One-billion-year-old Green Seaweeds

This week has seen the publication of a remarkable paper that documents the discovery of tiny one-billion-year-old fossils of green seaweeds that could be the ancestor of the first land plants.

Writing in the academic journal “Nature Ecology and Evolution”, the researchers from Virginia Tech (USA) and the Chinese Academy of Sciences, describe abundant millimetre-sized, multicellular fossils that were preserved in ancient marine sediments close to the city of Dalian in Liaoning Province (northern China).

Evidence of Ancient Green Seaweed

Picture credit: Virginia Tech

Proterocladus antiquus

The microscopic fossils, measuring around two millimetres in length are described as a new species of green algae (Proterocladus antiquus).  The fossil material is interpreted as benthic (living on the sea floor) and members of the Chlorophyta Phylum, which means that these ancient marine plants were photosynthesising 1,000 million years ago and that the fossils are the oldest evidence of green seaweeds known to science.

Shuhai Xiao (Geosciences and Global Change Centre at Virginia Tech), one of the co-authors of the scientific paper commented:

“These new fossils suggest that green seaweeds were important players in the ocean long before their land-plant descendants moved and took control of dry land.  The entire biosphere is largely dependent on plants and algae for food and oxygen, yet land plants did not evolve until about 450 million years ago.  Our study shows that green seaweeds evolved no later than 1 billion years ago, pushing back the record of green seaweeds by about 200 million years.  What kind of seaweeds supplied food to the marine ecosystem?”

Land Plants Evolved from Green Seaweeds

One of the theories proposed for the evolution of land plants is that they originated from marine chlorophytes.  These plants adapted to a life on dry land, the scientists propose that these Chinese fossils represent the ancestors of modern land plants that we see today.

However, Xiao added that not all geobiologists agree with this hypothesis, the debate as to how land plants originated goes on.  For example, some scientists think that green plants first evolved in freshwater environments before adapting to a terrestrial existence.

A Life Reconstruction of the Ancient Green Seaweed P. antiquus

Picture credit: Dinghua Yang/Virginia Tech

Different Types of Seaweed

Scientists have classified three main kinds of seaweed, commonly referred to by their predominant colour.  There is brown (Phaeophyceae), green (Chlorophyta) and red (Rhodophyta).  There are thousands of species of each kind.  Rhodophyta (red seaweed), have a fossil record that also dates back to more than a billion years ago.

Xiao added:

“There are some modern green seaweeds that look very similar to the fossils that we found.  A group of modern green seaweeds, known as siphonocladaleans, are particularly similar in shape and size to the fossils we found.”

Early Plant Fossils

The discovery of such an early photosynthetic plant represents a significant landmark in helping scientists to better understand the evolution and development of planetary ecosystems.  Plants that photosynthesise are essential to the ecological balance of our planet.  They produce carbon and oxygen through the process of photosynthesis and they are regarded as primary producers and comprise the basic components of most food chains.

It was Qing Tang of Virginia Tech, who discovered the micro-fossils of the ancient seaweeds, electron microscopy was used to spot the tiny specimens.  To more easily see the fossils, mineral oil was dripped onto the fossil to create a strong contrast.

Tang commented:

“These seaweeds display multiple branches, upright growths, and specialised cells known as akinetes that are very common in this type of fossil.  Taken together, these features strongly suggest that the fossil is a green seaweed with complex multicellularity that is circa 1 billion years old.  These likely represent the earliest fossil of green seaweeds.  In short, our study tells us that the ubiquitous green plants we see today can be traced back to at least 1 billion years.”

Everything Dinosaur acknowledges the assistance of a press release from Virginia Tech in the compilation of this article.

The scientific paper: “A one-billion-year-old multicellular chlorophyte” by Qing Tang, Ke Pang, Xunlai Yuan and Shuhai Xiao published in Nature Ecology and Evolution.

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Tiny Fossil Sheds Light on Reptile Diversification in the Triassic

Scientists writing in the on-line, open access journal “Scientific Reports”, have published details of a remarkable fossil discovery from a limestone quarry located close to the town of Vellberg in Baden-Württemberg (Germany).  The tiny fossilised remains of juvenile lizard-like reptile are helping palaeontologists to better understand the evolution of modern-day lizards and snakes as well as their taxonomic relationship with a “living fossil” – the tuatara of New Zealand.

A Tiny, Partially Articulated Fossil

The partially articulated fossil, including a beautifully preserved skull, is approximately 240 million-years-old (Middle Triassic – Ladinian faunal stage).  The entire specimen is around ten centimetres long and it has been named Vellbergia bartholomaei and classified as a stem-lepidosauromorph.

The Tiny Preserved Skull of Vellbergia bartholomaei

Picture credit: Scientific Reports

A Decisive Contribution to a Better Understanding of the Evolution of the Reptilia

The Middle Triassic represents a period in Earth’s history where tetrapod faunas were recovering from the global devastation caused by the end Permian extinction event.  However, the paucity of terrestrial vertebrate fossils has limited how much scientists can learn about how the fauna changed and developed during this time, prior to the emergence and eventual dominance of the Dinosauria.

Researchers from the Natural History Museum Stuttgart in collaboration with a colleague from Harvard University (USA), noted that the skeleton of V. bartholomaei showed anatomical traits that link it to both the Order Squamata (lizards and snakes) and the Rhynchocephalia, ancient lizard-like reptiles that includes only one living species, the tuatara (Sphenodon punctatus).

Co-author of the Scientific Paper Dr. Rainer Schoch Holding the Tiny Specimen of Vellbergia bartholomaei

Picture credit: Stuttgart Natural History Museum (Staatliches Museum für Naturkunde Stuttgart)

Vellbergia bartholomaei

Vellbergia is named after the nearby town, whilst the species name honours Alfred Bartholomä of Neuenstein, who was responsible for many of the significant fossil finds associated with rocks of the Middle Triassic age from Germany.  The new species described here falls into the smallest size cluster so far collected from the Vellberg location, and likely represents the first juvenile individual from the site.  This new taxon depicts a mosaic of features that are generally observed in both early evolving rhynchocephalians and squamates, providing a link between the two and suggesting stem-lepidosauromorphs may have survived up to the Middle Triassic.

The mudstones associated with the limestone quarry have proved to be a particularly successful hunting ground for vertebrate palaeontologists.  In 2015, Everything Dinosaur reported upon another discovery made by Dr. Rainer Schoch and his colleagues, the finding of the fossilised remains that provided a fresh insight into the origins of modern turtles (Chelonia).

To read about this fossil discovery: Pappochelys rosinae The Grandfather of all Tortoises and Turtles.

The scientific paper: “A tiny new Middle Triassic stem-lepidosauromorph from Germany: implications for the early evolution of lepidosauromorphs and the Vellberg fauna” by Gabriela Sobral, Tiago R. Simões and Rainer R. Schoch published in Scientific Reports.

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