[Paleontology • 2026] Austronaga minuta • Highly aquatic marine stem Archosaur with soft tissue preservation

Austronaga minuta Wang, Lei & Li, 2023

 

in Wang, Fraser, Spiekman, Z. Li, et C. Li, 2026. 

DOI: doi.org/10.1126/sciadv.aeb7528 

Artwork by Gabriel Ugueto

 

Abstract

Archosauromorpha is a dominant reptile clade that primarily occupied terrestrial ecosystems with limited secondarily aquatic invasions that are poorly known. Here we report on a well-preserved Triassic reptile representing the earliest stem-archosaur to evolve unequivocal aquatic specializations. This taxon exhibits a suite of aquatic adaptations previously unknown in stem-archosaurs, such as hyperphalangy, enhanced paddle-like forelimbs, and a loss of articulation between the sacrum and pelvis, indicating an advanced aquatic lifestyle. The fossil exhibits the oldest known stomach, liver, and intestinal preservations in reptiles. Our findings provide unexpected insights into the early aquatic diversification of Archosauromorpha during the Triassic marine ecosystem recovery and highlight a conservative gastrointestinal system in an early Mesozoic vertebrate. In the absence of clear terrestrial members of the other major Mesozoic marine reptile lineages (e.g., ichthyosaurs and sauropterygians), this discovery provides an unambiguous example of such a lineage including both decidedly terrestrial and extensively marine forms, providing tantalizing evidence for the land-to-sea transition in Triassic reptiles.

Systematic paleontology

Diapsida, Osborn, 1903.

Archosauromorpha, von Huene, 1946.

Tanysauria, Spiekman et al., 2024.

Trachelosauridae, Abel 1919 (sensu Spiekman et al., 2024).

Skeleton of the holotype of Austronaga minuta (IVPP V18579). Abbreviations are in the Supplementary Materials. Scale bars, 2 cm (A) and 1 cm (B to D).

Austronaga minuta, Wang et al., 2023.

Type specimen: Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) V18579, a complete articulated skeleton preserved on two slabs (Fig. 1).

Locality and horizon: Waina Village, Luoping County, Yunnan Province, China; Member II of Guanling Formation, middle Anisian (Pelsonian), Middle Triassic.

Emended diagnosis: A tanysaur with the following features: quadrate anteroposteriorly broad and plate-like in lateral view with concave posterior margin; 18 cervical, 24 dorsal vertebrae; tall axe-shaped neural spine on axis; cervical neural spines prominent, with convex dorsal margin and without anterodorsal or posterodorsal projections; chevrons of mid-caudal region hatchet-shaped, with prominent distal expansion and a notch at the midpoint of its ventral margin; forelimb distinctly longer than hindlimb with humerus to femur length ratio over two; hyperphalangy present in both manus and pes.

Reconstruction of the long-necked marine reptile Austronaga minuta.

Artwork by Gabriel Ugueto

Wei Wang, Nicholas C. Fraser, Stephan N. F. Spiekman, Zhiheng Li, Olivier Rieppel, Hong Lei, Torsten M. Scheyer and Chun Li. 2026. Highly aquatic marine stem Archosaur with soft tissue preservation. Science Advances. 12(31); DOI: doi.org/10.1126/sciadv.aeb7528 [29 Jul 2026]

[Paleontology • 2026] Zhengheornis buyu • Jurassic Avialan reveals stepwise Evolution of Bony Tail in Birds

Zhengheornis buyu

Wang, Tang, Deng, Dong, L. Xu, X. Xu, M. Lin,  Du, G. Lin, Chen, Zhang & Zhou, 2026 

 

DOI: doi.org/10.1126/sciadv.aeb5202 

Abstract

The evolutionary assembly of the flight-adapted bird body plan encompasses some of the most profound morphological changes in terrestrial vertebrate history. Beyond feathered wings, the short pygostyle-bearing tail has been pivotal to the clade’s ecological success. However, transition from the long bony tail to the short pygostyle-bearing tail remains a mystery, hindered by the scarcity of early branching avialans with transitional morphologies. Here, we report on a new avialan, Zhengheornis buyu, gen. et sp. nov., from the Upper Jurassic of southeastern China, suggesting that the vertebral reduction and shortening preceded pygostyle fusion in early avialan evolution, providing critical evidence for the stepwise evolution of the bird tail. Z. buyu is smaller than all known non-pygostylian paravians, expanding the species and body size diversity of stemward taxa.

Systematics

Theropoda Marsh, 1881  

Maniraptora Gauthier, 1986  

Avialae Gauthier, 1986 

Zhengheornis buyu gen. et sp. nov. 

Etymology: “Zhenghe” (Mandarin), referring to Zhenghe Country, where the holotype specimen was found; “ornis,” bird (Greek); “buyu,” unexpected (Mandarin), from the ancient Chinese book Guoyu, referring to the unique tail and pelvic morphologies preserved in this species. 

Holotype: Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) V34168, an articulated and partially complete skeleton (most limb bones are preserved as molds) with feathers preserved on a slab and counter slab (Fig. 1, figs. S1 and S2, and table S1). 

Locality and horizon: Near Yangyuan Village, Zhenghe Country, Nanping City, Fujian Province; Upper Jurassic, Nanyuan Formation [Tithonian stage]. 

Diagnosis: IVPP V34168 is distinguishable from all other paravians in the following combination of characters (*denotes probable autapomorphy): short tail comprising 15 vertebrae that is shorter than the hindlimb (combined length of femur, tibia, and metatarsal III)*; middle and posterior caudal vertebrae less elongate (opposite to the condition in other long tailed avialans); final two caudal vertebrae box-like*; manual phalanx III-1 shorter than III-2, opposite to the condition in Archaeopteryx and Fujianvenator [the three manual digits of maniraptorans are here identified as I, II, and III, as in (Tamura, et al. 2011)]; manual phalanx III-3 50% longer than III-2 (the length ratio greater than 2 in Anchiornis and Archaeopteryx); slender ischium that has a knob-like, distally located obturator process and lacks the posterior process*; short fibula that terminates far proximal to the ankle; metatarsal I that articulates at the distal third of metatarsal II; metatarsal II that ends far proximal to metatarsal III trochlea; short hallux with an ungual that is smaller than that of other pedal digits; and robust digit II that has the longest non-ungual (II-2) and ungual pedal phalanges.

 

Min Wang, Jianrong Tang, Ke Deng, Liping Dong, Liming Xu, Xing Xu, Min Lin, Honggang Du, Ganmin Lin, Runsheng Chen, Chi Zhang and Zhonghe Zhou. 2026. Jurassic Avialan reveals stepwise Evolution of Bony Tail in Birds. Science Advances. 12(27); DOI: doi.org/10.1126/sciadv.aeb5202 [1 Jul 2026]

[Paleontology • 2026] Earliest Octopuses were Giant Top Predators in Cretaceous Oceans

the Late Cretaceous finned octopus species Nanaimoteuthis sp. 

in Ikegam, Mutterlose, Sugiura, Takeda, Derin, ...et Iba, 2026.  

DOI: doi.org/10.1126/science.aea6285 

Artwork by Yohei Utsuki. 

Abstract

Top predators drive changes in ecosystem structure. For the last ~370 million years, large-sized vertebrates have dominated the apex of the marine food chain, while invertebrates have served as smaller prey. Here we describe invertebrate top predators from this “age of vertebrates,” the earliest finned octopuses (Cirrata) from Late Cretaceous sediments (~100 to 72 million years ago), as identified based on huge, exceptionally well-preserved fossil jaws and their wear. This extensive wear suggests dynamic crushing of hard skeletons. Asymmetric wear patterns further indicate lateralized behavior, suggesting advanced intelligence. With a calculated total length of ~7 to 19 meters, these octopuses may represent the largest invertebrates thus described, rivaling contemporaneous giant marine reptiles. Our findings show that powerful jaws, and the loss of superficial skeletons, convergently transformed cephalopods and marine vertebrates into huge, intelligent predators.

Huge lower jaws of fossil octopuses and of an extant giant squid. (A and B) The largest lower jaws of the Late Cretaceous finned octopus species Nanaimoteuthis jeletzkyi [(A) NMNS DS00042 3LmvTpM] and N. haggarti [(B) KMNH IvP 902001]. Both specimens show extensive loss of jaw material caused by wear.
(C) A lower jaw of the extant giant squid Architeuthis dux (NSMT-Mo 85956), a species having the largest jaw among modern cephalopods.
(A) is a digital fossil jaw visualized as a 3D model; (B) is an exceptionally well-preserved nondigital fossil jaw; and (C) is a modern jaw dissected from a carcass of ~10 m total body length. Solid lines indicate the extension of striation on the outer surface of the hood and broken lines show the estimated outline of the rostrum without wear. The hood and lateral walls lost by weathering, shown as shadowed areas, are reconstructed based on the holotype and specimens in fig. S4. (A) and (C) are exhibited in a mirrored position. Scale bar, 20 mm.

A sketch of the giant octopus.

artwork by Yohei Utsuki. 

 

Shin Ikegam, Jörg Mutterlose, Kanta Sugiura, Yusuke Takeda, Mehmet Oguz Derin, Aya Kubota, Kazuki Tainaka, Takahiro Harada, Harufumi Nishida and Yasuhiro Iba. 2026. Earliest Octopuses were Giant Top Predators in Cretaceous Oceans. Science. 392; 6796: 406-410. DOI: doi.org/10.1126/science.aea6285 [23 Apr 2026] 

Editor’s summary: The Kraken, the giant cephalopod of legend, was feared by sailors for centuries. Later interpretations suggested that it may have been based on sightings of the giant squid, which can be 10 meters long. Although they lived far too early to have been the source of the legend, Ikegami et al. describe fossil octopods from the late Cretaceous that truly would have fit the description of the monster, reaching up to 19 meters in length. Wear patterns on their jaws suggest that these octopods preyed upon the large reptiles present at the time, including plesiosaurs and mosasaurs. The authors interpret asymmetry in these wear patterns as an indication of corresponding asymmetry in behavior, suggesting complex brain development and, potentially, high intelligence. —Sacha Vignieri

[PaleoMammalogy • 2026] Masripithecus moghraensis • An Early Miocene Ape from the Biogeographic Crossroads of African and Eurasian Hominoidea

Masripithecus moghraensis

Al-Ashqar, Seiffert, El-Sayed, Salem, Gohar, El-Saka, Amin & Sallam, 2026

DOI: doi.org/10.1126/science.adz4102

nhm.org

Illustration by Mauricio Antón

Abstract

The Early Miocene fossil record documenting hominoid evolution has long been restricted primarily to sites in East Africa, whereas contemporaneous North African sites have only yielded remains of cercopithecoid monkeys. Here, we describe a fossil ape from North Africa, a new genus (Masripithecus) from the Early Miocene (~17 million to 18 million years) of northern Egypt, on the basis of mandibular remains. A combined molecular-morphological Bayesian tip-dating analysis positions Masripithecus closer to crown hominoids than coeval fossil apes from East Africa, thereby filling a phylogenetic and biogeographic gap in the evolution of stem hominoids. This evidence suggests that crown Hominoidea might have originated during the Early Miocene in the underexplored northeastern part of Afro-Arabia, rather than in eastern Africa or Eurasia.

 

Masripithecus moghraensis

Illustration of Masripithecus moghraensis by Mauricio Antón

Masripithecus moghraensis and the dispersal of crown hominoids in the Miocene. The map highlights Wadi Moghra, Egypt (star), which is the discovery site of Masripithecus—the first definitive North African ape—alongside key Miocene hominoid localities (see table S1) across Afro-Arabia and Eurasia. Arrows indicate inferred dispersal routes based on the phylogenetic and biogeographic analyses presented here. The inset phylogeny places Masripithecus as the closest sampled sister taxon of crown Hominoidea. At lower left, a life reconstruction of Masripithecus based on the Masripithecus mandible combined with the facial morphology of the middle Miocene hominoid Pierolapithecus. Illustration by Mauricio Antón

 

SHOROUQ F. AL-ASHQAR, ERIK R. SEIFFERT, SANAA EL-SAYED, BELAL S. SALEM, ABDULLAH S. GOHAR, HOSSAM EL-SAKA, MOHAMED AMIN, AND HESHAM M. SALLAM. 2026. An Early Miocene Ape from the Biogeographic Crossroads of African and Eurasian Hominoidea. SCIENCE. 391(6792); 1383-1386. DOI: doi.org/10.1126/science.adz4102 [26 Mar 2026]

https://nhm.org/stories/meet-masripithecus-newly-described-ancient-ape-fills-gap-evolutionary-history-primates

 facebook.com/TheLeakeyFoundation/posts/1414457444059470

Editor’s summary: The vast majority of early hominoid fossil hunting has occurred in East Africa, where a trove of early fossils and lineages have been found. Other regions in Africa have been less explored for various reasons, inspiring the question of whether a focus on East Africa has shaped opinions about where early hominoid evolution occurred. Al-Ashqar et al. now describe a Miocene ape from Egypt with crown hominoid affinities suggesting both that this lineage diverged before entering Eurasia and that a focus on one African region may have shaped our ideas about where hominoids first emerged (see the Perspective by Alba and Arias-Martorell). —Sacha Vignieri

[Paleontology • 2026] Spinosaurus mirabilis • Scimitar-crested Spinosaurus species from the Sahara caps stepwise spinosaurid radiation

Spinosaurus mirabilis

Sereno, Vidal, Myhrvold, Johnson-Ransom, Ciudad Real, Baumgart, Sánchez Fontela, Green, Saitta, Adamou, Bop, Keillor, Fitzgerald, Dutheil,  Laroche, Demers-Potvin, Simarro, Gascó-Lluna,  Lázaro, Gamonal, Beightol, Reneleau, Vautrin, Bertozzo, FGranados, Kinney-Broderick, Mallon, Lindoso, Ramezani & Jahandar, 2026

 

DOI: doi.org/10.1126/science.adx5486

Artwork: Dani Navarro

 Abstract

INTRODUCTION: The fossils of Spinosaurus aegyptiacus, a giant sail-backed, fish-eating theropod dinosaur from northern Africa, have inspired competing lifestyle interpretations, either as a semiaquatic ambush predator stalking shorelines and shallows or a fully aquatic predator in pursuit of prey underwater. Its bones and teeth have been found only in coastal deposits near marine margins, a locale potentially consistent with either lifestyle interpretation.

RATIONALE: In the central Sahara, a new fossiliferous area (Jenguebi) was discovered in beds equivalent in age [Farak Formation; Cenomanian ~95 million years ago (Mya)] to those yielding fossil remains of S. aegyptiacus. We describe from this area a new species, Spinosaurus mirabilis sp. nov., which is very similar to S. aegyptiacus in skeletal form but with a much taller, scimitar-shaped cranial crest. Two new sauropods were found in close association with the new spinosaurid buried in fluvial sediments indicative of an inland riparian habitat.

RESULTS: Spinosaurus mirabilis sp. nov. is distinguished by the low profile of its snout, a hypertrophied nasal-prefrontal crest, greater spacing of posterior maxillary teeth, and other features. Its features highlight the extraordinary specializations of both species of the genus Spinosaurus, including interdigitating upper and lower teeth. Principal component analysis of body proportions places spinosaurids between semiaquatic waders (e.g., herons) and aquatic divers (e.g., darters) distant from all other predatory dinosaurs. A time-calibrated phylogenetic analysis resolves three evolutionary phases: an initial Jurassic radiation when their distinctive elongate fish-snaring skull evolved and split into two distinctive designs, baryonychine and spinosaurine; an Early Cretaceous circum-Tethyan diversification when both reigned as dominant predators; and a final early Late Cretaceous phase when spinosaurines attained maximum body size as shallow water ambush specialists limited geographically to northern Africa and South America.

CONCLUSION: The discovery of the tall-crested S. mirabilis sp. nov. in a riparian setting within an inland basin supports a lifestyle interpretation of a wading, shoreline predator with visual display an important aspect of its biology. At the end of the Cenomanian about 95 million years ago, an abrupt eustatic rise in sea level and the attendant climate change brought the spinosaurid radiation to an end.

Sheathed bony head crests in extinct and living dinosaurs. Spinosaurus mirabilis sp. nov., evolved the tallest head crest of any theropod dinosaur, drawing attention to the midline ornamentation that characterizes the cranium and axial skeleton of all spinosaurids. In life, the crest would have been extended to some degree by a keratinous sheath, as in the living helmeted guinea fowl (Numida meleagris). Visual signaling, as is the case in guinea fowl and other crested avians, was likely the function of spinosaurid cranial crests and trunk and tail sails. Scale bar, 20 cm for S. mirabilis and 3 cm for N. meleagris.

Spinosaurus mirabilis

A single Spinosaurus mirabilis rears over a carcass of the coelacanth Mawsonia on the forested bank of a river some 95 million years ago in what is now the Sahara Desert in Niger. A scimitar-shaped head crest and interdigitating teeth characterize this wading giant, one of the last-surviving species of a spinosaurid radiation some 50 million years in the making.

Artwork: Dani Navarro

Sereno, Paul C.; Vidal, Daniel; Myhrvold, Nathan P.; Johnson-Ransom, Evan; Ciudad Real, María; Baumgart, Stephanie L.; Sánchez Fontela, Noelia; Green, Todd L.; Saitta, Evan T.; Adamou, Boubé; Bop, Lauren L.; Keillor, Tyler M.; Fitzgerald, Erin C.; Dutheil, Didier B.; Laroche, Robert A. S.; Demers-Potvin, Alexandre V.; Simarro, Álvaro; Gascó-Lluna, Francesc; Lázaro, Ana; Gamonal, Arturo; Beightol, Charles V.; Reneleau, Vincent; Vautrin, Rachel; Bertozzo, Filippo; Granados, Alejandro; Kinney-Broderick, Grace; Mallon, Jordan C.; Lindoso, Rafael M.; Ramezani, Jahandar. 2026. Scimitar-crested Spinosaurus species from the Sahara caps stepwise spinosaurid radiation. Science. 391 (6787) eadx5486. DOI: doi.org/10.1126/science.adx5486 [19 Feb 2026] 

 

Editor’s summary: Recent descriptions of and debates about the massive, fish-eating dinosaur Spinosaurus have brought this striking predator to the forefront of the dinosaur pantheon. Its huge size and distinctive morphology have stimulated much debate about the degree to which it lived an aquatic lifestyle. Sereno et al. describe a crested fossil Spinosaurus found in northern Africa as a new species. The researchers argue that this group of dinosaurs underwent three phases of evolution with increasing aquatic adaptations and existence in habitats around the Tethys Sea. —Sacha Vignieri

[Paleontology • 2025] Nektognathus evasmithae • A fossilized ventral ganglion reveals a chaetognath affinity for Cambrian nectocaridids

 

Nektognathus evasmithae 

 Vinther, Parry, Lee, Nielsen, Oh, C. Park, Kihm, DeVivo, Harper, Nielsen & T.-Y. S. Park, 2025

DOI: doi.org/10.1126/sciadv.adu6990 

Artwork by Robert Nicholls

Abstract

Nectocaridids are enigmatic Palaeozoic animals with a controversial phylogenetic position. Previous hypotheses have placed them in their own phylum, chordates, molluscs (specifically cephalopods), or radiodont panarthropods. We describe here a nectocaridid, Nektognathus evasmithae gen. et sp. nov. from the early Cambrian (~519 million years) Sirius Passet Lagerstätte of North Greenland. Key specimens preserve paired, phosphatized arcuate structures consistent with preservation of a ventral ganglion, a feature characteristic of extant and fossil chaetognaths, including the amiskwiid Timorebestia koprii also from Sirius Passet. Nektognathus shares a gnathostomulid-like jaw apparatus, lateral fins, subterminal anus, and large antennae with Timorebestia and Amiskwia, placing nectocaridids in the chaetognath stem lineage. The complex sensory anatomy of nectocaridids, which is partially shared with other extinct amiskwiids, highlights a more dynamic predatory lifestyle much higher in the trophic food chain during early chaetognath evolution.

Nektognathus evasmithae gen et sp. nov. holotype, MGUH34956.
 (A) Image with low-angle lighting illuminated from top left, coated with magnesium oxide smoke. (B) Illuminated submerged in water under high-angle illumination. (C) EPMA carbon elemental map. (D) Interpretative drawing. (E to G) Close-up of anterior trunk region preserving the jaw apparatus. (E) Carbon elemental map featuring the outline of the jaw apparatus due to splitting of the specimen. (F) Low-angle lighting illumination coated with magnesium smoke. (G) Low-angle illumination coated with magnesium smoke with outline of jaw apparatus superimposed. (H and I) Specimen of Isoxys in the anterior section of the digestive tract, outlined in (I). (J and K) Preservation of ventral ganglion with superimposed striated musculature outlined in (K). (L and M) Digestive tract preserved by modest relief in the posterior trunk and caudal region, outlined in (M). Colors in interpretative drawing represent gut (green), ventral ganglion and nervous system (blue), jaw apparatus (red and mustard yellow), eyes (light yellow), Isoxys specimen (pink) and body outline (gray). a, antennae; cr, caudal region; fr, fin rays.

Systematic Paleontology

Spiralia Schleip, 1929

Chaetognathifera Bekkouche and Gąsiorowski, 2022

Phylum Chaetognatha Leuckart, 1854 (stem group)

Family Nectocarididae Conway Morris, 1976

Diagnosis: Dorsoventrally flattened bilaterian with lateral fins supported by fin rays. The body is divided into a distinct head and trunk. The head is narrow and bears long frontal antennae and a pair of large, lateral eyes of camera type. A jaw apparatus flanks the digestive tract in the anteriormost part of the trunk, consisting of a bilateral set of very large, subtriangular elements and a basal, anterior, median plate. The tubular gut terminates subterminally anterior to the posterior fin region. Diagnosis was emended from Conway Morris (1976).

Genera included: Nectocaris Conway Morris 1976, Nektognathus gen. nov.

Genus Nectocaris Conway Morris 1976

Genus Nektognathus evasmithae gen. et sp. nov.

Locality and horizon: The material was collected at locality 1 in Sirius Passet, 82°47.6′N, 42°13.7′W, Peary Land, North Greenland.

Etymology: Nekto (Gr) for swimming and gnatha (Gr) meaning jaw. The species name is for Professor Emeritus Eva Smith in recognition of her enduring fight for impartial justice for everyone and holding politicians accountable.

Diagnosis for species and genus: Nectocaridid with distinct, caudal fin-region lacking fin rays. The eye stalks are short or absent. Ventral ganglion forms distinct arcuate structures in the midbody that is ~25% the length of the trunk.

 

 Jakob Vinther, Luke A. Parry, Mirinae Lee, Morten Lunde Nielsen, Yeongju Oh, Changkun Park, Ji-Hoon Kihm, Giacinto DeVivo, David A. T. Harper, Arne T. Nielsen and Tae-Yoon S. Park. 2025. A fossilized ventral ganglion reveals a chaetognath affinity for Cambrian nectocaridids. Science Advances. 11(30); DOI: doi.org/10.1126/sciadv.adu6990 [23 Jul 2025]

[PaleoOrnithology • 2025] Arctic Bird Nesting traces back to the Cretaceous

 

Newly hatched birds explore a 73-million-year-old Arctic environment.

in Wilson, Ksepka, Wilson, Gardner, Erickson, ... et Druckenmiller,. 2025. 

DOI: doi.org/10.1126/science.adt5189

Illustration: Gabriel Ugueto  facebook.com/serpenillus

Abstract

Polar ecosystems are structured and enriched by birds, which nest there seasonally and serve as keystone ecosystem members. Despite the ecological importance of polar birds, the origins of high-latitude nesting strategies remain obscured by a sparse fossil record. We report an extreme-latitude Arctic avialan assemblage from the Prince Creek Formation of Alaska—the northernmost Late Cretaceous terrestrial ecosystem. Numerous three-dimensionally preserved fossils constitute one of the most taxonomically rich Late Cretaceous avialan assemblages, including members of Hesperornithes, Ichthyornithes, and near-crown or crown birds (Neornithes), recording a previously undocumented interval in avialan evolution. Abundant perinatal fossils represent the oldest evidence of birds nesting at polar latitudes, which demonstrates that birds began using seasonal polar environments for breeding during the Cretaceous, long before their modern descendants.

Newly hatched birds explore a 73-million-year-old Arctic environment.
Modern birds breed in the Arctic to take advantage of abundant seasonal resources, but the evolutionary origins of this behavior remain elusive. Exceptional new fossils from northern Alaska reveal birds lived and nested alongside non-avian dinosaurs in Arctic Alaska long before the radiation of modern birds after the end-Cretaceous extinction.

Illustration: Gabriel Ugueto

 facebook.com/serpenillus

 

Lauren N. Wilson, Daniel T. Ksepka, John P. Wilson, Jacob D. Gardner, Gregory M. Erickson, Donald Brinkman, Caleb M. Brown, Jaelyn J. Eberle, Chris L. Organ and Patrick S. Druckenmiller. 2025. Arctic Bird Nesting traces back to the Cretaceous. Science. 388(6750); 974-978. DOI: doi.org/10.1126/science.adt5189 [29 May 2025]

  facebook.com/serpenillus/posts/1272281991565932

 

Editor’s summary: In the modern world, birds represent key components of polar ecosystems. This is true even in the face of the extreme seasonal changes that occur in these regions. Although the Cretaceous world was considerably warmer than ours, the polar regions still experienced months of near total darkness, suggesting that this was a challenging environment to colonize even when it didn’t experience extreme cold. Wilson et al. report on a fossil assemblage of birds from the late Cretaceous Arctic. This assemblage includes both chicks and adults of multiple species, suggesting that birds began breeding in Arctic regions early on in their evolution. —Sacha Vignieri

[PaleoMammalogy • 2025] Mesozoic Mammaliaforms illuminate the Origins of Pelage Coloration

in Li, D’Alba, Debruyn, Dobson, Zhou, ... Shawkey, 2025. 

DOI: doi.org/10.1126/science.ads9734 

Artwork by Chuang ZHAO

Abstract

Pelage coloration, which serves numerous functions, is crucial to the evolution of behavior, physiology, and habitat preferences of mammals. However, little is known about the coloration of Mesozoic mammaliaforms that coevolved with dinosaurs. In this study, we used a dataset of melanosome (melanin-containing organelle) morphology and quantitatively measured hair colors from 116 extant mammals to reliably reconstruct the coloration of six Mesozoic mammaliaforms, including a previously undescribed euharamiyidan. Unlike the highly diverse melanosomes discovered in feathered dinosaurs, hairs in six mammaliaforms of different lineages and diverse ecomorphotypes showed uniform melanosome geometry, corresponding to dark-brown coloration consistent with crypsis and nocturnality. Our results suggest that the melanosome variation and color expansion seen in extant mammals may have occurred during their rapid radiation and diversification after the Cretaceous-Paleogene extinction.

Ruoshuang Li, Liliana D’Alba, Gerben Debruyn, Jessica L. Dobson, Chang-Fu Zhou, ..., and Matthew D. Shawkey. 2025. Mesozoic Mammaliaforms illuminate the Origins of Pelage Coloration. Science. 387(6739); 1193-1198.  DOI: doi.org/10.1126/science.ads9734 

https://www.cugb.edu.cn/jdxw/47835.jhtml 

Editor’s summary: In the past decade or so, the identification of melanosomes in some dinosaur feathers and skin has led to the suggestion that many bore bright and complex coloration. Less work has been done to explore the coloration of early mammals. Li et al. looked at melanosome patterns in multiple species of Mesozoic mammals and compared these with those seen in more than 100 species of extant mammals. There was little color variation, and the animals were entirely dark in color. The authors argue that this was likely due to the animals’ nocturnal nature, and that brighter and more varied colors in mammals may have arisen after the extinction of dinosaurs at the end of the Cretaceous period. —Sacha Vignieri

  

[Paleontology • 2024] Timorebestia koprii • A Giant Stem-group Chaetognath

Reconstruction of Timorebestia koprii gen et sp. nov. in the pelagic ecosystem preserved in Sirius Passet. Other taxa shown in the foreground are Kiisortoqia, Siricaris, Kerygmachela, Pauloterminus, Kleptothule, and Isoxys. Further in the background is two radiodonts: Tamisiocaris and an amplectobeluid.    

 Park, Nielsen, Parry, Sørensen, Lee, ... et Vinther, 2024.

  DOI: 10.1126/sciadv.adi6678

Artwork by Robert Nicholls/BobNichollsArt.

 

Abstract

Chaetognaths, with their characteristic grasping spines, are the oldest known pelagic predators, found in the lowest Cambrian (Terreneuvian). Here, we describe a large stem chaetognath, Timorebestia koprii gen. et sp. nov., from the lower Cambrian Sirius Passet Lagerstätte, which exhibits lateral and caudal fins, a distinct head region with long antennae and a jaw apparatus similar to Amiskwia sagittiformis. Amiskwia has previously been interpreted as a total-group chaetognathiferan, as either a stem-chaetognath or gnathostomulid. We show that T. koprii shares a ventral ganglion with chaetognaths to the exclusion of other animal groups, firmly placing these fossils on the chaetognath stem. The large size (up to 30 cm) and gut contents in T. koprii suggest that early chaetognaths occupied a higher trophic position in pelagic food chains than today.

Holotype (MGUH 34286) of Timorebestia koprii gen et sp. nov. 
(A to C) Entire specimen. (D and E) Jaw apparatus in the anterior region of trunk.

Isoxys predation
(A to C) Timorebestia koprii gen et sp. nov. MGUH 34291, specimen with several specimens of the bivalved arthropod Isoxys volucris in its gut. (A) Specimen photographed with reflective light. (B) Specimen photographed with low angle light illuminated from top left. (C) Interpretative drawing (color guide: green, gut; dark yellow, Isoxys specimens).

Systematic paleontology

Unranked clade Spiralia Scleip, 1929

Unranked clade Chaetognathifera Bekkouche and Gąsiorowski, 2022

Phylum Chaetognatha Leuckart, 1854 (stem group)

 Timorebestia koprii gen. et sp. nov.

Diagnosis for genus and species: Wide-bodied “amiskwiiform” with lateral fins along most of the trunk length. The body and the lateral fins taper distally and terminate in a well-developed rounded caudal fin. Distinct fin rays are present with no rayless zone separating the trunk and tail fins. Anterior region of trunk tapers markedly into a short head bearing a pair of long antennae, which are about half the length of the body. An internal jaw apparatus in the anterior trunk region consists of a pair of larger subtriangular elements connected by a symphysis, a pair of blunt anterior elements, and a single anterior, presumed ventral/basal, plate. Longitudinal muscles occurring in discrete bands are present in the trunk with additional sparse and delicate outer circular/transverse muscles. The digestive tract extends from the trunk-head transition and terminates anterior to the caudal fin with no septum separating the caudal region from the trunk.

Locality and horizon: T. koprii occurs in several horizons at the main Lagerstätte locality in Sirius Passet, ..., Peary Land, North Greenland. Collections from which material is derived have been focused on an exposed section that totals 12 m, with collection focused on a particular fossiliferous interval between 5 and 7 m.

Etymology: Genus name: Timor, (Latin) for causing fear or dread and bestia (Latin), meaning beast. The species name is after Korea Polar Research Institute (KOPRI) for their support of the past, and ongoing, field expeditions to Sirius Passet.

  evolution of food web tiering.  
  Schematic presentation of the preserved and inferred components of the pelagic food web in Sirius Passet during the early Cambrian in comparison to modern pelagic food webs, highlighting the downward shift of arthropods and chaetognaths that took place during the Paleozoic as jawed vertebrates evolved to dominate the upper tiers in the food chain.

Reconstruction of Timorebestia koprii gen et sp. nov. in the pelagic ecosystem preserved in Sirius Passet. Other taxa shown in the foreground are Kiisortoqia, Siricaris, Kerygmachela, Pauloterminus, Kleptothule, and Isoxys. Further in the background is two radiodonts: Tamisiocaris and an amplectobeluid.

Artwork by Robert Nicholls/BobNichollsArt.

Tae-Yoon S. Park, Morten Lunde Nielsen, Luke A. Parry, Martin Vinther Sørensen, Mirinae Lee, ... and Jakob Vinther. 2024. A GIANT STEM-GROUP CHAETOGNATH. SCIENCE ADVANCES. 10(1); DOI: 10.1126/sciadv.adi6678

[Paleontology • 2024] Shishania aculeata • A Cambrian spiny stem mollusk and the deep homology of lophotrochozoan scleritomes

 

 Shishania aculeata 

Zhang, Parry, Vinther & Ma, 2024

DOI: doi.org/10.1126/science.ado0059

Abstract

Mollusks encompass enormous disparity, including familiar clams and snails alongside less familiar aculiferans (chitons and vermiform aplacophorans) with complex multicomponent skeletons. Paleozoic fossils trace crown mollusks to forms exhibiting a combination of biomineralized shells and sclerites (e.g., scales, spines, and spicules). We describe a shell-less, Cambrian stem mollusk, Shishania aculeata gen. et sp. nov., with conical, hollow chitinous sclerites and a smooth girdle, broad foot, and mantle cavity. The sclerites have a microstructure of narrow canals consistent with the impressions of chaetal microvilli found in annelids and brachiopods. Shishania sclerites provide a morphological stepping stone between typical chaetae (chitinous bristles) and the external organic part of aculiferan sclerites that encloses a mineralized body. This discovery reinforces a common origin of lophotrochozoan chaetae and the biomineralized aculiferan sclerites, suggesting that the mollusk ancestor was densely covered with hollow chitinous chaetae.

Complete specimen of Shishania aculeata seen from the dorsal (top) side (left). Spines covering the body of  Shishania aculeata (right). Credit: G Zhang/L Parry.

Artist’s reconstruction of  Shishania aculeata as it would have appeared in life as viewed from the top, side and bottom (left to right). Reconstruction by M. Cawthorne.

Shishania aculeata gen. et sp. nov.

 

Guangxu Zhang, Luke A. Parry, Jakob Vinther and Xiaoya Ma. 2024. A Cambrian spiny stem mollusk and the deep homology of lophotrochozoan scleritomes. Science. 385(6708); 528-532

DOI: doi.org/10.1126/science.ado0059

Half a billion-year-old spiny slug reveals the origins of molluscs

https://earth.web.ox.ac.uk/article/half-billion-year-old-spiny-slug-reveals-origins-molluscs

  x.com/OxUniEarthSci/status/1819281981483442461

 

Editor’s summary: Mollusca is one of the most diverse extant phyla, with forms varying widely from bivalves such as clams to snaily gastropods and highly complex cephalopods such as octopuses. Zhang et al. describe a new fossil, Shishania aculeata, from the Cambrian Period that displays basal molluscan traits, such as a foot and mantle, as well as traits that are more characteristic of other members of their superphylum, Lophotrochozoa. The authors place this taxon as a stem mollusk covered in sclerites, suggesting that it was intermediate in form between members of Lophotrochozoa and the soon to develop and diversify crown mollusks. —Sacha Vignieri