4億年前陸地上最大的生物體，科學家至今無法解釋

Recently CNN.com reported the following:

The largest life-form on land 400 million years ago was one that scientists can’t explain

CNN - By Katie Hunt

Updated Feb 5, 2026

Some 400 million years ago, long before dinosaurs or even trees had evolved, an enigmatic organism towered over the landscape like a prehistoric monolith.

Now, new research makes the case that the ancient life form is not a plant, animal or fungi and instead may be a completely unknown form of multicellular life.

“What we can say, based on all of those new analyses, is that it’s so different from any modern group we have,” said Corentin Loron, a palaeontologist at Edinburgh University and a co-lead author of the research, which published in the journal Science Advances last month.

First identified 160 years ago, the fossils — known as Prototaxites — measure up to 30 feet (around 9 meters) tall and have long defied easy classification.

In the 19th century, scientists initially thought Prototaxites was the rotten trunk of a conifer. Subsequent study, however, revealed it was composed of interwoven tubes, rather than the block-like cells that make up plant tissue.

Other scientists argued that it was a lichen-like mass, a symbiotic association between a fungus and algae. In recent years, some researchers thought the organism more closely resembled a fungus, in part because it didn’t appear to produce energy through photosynthesis.

The new research focused on three Prototaxites fossils unearthed in the Rhynie chert, a prehistoric land ecosystem near Aberdeen, Scotland. The Rhynie chert is home to the best-preserved examples of the earliest plants, fungi and fauna that colonized land 400 million years ago, during a period known as the early Devonian. The site was once an ancient hot spring like Yellowstone.

The exceptional preservation of the fossils embedded in the rock at the Rhynie chert allows scientists, with the right tools, to detect the chemical signatures of long-vanished molecules, known as fossilization products.

“We are able to still have signatures that inform us about the original composition of those fossils, meaning it’s not overcooked, it’s not overly transformed by the geology,” Loron explained.

Unanswered questions

The new analysis by Loron and his colleagues suggests that the biomarkers in Prototaxites fossils were chemically distinct from those of fossilized fungi found at the site and preserved in similar conditions. Fungi fossils preserved in the chert contained compounds from the breakdown of chitin and glucan, key structural molecules in fungi. Prototaxites, however, lacked these biomarkers.

“If Prototaxites was fungi, we would have expected it to follow the same trend as the fungi because they are next to each other in the same burial conditions,” Loron said.

Other structural features — such as a complex branching pattern within dark spherical spots in the fossil that could have carried out a gas, nutrient, water, or served another exchange function — were distinct from all known fungi, whether living or extinct, the researchers noted in the study. Based on these results, it is too early to shoehorn Prototaxites into a specific category, according to the team.

Different species of Prototaxites might have varied in size, but the largest would have really towered over the landscape at a time when plants were less than 1 meter tall, said Kevin Boyce, a professor of Earth and planetary sciences at Stanford University. His work on Prototaxites fossils has shown that the ancient organisms didn’t use photosynthesis to produce energy from light like plants, but likely consumed carbon sources in the environment — just as some living fungi live off decomposing organic matter.

“People have compared it to specific fungi or algae in the past, and they were doing their best with the information they had at the time, but we now have a much better handle on the overall tree of life and Prototaxites is too old for those comparisons to be valid,” Boyce, who wasn’t involved in the study, said in an email.

“You can compare it to mushrooms, but mushrooms just aren’t that old,” he added. “That doesn’t mean Prototaxites is or isn’t a fungus (or anything else), just that its form would have evolved independently from the mushrooms and other complex multicellular examples amongst fungi that we have now.”

Marc-André Selosse, a professor at the Natural History Museum in Paris, said the authors of the new study conducted “wonderful analyses” but noted the research only examined one of 25 known species of Prototaxites. Selosse, who also didn’t take part in the work, said he thought it was still possible that the organism functioned in a lichen-like way.

“The sampling is not encompassing the diversity of Prototaxites species,” Selosse said. “So for me, it doesn’t make it as a finished story.”

Loron said there is still much that is unknown about Prototaxites. For example, it’s not clear how Prototaxites were anchored to the ground or whether the organism, which is thought to have grown slowly, was upright for its whole lifespan. His team is planning follow-up studies on fossilized tubular organisms similar to Prototaxites to further the research.

“Sometimes it’s scary to not know what something is, but it’s also scientifically exciting,” Loron said.

Translation

4億年前陸地上最大的生物體，科學家至今無法解釋

大約4億年前，遠在恐龍甚至樹木出現之前，一種神秘的生物體如同史前巨石般聳立於大地之上。

如今，一項新的研究表明，這種古代生物體並非植物、動物或真菌，可能是一種完全未知的多細胞生物。

愛丁堡大學古生物學家、該研究的共同第一作者Corentin Loron說道:「基於所有這些新的分析，我們可以說，它與我們已知的任何現代生物類群都截然不同」。這項研究已於上月發表在《科學進展》（Science Advances）雜誌上。

這些化石－被稱為原杉菌（Prototaxites）- 在160年前首次被發現，它們高達30英尺（約9公尺），長期以來一直難以被歸類。

19世紀，科學家最初認為原杉菌（Prototaxites）是針葉樹腐爛的樹幹。然而，隨後的研究表明，它是由交織的管子組成，而不是構成植物組織的塊狀細胞。

另一些科學家則認為它是一種類似地衣的團塊，是真菌和藻類之間的共生體。近年來，一些研究人員認為這種生物更接近真菌，部分原因是它似乎不會透過光合作用產生能量。

這項新研究聚焦於蘇格蘭Aberdeen附近, 稱為瑞尼燧石層（Rhynie chert）的近史前陸地生態系中出土的三塊原杉菌化石。瑞尼燧石層保存著4億年前稱為Devonian（泥盆紀）最早期興盛的植物、真菌和動物群的最佳化石標本。該遺址曾像黃石公園一樣，是個古老的溫泉。

瑞尼燧石層中化石保存得異常完好，這使得科學家能夠借助合適的工具，探測到早已消失的分子（即化石化產物）的化學特徵。

Loron解釋道: 「我們仍然能夠獲得這些特徵，它們可以告訴我們這些化石的原始成分，這意味著它們沒有被過度熱化，也沒有被地質作用過度改變」。

未解之謎

Loron及其同事的最新分析表明，原杉菌化石中的生物標記與在同一地點發現的、保存條件相似的真菌化石的生物標記在化學成分上截然不同。保存在燧石中的真菌化石含有甲殼質和葡聚糖分解產生的化合物，而甲殼質和葡聚糖是真菌的關鍵結構分子。然而，原杉菌化石卻缺乏這些生物標記。

Loron說: 「如果原杉菌是真菌，我們原本預期它會與真菌的生物標記呈現相同的趨勢，因為它們彼此相鄰，且處於相同的埋藏條件下」。

研究人員在研究中指出，其他結構特徵 - 例如化石中深色球狀斑點內複雜的枝狀結構，這些結構可能負責氣體、營養物質、水分的輸送，或發揮其他交換功能 - 與所有已知的真菌（無論現存或已滅絕）都截然不同。研究團隊認為，基於這些結果，現在就將原杉菌（Prototaxites）歸入某個特定類別還為時過早。

史丹佛大學地球與行星科學教授Kevin Boyce表示，不同種類的原杉菌體型可能有所差異，但最大的原杉菌出現在一般植物高度不足1米的時代，無疑會成為地貌上的龐然大物。他對原杉菌化石造出的研究表明，這些遠古生物不像植物那樣利用光合作用從光中獲取能量，而是可能像某些現存真菌以分解有機物為生一樣，從環境中吸收碳源為生。

並未參與這項研究的Boyce 在一封電子郵件中寫道:「過去人們曾將它與特定的真菌或藻類進行比較，他們當時也只是盡力利用已有的信息進行分析。但現在我們對整個生命之樹有了更深入的了解，而原杉菌的出現時間太早了，當時的比較已經不再有效了」。

他補充道:“你可以把它和蘑菇比較，但蘑菇的出現時間並沒有那麼早”，“這並不意味著原杉菌是或不是真菌（或其他任何生物），只是說它們與我們現在所知的蘑菇和其他複雜的多細胞真菌是獨立地去演化的產物。”

巴黎自然歷史博物館的教授Marc-André Selosse表示，這項新研究的作者進行了“精彩的分析”，但他指出，這項研究只考察了已知的25種原杉菌中的一種。Selosse也未參與這項研究，但他表示，他認為這種生物體仍然有可能以類似地衣的方式運作。

Selosse說: “目前的採樣並未涵蓋原杉菌物種的全部” ， “所以對我來說，這還不足以說已寫出了一個完整的故事。”

Loron表示，關於原杉菌，我們仍然有很多未知之處。例如，目前尚不清楚原杉菌是如何固定在地面上的，也不清楚這種被認為生長緩慢的生物是否終生保持直立。他的團隊計劃對與原杉菌類似的管狀化石生物進行後續研究，以推進相關調查。

Loron說: 「有時候，不知道某些東西是什麼會讓人感到害怕，但從科學角度來說，這也令人興奮的」。

So, some 400 million years ago, long before dinosaurs or even trees had evolved, an enigmatic organism called Prototaxites towered over the landscape like a prehistoric monolith. Now, new research makes the case that this ancient life form is not a plant, animal or fungi and instead may be a completely unknown form of multicellular life. There is still much that is unknown about Prototaxites. Apparently, further the research is needed in order to know more about this organism.

Note:

1.Prototaxites (原杉菌) is an extinct genus of large macroscopic eukaryote dating from the Late Silurian until the Late Devonian periods. Prototaxites formed large trunk-like structures up to 1 metre (3 ft) wide, reaching 8 metres (26 ft) in height, made up of tiny interwoven tubules around 50 micrometres (0.0020 in) in diameter, making it by far the largest land-dwelling organism of its time. The taxonomy of Prototaxites has long been the subject of debate. (Wikipedia)

2. Rhynie chert (瑞尼燧石層) refers to a type of fossil-rich silica rock that originates from the Early Devonian period. It is significant in paleontology for preserving some of the oldest known land plants and their associated organisms. (ChatGPT)

3. The Devonian (泥盆紀) is a geologic period and system of the Paleozoic era during the Phanerozoic eon, spanning 60.3 million years from the end of the preceding Silurian period at 419.62 million years ago, to the beginning of the succeeding Carboniferous period. It is named after Devon, South West England, where rocks from this period were first studied. (Wikipedia)