underscore their ecological flexibility and evolutionary success. With the dinosaurs gone, these land-bound crocodilians surged to the top of the food pyramid. Some species attained impressive sizes, reaching lengths exceeding 20 feet, their bodies armored with osteoderms—bony structures embedded in the skin—providing defense against competitors and other predators. The discovery of their fossils in the Caribbean reshapes narratives about predator-prey dynamics and biogeography in that region during the Miocene.
The presence of sebecids in the Caribbean raises provocative questions about how such large, terrestrial predators traversed the marine barriers separating the islands from continental South America. The research team’s findings lend compelling support to the GAARlandia hypothesis, which posits that a series of ephemeral land bridges or a chain of islands once connected South America to the Greater Antilles, facilitating faunal exchanges during the early Cenozoic. This land connection would have allowed terrestrial animals, including complex predators like sebecids, to colonize these island environments. If corroborated by additional fossil evidence, this hypothesis could redefine our understanding of Caribbean paleoecology and faunal dispersal.
Beyond the remarkable biogeographic implications, the discovery indicates that sebecids likely played a critical role in shaping early West Indies ecosystems. If the serrated teeth previously recovered on other islands indeed belonged to sebecids, these formidable reptiles occupied a pivotal ecological niche, exerting top-down control over prey populations for millions of years. Today, the absence of large terrestrial predators in the Caribbean has left ecological voids filled by smaller endemic carnivores such as birds, snakes, and crocodiles, but the historical presence of sebecids hints at a vastly different ecosystem structure in the past.
Jonathan Bloch, curator of vertebrate paleontology at the Florida Museum of Natural History, reflected on the unexpectedness of these findings, emphasizing how modern ecosystems obscure the deep-time dynamics of predator communities in the Caribbean. “You wouldn’t have been able to predict this looking at the modern ecosystem,” he noted. The unearthing of sebecid fossils invites a reassessment of Caribbean paleobiodiversity and stimulates anticipation for future discoveries that may further illuminate the prehistoric complexities of island biotas.
Islands have long been recognized by ecologists as “museums of biodiversity,” refuges where biological lineages can persist even as related species vanish elsewhere. This phenomenon is observed globally and underscores the importance of tropical islands as reservoirs of evolutionary heritage. Despite being among the most biodiverse regions on Earth, the tropics harbor many paleontological enigmas. Tropical ecosystems, due to their climatic and geological characteristics, often lack extensive fossil preservation, making discoveries like the sebecid fossils all the more significant. Such finds enrich our understanding of tropical evolutionary history and the processes that have shaped biodiversity hotspots.
Traditional paleontological methods in the Caribbean often involved excavations in caves and blue holes—karstic environments rich in skeletal remains due to their suitability as animal refuges or predator accumulation sites. These depositional contexts, however, typically yield younger fossils, providing only glimpses into the recent past. The challenge of uncovering older, terrestrial fossils, like those of the sebecid, requires both serendipity and a proactive research approach. In this regard, the region is witnessing a renaissance of deep-time paleontology, driven by increased local scientific engagement and alertness to fleeting fossiliferous outcrops.
Fossil beds in the Caribbean are elusive; their exposed rock surfaces weather rapidly under tropical conditions, and dense vegetation quickly conceals potential sites. The chance discovery of the Dominican Republic locate by local road crews underscores the importance of timing and local collaboration in paleontological success. Graduate student Elson Core from the University of Puerto Rico in Mayagüez initially encountered the fossiliferous strata while conducting stratigraphic studies, highlighting how cross-disciplinary fieldwork can uncover unexpected treasures. Such discoveries reinforce the need for timely and sustained field investigations supported by local expertise.
The significance of the sebecid fossil discovery in the Caribbean is further contextualized by recent paleontological breakthroughs in the region. Among these is the documentation of the Caribbean’s first mosasaur fossils, colossal marine reptiles that dominated ancient seas, as well as the uncovering of the oldest known ground sloth fossils in Hispaniola, filling critical gaps in the paleobiogeographic record. Recent studies also suggest human arrival in the Caribbean contributed to the earliest known extinctions of native rodents, illustrating the complex interactions between humans and island ecosystems. Together, these findings mark a flourishing era of discovery that is reshaping Caribbean paleontology.
As research advances, the story of the sebecid in the Caribbean remains just the beginning. Each fossil find deepens insight into the ancient ecosystems that once thrived in the West Indies and reveals complex narratives of survival, extinction, and ecological change. “The sebecid is only the tip of the iceberg,” Lazaro Viñola Lopez remarked. Continued exploration promises to unveil further chapters of tropical evolutionary history hidden beneath the island soils, dramatically enhancing our understanding of biodiversity’s past and informing conservation in the present.
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Subject of Research: Paleontology; Miocene apex predators; Notosuchian crocodilians; Caribbean biogeography.
Article Title: A South American sebecid from the Miocene of Hispaniola documents the presence of apex predators in early West Indies ecosystems
News Publication Date: 30-Apr-2025
Web References:
– https://doi.org/10.1098/rspb.2024.2891
– https://www.sciencedirect.com/science/article/pii/S0895981122002607
– https://www.cambridge.org/core/journals/journal-of-paleontology/article/oldest-known-record-of-a-ground-sloth-mammalia-xenarthra-folivora-from-hispaniola-evolutionary-and-paleobiogeographical-implications/FD228BE96C7C27F74AA0562EA0B980A1
– https://www.floridamuseum.ufl.edu/science/rodent-extinctions-in-hispaniola-may-have-been-caused-by-humans/
Image Credits: Illustration by Jorge Machuky
Keywords: Paleontology, Dinosaur extinction, Dinosaurs, Animal fossils, South America, Islands, Reptiles
