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Crocodile family tree reveals 250 million years of crocodile evolution

Researchers at the University of York have made a breakthrough discovery in the field of evolutionary biology by mapping the family tree of crocodiles, including their extinct relatives known as Pseudosuchia. 

The comprehensive study offers new insights into the evolutionary history of crocodiles, particularly focusing on the question of why today’s world has such a limited variety of croc species compared to their avian relatives, birds.

Building the crocodile family tree

The team, led by Dr. Katie Davis from the Department of Biology, meticulously combined data from the fossil record with their detailed mapping of the crocodile lineage. 

This approach revealed significant insights into the factors influencing the survival and extinction of these species over millions of years. 

A key finding of the research is the crucial role that ecology played in the survival of different crocodile species. The team discovered that changes in global temperatures affected sea-dwelling and land-based crocodilians differently than freshwater species. 

Interestingly, while the diversity of sea-dwelling and land-based crocodiles increased with rising temperatures, they were more susceptible to extinction due to increased competition for resources, possibly with marine predators like sharks or dinosaurs. 

Bt contrast, freshwater species were less impacted by temperature changes but faced greater extinction risks due to rising sea levels.

Valuable fossil record

This study is not just a deep dive into the past, but holds significant implications for contemporary conservation efforts. 

With several crocodile species today classified as critically endangered or vulnerable, understanding the historical factors that influenced their survival becomes crucial in a world grappling with climate change. 

“The fossil record is a rich source of valuable information allowing us to look back through time at how and why species originate, and crucially, what drives their extinction,” said Dr. Davis. 

“By examining this record and mapping it against the crocodile family tree, our research reveals how important it is to think about ecology when we’re trying to predict how species might respond to today’s climate change.”

“With a million plant and animal species perilously close to extinction, understanding the key factors behind why species disappear has never been more important.”  

“In the case of crocodiles, many species reside in low-lying areas, meaning that rising sea levels associated with global warming may irreversibly alter the habitats on which they depend.”

Crocodile family tree significance

The research highlights the interconnectedness of abiotic factors like climate and biotic interactions such as competition in shaping the evolutionary journey of species. 

By constructing a large phylogeny for all crocodiles and their extinct relatives, the researchers could analyze speciation and extinction patterns in relation to historical climate changes. 

The team employed a type of mathematics called the Information Theory to estimate the impact of these environmental and interactive factors on species emergence and extinction rates.

Crocodiles and their extinct relatives offer unique insights into climate change and its impact on biodiversity in the past, present and future,” said Dr. Davis. “Our findings advance our understanding of what factors have shaped, and continue to shape, life on Earth.”

More about crocodiles

As discussed above, crocodiles, formidable and ancient reptiles, have roamed the Earth for millions of years, showcasing an evolutionary success that demands respect and fascination. These predators, primarily found in tropical regions, display a variety of species, each adapted to its unique environment, yet all sharing certain key characteristics that define their family.

Crocodile features

The most striking feature of a crocodile is its robust, elongated body, covered with tough, scaly skin, which provides defense against predators and harsh environments. Their eyes and nostrils, positioned on top of their heads, enable them to see and breathe while mostly submerged, a trait essential for their ambush hunting style. This positioning, coupled with their excellent night vision, makes crocodiles formidable nocturnal hunters.

Crocodiles boast an impressive set of sharp teeth, designed for gripping and tearing flesh, and their powerful jaws can exert tremendous pressure, ensuring that prey captured rarely escapes. They primarily feed on fish, birds, and mammals, showing a remarkable ability to adapt their diet based on the available prey.

Crocodile reproduction

One of the most fascinating aspects of crocodiles is their nurturing behavior. Despite their fierce reputation, they exhibit a gentle side when caring for their young. Females vigilantly guard their nests and assist hatchlings to water, displaying a level of parental care not commonly associated with reptiles.

Their role in their ecosystems is crucial. As apex predators, crocodiles help maintain the balance by controlling the population of other species, thereby ensuring a healthy ecosystem. Moreover, their nesting behavior contributes to shaping their habitat, influencing the geography of their environment.

Conservation status

Unfortunately, crocodiles face threats from habitat loss and human conflict. Their skins are highly valued in the fashion industry, leading to illegal hunting, which, along with habitat destruction, poses a significant risk to their survival.

In summary, crocodiles, with their ancient lineage and remarkable adaptations, are not just survivors of a bygone era but active, vital participants in their ecosystems. Their continued existence hinges on our ability to understand and protect these magnificent creatures, ensuring they continue to thrive in the wild.

The study is published in the journal Nature Ecology & Evolution.


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