Rosa Rubicondior: Refuting Creationism - Giant Fast-Running Croccodiles In the Caribbean

Sebecids dominated South American landscapes for millions of years, but scientists were perplexed when their fossils started appearing in the Caribbean, too.

Florida Museum image by Jorge Machuky.

Giant croclike carnivore fossils found in the Caribbean – Research News

Six million years before biblical literalist creationists assert Earth and all living creatures were created ex nihilo, giant long-legged, crocodile-like predators known as sebecids were hunting their prey on Caribbean islands. Remarkably, these creatures persisted long after similar species had vanished from South America, where sebecids had become apex predators following the extinction of the dinosaurs 66 million years ago.

Although sebecids went extinct on mainland South America about 11 million years ago, new evidence from Caribbean fossil records shows they survived considerably longer on islands, continuing as apex predators. This finding comes from recent research conducted by a team of palaeontologists from the Florida Museum, who have been compiling evidence over the past three decades. The team's detailed findings have now been published in the journal Proceedings of the Royal Society B. Further insights and context are available in an accompanying Florida Museum news article.

What information do you have on the sebecids? Sebecids were an extinct group of terrestrial crocodile relatives (Mesoeucrocodylia) that lived primarily during the Cenozoic era. Here is a concise overview of key information about sebecids:

Classification

Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Crocodyliformes
Family: Sebecidae
Era: Mainly Paleocene to Miocene epochs (approximately 66–11 million years ago)

Morphology and Adaptations

Sebecids were notable for their terrestrial adaptations. Unlike modern crocodiles, which primarily inhabit aquatic environments, sebecids were land-dwelling predators.
They exhibited elongated limbs, a high stance, and upright gait, adaptations that allowed them to pursue prey actively over land.
Their skull morphology featured elongated, narrow jaws with serrated teeth, suited to hunting and rapidly dispatching terrestrial prey.

Geographical Distribution

Sebecids originated in South America, where they diversified significantly in the Paleogene period following the extinction of the dinosaurs (about 66 million years ago).
Fossil evidence indicates they occupied various terrestrial ecosystems in South America, and recent findings demonstrate their prolonged survival on islands in the Caribbean, even after mainland extinction.

Ecological Role

Sebecids were apex predators in their ecosystems, occupying a niche similar to modern large terrestrial predators like wolves or big cats.
Their extinction on mainland South America about 11 million years ago was likely linked to climatic and ecological changes, competition from emerging mammalian predators, and habitat shifts.
Recent Discoveries

Recent research has uncovered evidence that sebecids persisted longer in the Caribbean islands than previously thought, becoming island apex predators. This has reshaped understanding of their evolutionary timeline and geographic distribution.

Significance in Palaeontology

Sebecids are valuable to science as they demonstrate how crocodilians once occupied diverse ecological niches beyond the semi-aquatic habitats they dominate today.
Studying sebecids helps palaeontologists understand evolutionary transitions and the ecological dynamics of post-dinosaur extinction terrestrial ecosystems.

Do they represent a return to a terrestrial existence of an aquatic ancestor?

Yes, sebecids represent a significant evolutionary shift—essentially a return to terrestrial life—by ancestors whose lineage had previously adapted to semi-aquatic or fully aquatic habitats.

Evolutionary Context:

Early Crocodylomorphs (the broader group including crocodiles and their extinct relatives) initially diversified in terrestrial habitats during the Mesozoic era (particularly the Triassic and Jurassic periods). Early forms, such as the sphenosuchians, were primarily terrestrial animals.
Through evolutionary history, many crocodylomorph lineages independently adopted semi-aquatic or fully aquatic lifestyles. The ancestors of modern crocodilians adapted to life in rivers, lakes, and coastal marine environments.

Return to Terrestrial Life:

Sebecids specifically evolved from ancestors that were predominantly aquatic or semi-aquatic, representing a reversal—an evolutionary return—to terrestrial life.
Their skeletal adaptations clearly indicate increased limb length, an upright gait, and skull features optimised for terrestrial predation.
Sebecids thus highlight evolutionary plasticity: their lineage reverted from aquatic or semi-aquatic forms back into highly specialised terrestrial predators.

Adaptive Significance:

This terrestrial shift allowed sebecids to exploit new niches, especially after the extinction of the dinosaurs left many predator roles vacant in terrestrial ecosystems.
Their terrestrial adaptations enabled them to occupy the apex predator role in the Cenozoic ecosystems of South America and later in Caribbean islands.

Comparison with Modern Crocodilians:

Modern crocodilians are semi-aquatic, but sebecids show clearly that the crocodilian lineage has repeatedly experimented with terrestrial lifestyles throughout their evolutionary history.
Sebecids exemplify convergent evolution: adapting independently to lifestyles similar to large mammalian terrestrial predators.

In summary, sebecids represent an evolutionary lineage of crocodile relatives that returned to terrestrial habitats, demonstrating the adaptability and evolutionary experimentation of crocodyliforms over millions of years.

Giant croclike carnivore fossils found in the Caribbean
Imagine a crocodile built like a greyhound — that’s a sebecid. Standing tall, with some species reaching 20 feet in length, they dominated South American landscapes after the extinction of dinosaurs until about 11 million years ago. Or at least, that’s what paleontologists thought, until they began finding strange, fossilized teeth in the Caribbean.

The first question that we had when these teeth were found in the Dominican Republic and on other islands in the Caribbean was: What are they?

Jonathan Bloch, co-author.
Florida Museum of Natural History
University of Florida, Gainesville, FL, USA.

This initial confusion was warranted. Three decades ago, researchers uncovered two roughly 18 million-year-old teeth in Cuba. With a tapered shape and small, sharp serrations specialized for tearing into meat, they unmistakenly belonged to a predator at the top of the food chain. But for the longest time, scientists didn’t think such large, land-based predators ever existed in the Caribbean. The mystery deepened when another tooth turned up in Puerto Rico, this one 29 million years old. The teeth alone weren’t enough to identify a specific animal, and the matter went unresolved.

That changed in early 2023, when a research team unearthed another fossilized tooth in the Dominican Republic — but this time, it was accompanied by two vertebrae. It wasn’t much to go on, but it was enough. The fossils belonged to a sebecid, and the Caribbean, far from never having large, terrestrial predators, was a refuge for the last sebecid populations at least 5 million years after they went extinct everywhere else.

A research team described the implications of their finding in a new study published in the Proceedings of the Royal Society B. The study’s lead author, Lazaro Viñola Lopez, conducted the research as a graduate student at the University of Florida. He knew his team members had come upon something exceptional when they unearthed the fossils.

That emotion of finding the fossil and realizing what it is, it’s indescribable

Lazaro W. Viñola Lope, lead author
Florida Museum of Natural History
University of Florida, Gainesville, FL, USA.

Sebecids were the last surviving members of the Notosuchia, a large and diverse group of extinct crocodilians with a fossil record that extends back into the age of dinosaurs. They varied widely in their size, diet and habitat preferences and were notably different from their crocodile relatives, as most of them lived entirely on land.

The sebecids acted like carnivorous dinosaurs, sprinting after prey on their four long, agile limbs and tearing through flesh with their notorious teeth. Many had protective armor made of bony plates embedded in their skin. The mass extinction event 66 million years ago that wiped out nonavian dinosaurs nearly destroyed notosuchians as well. In South America, only the sebecids endured, and with the dinosaurs gone, they quickly rose to be the apex predator.

The open sea separating the Caribbean islands and mainland South America would have posed a serious challenge for a terrestrial sebecid to swim across. In finding the fossils, the research team revealed possible evidence in support of the GAARlandia hypothesis. This theory suggests a pathway of temporary land bridges or a chain of islands once allowed land animals to travel from South America to the Caribbean.

If, as scientists hypothesize, the serrated teeth discovered on other Caribbean islands also belonged to a sebecid, the history of these giant reptiles extends beyond the Dominican Republic. They would have occupied and shaped the region’s ecosystems for millions of years. Yet today you’d be hard-pressed to find evidence of the large terrestrial predators. In their absence, smaller endemic predators like birds, snakes and crocodiles have evolved to fill the gap in the food chain.

You wouldn’t have been able to predict this looking at the modern ecosystem. The presence of a large predator is really different than we imagined before, and it’s exciting to think about what might be discovered next in the Caribbean fossil record as we explore back further in time.

Jonathan Bloch.

Sebecids dominated South American landscapes for millions of years, but scientists were perplexed when their fossils started appearing in the Caribbean, too. Florida Museum image by Jorge Machuky

This revelation aligns with similar observations ecologists have described worldwide. Islands are known to act as “museums of biodiversity,” providing a haven that allows plants and animals to survive even after their related species have gone extinct on the mainland.

Although the tropics are among the most biodiverse places on Earth, much of their natural history remains a mystery. That’s why, according to Bloch, they’re the most important — albeit challenging — regions for paleontologists to study.

Historically, many paleontologists in the Caribbean have excavated fossils from caves and blue holes, where large accumulations of remains are often found. Caves can serve as shelter against harsh conditions for animals, and predatory birds like owls and hawks frequently bring their prey inside to eat, leaving behind pellets or discarded bones. Blue holes preserve fossils exceptionally well, as they lack the oxygen that fuels decay.

But these locations only provide a narrow snapshot of past biodiversity because most of the fossils are relatively young. While these sites provide valuable insight into recent history, they have their limitations when it comes to older, less well-known fossils.

Today, Caribbean paleontologists are taking a new approach. Finding deep-time fossils often requires more effort and fortunate circumstances, but they’re willing to face the obstacles. “This is like a renaissance,” said Viñola-Lopez, describing the renewed interest and excitement in the region.

Local scientists have the advantage of being able to react quickly when a potential fossil bed is discovered. The dry, rocky landscapes that contain fossils are hard to come by in the Caribbean, where wind and rain erode outcrops and today’s forests cover fossil beds.

Outcrops don’t last too long, so you go there when you can. When they’re cutting the road or a few months after that, you find the fossils. If you’re looking in a few years, it will be gone.

Lazaro W. Viñola Lopez.

Finding sebecid fossils in the Dominican Republic site was possible because local work crews happened to be cutting a road directly through it. Elson Core, a graduate student from the University of Puerto Rico in Mayagüez at the time, came across the fossil beds while conducting stratigraphy research and alerted his colleagues. Viñola-Lopez learned about the site through fellow paleontologists and was eager to plan a visit for fieldwork.

This study represents one of many incredible discoveries that have recently come out of the Caribbean. Lazaro and his colleagues uncovered the Caribbean’s first record of mosasaurs, enormous reptiles that once dominated the seas. Meanwhile, the discovery of the oldest ground sloth fossils in Hispaniola has helped fill a gap in the region’s paleontological record.

Even more recent mysteries are coming into focus as well, with research suggesting the arrival of humans may be to blame for the extinction of the island’s native rodents. This flow of information and discovery emerging from the region is far from over. As Viñola-Lopez said, “The sebecid is only the tip of the iceberg.”

Jorge Vélez-Juarbe of the Natural History Museum of Los Angeles County, Philippe Münch of Géosciences Montpellier, Juan N. Almonte Milan of Museo Nacional de Historia Natural ‘Prof. Eugenio de Jesús Marcano’, Pierre-Olivier Antoine and Laurent Marivaux of Institut des Sciences de l’Evolution de Montpellier and Osvaldo Jimenez-Vasquez of La Oficina del Historiador de La Habana are also co-authors of the paper.

Publication:
Viñola López Lázaro W., Velez-Juarbe Jorge, Münch Philippe, Almonte Milan Juan N., Antoine Pierre-Olivier, Marivaux Laurent, Jimenez-Vasquez Osvaldo and Bloch Jonathan 2025
A South American sebecid from the Miocene of Hispaniola documents the presence of apex predators in early West Indies ecosystems Proc. R. Soc. B. 292: 20242891 http://doi.org/10.1098/rspb.2024.2891

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.

1. Introduction
The West Indies had a high diversity of endemic terrestrial vertebrates during the late Quaternary, resulting from millions of years of dispersal events (largely from South America) and subsequent in situ evolutionary radiations across the Cenozoic. The mode and tempo of vertebrate colonizations have been debated for over a century [1,2]. Some studies argue that the Core Greater Antilles (CGA; Cuba–Hispaniola–Puerto Rico) were colonized through a short-lived land connection or string of islands known as GAARlandia around the Eocene/Oligocene transition (EOT) (e.g. [3–8]). Geological reconstructions of GAARlandia suggest that it coincided with a drop in eustatic sea level and the uplift of the Aves Ridge at the EOT, connecting part of the CGA with northern South America for nearly two million years [4]. Results from recent geotectonic studies in the Lesser Antilles suggest that large islands in this area were exposed several times between the Eocene and the Pliocene, and that the distance between Puerto Rico and northern South America was significantly shorter than previously estimated, potentially facilitating dispersals from the continent to the islands [9–11]. Meanwhile, other studies argue that the island communities, which lack carnivores, marsupials, ungulates, and several clades of frogs and reptiles, were assembled as a result of colonization through long-distance overwater dispersal [12–17]. The absence of specialized terrestrial carnivores on islands has long-lasting ecological effects that ripple down through terrestrial ecosystems, often associated with mesopredator release and secondary flightlessness among birds [18–20]. These effects are well documented in modern and late Quaternary communities in the Caribbean, where crocodiles and birds acted as top predators with secondary adaptations to a more terrestrial lifestyle [21–23], and numerous clades of birds evolved flightlessness and terrestrial specializations independently (e.g. [21,24–26]).

In the late Eocene to early Oligocene, the time interval proposed for the GAARlandia landspan, the terrestrial carnivore guild in South America included metatherian mammals (Sparassodonta), large snakes (Madtsoiidae), large birds (Phorusrhacidae) and notosuchian crocodyliforms (Sebecidae) [27,28]. Sebecids had distinctive labio-lingually compressed and serrated (ziphodont) teeth and postcranial adaptations to terrestriality. They inhabited Europe in the late Cretaceous and South America through most of the Cenozoic until the early Late Miocene [28–30]. Fossil ziphodont crocodyliform teeth have previously been recovered from the Early Miocene of Cuba [22], but due to the independent evolution of this dental morphology in notosuchians and at least two other neosuchian clades, taxonomic attribution to a specific group has been lacking [31]. Here, we report the first unambiguous record of a sebecid outside of South America during the Cenozoic and argue that these South American terrestrial apex predators were probably a dominant part of the food web in the West Indies for much of the Neogene.

Viñola López Lázaro W., Velez-Juarbe Jorge, Münch Philippe, Almonte Milan Juan N., Antoine Pierre-Olivier, Marivaux Laurent, Jimenez-Vasquez Osvaldo and Bloch Jonathan 2025
A South American sebecid from the Miocene of Hispaniola documents the presence of apex predators in early West Indies ecosystems Proc. R. Soc. B. 292: 20242891 http://doi.org/10.1098/rspb.2024.2891

Copyright: © 2025 The authors.
Published by The Royal Society. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

The discovery of late-surviving sebecids in the Caribbean presents a significant challenge to Bible-literalist creationism, which asserts that all life on Earth was created in its present form around 6,000 to 10,000 years ago. The sebecid fossils found on Caribbean islands are dated to around 11 million years ago—millions of years before the supposed 'Creation Week'.

Firstly, these dates are established using multiple, independently verified radiometric dating techniques, corroborated by the geological context and biostratigraphic evidence. For this discovery to fit within a young-Earth framework, an entire scientific infrastructure—encompassing radiometric dating, sedimentology, comparative anatomy, and evolutionary biology—would have to be discarded or rewritten without credible alternative mechanisms. In other words, several entire, established bodies of science would need to be abandonned in favour of evidence-free dogma.

Secondly, the evolutionary history of sebecids illustrates a branching, adaptive process extending over tens of millions of years. Sebecids first appeared in South America after the extinction of the non-avian dinosaurs and diversified into terrestrial predators, eventually becoming extinct on the mainland around 11 million years ago. The survival of a remnant population in the Caribbean points to isolated evolutionary persistence, a scenario that makes sense within evolutionary theory and plate tectonic models but is wholly inconsistent with a global flood model or the notion of fixed 'kinds' created all at once. These patterns in the fossil record show not sudden appearance or stasis, but gradual adaptation, migration, and extinction—hallmarks of deep time and evolutionary change.

In essence, the existence of Caribbean sebecids at such a late geological date—and in such a specific ecological and geographic context—contradicts the central claims of young-Earth creationism. Their story is not one of static design but of long-term survival, adaptation, and eventual extinction—narratives that align with evolutionary processes and contradict the idea that Earth's biosphere is only a few thousand years old and unchanging since creation ex nihilo without ancestry.

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