The Ordovician Shallow Seas Diorama (Smithsonian)

Ce diorama de la vie ordovicienne a été réalisé en 1955 par George et Paul Marchand, nés dans un monde de dioramas de musée et d'art détaillé. Leur père, Henri Marchand, a étudié la sculpture auprès du célèbre Auguste Rodin en France, puis s'est installé avec sa femme Clothilde pour travailler aux États-Unis au New York State Museum. George et Paul ont collaboré avec leur père pour créer des dioramas époustouflants du monde naturel. Les Marchand ont poursuivi leur travail au Buffalo Museum of Science et, dans les années 1930, George et Paul ont repris le travail de leur père sur les dioramas. Les Marchand ont été les pionniers de techniques de création de scènes réalistes, grandeur nature, qui trompaient l'œil avec leurs arrière-plans incurvés et leurs spécimens empaillés.

Depuis lors, on a beaucoup appris sur ces fossiles étonnants. Qu'ont découvert les scientifiques ?

L'algue verte est hypothétique et probablement erronée. Les éléments qui ressemblent à des algues dans les dioramas pourraient être des interprétations erronées de ce que nous savons aujourd'hui être des traces fossiles. Si de véritables algues étaient représentées, elles aussi seraient courbées par le courant.

Dans les années 1970, les scientifiques ont utilisé pour la première fois des submersibles en eaux profondes pour explorer l'océan. Grâce à ces observations directes, nous savons aujourd'hui que les crinoïdes modernes s'inclinent avec le courant, les bras écartés formant un large cône. Il est donc probable que ces crinoïdes préhistoriques n'étaient pas aussi droits et tournés vers le haut.

Les coraux rugueux (« cornes ») sont représentés à la verticale. Les coraux modernes de forme similaire sont enfouis, seul le polype étant exposé ; nous les représenterions donc désormais sur ou dans le fond marin.

Comme leurs cousins plus petits du diorama, les grands céphalopodes nautiloïdes à coquille droite ne se reposaient pas passivement sur le fond marin. Il s'agissait probablement de prédateurs mobiles, nageant (à reculons, par propulsion par réaction) et chassant au ras du fond.

Les ventouses sur les tentacules de ces nautiloïdes pourraient être incorrectes. Leurs tentacules auraient pu avoir des gaines tentaculaires (comme le Nautilus moderne) plutôt qu'aucune (comme la pieuvre moderne).

Trouvé ici.

Virtual Silurian Reef Site (Field Museum)

Dans cette mer silurienne, les stromatoporoïdes et les coraux tabulés ont construit d'anciens récifs. Les prairies de crinoïdes et les fourrés de bryozoaires ont déjoué les forts courants, tandis que les stromatoporoïdes et les bryozoaires encroûtants ont lié et cimenté les sédiments meubles et la vase. Les céphalopodes nautiloïdes orthoconiques sillonnaient les récifs à la recherche de leurs proies : les trilobites, des arthropodes rampants et fouisseurs de boue aujourd'hui disparus. Pendant ce temps, des bancs denses de milliers de brachiopodes pentamérides filtraient l'eau pour se nourrir. Dans le Wisconsin, les récifs atteignaient 10 mètres de haut dans des eaux peu profondes, tandis qu'au sud, dans l'Illinois, des eaux plus profondes ont permis aux récifs de prospérer et de dépasser les 100 mètres de haut. Jusqu'alors, il s'agissait des plus grandes structures biologiques produites et de la biodiversité la plus riche au monde.

Trouvé ici.

Honeyman's Silurian Paradise (Nova Scotia Museum)

Un diorama du musée de la Nouvelle-Écosse représentant le fond marin du Silurien montrant un trilobite, un nautiloïde orthocère, un brachiopode et des gastéropodes.

Trouvé ici.

Diorama de la vie marine du Silurien (Institut de recherche paléontologique d'Ithaca)

Diorama de la vie marine du Silurien, autrefois exposé au Musée national d'histoire naturelle de la Smithsonian Institution. Il est aujourd'hui conservé à l'Institut de recherche paléontologique d'Ithaca, dans l'État de New York.

Trouvé ici.

The Arms Race That Made Insects Take Flight (PBS Eons)

 

Codex Eurypterida

Extraits de cette étude:

Codex Eurypterida: A Revised Taxonomy Based on Concordant Parsimony and Bayesian Phylogenetic Analyses

Abstract

Eurypterids, also known as sea scorpions, were aquatic chelicerate arthropods that were important components of Paleozoic marine and freshwater ecosystems from the Ordovician to the Permian. The group represents an excellent subject for studies into evolution due to their exceptionally preserved fossils which frequently reveal almost complete details of the exoskeleton, including the appendages, which allows for interpretation of their roles in ancient ecosystems. 

This contribution presents an overview of the 200-year history of eurypterid research and their occurrence in popular media before presenting an updated classification for Eurypterida based on concordant parsimony and Bayesian phylogenetic analyses of 238 morphological characters coded for 152 species. 

This represents the first comprehensive treatment of eurypterid systematics in 35 years and includes evaluation of every known described species of eurypterid. In the process several species names occurring in the Russian literature are shown to be invalid. The appropriate taxonomic authorities for Eurypterida, Stylonurina, and Eurypterina are revised and a revision conducted of all known species. Eighteen new taxa are proposed; the superfamily Waeringopteroidea, the families Brachyopteridae, Stylonurellidae, Strobilopteridae, Waeringopteridae, Nanahughmilleriidae, Parahughmilleriidae, Pittsfordipteridae, Ciurcopteridae, Herefordopteridae, and Hunanopteridae, and the genera Athenepterus, Waterstonopterus, Barusopterus, Cruinnopterus, Selkiepterella, and Hunanopterus. The species name Strobilopterus proteus is also formally made available for the first time. 

Eurypterid anatomical terminology is updated and standardized. Reviewing previous analyses of macroevolutionary and macroecological trends within eurypterids in light of the revised relationships suggested here indicates that their conclusions are still generally supported, although the history of eurypterid geographic occurrence and dispersal is more complicated than previously considered. 

Recent discoveries of eurypterids from the paleocontinent of Gondwana represent some of the more exciting new developments in eurypterid research and it is likely that more eurypterids will be found in these regions in the future. 

Ongoing research into eurypterid ontogeny and macroevolution is detailed and understudied aspects of eurypterid paleobiology, including their ichnological record, role in paleocommunities, and taphonomy are explored. Suggestions are made for inroads into these relatively neglected research programs. 

Common misconceptions about eurypterids are also addressed; no eurypterid is known to possess a venomous sting in its tail, and while eurypterids likely congregated to shed their exoskeletons there is no compelling evidence that they mated en masse.

 

Rare Fossil Discovery Sheds Light on Ancient Life in New York

Extrait de l'article:

A newly published scientific paper is highlighting a remarkable discovery from the New York State Museum’s paleontology collection: a 420-million-year-old fossil from the Silurian Period, identified as Naraoia bertiensis. This incredibly rare specimen is one of only two known fossils of its kind ever found from this era, offering groundbreaking insights into the evolution and distribution of early marine life. 

Naraoia were soft-bodied arthropods that once roamed the sea floor. During the Silurian Period, the region we now call New York was located south of the equator and submerged under a shallow tropical sea—ideal conditions for ancient marine ecosystems. However, due to their delicate, flexible exoskeletons, Naraoia fossils could only form under exceptional conditions, making discoveries like this exceedingly uncommon. 

The fossil was found on private property near Herkimer, New York, though the exact date of its discovery is unknown. Its presence in the Museum’s collection has now provided scientists with critical new data on the species’ geographic range and survival into the Silurian, long after its peak in the Cambrian Period. 

The study, titled Novel evidence for the youngest Naraoia and a reassessment of naraoiid paleobiogeography, was co-authored by Dr. Lisa Amati, New York State Paleontologist, along with researchers from the American Museum of Natural History and the Czech Republic. Their work highlights how even a single fossil can offer key insights into the history of life on Earth. 

This discovery also underscores the importance of museum collections in supporting cutting-edge research. Behind the scenes, Museum scientists continue to reveal hidden stories from New York’s deep past—stories that help us better understand the ancient world and the ever-evolving history of life on our planet.

 

There's An Invisible Ocean Between These Fossils (PBS Eons)

 

Clades de trilobites

Voici deux diagrammes des grands clades de trilobites. 

On voit que la disparition de ces animaux s'est faite en deux temps, à la fin du Dévonien puis à la crise Permien/Trias. 

Le dernier groupe, les proetida, ont quand même eut une grande répartition géographique et qui a plus ou moins comblé le manque de diversité. 

Les dinosaures n'ont jamais rencontré de trilobites ; il y a près de 20 millions d'années entre le dernier trilobite et le premier dinosaure.

En lien une vidéo d'Alexis Rastier sur le sujet : https://www.youtube.com/watch?v=KDC7sNFGwio

Faune cambrienne (Schistes de Burgess)

Hallucigenia:

Ottoia:

Wiwaxia:

Opabinia: 

Pikaia: 

Plus d'infos ici.

L’explosion cambrienne (The Economist)

Plus d'infos ici.

Roncellia perceensis

Marc R. Haensel: 

The largest trilobite you've never heard of: Roncellia perceensis from the Lower Devonian of Percé, Quebec. MHC-00639.

With a pygidium nearly 15cms wide, I'd imagine the complete trilobite to be over 40cms long!

Trouvé ici.

Musée de la paléontologie et de l'évolution (3 février 2024)

 

Eurypterus lacustris

A massive, 440 million year old Sea Scorpion (Eurypterus lacustris) from Fort Erie, Ontario.

Website: https://paleoarchives.square.site/

This might be the oldest creature to have ever lived on land

Extrait de l'article:

Scientists now believe that a fossilized relative of the modern millipede discovered in Scotland represents the earliest evidence of an animal living on land.

This terrestrial trailblazer that lived roughly 425 million years ago led the way for assemblages of land creatures that would come to dominate Earth.

One idea about how life began on Earth theorizes that it began in bodies of water. The cocktail of gases in the atmosphere mixed with lightning strikes is thought to have allowed monomers such as amino acids to spontaneously form in the oceans. This is known as the “primordial soup” theory. Out of this life-creating stew, bugs known as arthropods (which includes insects, spiders, crustaceans, and centipedes) are thought to have been some of the very first animals to venture onto land.

There’s indirect soil-based evidence that other insects like soil worms crawled on land before the myriapods. However, the evidence may only indicate fleeting trips to the land above water. Myriapods, we know, made land their permanent home. The fossil of the ancient millipede-like creature, Kampecaris obanensis, was first discovered in 1899 on the Scottish isle of Kerrera. Now, it’s been radiometrically dated to 425 million years ago. That would make these multi-legged critters the oldest land animal ever to have lived out of water. (At least, that we know of.) Their pioneering journey out of the sea set forth an explosive multiplication of new terrestrial life forms. Just 20 million years after Kampecaris made the move to land, the fossil record shows a plethora of bug deposits. Fast-forward another 20 million years and there is evidence that spiders, insects, and tall trees were thriving in ancient forest communities.

“It’s a big jump from these tiny guys to very complex forest communities, and in the scheme of things, it didn’t take that long,” said geoscientist Michael Brookfield from the University of Texas and the University of Massachusetts in Boston, in a press release. “It seems to be a rapid radiation of evolution from these mountain valleys, down to the lowlands, and then worldwide after that.”

We can’t be sure that Kampecaris is actually the very first creature to have lived on land, as it’s possible that there are older undiscovered fossils of both plants and bugs. However, no earlier findings have been made despite the fact that researchers have been investigating some of the most well-preserved fossils from this era. The team thinks this may indicate that they have reached the end of the land fossil record and that this ancient millipede represents the vital turning point at which life moved onto land.

According to this new study, Kampecaris is about 75 million years younger than the age other scientists have estimated the oldest millipede to be using a technique known as molecular clock dating, which is based on DNA’s mutation rate. Similarly, fossils of stemmed plants in Scotland have also been evaluated as being roughly 75 million years younger than researchers once thought. So, if this ancient critter really was the first bug to blaze the trail onto Earth, then scientists have been greatly underestimating how rapidly bugs and plants evolved to transition to life on land.

“Who is right, us or them?” study co-author Elizabeth Catlos said. “We’re setting up testable hypotheses – and this is where we are at in the research right now.”

Despite the potentially huge evolutionary significance of Kampecaris, this was the first study to address the fossil’s age. One reason for that could be the challenge of extracting zircons (a microscopic mineral necessary to accurately date fossils) from the ashy rock sediment in which the fossil was preserved. Extraction requires impeccable vision and a flawlessly steady hand, as the zircons can easily be flushed away by accident. There’s almost no room to err.

One of the co-authors of the study, geoscientist Stephanie Suarez, has been mastering the technique for separating the zircon grain from sediment since her time as an undergraduate student.

“That kind of work trained me for the work that I do here in Houston,” Suarez said. “It’s delicate work.”

As an undergrad, Suarez used the technique to find that a different millipede specimen that was once thought to be the oldest bug specimen was actually 14 million years younger than estimated. Her technique now passes the Oldest Bug To Walk The Earth title onto a new species; Kampecaris.

The study was published in Historical Biology.

 

La faute des oiseaux?

Selon cette nouvelle étude, la cause du déclin des insectes géants ne serait une baisse des niveaux d'oxygène, mais plutôt la conquête du ciel par les oiseaux:


The new study takes a close look at the relationship between insect size and prehistoric oxygen levels. Matthew Clapham, an assistant professor of Earth and planetary sciences at UC Santa Cruz, and Jered Karr, a UCSC graduate student who began working on the project as an undergraduate, compiled a huge dataset of wing lengths from published records of fossil insects, then analyzed insect size in relation to oxygen levels over hundreds of millions of years of insect evolution. Their findings are published in the June 4 online early edition of the Proceedings of the National Academy of Sciences (PNAS).


"Maximum insect size does track oxygen surprisingly well as it goes up and down for about 200 million years," Clapham said. "Then right around the end of the Jurassic and beginning of the Cretaceous period, about 150 million years ago, all of a sudden oxygen goes up but insect size goes down. And this coincides really strikingly with the evolution of birds."


With predatory birds on the wing, the need for maneuverability became a driving force in the evolution of flying insects, favoring smaller body size.

 

Paleo-Archives: Arthropodes et échinodermes du Paléozoïque de l'Ontario et du Québec (Marc R. Haensel)

Trouvé ici.

Ceraurus, région de Québec (Marc R. Haensel)

Trouvé ici.

Wonderful Early Silurian Life

Extraits de l'article:

The Waukesha Biota, a 437-million-year-old fossil assemblage from Wisconsin, USA, provides a rare glimpse into life in an ancient lagoon. In his book Wonderful Life Stephen Jay Gould (1989) compared the range of form of Cambrian animals in the Burgess Shale with only five other fossil sites in the world; one of them was at Waukesha.

Spectacular new fossils from the Waukesha Biota have been revealed for the first time.

 

Insectes géants, dinosaures à plumes, oiseaux archaïques: une nouvelle préhistoire (Documentaire Animalier)