Study: Dinosaurs’ Free-Range Parenting Strategy Fundamentally Reshaped Mesozoic World
University of Maryland paleontologist Thomas R. Holtz Jr. has spent decades puzzling over how dinosaurs fit into their ancient worlds — and how those worlds differ from our own. His latest research reveals that scientists may have missed something important when comparing ancient dinosaurs with modern mammals.
“A lot of people think of dinosaurs as sort of the mammal equivalents in the Mesozoic era, since they’re both the dominant terrestrial animals of their respective time periods,” Dr. Holtz said.
“But there’s a critical difference that scientists didn’t really consider when looking at how different their worlds are: reproductive and parenting strategies.”
“How animals raise their young impacts the ecosystem around them, and this difference can help scientists reevaluate how we perceive ecological diversity.”
“Young mammals remain under intensive maternal care until they’re nearly full-grown.”
“Mammal offspring occupy essentially the same ecological role as their parents — eating the same food and interacting with the same environment — because the adults do most of the heavy lifting.”
“You could say mammals have helicopter parents, and really, helicopter moms,” he explained.
“A mother tiger still does all the hunting for cubs as large as she is.”
“Young elephants, already among the biggest animals on the Serengeti at birth, continue to follow and rely on their moms for years.”
“Humans are the same in that way; we take care of our babies until they’re adults.”
“On the other hand, dinosaurs operated very differently. While they did provide some parental care, young dinosaurs were relatively independent.”
“After just a few short months or a year, juvenile dinosaurs left their parents and roamed alone, watching out for each other.”
Dr. Holtz pointed out a similar case in adult crocodilians, some of the closest living analogs for dinosaurs.
Crocodiles guard nests and protect hatchlings for a limited period, but within a few months, juveniles disperse and live independently, taking years to reach adult size.
“Dinosaurs were more like latchkey kids,” Dr. Holtz said.
“In terms of fossil evidence, we found pods of skeletons of youngsters all preserved together with no traces of adults nearby.”
“These juveniles tended to travel together in groups of similarly aged individuals, getting their own food and fending for themselves.”
Dinosaurs’ free-range parenting style complemented the fact that they hatched eggs, forming relatively large broods in a single attempt.
Because multiple offspring were born at once and reproduction occurred more frequently than in mammals, dinosaurs increased the chances of survival for their lineage without expending much effort or resources.
“The key point here is that this early separation between parent and offspring, and the size differences between these creatures, likely led to profound ecological consequences,” Dr. Holtz said.
“Over different life stages, what a dinosaur eats changes, what species can threaten it changes and where it can move effectively also changes.”
“While adults and offspring are technically the same biological species, they occupy fundamentally different ecological niches.”
“So, they can be considered different ‘functional species’.”
For example, a juvenile Brachiosaurus the size of a sheep can’t reach vegetation 10 m above the ground like a grown-up Brachiosaurus.
It must feed in different areas and on different plants and face threats from carnivores that would avoid fully grown adults.
As a young Brachiosaurus grows — rom dog-sized to horse-sized to giraffe-sized to its final enormous proportions — its ecological role shifts continuously.
“What’s interesting here is that this completely changes how scientists view ecological diversity in that world,” Dr. Holtz said.
“Scientists generally think that mammals today live in more diverse communities because we have more species living together.”
“But if we count young dinosaurs as separate functional species from their parents and recalculate the numbers, the total number of functional species in these dinosaur fossil communities is actually greater on average than what we see in mammalian ones.”
So, how could ancient ecosystems support all these functional roles? Dr. Holtz believes that two explanations could be plausible.
First, the Mesozoic world had different environmental conditions, such as warmer temperatures and higher carbon dioxide levels.
These factors would have made plants more productive, generating more food energy to support more animals.
Second, dinosaurs might have had somewhat lower metabolic rates than similarly sized mammals, meaning they needed less food to survive.
“Our world might actually be kind of starved in plant productivity compared to the dinosaurian one,” Dr. Holtz said.
“A richer base of the food chain might have been able to support more functional diversity.”
“And if dinosaurs had a less demanding physiology, their world would’ve been able to support a lot more dinosaur functional species than mammalian ones.”
Dr. Holtz believes his theories don’t necessarily indicate that dinosaur ecosystems were significantly more diverse than our own mammalian world — just that diversity might take forms scientists currently don’t recognize.
He plans to continue exploring similar patterns within this framework of functional diversity across different dinosaur life stages to better understand the world they lived in and how it evolved into the one humans live in today.
“We shouldn’t just think dinosaurs are mammals cloaked in scales and feathers,” Dr. Holtz said.
“They’re distinctive creatures that we’re still looking to capture the full picture of.”
His paper appears in the Italian Journal of Geosciences.
Dimetrodon (D DesignHub)
Meet the dinosaur that wasn't. This is Dimetrodon, the Pioneer of Predation. Long before T. rex, this creature wrote the first rulebook for being a top land predator.
In the Permian Period, over 280 million years ago, Dimetrodon was a revolutionary. It was a synapsid—a member of the lineage that leads to mammals. Its innovations were groundbreaking:
The First Complex Teeth: Its name means "two measures of teeth." It had differentiated canines, incisors, and shearing teeth, a first for large land animals and the blueprint for every mammalian smile since.
The Advanced Posture: Its legs were positioned more underneath its body than the sprawling reptiles of its time, granting it more efficient, powerful movement.
The Thermal Edge: That iconic sail likely acted as a solar panel, allowing it to warm up fast and remain active when other animals were sluggish.
Dimetrodon didn't just live in its world; it invented the rules that would govern land ecosystems for millions of years. It's not a dinosaur—it's the architect of the world dinosaurs would inherit.
Titanotylopus
We often think of modern animals as "big," but prehistoric North America had a different definition of the word. Take a look at this scale comparison to see just how much the "Ship of the Desert" has changed over time.
The Titanotylopus wasn't just tall—it was a literal skyscraper of a mammal, towering at 11 feet at the shoulder. Meanwhile, the Camelops hesternus (the "Yesterday's Camel") lived alongside mammoths and saber-toothed cats right here in the US.
While they eventually went extinct in their homeland, their cousins survived by migrating across the Bering Land Bridge into Asia and Africa. So, the next time you see a camel, remember: you’re looking at a true American expat!
Desmatosuchus
Before ankylosaurs invented the "tank" body plan, another group had already perfected it. Meet Desmatosuchus, the Triassic walking fortress.
This wasn't a dinosaur. It was an aetosaur—a heavily armored cousin of crocodiles and dinosaurs. In the river valleys of what is now Texas, over 220 million years ago, Desmatosuchus plodded along as a peaceful plant-eater. But "peaceful" didn't mean defenseless.
Its entire body, from neck to tail, was encased in interlocking bony plates (osteoderms). But its masterpiece was a pair of long, curved, spearlike spikes jutting from its shoulders, each as formidable as a bull's horns. This was a creature built to say, "Go ahead, try it," to any predator daring enough to attack.
Desmatosuchus represents the pinnacle of defensive evolution in its time. In a world of new and hungry predators, sometimes the best strategy isn't to outrun them, but to become literally too painful to eat.
Before dinosaurs ruled, the Triassic period was a laboratory of evolutionary experiments. One of its most successful—and intimidating—creations was a walking, grazing fortress named Desmatosuchus.
Imagine a 16-foot-long, heavily built herbivore, plodding through the river valleys of what is now Texas. Its entire back was covered in interlocking bony plates (osteoderms), forming a formidable suit of armor. But its pièce de résistance was a pair of long, curved spikes jutting from its shoulders, each as formidable as a bull's horns.
This wasn't a dinosaur, but an aetosaur—a heavily armored cousin of crocodiles and dinosaurs. In a world teeming with early crocodile-relatives and sharp-toothed predators, Desmatosuchus was built to survive. It likely used its pig-like snout to root for tubers and plants, while its intimidating shoulder spikes deterred even the most ambitious attackers.
Desmatosuchus is a masterpiece of defensive evolution. It proves that in the struggle for survival, sometimes the best strategy isn't to be the biggest or the fastest, but to be the one that's simply too much trouble to eat.
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With feathers into the afterlife
The approximately 9,000-year-old grave of the shaman from Bad Dürrenberg (Saalekreis district) is one of the most spectacular finds in Central European archaeology. Excavated under considerable time pressure in 1934, subsequent investigations at the site from 2019 onwards allowed for the recovery of remains of the burial pit, which were then removed as a block and examined under laboratory conditions. These investigations revealed a series of new insights. Microscopic evidence has now been obtained of feathers that likely belonged to an elaborate headdress.
Chiens de Ninive
Clay guard-dog figurines from North Palace in Nineveh, in present-day Iraq. About 2,700 years old, just 7cm long (3 in), with inscriptions of their fierce names ~ Loud is his bark / Biter of his foe / Catcher of the enemy / Expeller of evil / Don’t think, bite!
Torrent dévastateur
BIGGEST FLOOD EVER? - Imagine a huge wall of flood water thundering toward you and your family as you camp by a peaceful stream. That's what some unfortunate Clovis people in present-day Washington State undoubtedly saw after a 2000-foot ice dam broke and Lake Missoula gushed out 13,000 years ago.
The wall of water was backed by a flow that was BIGGER THAN ALL THE RIVERS IN THE WORLD COMBINED...TIMES TEN. Researchers have determined these numbers based on the evidence gathered from geomorphological features in the Channeled Scablands. Water speeds may have reached 80 mph!
Ripple marks (pictured - which are typically an inch or two in height) have been found that are 50 FEET tall. The flood was analogous to Lakes Erie and Ontario completely draining through a narrow gorge in under three days!
J. Harlen Bretz first proposed the cataclysmic flood idea in 1923, but he was roundly and rudely criticized by most other geologists. Evidence continued to grow, however, over the next 30 years, and Bretz's ideas were finally accepted. At the age of 96, he was awarded the prestigious Penrose Medal in 1979, whereupon he reportedly said, "All my enemies are dead, so I have no one to gloat over."
Geologists now believe the area has experienced at least 40 separate, large floods over time, and this is probably why floods are prominent in stories from many Native American cultures.
Hemipsalodon
La galerie de paléontologie et d'anatomie comparée ferme le 18 janvier 2026 avant la fermeture aller voir hemipsalodon, c'est un hyaenodonte de l'Eocène moyen nord-américain avec un crâne de 45cm de long pour 30 de large. Il est l'équivalent écologique de sarkastodon qui a vécu à la même époque en Asie.
L'animal est un proche parent de Simbakubwa et megistrotherium qui eux sont bien plus gros mais vivaient en Afrique bien plus tard au Miocène.
Hemipsalodon n'est connu que par son crâne et devait faire la taille d'un gros lion mais un peu plus court sur pattes.
On voit avec ces animaux l'influence importante des hyaenodontes pendant tout la Paléogène et même au début du Néogène. On peut dire qu'au Néogène (24 ma à nos jours) on a une faune qui ressemble à celle qu'on connait chez les mammifères prédateurs alors qu'au Paléogène (66 à 25 ma) c'est totalement différent.
Concernant la houppette à l'arrière du crâne, cette protubérance osseuse permet plus de surface d'insertions aux muscles de la mâchoire.
Ce fossile appartenait à un mammifère Celui-ci a vécu pendant l'Eocène, il y a environ 52 millions d'années dans ce qui est aujourd'hui le Wyoming, aux États-Unis.
L'espèce à laquelle elle appartient n'est pas encore décrite, mais elle appartient à la famille Cimolestidae. Cette famille a vécu du Crétacé à l'Eocène, étant l'un des rares groupes de mammifères qui ont survécu à l'extinction du K/Pg.
Sa longue queue est probablement liée à ses habitudes arboricoles. Et par curiosité, c'est la plus longue queue avec le plus grand nombre de vertèbres de tous les mammifères (environ 50-51).
Source :
Grande, L. (2013). Le monde perdu des lacs fossiles : des instantanés des temps profonds. University of Chicago Press.Saurornitholestes
Ordovicien (vers 420 Ma)
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Bonjour Patrick,
Je commence par résumer quelques éléments clés du contexte géologique gaspésien.
Ordovicien : l’est de Laurentia passe d’une marge passive tranquille à une zone tectoniquement
active, ce qui entraîne l’orogenèse taconienne et la formation des premières montagnes
appalachiennes.
Silurien : la grande collision continentale se produit au large de Laurentia, mais la Gaspésie
demeure une région stable, baignée par une mer tropicale peu profonde où se forment d’épaisses
successions de calcaires et, vers 420 Ma, une imposante barrière récifale.
Fin du Silurien : la fusion de Laurentia, Baltica et Avalonia mène à la création du
supercontinent Laurussia.
Il existe plusieurs reconstructions paléogéographiques pour le Silurien; il faut donc choisir une
carte fiable, cohérente et adaptée précisément à la fin du Silurien (~420 Ma). En géologie
sédimentaire, on utilise fréquemment les cartes de Scotese : elles ne sont pas parfaites, mais elles sont très lisibles et situent correctement la Gaspésie dans un environnement marin peu profond.
Maintenant une mise en contexte pour la grande barrière récifale silurienne. Il y a environ 420 millions d’années, la Gaspésie tropicale abritait une immense barrière récifale aujourd’hui fossilisée. Construite par des coraux anciens et des stromatoporoïdes, elle formait un système continu long de plus de 500 km, comparable aux grandes barrières récifales actuelles. Cette barrière s’est développée sur des hauts-fonds créés par des failles actives, entre une mer peu profonde au nord et un bassin plus profond au sud. À l’échelle moderne, c’est l’équivalent de la distance entre Montréal et Rimouski. Elle était donc plus grande que les barrières récifales actuelles de l’Atlantique Ouest comme celle du Bélize (~300 km), même si elle restait plus courte que la Grande Barrière de corail d’Australie (~2 000 km). La formation des Appalaches a ensuite cassé, déplacé et érodé cette structure, ne laissant aujourd’hui que des fragments isolés visibles à West Point et dans la baie des Chaleurs. Malgré sa fragmentation, elle demeure l’un des plus impressionnants récifs fossiles du Silurien au monde.
Carte montrant à la fin du Silurien, que la barrière récifale de West Point ne se limitait pas du tout à un petit secteur isolé comme aujourd’hui. Les reconstructions palinspastiques (c’est-à-dire avant la déformation des roches) montrent qu’elle formait une véritable ceinture récifale presque continue. Elle s’étendait le long de toute la marge nord du bassin gaspésien, depuis l’ouest de la Baie des Chaleurs jusqu’à l’est de la péninsule. Source (Malo, D., Lavoie, D., and Brisebois, D. Hydrocarbon Systems in Gaspé Peninsula: a Tour of Source Rocks, Reservoirs and Traps; Geological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Québec 2008, Guidebook to Field Trip B2, 157
Ophiolite de Thetford Mines
Une ophiolite représente un étape du formation de la Pangée, un morceau de la croute océanique (Iapetus) qui est obducté sur la croute continentale pendant le collision entre deux masses continentale - ici Gondwana et Laurentia. La trace d'ophiolite affleure à Mont-Orford (mais pas trop bien je crois), Thetford Mines, le Mont-Albert (Gaspésie) et va jusqu'à Bay-of-Islands-Gros Morne à Terre Neuve.
Pour ce qui est autour de Thetford Mines, le section inferieur de l'ophiolitique (le manteau oceanique) affleure dans le boisée du l'arrière cours d'une petite maison à Saint-Joseph-de-Coleraine (photos des roches mantelliques ci-jointes). Il y a aussi un bel affleurement des basaltes coussinés entre Thetford Mines et Saint-Daniel qui répresente la section supérieure de l'ophiolite (les coussins sont faciles à voir).
Néandertaliens cannibales?
NEANDERTHALS WERE PREDATORY CANNIBALS. Neanderthal cannibalism was relatively common, with Nobel-Prize-winning paleogeneticist, Svante Paabo saying that evidence of it is "typical of many, even most, sites where Neanderthal bones are found." But there has been disagreement about the cause of the cannibalism, with these two main theories: 1) It was ritualistic, or 2) It was predatory.
If done ritualistically, the cannibalism may have been for a wide variety of reasons - anything from wanting to honor your loved ones and keep them close to wanting to insult your enemies or extract their good attributes. But many researchers think most of the cannibalism was predatory with the El Sidron, Spain site, for instance, best explained by murderous cannibalism where humans were treated like prey. At El Sidron, thirteen individuals of one clan were eaten over a short stretch - probably by a marauding neighboring clan. Evidence such as cranial trauma indicates that violence was involved.
And now, Cosnefroy and others (2025) have documented that the cannibalism found at Goyet Cave in Belgium was also likely predatory in nature. There, 45,000 years ago, Neanderthals cannibalized six outsiders, deliberately targeting women and children. The treatment of the human remains was indistinguishable from butchery evidence found on other faunal bones. Many are calling this cannibalism the most compelling evidence for inter-group competition among Late Pleistocene Neanderthal populations.
Slimak et al. (2024) sequenced the genome of a roughly 50k-year-old Neanderthal ("Thorin") and found that he was part of a small group that had been genetically isolated from other, nearby Neanderthals for a staggering 50k years. Could it be that such insularity was prompted in part by one group's fear of cannibalism by another?
Panderodus (Joschua Knüppe)
Panderodus, a genus of jawless fish from middle Ordovician to late Devonian North America.
Their size varied from 5 to 40 cm depending on the species.
L’IA vient d’entendre les murmures de créatures vieilles de 3,3 milliards d’années
Les roches peuvent mentir, se transformer, effacer leurs secrets pendant des milliards d’années. Pourtant, elles conservent des murmures chimiques imperceptibles à l’œil humain. Des chercheurs ont mis au point une technique révolutionnaire combinant analyse moléculaire et apprentissage automatique pour déchiffrer ces messages fossilisés. Résultat : ils viennent de repousser de plus d’un milliard d’années notre capacité à détecter les traces de vie sur Terre, avec des implications fascinantes pour la recherche extraterrestre.
Quand les molécules disparaissent mais laissent leur empreinte
Imaginez un crime parfait où le coupable aurait effacé toutes les preuves directes de son passage. Pas d’empreintes digitales, pas de témoins, pas d’ADN. Pourtant, sa présence a subtilement modifié l’environnement de manière indélébile. C’est exactement ce qui se produit avec la vie ancienne.
Les molécules biologiques originales, ces protéines et lipides qui composaient les premiers organismes terrestres, se sont désintégrées depuis des éternités. Mais leur interaction avec les minéraux environnants a laissé une signature chimique durable, une sorte d’ombre moléculaire gravée dans la pierre. Le problème ? Ces traces sont si ténues, si altérées par les transformations géologiques, qu’elles demeuraient jusqu’ici indéchiffrables.
Katie Maloney, professeure adjointe à l’Université d’État du Michigan et co-auteure de l’étude parue dans les Actes de l’Académie nationale des sciences, résume parfaitement le défi : les roches anciennes regorgent d’énigmes fascinantes qui racontent l’histoire de la vie terrestre, mais il manquait des pièces cruciales au puzzle.
L’apprentissage automatique comme détective moléculaire
La solution est venue d’une alliance inattendue entre géochimie et intelligence artificielle. L’équipe de recherche a développé un algorithme d’apprentissage automatique capable de reconnaître les signatures chimiques fossilisées avec une précision stupéfiante de 90%.
Pour entraîner cet algorithme, les scientifiques lui ont fourni une bibliothèque de références : des signatures chimiques d’animaux et de plantes contemporains, ainsi que de molécules organiques provenant de météorites. Ces dernières servent de témoins non biologiques, permettant à l’intelligence artificielle de distinguer ce qui relève du vivant de ce qui n’en provient pas.
Robert Hazen, chercheur principal à la Carnegie Institution for Science et co-auteur principal de l’étude, souligne l’importance de cette percée : la vie ancienne ne laisse pas seulement des fossiles visibles, elle laisse des traces chimiques que nous pouvons désormais interpréter de manière fiable pour la première fois.
Un bond spectaculaire dans le temps profond
Les implications de cette technique sont vertigineuses. Avant ces travaux, les méthodes les plus avancées permettaient de détecter des traces moléculaires dans des roches âgées d’environ 1,7 milliard d’années. Cette nouvelle approche double littéralement la portée temporelle de nos investigations.
Les chercheurs ont ainsi identifié des signatures biologiques dans des matériaux vieux de 3,3 milliards d’années, parmi les plus anciens jamais étudiés. Plus spectaculaire encore, ils ont détecté dans des roches datant d’au moins 2,5 milliards d’années des preuves d’organismes producteurs d’oxygène.
Cette dernière découverte pourrait résoudre l’une des énigmes les plus tenaces de la géobiologie : l’origine de la Grande Oxydation.
Le mystère de l’air que nous respirons
Il y a environ 2,4 milliards d’années, la Terre a connu une transformation radicale. L’oxygène, jusqu’alors quasi absent de l’atmosphère, s’est mis à s’accumuler rapidement dans l’air. Cet événement, baptisé la Grande Oxydation, a fondamentalement reconfiguré la chimie planétaire et ouvert la voie à l’évolution de formes de vie complexes.
Le consensus scientifique attribue ce phénomène aux organismes photosynthétiques, capables de produire de l’oxygène en transformant la lumière solaire. Mais quand ces producteurs d’oxygène sont-ils apparus exactement ? Existaient-ils avant la Grande Oxydation, préparant silencieusement le terrain de cette révolution atmosphérique ?
Les preuves géologiques directes restaient jusqu’ici floues et controversées. Cette nouvelle méthode pourrait enfin identifier avec certitude les acteurs biologiques de ce bouleversement planétaire.
(...) Cette alliance entre géologie, biochimie et apprentissage automatique illustre magnifiquement comment les technologies contemporaines peuvent illuminer les chapitres les plus reculés de l’histoire cosmique. Les pierres parlent, il suffisait d’apprendre leur langage.
Flightless ancestor shows brain evolution in pterosaurs and birds took different paths
Flight is a rare skill in the animal world. Among vertebrates, it evolved only three times: in bats, birds, and the long-extinct pterosaurs. Pterosaurs were the pioneers, taking to the skies more than 220 million years ago, long before early bird relatives such as Archaeopteryx appeared, around 150 million years ago. While scientists have a detailed fossil record that sheds light on how birds' brains evolved for flight, the same story for pterosaurs has been far less clear. Until now.
In a new study published in Current Biology, an international team now reveals how pterosaurs evolved the neurological structures required for powered flight.
"The breakthrough was the discovery of an ancient pterosaur relative, a small lagerpetid archosaur named Ixalerpeton from 233-million-year-old Triassic rocks in Brazil," said Mario Bronzati, an Alexander von Humboldt fellow at the University of Tubingen in Germany and lead author of the study.
"We've had abundant information about early birds and knew they inherited their basic brain layout from their theropod dinosaur ancestors," added co-author Lawrence Witmer, professor of anatomy at the Ohio University Heritage College of Osteopathic Medicine. "But pterosaur brains seemed to appear out of nowhere. Now, with our first glimpse of an early pterosaur relative, we see that pterosaurs essentially built their own 'flight computers' from scratch."
How researchers mapped brain evolution
To piece together this evolutionary story, the researchers used high-resolution 3D imaging techniques, including microCT scanning, to reconstruct brain shapes from more than three dozen species. These included pterosaurs, their close relatives like Ixalerpeton, early dinosaurs and bird precursors, modern crocodiles and birds, and a wide range of Triassic archosaurs, the larger group that includes all these animals.
"Then, using statistical analysis of the size and 3D shape of their cranial endocasts, we were able to map the stepwise changes in brain anatomy that accompanied the evolution of flight," said co-author Akinobu Watanabe, associate professor of anatomy at the New York Institute of Technology College of Osteopathic Medicine.
Flight is a physiologically demanding form of locomotion and has long been assumed to require major neurological adaptations including enlargement of the brain to coordinate the complicated sensory and motor information required for powered flight. Previous studies of pterosaur brain structure had shown that they indeed shared some neurological similarities with bird precursors like Archaeopteryx, such as some enlargement of brain regions like the cerebrum and cerebellum involved with sensorimotor integration, as well as enlargement of visual centers like the optic lobes.
Ixalerpeton, the lagerpetid close relative of pterosaurs showed some but not all neurological traits of pterosaurs. For example, as Bronzati notes, "lagerpetids were probably tree-dwellers, and their brains already show features linked to improved vision, such as an enlarged optic lobe, an adaptation that may have later helped their pterosaur relatives take to the skies, but they still lacked key neurological traits of pterosaurs."
Lagerpetids like Ixalerpeton had brains intermediate in shape between more primitive archosaurs and pterosaurs but retain greater similarity to early dinosaurs. Other than the enlarged optic lobe that occupies a position in the brain similar to that in pterosaurs and birds and their close theropod relatives, there is little in Ixalerpeton that indicates what was to come in pterosaurs.
A unique feature of the brain of pterosaurs is a greatly enlarged flocculus, a structure of the cerebellum likely involved in processing sensory information from their membranous wings to keep their eyes fixed on a target while in flight. The flocculus in Ixalerpeton wasn't expanded like pterosaurs, instead resembling the modest flocculus of other archosaurs, including early birds and their close nonavian theropod relatives.
Likewise, the new analyses show that pterosaurs retained modest brain sizes.
Comparing pterosaur and bird brains
"While there are some similarities between pterosaurs and birds, their brains were actually quite different, especially in size," said co-author Matteo Fabbri, assistant professor of Functional Anatomy and Evolution at the Johns Hopkins University School of Medicine. "Pterosaurs had much smaller brains than birds, which shows that you may not need a big brain to fly."
Surprisingly, the overall brain shape of pterosaurs most closely resembled that of small, bird-like dinosaurs such as troodontids and dromaeosaurids, animals that had little or no powered flight ability. Yet pterosaurs and birds still represent two entirely independent experiments in the evolution of flight. Birds inherited a brain already adapted from their non-flying dinosaur ancestors, while pterosaurs evolved their flight-ready brains at the same time they developed their wings.
Birds' notably large brains, the authors note, likely came later and were tied more to increasing intelligence and complex behaviors rather than the act of flying itself. A key takeaway from the study is that, according to Witmer, "it apparently doesn't take a large brain to get into the air, and the later brain expansion in both birds and pterosaurs was likely more about enhancing cognition than about flying itself."
Another important takeaway is that paleontological fieldwork remains an engine for new breakthroughs.
"Discoveries from southern Brazil have given us remarkable new insights into the origins of major animal groups like dinosaurs and pterosaurs," co-author Rodrigo Temp Müller, a paleontologist at Universidade Federal de Santa Maria, Brazil, noted. "With every new fossil and study, we're getting a clearer picture of what the early relatives of these groups were like, something that would have been almost unimaginable just a few years ago."
Fossil vomit contains new species of pterosaur from Brazil
One hundred and ten million years ago in what is now Brazil, a dinosaur’s dinner got the best of it. The reptile regurgitated its meal, leaving behind a pile of vomit that happened to fossilize—a stroke of geologic luck that preserved the remains of a newly discovered species.
When paleontologists recently examined the petrified puke (pictured), known scientifically as a regurgitalite, they found the bones within it came from two pterosaurs representing a previously unknown species. The discovery, published this week in Scientific Reports, is the first instance of an animal being described based on remains found in fossilized vomit.
The team named the new pterosaur Bakiribu waridza, which means “comb mouth” in the Indigenous Kariri language spoken in northeastern Brazil’s Araripe region, where the fossil was unearthed. The name references the animal’s bristlelike teeth, which it likely used to catch crustaceans and other small aquatic animals. The first filter-feeding pterosaur ever found in Brazil, B. waridza exhibits a mix of features seen in both older pterosaurs from Germany and slightly younger species from Argentina.
It's hard to tell which species of dinosaur devoured the two pterosaurs and then threw them back up. The researchers think the most likely culprit is a spinosaur (illustration), a group of dinosaurs with crocodilelike jaws that dominated the region during the early Cretaceous period. These predators apparently had a taste for pterosaurs: Another pterosaur skeleton from this area of Brazil was found with a spinosaur tooth lodged in its neck.
Andrias matthewi (Hodari Nundu)
Do you know what Hodari and a giant salamander have in common? Neither of us knows if a giant salamander can eat a baby gomphothere. But that didn´t stop us from trying :B
This encounter may have taken place somewhere in North America during the Miocene, around 16-13 million years ago. Lakes and rivers at the time would've been inhabited by an incredible amphibian, the giant salamander Andrias matthewi. Today, Andrias salamanders are found only in Asia, specifically China and Japan, and they are still the largest amphibians in the world, reaching up to 1.5, sometimes 1.8 m long in the largest species! Andrias has an interesting story because it was first named based on a fossil skeleton found in Germany in 1726. People at the time thought it was a human skeleton (it was missing its tail, which surely helped), and because the concepts of evolution, extinction and deep time were not yet well understood or accepted, it was named Homo diluvii testis, meaning, "the man who witnessed the Flood".
Subsequently it was found to be non human and variously suggested to be a catfish and even a lizard, before finally being recognized as a salamander in the early 19th century. Eventually it was named "Andrias", meaning something like "after man's image" as a reference to the initial confusion.
Both the European fossils and the North American ones show that giant salamanders, today critically endangered and geographically restricted, were once much more widespread. They also got bigger- potentially much bigger. Andrias matthewi here may be the largest true salamander known from the fossil record. One specimen from the US, known from its fossil jaw was estimated in 1.52 m which is plenty big, but the biggest come from Saskwatchewan, Canada, where another specimen was estimated at up to 2.3 m!
Other than their size they would've been pretty similar in habits to today's giant salamanders from Asia; ambush predators, entirely aquatic, mostly nocturnal, and pretty voracious, tho here its attacking a baby Zygolophodon may be more a defensive reaction at being stepped on, or maybe confusion due to poor eyesight. Tho not dangerous to humans, giant salamanders are known to bite hard!
There's more than one way to build a tree, 374m-year-old fossils reveal
In the world of knee-high land plants 400m years ago, the battle to grow tall was won by plants which found biomechanical solutions to fight gravity. Vascular plants had already evolved a plumbing system, allowing them to transport water, and the food produced by photosynthesis, around the plant. The water-conducting cells in the xylem – dead, hollow and stiffened by the polymer lignin – also afforded them some structural support. But there are limits to the height that a plant can grow with a stem of fixed girth.
In modern trees, trunks grow outwards as well as upwards. Known as secondary thickening, a ring of dividing cells beneath the bark, called the vascular cambium, produces new xylem and phloem tissue. This is what wood is: secondary xylem, composed of dead lignified cells, now employed by trees as a building material to allow them to continue to grow tall.
Plants producing wood locked up carbon extracted from the atmosphere during photosynthesis and, when trees died, resulted in its burial in sediments. This storage over geological time as coal (which humans are so keen to dig up, burn and release the carbon from) changed how carbon cycled through our ecosystems. The first forests transformed our planet in other, less obvious, ways too. Tree root systems stabilised soil, changing the landscape and affecting how minerals in the sediments weather. These changes in weathering take carbon dioxide from the atmosphere, producing carbonic acid, which ends up in river systems, and ultimately puts the carbon in the ocean. The Earth’s carbon cycle, climate and the evolution of forests are inextricably linked.
How did the first trees solve their engineering challenge? Some of them used the same strategy as modern trees. Archaeopteris (not to be confused with the much more famous Jurassic bird Archaeopteryx) was one of the earliest trees, appearing in the Late Devonian, around 380 millon years ago, and found world-wide. Up to 20 metres tall, and with a trunk up to 1.5 metres in diameter, Archaeopteris has typical secondary thickening produced by a vascular cambium ring. It had seasonal growth rings like a modern temperate tree, and had flattened photosynthesising branches which could almost be described as leaves. Archaeopteris is one of several types of plant grouped together as progymnosperms: plants which had seed plant characteristics like wood production, but which still reproduced with spores.
Another group of early trees solved the structural problem of being a tree very differently. The gloriously-named cladoxylopsids first appeared around 390 Ma, and have been well-studied from sites in Germany, Scotland and USA. The fossil forest at Gilboa quarry in New York state, where tree stumps known as Eospermatopteris, preserved as sandstone casts, up to one metre in diameter, in life position, has been studied since the 1870s. These trees were reconstructed in 2007 as Wattieza, after a fossil tree complete with a palm-like crown of leafy fronds was discovered nearby.
New discoveries in China from Hong-He Xu and colleagues, from Nanjing Institute of Geology and Palaeontology, Cardiff University and Binghamton University, have revealed the strange anatomy of the trunk of cladoxylopsid trees. Where the Gilboa Wattieza trees are preserved as sandstone casts with little detail, the new fossils dating from 374Ma, from Xinjiang, China, are silicified, preserving the cellular details of their wood. They show that rather than a simple ring producing secondary tissue, cladoxylopsids had many separate and distinct xylem strands around the outside of the trunk, each one producing its own thickening rings, almost like a mini tree. An intricate network of interconnecting xylem tissue joined up the strands throughout the trunk, which was otherwise hollow.
It is the “ordinary” cortical tissue between the xylem strands which appears to have driven girth increase in these trees, by having such a high rate of cell proliferation that it pushed the ever thicker mini-trees apart, ripping the connecting xylem tissues in the process. The tree was in a state of continual, controlled internal collapse, repairing its internal tears as it grew. This seems like an incredibly over-complicated way to be a tree. Some modern palm trees do increase their girth by primary growth but in a much less complex way. Perhaps the cost of this elaborate anatomy was a factor in the demise of the cladoxylopsids, which disappear from the fossil record soon after these Chinese finds. These findings are yet another demonstration how much we still do not know about the diversity of plants and their anatomy through deep time.
Les pélycosaures
Cette mâchoire de pélycosaure a été découverte dans un puits sur l’Île-du-Prince-Édouard au 19e siècle.
Bien avant l’ère des dinosaures, les pélycosaures dominaient la Terre. Ces vertébrés font partie des premiers synapsides, le groupe ancestral qui donnera naissance aux mammifères.
Le célèbre Dimetrodon, reconnaissable à sa grande voile dorsale, est l’un des exemples les plus fascinants de ce groupe !
Le bloc erratique du mont Royal
On appelle "bloc erratique" tout bloc rocheux déplacé par un glacier, jusqu'à ce qu'il se retrouve sur de la roche en place de composition différente. Ce bloc de gabbro montérégien se retrouve sur les roches calcaires du groupe de Trenton. La distance de transport du bloc demeure inconnue et pourrait être aussi courte que 100 mètres. Le poids du bloc est estimé à environ 7 000 kilos.
La photo a été prise tôt au printemps, avant que la végétation dissimule le bloc.
Le mont Royal étant situé au coeur d'une ville depuis quelques siècles, il n'est pas assuré que le déplacement du bloc ait une cause naturelle. Cependant, l'état de désagrégation de la partie basale du bloc indique que le dernier mouvement est très ancien.
Compte tenu de l'altitude du bloc (190 m), en dessous du niveau maximum (200 m) de la mer de Champlain, il est possible que ce bloc ait été transporté par des glaces flottant sur l'ancienne mer de Champlain. Le transport aurait alors une origine glacielle (glace flottante) plutôt que glaciaire (glacier s'écoulant par gravité).
En conclusion, si la cause du transport du bloc est naturelle, seule la glace peut déplacer une telle charge. Cette glace peut être celle du glacier qui recouvrait la totalité du territoire, il y a 20 000 ans, mais cette glace peut aussi être celle de la banquise qui dérivait sur la mer de Champlain, il y a 13 000 ans.
Comment s'y rendre :
À partir de la maison Smith, suivez le chemin Olmstead jusqu'à l'intersection du premier sentier qui coupe le chemin Olmstead pour descendre vers le lac des castors. Avancez de 20 mètres dans ce sentier forestier et tournez à droite au premier embranchement rencontré. Avancez d'un autre 15 mètres, jusqu'à un autre embranchement, côté gauche, cet embranchement est maintenant condamné par une clôture. On peut encore apercevoir le bloc erratique dans la forêt, à une distance d'environ 10 mètres de la clôture, en hiver et au printemps, avant l'apparition du feuillage des végétaux.
Localisation au GPS :
45˚ 29' 58,6"N
73˚ 35' 35,5"W
Griffes de droméosauridés
Scénarios proposés pour la fonction faucille-griffe, avec C, D et F comme comportements les plus plausibles.
Grande barrière gaspésienne
Peut-on comparer la barrière récifale du Silurien en Gaspésie à la Grande Barrière australienne?
Oui, d’un point de vue morphologique, il y a un parallèle intéressant entre les deux.
La barrière récifale du Silurien en Gaspésie jouait un rôle semblable à celui de la Grande Barrière australienne actuelle : elle protégeait la côte, abritait une riche vie marine et accumulait d’épaisses couches de calcaire.
La grande différence vient de sa composition. En Gaspésie, les récifs siluriens étaient construits surtout par des stromatopores (des éponges calcaires massives) ainsi que des coraux tabulés et rugueux. Ensemble, ils formaient une structure solide, arrondie et compacte, plutôt beige, sans les formes branchues ni les couleurs éclatantes des coraux modernes.
En somme, l’architecture (avec avant-récif, crête, et lagon) était similaire, mais l’aspect visuel évoquait davantage un mur de pierre vivante qu’une forêt tropicale de coraux colorés.
Qu’est-ce qu’un stromatopore?
Le stromatopore (ou stromatoporoïde) était un animal marin qui vivait dans les mers chaudes et peu profondes, bien avant l’apparition des coraux modernes.
Ce n’était pas un corail, mais une éponge qui sécrétait un squelette calcaire très solide.
Ce squelette se formait par couches successives, un peu comme un mille-feuille de calcaire, d’où son nom, issu du grec stromato (couche) et pore (trou).
L’eau de mer circulait dans de fins canaux à l’intérieur de la structure, permettant à l’éponge de filtrer sa nourriture.
À quoi cela ressemblait-il?
Les stromatopores formaient :
des dômes, monticules ou plaques de calcaire, souvent beige, parfois de plusieurs dizaines de centimètres, voir mètres, de diamètre ;
une surface lisse ou légèrement bosselée, percée de minuscules pores visibles seulement au microscope;
des récifs massifs et compacts, en s’accumulant les uns sur les autres, un peu comme le font les coraux d’aujourd’hui; mais avec un aspect plus rocheux et uniforme.
Ci-joint une illustration schématique d’un récif dévonien (un peu plus jeune) : sa structure est semblable à celle du Silurien gaspésien, à la différence que ce dernier comportait davantage de stromatopores et moins de coraux tabulés ou rugueux.
Bref, pas si simple, mais fascinant tout de même !
Anticosti, fin de l'Ordovicien
André Desrochers:
Pour une image plus représentative des fonds marins, avant et après la crise de biodiversité de la fin de l’Ordovicien :
Elle devrait illustrer principalement des invertébrés, comme sur les figures ci-jointes.
Il faudrait déterminer si l’on souhaite représenter une faune benthique ou récifale; la seconde étant nettement plus diversifiée et visuellement intéressante (voir les figures jointes).
Aller doucement avec les représentations d’euryptérides et de poissons, puisque aucun fossile confirmé de ces groupes n’a encore été trouvé dans les formations ordoviciennes ou siluriennes d’Anticosti.
Cela suggère que, bien que les conditions du bassin aient pu convenir à ces organismes, le registre fossile local ne les a pas préservés, probablement à cause de la nature des dépôts calcaires, peu favorables à la conservation des arthropodes non calcifiés.
Oui, les euryptérides existaient déjà avant la fin de l’Ordovicien, mais ils étaient encore rares et de petite taille.
Oui, les poissons primitifs (agnathes) existaient aussi, mais il s’agissait de petits individus (5–20 cm), allongés, sans mâchoires ni nageoires appariées, se nourrissant par succion de particules sur le fond marin.
Je joins deux figures tirées du dossier d’inscription au Patrimoine mondial, pour mieux visualiser la faune marine typique de cette époque.
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