Reconstruction of Silescelida acristata in it's natural setting
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Silescelida acristata gen. et sp. nov. life reconstruction.
Artwork by Matheus Fernandes Gadelha.
From Garcia, M.S., Cerqueira, G.M., Battista, F. et al. (2026)
From Garcia, M.S., Cerqueira, G.M., Battista, F. et al. (2026)
A fundamental problem for biblical literalism—the belief that the ancient, pre-scientific authors and compilers of Genesis possessed, through divine revelation, a more accurate understanding of the universe than modern science—is that its claims can be tested against reality. Whenever that is done, reality wins.
Creationists must therefore find ways to dispose of the contrary evidence. It can be declared fraudulent, mistaken, misinterpreted or irrelevant—or, safest of all, simply not examined too closely. Within creationist culture, refusing to change one's mind when the evidence shows that a belief is wrong has somehow been transformed from an intellectual failure into a supposed demonstration of strength of faith.
Another piece of inconvenient reality has now been added to the list. A paper recently published in the journal Scientific Reports by Maurício S. Garcia of the Universidade Federal de Santa Maria, Rio Grande do Sul, Brazil, and colleagues describes Silescelida acristata, a new species of archosauriform reptile known from a fragmentary skeleton discovered near Dona Francisca in Brazil’s Rio Grande do Sul state.
Silescelida acristata lived about 240 million years ago, during the Middle Triassic, when terrestrial ecosystems were still recovering from the devastating Permian–Triassic mass extinction some 12 million years earlier. It was a relatively small, slender, four-legged predator, probably about the size of a small alligator, with its limbs held in a more semi-erect posture than those of earlier, sprawling reptiles.
Besides being some 240 million years older than the biblical chronology can accommodate, the fossil helps to narrow one of the gaps in the fossil record that creationists are so fond of presenting as evidence against evolution. Phylogenetic analyses consistently place Silescelida among the early-diverging eucrocopodan archosauriforms—stem forms outside Archosauria that help to reveal how the ancestral archosaur body plan evolved. Some analyses suggest that it may have been related to the poorly understood Euparkeriidae, although that placement remains uncertain.
The discovery therefore illuminates an important stage preceding the emergence of the true archosaurs—the great reptilian lineage that includes the crocodilian branch and the dinosaur branch, including birds. It also shows that these early archosauriforms were more geographically widespread, and their diversification more complex, than the previously known fossil record suggested. As so often happens, another supposed “gap” has become smaller as scientists have discovered and examined more evidence.
The paper’s lead author, Maurício Garcia, has also written an account of the discovery in The Conversation. His article is reprinted below under a Creative Commons licence, reformatted for stylistic consistency:
Reptile fossil found in Brazil helps shed light on the common origins of dinosaurs and crocodiles
About the size of a small alligator, the Silescelida acristata lived 240 million years ago and holds clues to the origin of animal groups that would transform terrestrial ecosystems forever.
Illustration by Matheus Fernandes
Long before dinosaurs ruled the continents and modern crocodiles first appeared, their ancestors were already going through a decisive phase in their evolutionary history. It was in this ancient world, shortly after the greatest mass extinction in Earth’s history that a new species of fossil reptile discovered in the interior of Brazil’s Rio Grande do Sul state.
Named Silescelida acristata, the species lived about 240 million years ago, during the Middle Triassic Period. The fossil was found in Dona Francisca, in central Rio Grande do Sul, in rocks that are part of the UNESCO Quarta Colônia Geopark.
The discovery helps fill an important gap in our understanding of the evolution of archosauriformes, a group of reptiles that gave rise to the archosaurs. Archosaurs, in turn, are the lineage that encompasses two of the best-known groups of terrestrial vertebrates: crocodiles and dinosaurs, including birds.
The study was conducted by researchers from the Quarta Colônia Center for Paleontological Research at the Federal University of Santa Maria, CAPPA/UFSM, in collaboration with researchers from the Federal University of Rio Grande do Sul (UFRGS) and the Pontifical Catholic University of Rio Grande do Sul (PUCRS), and was published in the scientific journal Scientific Reports.
A small animal in a world under reconstruction
When Silescelida acristata lived, terrestrial ecosystems were still recovering from the Permian–Triassic extinction event, which occurred about 252 million years ago. This event wiped out much of the life on the planet and paved the way for the diversification of new groups of animals.
It was against this backdrop of ecological recovery that different lineages of reptiles began to take on new roles in terrestrial environments. Among them were the archosauriforms, which underwent extensive diversification during the Triassic. Silescelida acristata was a relatively small, slender animal that moved on all four limbs. Its size can be compared to that of a small alligator.
Although it was neither a dinosaur nor a crocodile, it belonged to a lineage closely related to the forms that preceded the origin of these groups. Its diet likely included smaller animals, suggesting that it played the role of a small predator in the Triassic ecosystems of southern Brazil.
Why is this fossil important?
The fossil primarily preserves parts of the limbs, and at first glance, this type of material may seem limited, but it carries important information about the animal’s locomotion and evolutionary relationships.
One of the most significant characteristics of Silescelida acristata lies in its femur, the thigh bone. Like some of its close relatives, it had legs in a more semi-erect position, lower on the body than to the side.
This change allowed for more efficient locomotion, reducing drag as the body moved across the ground. In evolutionary terms, this type of transformation is related to the set of anatomical changes that would later prove fundamental to the success of archosaurs.
In other words, the new fossil helps us understand a phase preceding the rise of dinosaurs and crocodiles, when their close relatives were still experimenting with different body shapes, postures, and modes of locomotion.
Rare phylogenetic relationship
Phylogenetic analyses indicate that Silescelida acristata may be related to the Euparkeriidae, a rare group of archosauriforms that is still poorly understood by science.
Until now, fossils associated with this group were known primarily from the continents of Africa, Asia and Europe. The presence of a form related to the Euparkeriidae in South America significantly expands the known geographic distribution of these animals.
This suggests that these reptiles were more widely distributed across the world during the Triassic than the fossil record indicated. It also reinforces the importance of South America for the study of the origin and diversification of major groups of terrestrial vertebrates.
The ‘rediscovery’ of a forgotten fossil
The discovery of Silescelida acristata also has an unusual history. Part of the fossil – precisely the portion that preserved essential information about its provenance – was accidentally lost for more than two decades.
It was not until 2022, during a technical visit to the scientific collection at the Pontifical Catholic University of Rio Grande do Sul (PUCRS), that researchers located the missing fragment. This rediscovery made it possible to confirm the specimen’s origin and formally describe it as a new species.
The animal’s very name refers to this story. Silescelida combines words associated with “silence” and “leg.” “Silence” refers to the long period during which part of the fossil lay forgotten, while “leg” refers to the type of preserved material, consisting mainly of limb bones.
The name acristata, meanwhile, means “without a crest.” It was chosen because this animal’s femur lacks a crest or raised bony protrusion – known as a trochanter – where part of the tail musculature would attach. This absence distinguishes Silescelida acristata from nearly all of its close relatives.
What does the discovery change?
The presence of Silescelida acristata in the Middle Triassic of Brazil shows that the evolutionary history of archosauriforms was broader and more complex than previously thought. The fossil indicates that lineages closely related to the Euparkeriidae were also present in South America, highlighting the continent’s role in the early diversification of the relatives of dinosaurs and crocodiles.
Furthermore, the discovery reinforces Rio Grande do Sul’s status as one of the world’s most important regions for the study of Triassic fauna. The region’s rocks preserve fossils from different stages in the evolution of terrestrial vertebrates, including some of the oldest known dinosaurs and large predators that lived before the Age of Dinosaurs.
Every new fossil found in this context helps reconstruct how terrestrial ecosystems reorganized after the Permian–Triassic extinction and how the groups that would later dominate the continents emerged.
Small bones, big stories
Incomplete fossils are often viewed as less informative than nearly complete skeletons. However, it is important to remember that the vast majority of fossils found during excavations are fragmentary. Discoveries such as Silescelida acristata show that even isolated parts of the skeleton can reveal fundamental information about evolution.
In this case, limb bones made it possible to identify a new species, infer aspects of its locomotion, investigate its phylogenetic relationships, and expand the known distribution of a rare group of Triassic reptiles.
More than just describing a new animal, the study shows how Brazilian paleontology continues to contribute to our understanding of central chapters in the history of life on Earth. In rocks from the interior of Rio Grande do Sul, 240-million-year-old fossils still hold clues about the origin of the animal groups that would transform terrestrial ecosystems forever.
Mauricio Garcia, Doutorando no Programa de Pós-Graduação em Biodiversidade Animal , Universidade Federal de Santa Maria (UFSM)
This article is republished from The Conversation under a Creative Commons license. Read the original article.
The remains of Silescelida acristata are fragmentary — little more than a shoulder blade, part of the pelvis and a thigh bone — yet those bones preserve enough anatomical information to identify a distinct species and illuminate its evolutionary relationships, posture and geographical distribution. This is how palaeontology advances: not by waiting for a conveniently complete “missing link”, but by combining each new piece of evidence with everything already known.
The researchers are appropriately cautious about precisely where Silescelida belongs. Their analyses consistently identify it as an early-diverging eucrocopodan archosauriform, while its possible membership of Euparkeriidae remains uncertain. That uncertainty is not a weakness in the science; it is an honest acknowledgement of what the available evidence can and cannot yet establish. Future discoveries may refine or revise its position — something no evidence could ever be permitted to do to a literal reading of Genesis.
What is not uncertain is that this animal inhabited southern Pangaea about 240 million years ago, during the evolutionary recovery following the Permian–Triassic mass extinction and before dinosaurs came to dominate terrestrial ecosystems. It adds another branch to a complex, geographically widespread radiation of reptiles acquiring anatomical characteristics associated with the later success of archosaurs. Nothing about this history resembles the instantaneous magical creation of fixed “kinds”.
Creationists can dismiss the fossil, dispute its age or refuse to consider its significance, but none of those responses explains it. They merely demonstrate that creationism has no room for evidence that contradicts its conclusion. Closing one’s eyes may preserve a belief, but it cannot erase a single bone from 240-million-year-old rock.
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