Ancient rays were more diverse than previously thought

A new study led by the University of Vienna has highlighted the puzzling diversity of ancient rays that thrived 150 million years ago. 

The investigation not only reveals a new species of ray but also significantly enriches our comprehension of these prehistoric cartilaginous fish, shedding light on the marine ecosystems of the past.

Late Jurassic fossils

The scientists meticulously examined 52 fossil specimens from the Late Jurassic period, a time when much of Europe was submerged under a sea similar to the modern Caribbean, dotted with islands. These specimens are among the oldest known fully preserved rays, providing a rare and invaluable glimpse into the group’s early evolution. 

Body shape variation among ancient rays

Typically, only the teeth of fossil rays are found, making these complete skeletal finds from Germany, France, and the UK pivotal for understanding their early diversity. 

The research marks the first in-depth analysis of body shape variation among these ancient rays, previously unexplored despite the fossils’ long-standing recognition.

Two new species of ancient rays

The study’s findings challenge previous notions of diversity within Late Jurassic rays, increasing the count of confirmed species from three to five. 

“Until now, only three holomorphic ray species have been confirmed from the Late Jurassic, but thanks to this study, a total of five species have now been identified,” said lead author Julia Türtscher, a paleobiologist at the University of Vienna. 

This includes the validation of a fourth species long debated among scientists and the discovery of a new species, Aellopobatis bavarica. This new species, distinguished from the smaller French Spathobatis bugesiacus by its larger size (up to 170 cm in length) and distinct skeletal and body shape, highlights the hidden diversity within these ancient seas.

Evidence of a complex ecosystem 

The researchers also noted the localized distribution of these five species, suggesting a complex ecosystem but cautioning against premature conclusions regarding their specific habitats. 

“Further studies on the tooth morphology of the specimens and subsequent comparisons with isolated teeth from other sites may help to reconstruct the palaeogeographic distribution of Late Jurassic rays,” Türtscher said.

Ongoing discovery of ancient rays 

These findings not only enhance our understanding of ray biodiversity and evolution during the Upper Jurassic but also inform the identification of fossil ray species known solely through isolated teeth. 

The ongoing discovery of these ancient creatures illuminates the dynamics of past marine ecosystems and emphasizes the value of well-preserved fossils in piecing together Earth’s geological history.

Understanding the past to protect living species

“We can only draw accurate conclusions about living species if we also understand the past of a group, including its evolution, its adaptations to changing environmental factors over time, and the extinction this group has faced during its evolutionary history,” said co-author Patrick L. Jambura, a paleobiologist at the University of Vienna. 

“Palaeobiological knowledge enables us to better understand the dynamics behind evolution and extinction of species and thus aids to develop more effective conservation measures for today’s endangered species,” he concluded. 

Modern rays

Rays are a fascinating group of cartilaginous fish that are closely related to sharks. These creatures are known for their distinctive flat bodies and long, wing-like pectoral fins which span their entire width, giving them a shape reminiscent of a bird or a bat in flight. This unique form allows rays to glide gracefully through the water. 

There are several types of rays, including stingrays, manta rays, electric rays, and eagle rays, each adapted to different environments and lifestyles.

Stingrays

Stingrays are perhaps the most well-known, recognized by their whip-like tails equipped with one or more venomous barbs, which they use defensively against predators. 

Manta rays

Manta rays, on the other hand, are giants that can reach a wingspan of up to 7 meters. Unlike stingrays, they do not have a venomous stinger and are harmless to humans. They feed on plankton, which they filter from the water by swimming with their mouths open wide.

Electric rays 

Electric rays have the ability to produce an electric shock, which they use to stun prey and deter predators. Their bodies contain special organs capable of generating significant voltage. 

Eagle rays

Meanwhile, eagle rays are known for their spotted appearances and deep bodies, often seen leaping out of the water, possibly to escape predators or to dislodge parasites.

Ecological role

Rays play crucial roles in their ecosystems, acting as predators to keep populations of smaller marine organisms in check, and also as prey for larger marine animals. They are found in oceans worldwide, from shallow coastal waters to deep ocean basins. 

Multiple threats

Despite their beauty and ecological importance, many ray species face threats from overfishing, habitat loss, and pollution, leading to declining populations in some areas. Conservation efforts are crucial to ensuring the survival of these remarkable creatures for future generations.

The study is published in the journal Papers in Paleontology.

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