In a small limestone cave in southwestern Dominican Republic, the fossil record is written not only in bones but inside them. The empty tooth sockets of extinct rodents, and even the pulp cavity of a sloth molar, are packed with tiny clay capsules: the brood cells of ground-nesting bees that chose dead mammals as a place to raise their young.
Most people know bees for their role as pollinators or think of honeybees and hives. In reality, the majority of bee species are solitary and nest in the ground. They dig burrows, build individual brood cells, seal in pollen and nectar, and leave the larvae to grow on their own. These nests almost never fossilize, but when they do, they give us something rare in paleontology - direct window into behavior of long-gone organisms, not just bones or shells.
Life reconstruction of the trace-making bee nesting inside a cave and using bone cavities as containing chambers for some of the brooding cells. Copyright: Jorge Mario Macho (Machuky Paleoart).
Our material comes from Cueva de Mono, a cave in the dry karst of southwestern Dominican Republic. The cave floor is made of red clay packed with fossils of extinct mammals, reptiles, and birds. Most of the bones were probably brought in by an owl that used the cave as a roost and dropped or regurgitated its prey there. When we looked closely at some of the rodent jaws and other bones, we noticed that a few of the empty tooth sockets were filled with tiny, smooth-walled capsules of sediment, neatly shaped and clearly different from the surrounding clay.
To see what these structures really were, we turned to micro-CT scans. On the computer screen, the bone and the infilling sediment separate into different shades of gray and we can rotate the specimen in three dimensions. Inside several mandibles and skulls of the extinct rodent Plagiodontia araeum, and in the vertebral canal of another rodent and a sloth tooth, we found small, ellipsoidal capsules with a rounded end and a narrow opening. In some sockets, several of these capsules were stacked on top of each other, like a column of overlapping cups inside the same cavity. That pattern is exactly what you expect from generations of brood cells built in the same place.
The shape, size, and construction of these cells match what we know from ground nesting bees. The inner walls are smooth and multilayered. Under the scanning electron microscope, you can see that they are made of very fine clay grains packed tightly together, with a slightly different texture than the outer sediment. This kind of lining is typical of bees that smooth their brood cells and add an organic, water-resistant coating. The trace-maker was probably a medium sized solitary bee, likely related to modern halictid bees that nest in soil.
CT scan and photograph images of left dentary of Plagiodontia araeum (MNHNSD.FOS 25.5282) and type specimen of the ichnofossil Osnidum almontei.
What makes this behavior special is the choice of nesting site. Instead of excavating fresh burrows in open ground, these bees used preexisting cavities inside bones that had accumulated in the cave sediment. The tooth sockets and vertebral canals acted as natural molds, giving the brood cells mechanical protection and a fixed shape. Micro CT shows that some cavities were reused over and over, with up to six generations of cells preserved in a single rodent alveolus. That kind of repeated use points to strong nest site fidelity and to a long-term nesting aggregation inside the cave.
Why would a bee do this? The landscape around Cueva de Mono is a rugged limestone karst where soil is thin or absent on much of the surface. Deeper, better developed red clays tend to collect inside caves and sinkholes. If you are a ground nesting bee, searching for stable, fine-grained sediment to dig into, those underground pockets become very attractive. In this case, the bees appear to have gone one step further and taken advantage of the readymade cavities provided by accumulated bones in the cave floor.
We also looked at the cells at much smaller scales. Scanning electron microscopy (SEM) and palynomorph analysis shown traces of bacterial and fungal communities on the inner walls, tiny mineral crystals, and a few scattered plant microfossils. The cells glow faintly under ultraviolet light, which suggests remnants of organic coatings. Most of the original pollen provisions have probably been eaten by the larvae and then broken down by microbes over thousands of years, but the structure of the cells and their context are still clear enough to reconstruct how they were built and used.
Because these are trace fossils, not body fossils of the bees themselves, we cannot say exactly which species made them. Based on size and architecture, we argue that a halictid bee or a similar ground nesting form is the best candidate. What is certain is that this behavior is extreme by modern standards. Bees are known to nest in soil, wood, plant stems, snail shells, and even abandoned wasp nests. Using the tooth sockets and vertebral canals of extinct mammals in the dark zone of a cave is something new.
For me, the larger story is about how much ecological information can be hidden in a handful of small fossils. In these bee cells you see the imprint of late Quaternary Caribbean ecosystems: owls hunting rodents, caves trapping bones, soils enriched with phosphate, and solitary bees solving a nesting problem by turning dead mammals into shelter for their larvae. You also see the value of careful collecting and curation. Without detailed excavation, micro-CT scanning, and museum access, these structures would remain anonymous bits of clay in old bones.
This blog post is based on our open access article in
Royal Society Open Science, where we formally name the new ichnogenus and
ichnospecies Osnidum almontei and explore its implications for bee
evolution, cave ecology, and Caribbean paleontology (free access here).
Juan N. Almonte at the entrance of Cueva del Mono, Dominican Republic. Photograph of Lázaro W. Viñola López.
---
Note: The trace fossil Osnidum almontei is a
generic name that combines the Latin os or ossis (bone) and nidum (nest),
a reference to bees that chose bone cavities instead of soil burrows to build
their brood cells. The species name honors Juan N. Almonte Milán, curator of
the paleobiology collection at the Museo Nacional de Historia Natural in Santo
Domingo, whose careful fieldwork, curation, and long-term care of the Cueva de
Mono material made this study possible.
This project was led by paleontologist Lázaro W. Viñola López, whose discovery, insight and attention to detail guided the study from fieldwork to publication. I am deeply grateful for his invitation to join this remarkable collaboration.
Recommended citation:
Viñola-López, L. W., Riegler, M., Olson, S. L., Orihuela, J., & García, J. A. (2025). Osnidum almontei ichnogen. et ichnosp. nov.: A new bee trace fossil from the Quaternary of the Dominican Republic. Royal Society Open Science, 12(251748). https://doi.org/10.1098/rsos.251748
Remember the asteroid that probably wiped out the dinosaurs? That was an extreme case of a meteorite impact. Today, far smaller pieces of rock from space land all over the planet, and others collected ages ago, sit quietly in museum drawers and private collections. Across Cuba, a small group of dense, dark rocks carry an attractive label: meteorite. For decades they have been treated as fragments of asteroids that landed on the island, even though most were never examined with modern analytic tools. When we finally put them under the microscope, several of these supposed "space rocks" turned out to be something else entirely.
Before getting to those cool results, it is worth asking: what is a meteorite, and why does it matter? Most meteorites are pieces of asteroids, small bodies that never grew into full planets. A few rare ones come from the Moon or Mars. They are leftovers from the early solar system, frozen records of how dust, rock, metal, and ice first came together 4.5 billion years ago and gave rise to bodies like our own planet. By studying their minerals and chemistry, we learn how planets formed, how they differentiated into cores and mantles, how water and organic molecules moved around, and how often large objects have hit Earth in the past. In other words, meteorites are not just “space souvenirs”, they are physical pages from the early history of our planetary system, with direct relevance to questions about Earth's origins, impact hazards, and even the conditions that probably made life possible.
With that in mind, it becomes clearer why it matters to know which rocks really came from space and which did not. If a specimen is misidentified, it can mislead the statistics, comparisons, and models that scientists build from it. If it is correctly recognized, even a small fragment can become part of a much bigger scientific story.
This blog post is about what happened when we went back to test some of those “meteorites” samples, in detail. I will walk through two kinds of stories from our recent work: how several classic Cuban meteorites turned out to be meteor-wrongs, and how a very weathered meteorite from Jamaica, Lucky Hill, could still confirm its extraterrestrial origin under the microscope. Together, they show how old specimens in museums can still change what we think we know. Museum collections are today more alive than ever!
One of the first objects we revisited was a famous iron lump in the National Museum of Natural Sciences in Madrid, long listed in catalogs as the official “Cuba” meteorite. On paper it sounded convincing: heavy, metallic, and backed by an old story linking it to the island. Under the microscope, however, it behaved like something entirely different. It lacked the nickel-rich alloys and internal patterns we expect from iron meteorites that cooled slowly inside an asteroid. Its chemistry also matched man-made metal far better than any known natural iron from space. In other words, the “Cuba meteorite” is almost certainly not a meteorite at all, but a “meteor-wrong” (a term used for rocks that resemble them) that sat in the meteorite record for more than a century before being really tested.
That result pushed us to look more systematically at the broader set of suspected meteorites from Cuba. The island's geology is remarkably varied, with ultramafic rocks, basalts, laterites, iron crusts, and industrial ferrosilicon slags all occur in a country with a long mining and metallurgical history. It is the perfect recipe for confusion. Dense, dark, magnetic rocks turn up in fields, quarries, riverbeds, construction sites, and even archaeological digs. Some end up in museum drawers. Many others are passed from hand to hand with a confident “meteorite” label.
When we compiled and examined a series of these celebrated specimens, most turned out to be very down to earth. Some were ordinary basalts. Others were iron-rich concretions formed in soils. Several were industrial slags from smelting or foundry work, full of bubbles and strange textures that make them look extraterrestrial at first glance. Their magnetism and odd shapes make them ideal candidates to fool both the public and older scientific catalogs. Yet simple tests, such as checking density, looking for the minerals that really belong in meteorites, and using standard tools like X-ray diffraction and scanning electron microscopy (SEM), were enough to show that many of these supposed specimens never fell from space at all.
This is one of the quiet surprises of working with old collections. A specimen collected in the nineteenth century, mislabeled and slowly dusting in a drawer, can still become new data once you point the right instruments at it. Museum shelves turn into laboratories, and long accepted stories about certain objects can change in a matter of hours once the measurements are in. Our work on the Cuban meteor-wrongs and on the old catalogs is a reminder that museums are not static storage rooms. Instead, they are active archives of planetary material, where forgotten samples can still change what we think we know.
Not everything we studied ended up being a meteor-wrong, though. The Caribbean does have genuine meteorites, and one of the most intriguing is Lucky Hill, found in Jamaica in 1885. By the time we see it today, Lucky Hill barely looks like a meteorite. The surviving pieces are small and heavily rusted, and in some collections, they are little more than reddish powder in small vials. For decades, that weathering made it hard to say much beyond “yes, it probably came from space.”
In our most recent work, we focused on one of the best-preserved Lucky Hill fragments, kept at the Smithsonian in Washington, D.C. Using a scanning electron microscope with an X-ray detector, essentially a very powerful magnifying glass that also tells you what each tiny grain is made of, we were able to pick out what remains of the original metal. Most of the iron has been converted into rust minerals, but small pockets of nickel-bearing alloy still survive, together with tiny crystals of schreibersite, a phosphorus rich iron nickel mineral that is typical of iron meteorites. At the same time, we see minerals such as akageneite that form when chloride rich moisture attacks iron, exactly what you would expect for an object exposed for a long time in a warm, probably coastal environment.
From Cuba to Jamaica, the same approach gives two very different answers. In Cuba, several well-known "meteorites" dissolve into a mixture of basalts, concretions, and industrial slag once you look closely enough. In Jamaica, a heavily rusted lump that barely looks meteoritic at first sight turns out, under the microscope, to preserve just enough of its original structure to confirm that it really is a fragment of an iron body from space. In both cases we move from rusted pebbles, a few centimeters across, to questions about how metal bodies formed and cooled in the early solar system. That jump, from micrometers under the electron beam to millions of kilometers across the asteroid belt, is part of the quiet awe behind this work.
Lucky Hill meteorite scattered fragments stored at the British Museum, London, UK. Courtesy and photograph of Natasha Vasiliki Almeida (BNHM).
All this also says a lot about museums and old collections. Many of the specimens we studied were collected in the nineteenth and early twentieth centuries, when analytic tools were limited and labels were sometimes vague. Tropical climates, salty air, and decades in storage have taken their toll. Re-examining this material with modern methods is not just an academic exercise; it tells curators which objects need better conservation, which labels should be rewritten, and which specimens are truly reliable for future research. It also shows why careful labeling and proper storage matter. A rock that is recorded with its place and date of collection, and preserved under decent conditions, can still be reanalyzed a century later and yield new information. Without that chain of care, the scientific value is lost.
For anyone who has ever picked up a heavy, dark rock and wondered whether it came from space, the message is simple: curiosity is essential, but the evidence decides. Magnets and good stories are a starting point, not a final verdict. Some candidates will prove to be genuine messengers from the asteroid belt; many will be meteor-wrongs with interesting but entirely terrestrial histories. In both cases, careful observation and a bit of geo-chemistry are what turn guesses into knowledge, and what keep the process of scientific discovery very much alive and connected to the wider public that ultimately supports and benefits from it.
Further reading
Ceballos-Izquierdo, Y., Orihuela, J., Gonçalves, G., et al. (2021). Meteorite and bright fireball records from Cuba. Mineralia Slovaca, 53(2), 131–145.
Ceballos-Izquierdo, Y., Nieto Codina, A., & Orihuela, J. (2024). From meteorite to meteor-wrong: Investigating a controversial specimen from Cuba. Revista Mexicana de Ciencias Geológicas, 41(1), 1–10.
From meteorite to meteor-wrong …
Ceballos-Izquierdo, Y., Orihuela, J., & Borges-Sellén, C. R. (2024). Checklist of Cuban meteor-wrongs. Revista de la Sociedad Geológica de España, 37(1), 32–44.
Ceballos-Izquierdo, Y., Gonçalves Silva, G., & Orihuela, J. (2025). Rediscovering Lucky Hill: SEM-EDS insights into the composition and weathering of a Jamaican meteorite. Geologia USP Série Científica, 25(4), 89–98. Here...
A new study by Turvey and colleagues (2025), just published in iScience, re-examines the Puerto Rican island-shrew Nesophontes edithae from the classic Morovis caves using precise radiocarbon and U-series dating, morphometrics of jaws and limb bones, and carbon-isotope analyses of tooth enamel to document an earlier, smaller morph in more open, savanna-like habitats and a later, larger morph in closed forests between about 50,000 years ago and the mid-Holocene. Recent work on the Puerto Rican Nesophontes therefore complements, rather than contradicts, the Cuban record, and together both datasets help refine our view of how this extinct group lived and evolved in the Greater Antilles since the Ice Age.
A brief introduction to an odd little mammal
Nesophontes were small, shrew-like mammal endemic to the Greater Antilles. These 'island-shrews' belonged to the order Eulipotyphla, the same broader group that includes living shrews, moles, hedgehogs, and their relatives. Fossils show that Nesophontes were likely nocturnal, semi-fossorial insectivores, and possibly venomous. Each large island had its own endemic forms: three species are currently recognized in Cuba (N. micrus, N. major, N. longirostris), three in Hispaniola (N. paramicrus, N. hypomicrus, N. zamicrus), one in Puerto Rico (N. edithae), and one in the Cayman Islands (N. hemicingulus).
The history of their discovery is closely tied to the American Museum of Natural History in New York. Harold E. Anthony described Nesophontes edithae in 1916 from material collected near Morovis, Puerto Rico. The type specimen was found in Cueva Clara by his wife, Edith I. Anthony, whose name the species still carries. In 1917, Glover M. Allen described N. micrus from material collected in Matanzas by Carlos de la Torre. Later, Anthony described N. longirostris from a cave in Daiquirí, southeastern Cuba. These early discoveries laid the groundwork for more than a century of work on this unusual mammal.
In recent years, new biomolecular methods have greatly improved our understanding of Nesophontes evolution. Collagen sequence analyses (proteomics) published by Buckley et al. (2020) helped clarify the relationships within the group and re-confirmed that Nesophontes and the living solenodons form sister lineages within Solenodontidae-Solenodonota. For the Cuban material, that molecular work showed that most specimens fall into two main collagen lineages corresponding to a smaller morph N. micrus and a larger morph N. major, with the large, long-snouted N. longirostris forming a close relative of N. major rather than a separate deep lineage. These proteomic results provide an independent framework that is consistent with, and helps to refine, the species limits later formalized on morphological grounds by Orihuela (2023).
Against this background, two recent lines of research help refine the picture: Turvey and colleagues’ 2025 study of N. edithae in Puerto Rico, and Orihuela's 2023 revision of the Cuban species.
Nesophontes edithae holotype AMNH 14174 (female?) From original photograph published by Anthony (1916).
The Puertorican story: one species, two sizes phases in time
Turvey et al. focus on a single taxon, N. edithae, in one restricted landscape in northern Puerto Rico (the Morovis caves). Their core result is that the striking size variation observed in Puerto Rican Nesophontes corresponds to two allochronic size morphs rather than to coexisting “small” and “large” individuals of the same population. Using morphometrics of mandibles and femora, they show that material from the upper layer of Nesophontes II Cave represents a single, distinctly large and robust morph, whereas material from the lower layer and from Nesophontes Cave represents a smaller morph, with each stratigraphic unit showing unimodal size distributions. Mean body mass is estimated at about 200 g for the large Holocene morph and ~ 83–98 g for the smaller Late Pleistocene morph, based on established regressions for eulipotyphlan molar dimensions.
The Puerto Rican material is firmly anchored in time. Radiocarbon dating of associated charcoal and U-series dating of bones show that the small morph spans at least ~50,000–16,000 years before present, whereas the large morph appears rapidly around 13,500 years ago and continues into the middle Holocene. Turvey et al. then add stable carbon isotopes from tooth enamel to this framework. The small, older morph has more positive δ¹³C values (mean −7.9‰), while the large, younger morph shows more negative values (mean −10.3‰). This difference is interpreted in terms of habitat: the small morph is associated with more open savanna-type environments rich in C₄ grasses, typical of the Late Pleistocene, whereas the large morph is associated with more closed, C₃-dominated forests typical of Holocene Puerto Rico. In this setting, size change is explicitly tied to a well-constrained climatic and vegetational transition. Because the bones have lost almost all organic content, neither collagen nor DNA could be recovered, and delicate elements such as pelvises were not analyzed molecularly or morphologically; their conclusions rest on stratigraphy, morphometrics, and enamel δ¹³C.
Choate and Birney’s classic paper, “Sub-recent Insectivora and Chiroptera from Puerto Rico, with the description of a new bat of the genus Stenoderma”, was published in 1968 in the Journal of Mammalogy. In that work they already noted that the marked size variation in Puerto Rican Nesophontes could reflect differences between cave assemblages of different ages (a “chrono-temporal” effect), rather than only individual or sexual variation. Turvey et al.’s new study effectively tests and refines that idea. By tying the small and large N. edithae morphs to separate, radiometrically dated Late Pleistocene and Holocene layers at Morovis, and showing that they do not overlap in time while also occupying different isotopic (habitat) niches, their results are consistent with the chrono-temporal interpretation outlined by Choate and Birney, but go further by rejecting the need for strong sexual dimorphism and by quantifying the timing and environmental context of the size shift.
The Cuban story: three species, each with incipient sexual dimorphism
By contrast, recent work on Cuban taxa (Orihuela et al., 2020), and specially the most recent revision (Orihuela 2023) has been explicitly island-wide and taxonomic in scope. Following one species through time at a single locality, that study assembled and statistically analysed large numbers of Nesophontes specimens—thousands of bones—from several carefully radiocarbon dated beds and specimens. Where layers could be assigned to the same age, specimens from those single-age horizons were compared directly. Those results were then contrasted with material from older and younger units in the same sites, and finally with samples from other regions of the island, but in some cases precise chronological control was not available. This stepwise approach allowed Orihuela to ask both how many species were present and how much variation occurred within each species across space and, where possible, through time.
Morphologically, the Cuban revision re-examines N. micrus, N. major, and N. longirostris based on a large sample integrating cranial, dental, petrosal, endocranial, and postcranial measurements. Statistical distributions of key variables such as maxillary toothrow length, breadth across canines, and femoral length are distinctly bimodal when all Cuban Nesophontes are pooled, and do not fit a single Gaussian population, supporting the recognition of at least two Cuban species rather than extreme intraspecific variation. Within this framework, body mass is estimated with several independent methods (molar area, cranial length, limb shaft circumference). For N. micrus, the range is ~37–56 g, and for N. major ~33–67 g, with N. longirostris slightly larger than N. major. These values are consistent with a clade of small, mouse-to-rat sized insectivores and fall below the values obtained for N. edithae in Puerto Rico, in line with the long-standing view that N. edithae was among the largest members of the genus.
In recent years, new biomolecular methods have also improved our understanding of Nesophontes evolution. Collagen sequence analyses (proteomics) published by Buckley et al. (2020), with Orihuela as co-author, clarified relationships within the group and confirmed that Nesophontes and the living solenodons form sister lineages. For the Cuban material, that molecular work showed that most specimens fall into two main collagen lineages corresponding to N. micrus and N. major, with the large, long-snouted N. longirostris closely allied to N. major rather than representing a completely separate deep lineage. These proteomic results provide an independent framework that is consistent with, and helps to refine, the species limits formalized on morphological grounds by Orihuela (2023).
Both studies also incorporate stable isotopes, but with different substrates, resolutions, and goals. Turvey et al. analyse δ¹³C in tooth apatite, which is robust to diagenesis and directly reflects the carbon-isotope composition of plants at the base of the local food web. Their key signal is a statistically significant shift in enamel δ¹³C between the small and large morphs that closely tracks the Pleistocene–Holocene transition from open to closed habitats. Isotopes in this case are used primarily to support a chronoclinal habitat shift already suggested by the dated stratigraphy.
In Cuba, the isotopic work is an initial attempt to understand diet and habitat in two species that are already known to be sympatric (Orihuela et al., 2020; Orihuela, 2023). Collagen δ¹³C and δ15N values are reported for N. micrus, N. major, and Solenodon cubanus from several well-dated Holocene cave deposits. Carbon values for Cuban Nesophontes span roughly −20‰ to −9‰, implying a mixture of C₃ and C₄ resources, and hence use of both open and closed environments. When plotted against body size and compared with Solenodon, the data suggest that N. major was slightly more associated with shaded, closed habitats (more negative δ¹³C), whereas N. micrus tended toward more open grassland–savanna conditions (more positive δ¹³C). At the same time, the isotope data indicate that both species foraged across a heterogeneous landscape of mixed and riverine woodland interspersed with more open areas. he results presented by Orihuela et al. (2020) and Orihuela (2023) are best regarded as a first baseline for Nesophontesisotope ecology in Cuba, to be refined as larger and better time-constrained samples become available; the aim was to establish this baseline to be built upon later, rather than to provide a definitive picture.
Paleoart reconstruction of Nesophontes major by Adrian Tejedor (C)
Different islands, complementary stories?
The two papers reach different conclusions about the role of sexual dimorphism in explaining size variation, but under different empirical conditions. In Puerto Rico, Turvey et al. test the long-standing hypothesis that the size disparity in N. edithae reflects strong sexual size dimorphism. They find that within each stratigraphic unit the size distributions of their largest measurement series are unimodal, and that small and large morphs never co-occur in the same temporal horizon at the Morovis sites. Combined with the isotopic and chronological evidence for distinct palaeoenvironments, they interpret the small and large morphs as allochronic populations tied to different climatic and habitat regimes, and conclude that their results refute the earlier hypothesis of pronounced sexual dimorphism in Puerto Rican nesophontids. Because pelvises and other delicate postcranial elements are not preserved in sufficient numbers or investigated, their analysis appropriately does not include on pelvic anatomy.
In Cuba, the situation is more complex. The revision shows that N. micrus and N. major form two morphometrically distinct clusters at the species level, but also that within each species there is low, but detectable, morphometric variation that is consistent with modest sexual size dimorphism. Finite mixture analyses of selected cranial, petrosal, humeral, and femoral measurements suggest two overlapping subgroups per species with an average male:female ratio of about 1:1.03, similar to values reported for N. edithae femora by McFarlane (1999). Pelvic morphology shows additional differences: more robust morphotypes have more curved sciatic notches and thicker, rounder and more angost pubic symphyses than gracile morphotypes, patterns interpreted as male and female respectively. These pelvic contrasts parallel differences in humeral and femoral robustness: robust morphotypes have thicker shafts, larger femoral heads and more strongly marked muscle attachment scars, whereas gracile morphotypes are smaller and lighter. Orihuela (2023) emphasizes that these differences are modest and that Cuban Nesophontes “do not display substantial sexual size dimorphism” overall, with sex-linked variation treated as just one part of the size range within each species. This naturally raises the question of which morphotype is male and which is female: Anthony (1916) assumed the larger form was male, but the Cuban data do not require that, and the reverse could just as well be true. Resolving this would require independent sexing: for example, genetic or chromosomal markers in suitable material, to see who caries the female or male chromosomes.
Chronologically, the Puerto Rican and Cuban records complement each other. Turvey et al. work with a vertical, high-resolution Late Pleistocene–Holocene sequence at a single locality, and are able to document a relatively rapid size shift (on the order of three millennia) against a well-dated climatic backdrop. The Cuban data, in contrast, are dominated by late Holocene cave assemblages spanning roughly the last two millennia, with emphasis on spatial variation among sites and co-occurrence of species rather than on long-term chronoclinal trends. The isotope section of the Cuban work explicitly highlights temporal averaging and seasonal effects as potential complications, and calls for larger, stratigraphically constrained datasets to explore diachronic patterns in more detail.
Taken together, both studies point to a picture in which Nesophontes were neither ecologically rigid nor morphologically static. In Puerto Rico, a single lineage (or closely related lineages) shows large, environmentally correlated changes in body size and habitat use through the Late Quaternary, without evidence for strong sexual dimorphism driving the pattern. In Cuba, two smaller-bodied species coexist in Holocene landscapes, partitioning habitats and resources in subtler ways, with only modest sex-linked size differences within each taxon.
The methods are also complementary: Turvey et al. combine enamel isotopes with precise dating to frame a local chronoclinal story, while the Cuban revision uses extensive morphometrics, pelvic anatomy, collagen isotopes, and broader geographic coverage to refine taxonomy and ecological reconstruction.
Taken together, these differences also remind us that Cuba and Puerto Rico do not share the same geological or environmental history. Island size, topography, climate trajectories, and habitat mosaics have all differed through the Late Quaternary, and it is plausible that Nesophontes did not play exactly the same ecological roles or follow identical evolutionary paths on each island. At the same time, the present records are still incomplete and unevenly sampled, so these contrasts are best viewed as indications that island context matters for Nesophontes evolution, rather than as proof of any single evolutionary scenario. Future work will be needed to test how far these island-specific patterns really extend.
Conclusions
The key message is that these “island shrews” were dynamic components of Antillean ecosystems, tracking environmental change over tens of thousands of years and partitioning habitats at fine scales, long before human arrival. The Puerto Rican and Cuban records do not contradict each other; rather, they describe different facets of the same lineage’s history under different island contexts, and both leave open important questions that will be addressed as new material and methods become available.
Cited Literature
Turvey, S. T., Lamb, A. L., Rye, P., Vale Nieves, A., Cooper, J. H., & van Calsteren, P. 2025. Major body size change in an extinct tropical island mammal associated with glacial–interglacial environmental shifts. iScience 113968, in press. https://doi.org/10.1016/j.isci.2025.113968Cell+1
Orihuela León, J. 2023. Revision of the extinct island-shrews Nesophontes (Mammalia: Eulipotyphla: Nesophontidae) from Cuba. Journal of South American Earth Sciences 130, 104544. https://doi.org/10.1016/j.jsames.2023.104544ResearchGate
Orihuela, J., Pérez Orozco, L., Álvarez Licourt, J. L., Viera Muñoz, R. A., & Santana Barani, C. 2020. Late Holocene land vertebrate fauna from Cueva de los Nesofontes, western Cuba: Stratigraphy, chronology, diversity, and paleoecology. Palaeontologia Electronica 23(3), a57. https://doi.org/10.26879/995Palaeontologia Electronica
Buckley, M., Harvey, V. L., Orihuela, J., Mychajliw, A. M., Keating, J., Almonte Milán, J. N., Lawless, C., Chamberlain, A. T., Egerton, V. M., & Manning, P. L. 2020. Collagen sequence analysis reveals evolutionary history of extinct West Indies Nesophontes (“island-shrews”). Molecular Biology and Evolution 37(10), 2931–2943. https://doi.org/10.1093/molbev/msaa137PMC
Choate, J. R., & Birney, E. C. 1968. Sub-Recent Insectivora and Chiroptera from Puerto Rico, with the description of a new bat of the genus Stenoderma. Journal of Mammalogy 49(3), 400–412. Nature
McFarlane, D. A. 1999. A note on dimorphism in Nesophontes edithae (Mammalia: Insectivora), an extinct island-shrew from Puerto Rico. Caribbean Journal of Science 35, 142–143. BioMed Central
Anthony, H. E. 1916. Preliminary diagnosis of an apparently new family of insectivores. Bulletin of the American Museum of Natural History 35, 725–728.
In the Sierra de los Órganos in western Cuba, the steep limestone mogotes preserve sediments that accumulated on the floor of the Proto-Caribbean about 135 million years ago, at a time when dinosaurs dominated terrestrial ecosystems. Thin dark, organic-rich bands alternate with paler grey limestones, forming a barcode-like pattern laid down by an ocean whose deeper waters were periodically starved of oxygen. These strata record one of the earliest major climate disturbances of the Cretaceous: an oceanic anoxic event.
In our recently published open-access article in Frontiers in Earth Science (here), we analyzed sediments from a quarry near the town of Pons, in the Sierra de los Órganos, to reconstruct how the early Proto-Caribbean responded when Earth’s carbon cycle shifted into a different state. During the Valanginian (Early Cretaceous Period), greenhouse conditions were already in place, but something pushed the system further. Some scientists think in terms of volcanic outgassing, high CO₂, intensified weathering, and nutrient-rich runoff. The oceans stored this disturbance in the only way they can, by changing how they circulate, how they feed life, and how much oxygen reaches the depths. In many basins worldwide, that change shows up as intervals of dark, organic-rich sediments and a global shift in carbon isotopes. This coupled package of carbon-cycle disruption and marine deoxygenation is what we call the Weissert Event.
La Lata sits on what was then a marine slope along the margin of the young Proto-Caribbean Basin, between the evolving Americas and the Tethyan realm. Today it’s an active quarry. In the early Cretaceous it was a quiet pelagic seafloor, slowly accumulating the skeletal rain of coccolithophores, radiolarians, and tiny foraminifera. In that setting, any disturbance in oxygen, productivity, or sediment flux is recorded very efficiently.
We focused on just the lowermost ~4 meters of a ~30-meter section of the Pons Formation. At first glance it seems simple: comparatively thick, medium-gray limestones rich in carbonate are interbedded with much thinner, darker, carbonaceous marls and marly limestones. Under the microscope, however, this “barcode” resolves into five distinct microfacies, ranging from bioturbated, fossil-rich limestones to laminated, nearly barren, organic-rich levels with abundant sulphate minerals, like pyrite.
The first key result is how carbon cycle is distributed and sequestered within the sediments. The dark marls contain total organic carbon up to ~10-11 wt%, while the paler limestones usually sit around 1-3 wt%. Total inorganic carbon behaves in the opposite way: carbonate-rich in the thick gray beds, diluted where organic matter and clay concentrate. That alternation already hints at fluctuating conditions at the seafloor. These were intervals more favorable to the preservation of organic matter, separated by more “normal” background sedimentation.
Superimposed on that fabric is a clear negative excursion in δ¹³Corg of about 1.7‰. That excursion is not random in time. Biostratigraphic markers, especially the presence of specific calcareous nanoplankton place this interval in the late Valanginian subzone NK3B, the very window classically associated with the Weissert Event elsewhere in the world, and linking our local curve to the global record.
The dark beds do more than carry isotopes. They are loaded with mineral and microscopic evidence that oxygen in bottom waters dropped sharply during certain pulses. Under SEM we see framboidal pyrite and small cubic aggregates, often growing inside foraminiferal tests, mingled with illite-smectite clays and microbial fabrics. Redox-sensitive trace elements peak in the same horizons: vanadium, nickel, chromium, molybdenum, uranium, thallium, and sulfur all show marked enrichments where total organic carbon is highest. At the same levels, detrital indicators such as Al, Si, Ti, and Li also increase, suggesting stronger terrigenous flux -probably the fingerprint of enhanced runoff and weathering on land.
Bioturbation tells a complementary story. In the thick gray limestones, burrows are common and the bioturbation index often reaches 3–4: the seafloor was oxygenated enough for infauna to churn the sediment. In the organic-rich marls, the index drops to 1–2, and X-ray images reveal only faint, incomplete structures. These are intervals where oxygen availability was restricted enough to suppress most benthic activity.
Put together, the picture that emerges is not a single, monolithic “black shale” horizon but a series of deoxygenation pulses, closely tracking the negative carbon isotope excursion. During those pulses, Los Órganos lay beneath waters that were more stagnant or less ventilated, but more superficially nutrient-rich. Organic matter arriving at the seafloor was less efficiently destroyed, sediment input from land was boosted, and trace metals were scavenged from the water column into the accumulating muds.
Why does this matter beyond the satisfaction of matching a Cuban cliff to a named global event? First, it demonstrates that the Proto-Caribbean Seaway did not sit on the sidelines of Valanginian climate change. It participated fully in the Weissert disturbance. The same isotope signal, the same style of organic-rich sedimentation, and comparable redox signatures appear here as in better-known Tethyan sections. Second, the section at La Lata shows how a marginal to hemipelagic basin can register global forcing factors like higher CO₂, weathering, in its own local language of facies, microfossils, and chemical inventories.
Finally, there is an uncomfortable echo with the present. The rocks at La Lata, Sierra de los Órganos, formed under long-term CO₂ buildup, intensified weathering, and nutrient loading. The ocean responded by reorganizing circulation and oxygen distribution, carving “dead-zone” intervals into the sedimentary archive. Today we are driving the carbon cycle far faster, but the physics and chemistry of seawater have not changed. Ancient barcodes like those of the Pons Formation are not predictions, but warnings. When the carbon cycle is pushed hard, oceans everywhere, from open basins to narrow seaways, can slide toward deoxygenation affecting not just the carbon cycle, but all life in earth.
In that sense, each black band in the quarry is both a record of a vanished ocean and a quiet reminder that Earth’s climate system has thresholds. Our goal at La Lata was to read that record as clearly as possible, and to place the Proto-Caribbean firmly on the map of ocean anoxic event research. The story those limestones tell is simple and stark = when the planet breathes carbon too quickly, the oceans are often the first to lose their breath.
Recommended paper
Our pen-access article: Orihuela J., Melinte Dobrinescu M.C. and Maurrasse F.J-M.R. (2025) “Characterization of the Weissert oceanic anoxic event in lower Cretaceous limestones of the Guaniguanico terrain, Sierra de los Órganos, Western Cuba,” published in Frontiers in Earth Science (Vol. 13, 1549274) on 20 April 2025 (doi: 10.3389/feart.2025.1549274).
A new study published in the Journal of South American Earth Sciences opens a small window on the flora and environmental conditions of tropical South America during the Late Jurassic.
The paper, "Jurassic fern Piazopteris from the Girón Group, Colombia: A taxonomic and paleoenvironmental evaluation," presents the discovery and analysis of six fossil fern specimens from the Eastern Cordillera of Colombia, helping expand a bit of knowledge of Jurassic plant life in the paleo-Caribbean region.
The fossils were collected from the carbonaceous mudstones of La Honda Creek, part of the Girón Group—an important but underexplored sedimentary unit that preserves traces of Mesozoic terrestrial ecosystems. The ferns are tentatively identified as Piazopteris cf. branneri, a member of the now-extinct genus of the Matoniaceae. Piazopteris once thrived in humid, equatorial climates.
What makes this study particularly compelling is its multidisciplinary approach. Using thin-section petrography, scanning electron microscopy (SEM), and carbon geochemistry—including total organic carbon (TOC) and stable isotope (δ¹³Corg) analyses—the researchers aproximated the depositional environment and climate context of these fossils. The results point to a low-energy, swamp-like setting with significant organic accumulation, likely influenced by a humid, tropical to subtropical climate. The geochemical data not only support this interpretation but also provide a valuable window into the carbon cycling and preservation conditions of Jurassic terrestrial environments.
The genus Piazopteris is a biostratigraphically and paleoecologically relevant genus, typically associated with Jurassic-Cretaceous floras of Gondwanan affinity. The occurrence of Piazopteris cf. branneri in Colombia contributes to a growing record of Jurassic ferns in South America and provides important taxonomic refinements for this group, which has often been misidentified or found poorly preserved.
Importantly, this work also underscores the scientific potential of the Girón Group as a paleobotanical archive. While the Girón Group has been recognized for its sedimentological and tectonic significance, its paleontological potential remains vastly underutilized. This new contribution highlights the need for further research, particularly stratigraphic refinement, paleobotanical and geochemical work in this region.
This study was carried out by a multidisciplinary team of geologists and paleontologists from several institutions in Colombia and abroad, including the Universidad Industrial de Santander (UIS), Florida International University (FIU), and research institutes focused on stratigraphy and paleontology. The collaboration brought together the fields of sedimentology, paleobotany, geochemistry, and microscopy to advance understanding of Jurassic floras in tropical settings.
Special thanks go to all who helped make this discovery and research possible.
Citation:
Torres-Parada, J.M., Orihuela, J., Alarcón Gómez, C.M., Diaz Villamizar, J.S., Gómez-Coronado, J.S., Márquez-Prada, J.J., Lizarazo-Pabón, J.A., Patarroyo, G. (2025). Jurassic fern Piazopteris from the Girón Group, Colombia: A taxonomic and paleoenvironmental evaluation.Journal of South American Earth Sciences, 158, 105488. https://doi.org/10.1016/j.jsames.2025.105488
Images created with AI (ChatGPT Image creator, 2025).
