Top fossil discoveries of 2025

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Shri rapax sp. nov. From Moutrille et al., 2025.

Fascism is spreading. We face an unprecedented era of scienticide, genocide, and normalized cruelty. Yet, as Milan Kundera reminds us, “Man’s struggle against power is the struggle of memory against forgetting” (The Book of Laughter and Forgetting, 1979). Against this dystopian backdrop, researchers worldwide are leading a vital resistance: the fight to preserve and advance knowledge.

Here is my very biased list of the most outstanding discoveries of 2025.

  • Duonychus tsogtbaatari.

Therizinosauria is a group of unusual theropod dinosaurs known from Cretaceous deposits in Asia and North America. The clade exhibits unique features, including lanceolate teeth, a rostral rhamphotheca, and a broad, opisthopubic pelvis. Some of those characteristics are associated with a shift in dietary preferences and an adaptation to herbivory. But the most striking feature, as exemplified by the large-bodied Therizinosaurus from the Late Cretaceous of Mongolia, is the presence of tridactyl (three-fingered) hands with three large claw-like unguals.

Duonychus tsogtbaatari,  a new specimen from the Upper Cretaceous Bayanshiree Formation (Cenomanian to Santonian) of southeastern Mongolia, sheds light on the evolution of digit reduction in avetheropods and the implications for feeding behavior associated with large claws in therizinosaurs.

  • Baminornis zhenghensis.
extended data figure 1

Holotype of Baminornis zhenghensis. From Chen, et al.,, 2025.

Baminornis zhenghensis, from the Late Jurassic Zhenghe Fauna, is an early Jurassic bird. The new specimen exhibits a unique combination of characters, including a fused, dorsally-curving pygostyle longer than metacarpal II, a boomerang-shaped furcula with an interclavicular angle of 65°, a semilunate carpal lacking contact with metacarpal III, and an ischium lacking both the obturator and posterior processes.

The presence of derived features in Baminornis, the first Jurassic short-tailed avialan, indicates that the avialan lineage diverged significantly earlier than previously thought.

  • Khankhuuluu mongoliensis.

Khankhuuluu mongoliensis. Image credit: : Julius Csotonyi/University of Calgary

Eutyrannosauria, the superfamily of carnivorous dinosaurs that includes the iconic Tyrannosaurus rex, dominated the Asian and North American terrestrial faunas during the latest Cretaceous.

Khankhuuluu mongoliensis roamed Mongolia around 86 million years ago. It had an estimated total body length of 4 meters (13 feet) and a weight of around 750 kilograms (1,650 pounds). The features that characterise Khankhuuluu mongoliensis include a shallow, rugose midline ridge on the nasal bone that extends along most of the vaulted region, and a small pneumatic recess at the anterior end of the lacrimal bone. The new species differs from Alectrosaurus in that metatarsal III lacks the hyperextension of the plantar distal articular surface.

  • Shri rapax.

Right manus of Shri rapax in distoventral view. Scale bar = 20 mm. From Moutrille et al., 2025.

Dromaeosauridae is a clade of highly specialised small- to mid-sized theropod dinosaurs closely related to birds. Their fossils have been found in North America, Europe, Africa, Asia, South America, and Antarctica. The group is characterized by the presence of long, three-fingered forelimbs that ended in sharp, trenchant claws, and a tail stiffened by the elongated prezygapophyses.

Shri rapax is the second species of the genus Shri (named after Palden Lhamo, a Buddhist deity, the principal protectress of Tibet). The specific name refers to the enlarged falciform pollex ungual found in this species, along with its associated raptorial behaviour. The holotype, a nearly complete skeleton, was originally preserved with a skull that has subsequently been lost.

  • Joaquinraptor casali.

Joaquinraptor casali. Image credit: Andrew McAfee – Carnegie Museum of Natural History.

The Cretaceous beds of Patagonia contain the most comprehensive record of non-avian theropods from the Southern Hemisphere. This includes Megaraptora, a clade of medium-sized, highly pneumatized theropods characterized by elongated skulls and formidable manual claws on digits I and II.

Joaquinraptor casali is a large-bodied megaraptorid from the Upper Cretaceous (Coniacian–Maastrichtian) Lago Colhué Huapi Formation of south-central Chubut Province, in central Patagonia, Argentina. The holotype (UNPSJB-PV 1112) is a partially articulated skeleton that includes a disarticulated partial skull (right maxilla, skull roof and braincase, probable right postorbital and quadrate, both dentaries, and in situ and isolated teeth), complete or nearly complete axial and appendicular skeletons, and numerous fragments.

  • Zavacephale rinpoche.

Z. rinpoche. From Chinzorig et al., 2025.

Pachycephalosaurians, with their distinctive domed heads, are an enigmatic group of small ornithischian dinosaurs. Most pachycephalosaurid remains are known from the Late Cretaceous of North America, Asia, and possibly Europe. Notable species include Pachycephalosaurus, Stegoceras, and Stygimoloch.

Zavacephale rinpoche from the Lower Cretaceous Khuren Dukh Formation of Mongolia, is the oldest and most complete pachycephalosaurian skeleton ever found. The genus name is derived from the Tibetan word ‘zava’, meaning ‘root’ or ‘origin’, and the Latin word ‘cephal’, meaning ‘head’. The specific name, ‘rinpoche’ (meaning ‘precious one’ in Tibetan), refers to the domed condition of the skull.

  • The Nanotyrannus debate is settled.

Snout of Nanotyrannus. Image credit: N.C. Museum of Natural Sciences

Tyrannosaurus rex is the most iconic dinosaur of all time. However, despite its status, the fossil record of T. rex is controversial, particularly about the taxonomic identity of specimens hypothesised to be juveniles. In recent decades, a major and heated debate has centered around Nanotyrannus lancensis, a  small tyrannosauroid discovered in the Hell Creek Formation of Montana. Most paleontologists rejected Nanotyrannus as a valid genus and considered all specimens were juvenile or subadult Tyrannosaurus rex. But a recent study by L. Zanno and J. Napoli shed light on the controversy.
The team found an exceptionally well-preserved and somatically mature tyrannosaur skeleton from the Hell Creek Formation that shares autapomorphies with the holotype specimen of Nanotyrannus lancensis.

  • Huayracursor jaguensis 

Selected bones of Huayracursor jaguensis holotype. From Hechenleitner et al., 2025.

The Triassic deposits of Argentina, renowned for their diverse tetrapod assemblage, offer crucial insights into dinosaur origins by preserving some of the oldest dinosaurs ever discovered. These skeletal records of early dinosaurs document a time when they were not numerically abundant, and they were still of modest body size (Eoraptor had a slender body with an estimated weight of about 10 kilograms).

Huayracursor jaguensis was a primitive sauropodomorph, an early member of the highly successful herbivorous lineage that later produced long-necked giants like Argentinosaurus and Patagotitan. Phylogenetic analysis places it within the Bagualasauria group. The holotype (CRILAR-Pv 151) is an articulated partial skeleton composed of cranial and postcranial material. The genus name combines the Quechuan word “huayra,” meaning “wind,” with the Latin “cursor,” meaning “runner.” The species name is derived from the village of Jagüé in La Rioja, which lies 40 kilometers from the discovery site at Quebrada Santo Domingo.

 

References:

Kobayashi et al., (2025), Didactyl therizinosaur with a preserved keratinous claw from the Late Cretaceous of Mongolia, iScience  https://doi.org/10.1016/j.isci.2025.112141

Chen, R., Wang, M., Dong, L. et al. Earliest short-tailed bird from the Late Jurassic of China. Nature 638, 441–448 (2025). https://doi.org/10.1038/s41586-024-08410-z 

Voris, J. T., Zelenitsky, D. K., Kobayashi, Y., Modesto, S. P., Therrien, F., Tsutsumi, H., Chinzorig, T., & Tsogtbaatar, K. (2025). A new Mongolian tyrannosauroid and the evolution of Eutyrannosauria. Nature. https://doi.org/10.1038/s41586-025-08964-6

Moutrille, L., Cau, A., Chinzorig, T., Escuillié, F., Tsogtbaatar, K., Ganzorig, B., Mallet, C., & Godefroit, P. (2025). A new bird-like dinosaur from the Upper Cretaceous of Mongolia with extremely robust hands supports niche partitioning among velociraptorines. Historical Biology, 1–32. https://doi.org/10.1080/08912963.2025.2530148

Ibiricu, L.M., Lamanna, M.C., Alvarez, B.N. et al. Latest Cretaceous megaraptorid theropod dinosaur sheds light on megaraptoran evolution and palaeobiology. Nat Commun 16, 8298 (2025). https://doi.org/10.1038/s41467-025-63793-5

Chinzorig, T., Takasaki, R., Yoshida, J., Tucker, R. T., Buyantegsh, B., Mainbayar, B., Tsogtbaatar, K., & Zanno, L. E. (2025). A domed pachycephalosaur from the early Cretaceous of Mongolia. Nature, 1–8. https://doi.org/10.1038/s41586-025-09213-6

Zanno, L.E., Napoli, J.G. Nanotyrannus and Tyrannosaurus coexisted at the close of the Cretaceous. Nature 648, 357–367 (2025). https://doi.org/10.1038/s41586-025-09801-6

Hechenleitner, E.M., Martinelli, A.G., Rocher, S. et al. A long-necked early dinosaur from a newly discovered Upper Triassic basin in the Andes. Nature (2025). https://doi.org/10.1038/s41586-025-09634-3

Christmas edition: Xmas love letters, Mary Stopes, and the discovery of the oldest flowers.

Posted on by under Earth Science

London, December 24th.

“…I am glad that you are saving all your kisses for me when I come. By that time I shall be starving for kisses – so terribly hungry that you must kiss me very gently at first, or I will die – as a too hungry man must be fed very little at first.”

The fragment of this passionate letter was attributed to Mertyl Meredith, a young geologist from the U.K. The letter is part of ‘Love-Letters of a Japanese’, published in 1911. The book follows the affair between Mertyl and Kenjiro Watanabe, a fellow geologist whom she had met previously in Munich. The exchange of letters between the two took place over three consecutive Christmases. But while the letters are real, the true identity of the infatuated young “Mertyl” is revealed in the book’s foreword, written by none other than Marie Stopes herself.
Marie Charlotte Carmichael Stopes was born in Edinburgh, Scotland, on October 15, 1880. Her father, Henry Stopes, a brewer, architect and amateur paleontologist and archeologist, amassed the largest private collection of fossils and ancient stone tools in Britain. Her mother, Charlotte Carmichael, wrote British Freewomen: Their Historical Privilege. The book, published in 1894, was a great influence on the early twentieth-century British women’s suffrage movement. They were both members of the British Association for the Advancement of Science.

Marie Stopes (From Wikimedia Commons)

She enrolled at University College London, where she studied botany and geology. She graduated with honors after only two years and received the Gold Medal in Botany. Shortly after, she went to study at the University of Munich and received a Ph.D. in palaeobotany in 1904. During that time, she met Professor Kenjiro Fujii, a distinguished botanist at the Imperial University of Tokyo, the real “Kenjiro Watanabe”.
In 1907, she convinced the Royal Society to fund an excursion to Japan, where Marie discovered some of the earliest fossilised angiosperms and some fossil insects from the Cretaceous period. These ancient specimens were embedded in the coal faces of Hokkaido’s deepest mines.
The affair between Marie and Kenjiro did not end well. The passionate relationship directly inspired Stopes’s Love-Letters of a Japanese, a work she drafted prior to the groundbreaking release of Married Love.
In 1957, Marie Stopes was diagnosed with cancer. She died on October 2, 1958.

References:

FALCON-LANG, H.J. & MILLER, R.F. 2007. Marie Stopes and the Fern Ledges of Saint John, New Brunswick. In Burek, C.V. (ed.) The Role of Women in the History of Geology. Special

Falcon-Lang, H.J., 2008. Marie Stopes: Passionate about Palaeobotany. Geology Today, 24: 132-136.

Mortlake, G. N. (Ed.). (1911). Love Letters of a Japanese. Stanley Paul & Company.

On brains and the evolution of flight.

Posted on by under Earth Science

Water colour by the Reverend G. E. Howman (From Martill 2015)

Lagerpetids were small to medium-sized (less than 1 m long), cursorial, non-volant reptiles that lived during the Middle to Upper Triassic periods in Argentina, Brazil, Madagascar, and North America. The recognition of lagerpetids as the sister taxon to pterosaurs provides clues to study the origin of Pterosauria, its specialized body plan, and its flying abilities.

Pterosaurs were the first flying vertebrates. The oldest-known pterosaurs appear in the fossil record about 220 million years ago. Their reign extended to every continent, and they achieved high levels of morphological and taxonomic diversity during the Mesozoic. Most Triassic pterosaurs are small but already had a highly specialized body plan linked to their ability to fly: a shoulder girdle with a strongly posteroventrally enlarged coracoid braced with the sternum and laterally facing glenoid fossa; a forelimb with a pteroid bone and hypertrophied fourth digit supporting a membranous wing; and a pelvic girdle with a prepubic bone and strongly developed preacetabular process.

The evolution of the pterosaur brain. From Bronzati et al., 2025.

Pterosaur brains have been thought to resemble those of birds. Both share some features like a shortened olfactory tract, enlarged and repositioned optic lobes, and expanded cerebral and floccular lobes—some of which are thought to be convergent adaptations for flight. Unfortunately, it has been challenging to trace the evolution of the pterosaur brain due to the scarcity of fossils with well-preserved, three-dimensional cranial material. New cranial endocast data from the terrestrial lagerpetid Ixalerpeton polesinensis sheds light on the ancestral brain condition of pterosauromorphs prior to the evolution of flight.

A 3D printed model of the C. hanseni skull discovered in Utah.

The cranial endocast of Ixalerpeton reveals modestly enlarged and laterally displaced optic lobes but lacks the enlarged floccular lobe of the cerebellum. The flocculus plays a crucial role in coordinating eye movements and tends to be enlarged in taxa that rely on rapid movements of the head and body. This condition in Pterosaurs has been hypothesized to be important for information processing related to flight. Using the endocranial morphology of Caelestiventus hanseni, a Late Triassic pterosaur from North America, the team led by M. Bronzati found  that cerebral hemisphere expansion and reduction of the olfactory tract already occurred among the oldest pterosaurs, 60 million years before similar changes occurred in non-avian paravians, prior to the origin of birds.

Birds have undergone remarkable encephalization, in which brain size has increased without corresponding changes in body size. Brain size has been correlated with major evolutionary innovations like cognition, flight, environmental adaptability, and enhanced sensory capabilities. The new data indicate that the later brain expansion in both birds and pterosaurs was likely more about enhancing cognition than about flying itself.

 

References:

Bronzati, M., Watanabe, A., Benson, R. B. J., Müller, R. T., Witmer, L. M., Ezcurra, M. D., Montefeltro, F. C., Baczko, von, Bhullar, B.-A. S., Desojo, J. B., Knoll, F., Langer, M. C., Lautenschlager, S., Stocker, M. R., Turner, A. H., Ingmar Werneburg, Nesbitt, S. J., Fabbri, M., Bronzati, M., & Watanabe, A. (2025). Neuroanatomical convergence between pterosaurs and non-avian paravians in the evolution of flight. Current Biology. https://doi.org/10.1016/j.cub.2025.10.086

Ezcurra, M.D., Nesbitt, S.J., Bronzati, M. et al. Enigmatic dinosaur precursors bridge the gap to the origin of Pterosauria. Nature (2020). https://doi.org/10.1038/s41586-020-3011-4

Brooks B. Britt et al. Caelestiventus hanseni gen. et sp. nov. extends the desert-dwelling pterosaur record back 65 million years, Nature Ecology & Evolution (2018). DOI: 10.1038/s41559-018-0627-y

Forgotten women of paleontology: Estella Bergere Leopold.

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Estella Leopold in 1938. Image credit: The Aldo Leopold Foundation

Paleoecological records suggest that the transition to agriculture marked a pivotal turning point in the environmental history of our planet. Tropical forests have been reduced by agricultural expansion associated with growing human populations, which has triggered soil loss due to deforestation and erosion. These changes eventually sparked a movement for responsibility, pioneered by the foundational works of Aldo Leopold’s A Sand County Almanac (1949) and Rachel Carson’s Silent Spring (1962), which sowed the seeds of modern environmental activism.
One of the most powerful statements in Leopold’s work is about the relationship between nature and community: ‘When we see land as a community to which we belong, we may begin to use it with love and respect. There is no other way for land to survive the impact of mechanised man, nor for us to reap the aesthetic benefits that it is capable of contributing to culture under science.”
These words had a profound effect on his youngest daughter, Estella.

Estella Leopold planting pine trees on the family farm in 1938. Image credit: University of Wisconsin Digital Collections.

Estella Bergere Leopold was born on January 8, 1927, in Madison, Wisconsin. She earned a degree in botany from the University of Wisconsin in 1948, followed by a master’s degree from the University of California in 1950, and then completed her doctoral studies at Yale in 1955 under the guidance of Paul Sears and Edward Deevey Jr., two pioneering palynologists in the United States.  Soon after her graduation, she became one of the few women who joined the US Geological Survey in Lakewood, Colorado, where she worked studying pollen taken from deep cores in the Rocky Mountains, Alaska, China, Eniwetok, and other atolls in the South Pacific.
Estella used pollen and other palynomorphs to study how plants responded to mountain building, volcanism, and climate change over the past 65 million years. Her research, on Miocene forests that grew on coral atolls, supported Darwin’s hypothesis that the corals had colonized subsiding volcanoes.

 

Estella B. Leopold (2012). Image credit: Aldo Leopold Foundation.

After working in the Florissant Valley, Colorado, she began leading field trips with ecologist Bettie Willard to show the extraordinary fossils that had been preserved there for 34 million years in volcanic mud and ash. To protect the area, she and her colleagues formed Defenders of Florissant in 1964. The group won one of the first explicitly environmental lawsuits against the US government. Like her father, she was an advocate for a “land ethic,” and that same year she was awarded the Conservationist-of-the-Year Award by the Colorado Wildlife Federation.

In 1974, she was elected to the prestigious National Academy of Sciences. Two years later, Estelle Leopold became director of the Quaternary Research Center (QRC) at the University of Washington, Seattle. In 2010, she received the Cosmos International Award in recognition of her professional career. Her acceptance speech emphasized that restoration is one way to interact with ecosystems, but not the only one, and that one of these ways involves carefully observing how they function.

She died on February 25, 2024.

References:

Leopold, Estella B.. Keeping the land alive and well : The 2010 International Cosmos Prize commemorative lecture. SANSAI : An Environmental Journal for the Global Community. 2011, 5: 5-18. http://hdl.handle.net/2433/143611

Dunwiddie, P., Strömberg, C. A. E., & Whitlock, C. (2024). Estella Bergere Leopold: Paleobotanist and conservationist extraordinaire. Proceedings of the National Academy of Sciences, 121(25). https://doi.org/10.1073/pnas.2408242121

Leopold, A. (1949). A Sand County Almanac. New York: Oxford, 158(209), 178.

 

Halloween special XIII: Poe, Cuvier, and memento mori

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Master of the macabre

Edgar Allan Poe (1809-1849)

“Deep into that darkness peering, long I stood there, wondering, fearing, doubting, dreaming dreams no mortal ever dared to dream before.” This quote from the poem The Raven illustrates the profound and dramatic lyricism of one of the most influential authors in world literature: Edgar Allan Poe. He was born in Boston, Massachusetts, on January 19, 1809, and died on October 7, 1849, in Baltimore, Maryland.

Writer, poet, and literary critic, Poe was the epitome of the artist tormented by his own demons. He was the master of terror and invented the modern detective story with “The Murders in the Rue Morgue.” His dark landscapes, gothic mansions, and ancestral families steeped in madness function as powerful metaphors for the inevitable decay of everything around us. This is something he expresses in the introduction to his prose poem “Eureka”, where he articulates his ideas about the origin of the cosmos: “—In the Original Unity of the First Thing resides the Secondary Cause of All Things, with the Germ of their Inevitable Annihilation.” This universal sequence of birth and death is the ultimate memento mori: a reminder that extinction is the final destiny of all species, and even the Universe.

The Conchologist’s First Book by Edgar Allan Poe (1839)

One of his most successful publications, and certainly the most unusual, was “The Conchologist’s First Book“ (a more affordable and popular edition of Thomas Wyatt’s “Manual of Conchology“, published by Harper and Brothers, who used Poe’s name to avoid copyright issues). Although Poe only wrote the preface and introduction, he incorporated a new classification system based on the work of the renowned paleontologist and naturalist Georges Cuvier.
Poe was fluent in French and translated Cuvier’s scientific classification. Furthermore, he learned the scientific method and incorporated it into the creation of his famous detective, Auguste Dupin. His sharp and meticulous mind was the literary model for Sherlock Holmes and Hercule Poirot.

llustration by Daniel Vierge of “The Murders in the Rue Morgue”, 1870, From Wikimedia Commons

Georges Léopold Chrétien Frédéric Dagobert Cuvier (1769-1832) is considered the founding father of paleontology and comparative anatomy. At the beginning of the 19th century, Cuvier published “Discours sur les révolutions de la surface du globe” (1812) where he introduced a revolutionary theory: catastrophism, which postulated that the history of life on Earth was marked by extinction events.

In The Murders in the Rue Morgue, Dupin uses a description by Cuvier of an orangutan, detailing the animal’s strength, ferocity, and ability to mimic other behaviors, to solve the murders of Madame L’Espanaye and her daughter Camille. Dupin’s analytical method echoes Cuvier’s theory, according to which all parts of a being are correlated. Later, in his 1846 essay “The Philosophy of Composition,” Poe himself draws a striking parallel between the scientific method and the writing process, using his most famous poem, “The Raven,” to illustrate his writing principles.

References:

Poe, Edgar Allan, ed. The First Conchologist’s Book; or, A System of Testaceous Malacology. Based on Thomas Wyatt’s Manual of Conchology. 1839.

Poe, E. A. (1841). The Murders in the Rue Morgue. https://americanenglish.state.gov/files/ae/resource_files/the_murders_in_the_rue_morgue.pdf

Baldellou, M. M. (2013). FORETELLING DARWINISM, REVISING RACE: POE’S SCIENTIFIC DISCOURSE IN “THE MURDERS IN THE RUE MORGUE”. REVISTA CANARIA DE ESTUDIOS INGLESES, 66, 127-135.

Once upon a time in New Mexico

Posted on by under Earth Science

The San Juan Basin, New Mexico. Photo credit: Daniel J. Peppe

Asteroids, as Neil deGrasse Tyson explains, are ancient remnants from our early solar system, wandering through space, potential bearers of life’s ingredients or agents of apocalyptic death.
In 1980, in a landmark lecture, U.S. physicist Luis Alvarez declared, “Lucifer’s Hammer killed the dinosaurs,” presenting the geochemical evidence he and his son had uncovered for a colossal asteroid strike at the end of the Cretaceous period. The following year, the Mexican oil company Pemex identified the Chicxulub crater on the Yucatán Peninsula as the site of this massive asteroid impact. The impact released an estimated energy equivalent of 100 teratonnes of TNT. Three-quarters of the plant and animal species on Earth disappeared, including non-avian dinosaurs, pterosaurs, marine reptiles, ammonites, and planktonic foraminifera.

Paleogeography of North America during the late Campanian Stage of the Late Cretaceous (∼75 Ma). From Sampson et al., 2010

In recent decades, there has been a heated debate over whether the dinosaurs were in decline or whether they continued to thrive until they were abruptly wiped out by the asteroid impact, the main pulse of the K/Pg extinction. This controversy is worsened by a geographical bias, as most data comes from the Northern Hemisphere. The Naashoibito Member (San Juan Basin, New Mexico) provides a crucial piece of this puzzle, capturing a snapshot of the continent’s final dinosaur communities and their diversity at the Cretaceous boundary.

The emplacement of the Western Interior Seaway (about 99.5 Mya) split the North American continent into two separate landmasses: Laramidia (a long, narrow landmass from present-day Alaska to Mexico) and Appalachia (the eastern part of the continent). During the Campanian (83.6–72.1 million years ago), Laramidia had a high regional diversity, with distinct northern and southern faunas. In the Maastrichtian (72.1–66.0 Ma), those ecosystems became more uniform. The “homogenization” of those ecosystems could have pushed non-avian dinosaurs into a prolonged decline, setting the stage for their eventual extinction. A new study provides a new look at the last-surviving dinosaur-dominated ecosystems by presenting a revised geochronology of the Naashoibito Member (contemporaneous with the Hell Creek faunas) to test whether there were changes in faunal provinciality during the Cretaceous-Paleogene boundary.

Latest Cretaceous–early Paleogene terrestrial basins in western North America and their faunas. From Flynn et al., 2025

Ecological analysis shows that the Naashoibito dinosaurs were highly diverse, spanning many species, body sizes, and diets. This diversity matches that of earlier periods and suggests that dinosaurs continued to thrive in New Mexico until the Cretaceous-Paleogene boundary. The new study further indicates that temperature was a key factor of dinosaur distribution, with sauropods dominating warmer environments (southwestern North America), and hadrosaurines dominating the cooler temperate regions (modern Great Plains). These results emphasise the importance of abiotic factors in promoting heterogeneity in dinosaur-dominated ecosystems prior to the Cretaceous–Paleogene extinction event.

References:

Flynn, A. G., Brusatte, S. L., Chiarenza, A. A., García-Girón, J., Davis, A. J., Fenley, C. W., Leslie, C. E., Secord, R., Shelley, S., Weil, A., Heizler, M. T., Williamson, T. E., & Peppe, D. J. (2025). Late-surviving New Mexican dinosaurs illuminate high end-Cretaceous diversity and provinciality. Science, 390(6771), 400–404. https://doi.org/10.1126/science.adw3282

‌Dean, C. D., Chiarenza, A. A., Doser, J. W., Farnsworth, A., Jones, L. A., Lyster, S. J., Outhwaite, C. L., Valdes, P. J., Butler, R. J., & Mannion, P. D. (2025). The structure of the end-Cretaceous dinosaur fossil record in North America. Current Biology: CB. https://doi.org/10.1016/j.cub.2025.03.025

Sampson SD, Loewen MA, Farke AA, Roberts EM, Forster CA, Smith JA, et al. (2010) New Horned Dinosaurs from Utah Provide Evidence for Intracontinental Dinosaur Endemism. PLoS ONE 5(9): e12292. https://doi.org/10.1371/journal.pone.0012292

Meet Huayracursor jaguensis, an early sauropodomorph from Argentina.

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Huayracursor jaguensis. Image credit: Jorge Blanco

Dinosaurs likely originated in the Middle Triassic, but the earliest unambiguous dinosaur specimens are from the middle-late Carnian age, primarily in the Southern Hemisphere, with potential evidence in North America. This gap highlights a significant uncertainty in the geological and temporal context of early dinosaur evolution. The Triassic deposits of Argentina, renowned for their diverse tetrapod assemblage, offer crucial insights into dinosaur origins by preserving some of the oldest dinosaurs ever discovered. These skeletal records of early dinosaurs document a time when they were not numerically abundant, and they were still of modest body size (Eoraptor had a slender body with an estimated weight of about 10 kilograms)

Located along the Pacific margin of Southwest Gondwana, the narrow, NW-SE trending Triassic basins of western Argentina include the Santo Domingo Formation in La Rioja. Fossil assemblages from this formation, comparable to the Hyperodapedon–Exaeretodon–Herrerasaurus biozone, constrain its deposition to the late Carnian to Norian. This timeframe coincides with the Ischigualasto and Los Colorados formations. A newly recovered specimen from the base of the Santo Domingo Formation (Northern Precordillera Basin; Upper Triassic) provides the earliest evidence that body mass increase and neck elongation occurred synchronously in Sauropodomorpha, indicating that these pivotal traits emerged at the dawn of the dinosaur lineage.

Selected bones of Huayracursor jaguensis holotype. From Hechenleitner et al., 2025.

Huayracursor jaguensis was a primitive sauropodomorph, an early member of the highly successful herbivorous lineage that later produced long-necked giants like Argentinosaurus and Patagotitan. Phylogenetic analysis places it within the Bagualasauria group. The holotype (CRILAR-Pv 151) is an articulated partial skeleton composed of cranial and postcranial material. The genus name combines the Quechuan word “huayra,” meaning “wind,” with the Latin “cursor,” meaning “runner.” The species name is derived from the village of Jagüé in La Rioja, which lies 40 kilometers from the discovery site at Quebrada Santo Domingo.

The earliest known sauropodomorphs were small, bipedal animals, weighing around 10 kg with relatively short necks. Body mass estimates indicate that H. jaguensis weighed around 18.0 kg (~40 lb), surpassing the body mass predicted for othercontemporaneous sauropodomorphs (e.g., Buriolestes, Pampadromaeus, Saturnalia, Mbiresaurus, and Chromogisaurus). Furthermore, Huayracursor preserves a nearly complete cervical series, revealing a long neck compared to other contemporary specimens. This combination of features suggests that the acquisition of larger body size and neck elongation did not occur as separate, sequential events, but were already linked by the first appearances of dinosaurs in the Late Carnian.

 

References:

Hechenleitner, E.M., Martinelli, A.G., Rocher, S. et al. A long-necked early dinosaur from a newly discovered Upper Triassic basin in the Andes. Nature (2025). https://doi.org/10.1038/s41586-025-09634-3

Desojo, J.B., Fiorelli, L.E., Ezcurra, M.D. et al. The Late Triassic Ischigualasto Formation at Cerro Las Lajas (La Rioja, Argentina): fossil tetrapods, high-resolution chronostratigraphy, and faunal correlations. Sci Rep 10, 12782 (2020). https://doi.org/10.1038/s41598-020-67854-1

 

Paleo-streaming: the resistance of Argentinian Science.

Posted on by under Earth Science

Image credit: LACEV, CONICET-Argentine Museum of Natural Sciences.

Following on the unexpected success of a scientific livestream that drew 61,000 viewers—tripling the audience of The Voice Argentina—a team of paleontologists is preparing for a new groundbreaking broadcast. On August 4th, the public was captivated by a live journey to the depths of the South Atlantic; this October, they will be transported 70 million years back in time.

The ‘Cretaceous Expedition I – 2025’ will investigate a key fossil site in General Roca, Río Negro. For the first time, from October 6-10, part of the excavation will be broadcast live via satellite internet, allowing the public to witness paleontology in real-time.

The site is a uniquely complete window into the Mesozoic, just before the mass extinction that reshaped our planet. It contains the remains of at least ten previously unknown species, including amphibians, reptiles, and mammals. The primary goal is to uncover more of the enigmatic Bonapartenykus ultimus—an Alvarezsaurid theropod dinosaur from the late Cretaceous. To date, only a single, poorly preserved partial skeleton associated with two eggs has been found. The team now hopes to recover more complete remains, piecing together a clearer picture of this elusive dinosaur.

The quarry studied by the LACEV team. Image credit: LACEV, CONICET-Argentine Museum of Natural Sciences.

This groundbreaking digital initiative is a collaboration between the Laboratory of Comparative Anatomy and Vertebrate Evolution (LACEV), the Félix de Azara Natural History Foundation, and National Geographic. It focuses on a 70-million-year-old site in Patagonia, a location recognized as a preeminent window into the continent’s pre-extinction ecosystems. Launched at a time when Argentina’s scientific community is confronting severe challenges under the administration of libertarian President Javier Milei, the project stands as a testament to resilience, aiming to democratize knowledge by showcasing science in real-time, against all odds.

References:

Agnolin, F. L., Powell, J. E., Novas, F. E., & Kundrát, M. (2012). New alvarezsaurid (Dinosauria, Theropoda) from uppermost Cretaceous of north-western Patagonia with associated eggs. Cretaceous Research, 35, 33–56. https://doi.org/10.1016/j.cretres.2011.11.014

Links:

YouTube: @paleocueva_lacev

Instagram: @paleocueva.lacev

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Introducing Joaquinraptor casali, a new megaraptoran dinosaur from Patagonia.

Posted on by under Earth Science

Joaquinraptor casali. Image credit: Andrew McAfee – Carnegie Museum of Natural History.

The Cretaceous beds of Patagonia contain the most comprehensive record of non-avian theropods from the Southern Hemisphere. This includes Megaraptora, a clade of medium-sized, highly pneumatized theropods characterized by elongated skulls and formidable manual claws on digits I and II. Megaraptorids were the top predators in central and southern Patagonian ecosystems at the end of the Cretaceous, unlike more northerly areas of South America, where other non-avian theropod groups were dominant. The phylogenetic affinities of megaraptoran theropods within Tetanurae —as either carcharodontosaurian allosauroids or early-branching coelurosaurs, potentially basal tyrannosauroids—are highly controversial, due to the incomplete nature of most available megaraptorid skeletons and the little information about their cranial anatomy. However, despite the lack of consensus, the megaraptorans themselves remain a well-supported clade. Now, a new megaraptoran theropod dinosaur, discovered in the Upper Cretaceous of Argentina’s Chubut Province, sheds light on these enigmatic predators and their evolutionary history.

Skeletal reconstruction of Joaquinraptor in left lateral view with preserved elements in blue. From Ibiricu et al., 2025.

Joaquinraptor casali gen. et sp. nov. is a large-bodied megaraptorid from the Upper Cretaceous (Coniacian–Maastrichtian) Lago Colhué Huapi Formation of south-central Chubut Province, in central Patagonia, Argentina. The holotype (UNPSJB-PV 1112) is a partially articulated skeleton that includes a disarticulated partial skull (right maxilla, skull roof and braincase, probable right postorbital and quadrate, both dentaries, and in situ and isolated teeth), complete or nearly complete axial and appendicular skeletons, and numerous fragments. The generic name is derived from the words “Joaquin” (name of the first author’s son, and the informal name given to the locality when the skeleton of the taxon was discovered, Valle Joaquín), and the latin word “raptor” (thief). The specific name honours Dr Gabriel Andrés Casal for his many contributions to the study of Cretaceous palaeontology and geology in central Patagonia.

Dentaries of Joaquinraptor (UNPSJB-PV 1112) and an associated crocodyliform right humerus. From Ibiricu et al., 2025

Joaquinraptor is distinguished by the following autapomorphies: strong transverse compression of the parietals, making them narrower than the frontals; a sigmoid contour on the anterior margin of the supratemporal fossa; the absence of a median septum within the pneumatic recess of the braincase; a subrectangular deltopectoral crest on the humerus; and a vertical ridge on the medial surface of the ulna’s proximal end. Compared to Maip macrothorax, Joaquinraptor possesses a coracoid with a subglenoid ridge, a posteroventral fossa, and a hooked posteroventral process. Their preserved dorsal ribs also differ, though this variation may be positional rather than taxonomic. Additionally, a crocodile humerus was found nestled between the jawbones of Joaquinraptor. The bone shows potential tooth marks, suggesting that the crocodile may have been its prey.

Hypothesized distribution of medium- to large-bodied theropod dinosaurs occupying apex predator niches in selected South American depositional basins during the Campanian and Maastrichtian. Adapted from Ibiricu et al., 2025.

In Patagonia, after the Turonian extinction of carcharodontosaurids, megaraptorids appear to have undergone a significant size increase compared to their older Australian counterparts, with some Late Cretaceous taxa, such as Maip, possibly reaching lengths of 9 m or more. This evolutionary development likely facilitated their ascent into the apex predator niche. The presence of Joaquinraptor in probable late Maastrichtian strata indicates the lineage persisted until the Cretaceous-Paleogene boundary, ultimately succumbing to the end-Cretaceous mass extinction.

 

References:

Ibiricu, L.M., Lamanna, M.C., Alvarez, B.N. et al. Latest Cretaceous megaraptorid theropod dinosaur sheds light on megaraptoran evolution and palaeobiology. Nat Commun 16, 8298 (2025). https://doi.org/10.1038/s41467-025-63793-5

Porfiri, J. D., Novas, F. E., Calvo, J. O., Agnolín, F. L., Ezcurra, M. D. & Cerda, I. A. 2014. Juvenile specimen of Megaraptor (Dinosauria, Theropoda) sheds light about tyrannosauroid radiation. Cretaceous Research 51: 35-55.

 

Meet Zavacephale rinpoche

Posted on by under Earth Science

A pair of Z. rinpoche Image credit: Masaya Hattori

Pachycephalosaurians, with their distinctive domed heads, are an enigmatic group of small ornithischian dinosaurs. Most pachycephalosaurid remains are known from the Late Cretaceous of North America, Asia, and possibly Europe. Notable species include Pachycephalosaurus, Stegoceras, and Stygimoloch. The macroevolution of the pachycephalosaurian cranial dome has been debated due to the absence of early species and the fragmentary nature of all pachycephalosaurian fossils. Over the years, scientists have named numerous pachycephalosaurid genera and species based on isolated and incomplete material. Consequently, the group has had a rather volatile and contentious taxonomic history.

Zavacephale rinpoche gen. et sp. nov., from the Lower Cretaceous Khuren Dukh Formation of Mongolia, is the oldest and most complete pachycephalosaurian skeleton ever found. The genus name is derived from the Tibetan word ‘zava’, meaning ‘root’ or ‘origin’, and the Latin word ‘cephal’, meaning ‘head’. The specific name, ‘rinpoche’ (meaning ‘precious one’ in Tibetan), refers to the domed condition of the skull.

Z. rinpoche. From Chinzorig et al., 2025.

The holotype (MPC-D 100/1209) is a partially articulated skeleton with an almost complete skull and a tail covered in petrified tendons, corresponding to an immature individual. The skeleton measures approximately 1 metre in length (3.3 ft), and the animal was likely to weigh around 5.85 kilograms (12.9 lb) in life. Additionally, a mass of geo-gastroliths with sharp edges and inlets has been found. This morphology is more consistent with an omnivorous diet than a herbivorous one.

The new specimen exhibits a well-developed frontoparietal dome, widely suggested as a sociosexual structure, with an elongated preorbital region. Unlike other pachycephalosaurians, the parietal process of the squamosal in Z. rinpoche is narrow and does not form a dorsal platform or contribute to the dome. Zavacephale’s cranium is also weakly ornamented. The new study indicates that the initial phase of dome evolution proceeded via a frontal-first developmental sequence, exhibiting the retention of an open supratemporal fenestra. This observation is consistent with the proposed ontogenetic trajectories observed in certain Late Cretaceous taxa.

 

 

References:

Chinzorig, T., Takasaki, R., Yoshida, J., Tucker, R. T., Buyantegsh, B., Mainbayar, B., Tsogtbaatar, K., & Zanno, L. E. (2025). A domed pachycephalosaur from the early Cretaceous of Mongolia. Nature, 1–8. https://doi.org/10.1038/s41586-025-09213-6

Horner JR, Goodwin MB (2009) Extreme Cranial Ontogeny in the Upper Cretaceous Dinosaur Pachycephalosaurus. PLoS ONE 4(10): e7626. https://doi.org/10.1371/journal.pone.0007626

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