Fossilized Kelp Holdfasts Shed Light on the Evolution of Seaweed and Marine Mammals

Kelp forests are among the most productive and diverse habitats on Earth, providing food and shelter for thousands of species of fish, invertebrates, mammals, and birds.

They also play a vital role in regulating the climate by absorbing carbon dioxide and producing oxygen. But kelp forests are not a recent phenomenon.

They have a long and fascinating history that dates back to the Cenozoic Era, when the world was very different from what we know today.

In this article, we will explore the secrets of the past hidden in the fossilized remains of ancient kelp forests. We will learn how scientists discovered a 32-million-year-old fossil holdfast that challenges previous assumptions about the age and evolution of kelp forests.

The Mystery of the 32-Million-Year-Old Fossil Holdfast

A recent discovery has unveiled a 32-million-year-old fossil holdfast, challenging previous assumptions about the age of kelp forests along the Pacific Coast.

Scientists initially believed these underwater ecosystems, home to a diverse array of marine life, evolved over the past 14 million years. However, this new finding suggests that kelp forests have been thriving for more than double that time.

The ancient holdfast offers insights into an era where the biodiversity we associate with modern kelp forests was yet to emerge.

This prehistoric underwater world was devoid of otters, sea lions, seals and many bird species that today find sanctuary in these lush green environments.

The holdfast is the root-like part of the kelp that anchors it to rocks or other seafloor structures. The stipe, or stem, extends from the holdfast, supporting the blades that typically float in the water, aided by air bladders.

The fossilized holdfast, which still grasps clams and envelops barnacles and snails, was dated to 32.1 million years ago, in the middle of the Cenozoic Era, which stretches from 66 million years ago to the present.

The oldest previously known kelp fossil, consisting of one air bladder and a blade similar to that of today's bull kelp, dates from 14 million years ago and is in the collection of the University of California Museum of Paleontology.

The new discovery, reported in the journal Proceedings of the National Academy of Sciences, extends the history of kelp forests by more than 18 million years.

Also Read: Scientists Are Growing Kelp in the Lab To Save California's Kelp Forests From Urchin Invasion

The Ancient Inhabitants of the Kelp Forests

More than 32 million years ago, before the appearance of modern groups of marine mammals and birds, these coastal kelp forests were already a rich ecosystem.

They provided sustenance for an ancient now-extinct mammal called a desmostylian - a creature thought to be related to today's sea cows, manatees and their terrestrial relatives, elephants.

Desmostylians were large, hippopotamus-sized grazers that wandered around in the underwater world, feeding on kelp and other plants. They had distinctive teeth that grew continuously throughout their lives, similar to those of rodents.

They also had strong limbs and claws that helped them cling to the seafloor and resist the currents.

Desmostylians are among the most enigmatic groups of marine mammals, as their evolutionary origins and relationships are still unclear.

They first appeared in the fossil record about 33 million years ago and went extinct about 10 million years ago, leaving no living descendants.

Their fossils have been found mostly in the North Pacific, from Japan to Alaska and California, but also in Peru and New Zealand.

The fossilized holdfast provides good evidence for kelp being the food source for desmostylians, as it shows signs of grazing and bite marks. It also suggests that kelp forests were widespread and abundant enough to support these large herbivores.

This revelation not only extends the history of kelp forests but also opens up avenues for understanding prehistoric marine life and ecosystems.

It prompts scientists and researchers to delve deeper into uncharted territories unveiling secrets buried within Earth's ancient oceans.

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