Rosa Rubicondior: Refuting Creationism - Now It's A Transitional Early Insect - From 324 Million Years Before 'Creation Week'

Friday, 28 August 2026

Refuting Creationism - Now It's A Transitional Early Insect - From 324 Million Years Before 'Creation Week'

Amphibious stem-insect rewrites the evolutionary history of insect terrestrialization---- Nanjing Institute of Geology and Palaeontology Chinese Academy of Sciences

A favourite creationist debating tactic is to point to a gap in the fossil record and pretend that the absence of a known transitional form is evidence that no transition occurred. When a suitable fossil is eventually found, the manoeuvre simply creates two smaller gaps on either side of it—or the fossil is arbitrarily declared to be “fully formed” and therefore not transitional. A simple trick which exposes the ignorance and disingenuity of creationism, is to ask them to describe exactly what they would expect a transition fossil to look like. They tend to abruptly break off the debate, because to answer it would violate two unwritten rules of creationism - never consider being wrong and never state what evidence would cause you to change your mind in case it's produced.

This 'god of the gaps' rhetorical game depends upon treating an inevitably incomplete geological record as though it ought to contain a specimen from every generation of every evolving lineage - something that if it were true, would be hard for science to explain, given what we know of the circumstances in which fossils are formed, which actually predicts that the record will be discontinuous.

The early history of insects has offered particularly fertile ground for this tactic. Molecular-clock studies indicate that hexapods diverged from aquatic crustacean relatives hundreds of millions of years ago, yet their small, delicate bodies were poorly suited to fossilisation, especially in the environments through which they were making the transition onto land. Consequently, there has been a conspicuous interval—the so-called “hexapod gap”—between the earliest evidence of hexapods and the abundance of unmistakable insects in later Carboniferous rocks.

Now, an international team led by Erik Tihelka and Chenyang Cai has described a remarkable fossil that helps to narrow that gap while illustrating how the familiar insect body plan was assembled. The approximately 324-million-year-old animal, named Chosha praecursor, came from the Late Mississippian Tesnus Formation of western Texas. Collected in 1985 and long misidentified as a juvenile crustacean, it remained in a museum collection until examination under cross-polarised light revealed anatomical details that had previously been almost invisible. The findings are reported in Nature.

Chosha presents precisely the sort of evolutionary mosaic that creationists insist should not exist. Its three-segmented thorax carried the three pairs of walking legs characteristic of insects, while its ovipositor, antennae and terminal filaments provide further derived insect features. Yet nine abdominal segments still bore pairs of multisegmented appendages—eighteen additional limbs—with the rear pairs modified into flattened, paddle-like structures. In effect, this was a 24-legged early insect combining recognisably insect-like anatomy with appendages inherited from more aquatic, many-legged ancestors.

The surrounding sediments represent a shallow, near-shore environment, while the paddle- or gill-like abdominal limbs suggest that Chosha remained semi-aquatic. It should not be portrayed as the direct ancestor of modern insects; as a stem insect, it was an early relative lying outside the crown group containing all living insects. Nevertheless, its mixture of ancestral and derived characteristics records an evolutionary stage in which some members of the insect lineage still inhabited the boundary between water and land and had not yet lost the abdominal limbs absent from modern adult insects.

Together with the researchers’ reassessment of other enigmatic Devonian and Carboniferous fossils, Chosha praecursor shows that early insects possessed a much greater variety of body plans than their living descendants. The modern six-legged form did not appear suddenly as a completed design. It emerged through the modification and loss of inherited structures as populations adapted to new environments—a gradual, unplanned transition written into a 324-million-year-old fossil that predates creationist “Creation Week” by almost the entire history of complex life on land. As so often happens, a supposed gap has proved not to be evidence against evolution but merely a place where more evidence was waiting to be recognised.

From Many-Legged Ancestor to Six-Legged Insect. The name Hexapoda means “six feet”, reflecting one of the most familiar features of modern insects and their closest relatives. An insect’s body is divided into a head, a three-segmented thorax and an abdomen. Each thoracic segment carries one pair of walking legs, producing the characteristic total of six, while the abdomen normally lacks jointed walking limbs.

That arrangement did not appear suddenly as a finished body plan. Insects belong within Pancrustacea, an evolutionary group that also includes crustaceans, and their remote aquatic ancestors possessed paired appendages on many body segments. As different segments became specialised, some appendages were incorporated into the mouthparts, three pairs were retained as thoracic walking legs, and most of those on the abdomen were reduced, lost or modified for other purposes.

Chosha praecursor preserves an extraordinary mosaic from partway through that evolutionary transformation. Its thorax already carried the three pairs of walking legs associated with insects, and it possessed other insect characteristics, including an ovipositor and a central terminal filament. Nevertheless, nine abdominal segments retained pairs of jointed limbs. The rearmost of these bore flattened, paddle-like structures that may have assisted swimming or respiration in its shallow-water habitat.

This combination does not mean that Chosha was necessarily the direct ancestor of living insects. Evolution is a branching process, so transitional fossils will usually represent close relatives of the ancestral population rather than that population itself. What matters is that they preserve combinations of characteristics expected at intermediate stages in the evolution of a major body plan.

Stem Groups and Crown Groups

Crown-group insects comprise the most recent common ancestor of all living insects and all its descendants, living and extinct.

Stem insects are extinct species more closely related to crown-group insects than to any other living animals, but which branched off before the crown group’s last common ancestor.

A transitional mosaic is an organism possessing some derived characteristics of a later group while retaining ancestral features that the later group has lost or modified.

Calling Chosha a stem insect therefore does not require it to look exactly like a modern insect. Indeed, its importance lies in the fact that it does not. The three-paired thoracic arrangement had evolved while numerous abdominal appendages remained. Subsequent changes in developmental regulation could reduce or suppress those appendages, with natural selection preserving combinations suited to increasingly terrestrial ways of life.

The creationist demand that Chosha must be either “fully insect” or “fully crustacean” imposes modern categories upon an evolutionary continuum. Transitional organisms are not malformed creatures caught halfway between two predetermined designs. They are functional organisms adapted to their own environments, but bearing the inherited anatomical record of the evolutionary changes through which their descendants’ body plans were assembled.

The paper in Nature was accompanied by a news release from the Nanjing Institute of Geology and Palaeontology:

Amphibious stem-insect rewrites the evolutionary history of insect terrestrialization
The establishment of complex terrestrial ecosystems represents a milestone innovation in the evolutionary history of life on Earth. It marks the definitive release of organisms from marine constraints and inaugurates a brand-new phase for the diversification of terrestrial biota. Evidence from molecular‑clock estimates, trace fossils and exceptional‑preservation biotas indicates that the terrestrialization of arthropods stretches back to the Cambrian‑Ordovician, far earlier than inferred from conventional body-fossil records. As the most species‑rich animal group on our planet, insects have long posed major gaps in research regarding their early origins and the evolutionary transition to land.
Paleontology has long grappled with the well-known hexapod gap. Molecular‑clock reconstructions suggest that hexapods diverged from marine crustacean relatives and initiated terrestrial adaptation as early as the Cambrian‑Ordovician. However, globally undisputed hexapod body fossils are only documented from the Early Devonian Rhynie Chert (ca. 405 Ma), and unambiguous insect fossils do not occur in abundance until the Late Carboniferous. This creates an 80-million-year gap in the fossil record. Moreover, direct fossil evidence documenting how early insects gradually adapted to terrestrial habitats from aquatic and semi‑aquatic settings, as well as the transformation of their body plans, has remained scarce. Consequently, evolutionary pathways, morphological innovations and ecological adaptive mechanisms underlying insect terrestrialization have remained poorly constrained.

Recently, an international research team including Prof. CAI Chenyang (Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences) and Erik Tihelka (joint-training PhD student, University of Cambridge), together with collaborators from the United States, Spain and other countries, reported a new stem‑group insect, Chosha praecursor Tihelka, Engel & Cai, 2026 (Fig. 1), from the Late Mississippian (~324 Ma) of Texas, USA. The team also investigated enigmatic stem‑insect material from the Early Devonian chert biota of Britain and the Late Carboniferous Mazon Creek biota of the United States (Fig. 2). These insect fossils fill critical gaps in early insect evolution, revise long‑standing interpretations of insect body-plan transformation and pancrustacean terrestrialization, and furnish key empirical evidence for the gradual aquatic‑to‑terrestrial evolutionary transition of insects. The findings were published online 26 August 2026 in Nature.

Fig. 1 The stem-group insect Chosha praecursor Tihelka, Engel & Cai, 2026 from the Carboniferous Tesnus Formation (ca. 324 Ma), Texas, USA.

Fossils of Chosha praecursor derive from calcareous claystone concretions within the Tesnus Formation of the Marathon Uplift, western Texas, and exhibit exquisite, well‑preserved anatomical details. Using cross-polarized light imaging, the team resolved its distinctive morphological traits and corrected long‑standing misinterpretations that these specimens represented crustacean larvae. The studied material corresponds to adult females with a body length of 32.09 mm; a median caudal filament plus two cerci extend the total length to 49.66 mm. The fusiform body displays derived traits diagnostic of hexapods and insects, while retaining plesiomorphic ancestral features (Fig. 1).

Systematic analyses demonstrate that Chosha praecursor possesses hallmark insect structures including an ovipositor and terminal caudal filament. Its thorax bears a segmented trunk and six walking legs, conforming to the canonical insect body plan. Most strikingly, however, segments 1‑9 of the abdomen bear segmented appendages; posterior abdominal limbs are modified into paddle‑like structures — a morphology unknown among extant crown‑group insects (Fig. 1). Palaeoenvironmental reconstructions indicate that the host strata represent near‑shore shallow‑water delta‑coastal settings, confirming that this early stem‑insect led a semi‑aquatic, amphibious lifestyle, occupying humid microhabitats across aquatic‑terrestrial interfaces.

Fig. 2 Comparative anatomical details of stem-insects and extant apterygote insects.

Based on detailed comparative morphology and phylogenetic analyses, the researchers re‑evaluated three enigmatic Palaeozoic hexapod fossils: Leverhulmia from the Early Devonian of Scotland, and an unnamed hexapod from the Mazon Creek biota, USA. Phylogenetic results recover Chosha praecursor together with these taxa as a primitive insect stem clade. Representing the oldest documented insect assemblage globally, this clade substantially connects the evolutionary genealogy of early insects (Fig. 3).

This study delivers paradigm-shifting scientific advances that reshape our framework for understanding insect terrestrial evolution. First, it fills the long‑persistent 80‑million‑year hexapod gap. Reliable evidence for insect origins and early diversification is pushed back from the Late Carboniferous into the Early Devonian, reconciling to some degree discrepancies between molecular‑clock estimates and the body-fossil record. Prior models assumed that insects evolved fully terrestrial body plans immediately following land colonization. The paddle‑shaped abdominal appendages and amphibious habit demonstrated here prove that insect terrestrialization was not an abrupt leap, but unfolded via a prolonged semi-aquatic amphibious transitional phase (Fig. 4).

Fig. 3 Phylogeny of early hexapods and the evolution of key morphological traits.

Second, the fossils illuminate pivotal transformations in the insect body plan. Extant hexapods retain only six thoracic legs; abdominal appendages are almost entirely lost. By contrast, Palaeozoic stem-insects commonly preserve segmented abdominal limbs. This confirms that reduction of abdominal appendages constituted a key evolutionary innovation for terrestrial adaptation. These structures were progressively simplified and lost from the swimming appendages of crustacean ancestors, ultimately yielding the body organization seen in modern insects. The findings clarify the morphological transition from pancrustacean ancestors to hexapod insects (Figs 1, 4). Furthermore, the plesiomorphic ovipositor preserved in Chosha praecursor demonstrates that early insects already possessed diverse oviposition adaptations, providing the structural foundation for subsequent colonization of heterogeneous terrestrial microhabitats and later insect radiations.

In addition, the research reconstructs ecological scenarios for early insects. Stem-group insects combined aquatic locomotor and respiratory adaptations with terrestrial body architectures. Their diets likely included humus, plant detritus and fungal spores. Early insects thus fulfilled multifunctional ecological roles as decomposers and consumers within aquatic‑terrestrial ecotones, acting as pivotal components driving the maturation of Palaeozoic terrestrial ecosystems (Figs 2, 4).

Fig. 4 Palaeoecological reconstruction of the Carboniferous stem-insect Chosha praecursor.

Fossils of Chosha praecursor and related Palaeozoic stem-insects reconstruct the early terrestrialization trajectory of Earth’s most species‑rich animal group, revising interpretations of body-size evolution, ecological adaptation and co‑evolution with terrestrial ecosystems. Terrestrial colonization by insects was a gradual process; retention, remodelling and reduction of ancestral aquatic structures permeated their early evolutionary history. An amphibious transitional phase formed the critical evolutionary bedrock enabling insects to conquer land. These results supply invaluable fossil evidence for deciphering hexapod origins and body‑plan evolution, and offer fresh perspectives on the origin and early diversification of complex terrestrial ecosystems on Earth.

Publication:
Tihelka, E., Vásquez, C., Engel, M.S. et al. Amphibious stem-insect sheds light on colonization of land. Nature (2026). https://doi.org/10.1038/s41586-026-10961-2

Abstract
Molecular clock analyses^1,2,3, trace fossils⁴, exceptionally preserved amphibious stem-myriapods⁵ and sea scorpions⁶ have recently challenged classical assumptions about the timeline of the animal colonization of land⁷, suggesting that terrestrial ecosystems may date back as far as the Cambrian period. However, the early evolutionary history of the most successful clade of animals, the insects, has remained elusive, as the period of their early diversification constrained by time divergence estimates falls within the notorious ‘hexapod gap’ in the fossil record8. Here we describe Chosha praecursor gen. et sp. nov. from the Carboniferous period (Late Mississippian epoch, approximately 324 million years ago) Tesnus Formation in Texas. Cross-polarized light imaging reveals that C. praecursor possesses insect apomorphies including an ovipositor and a terminal filament but differs from crown-group insects, most notably with respect to the presence of multisegmented abdominal legs with paddle-like modifications. Our phylogenetic reconstruction recovers C. praecursor as a hexapod, strongly favouring its placement as an early-diverging insect. A revision of three other enigmatic hexapod fossils, the Devonian period Leverhulmia and two undescribed Carboniferous fossils from the Mazon Creek Lagerstätte, demonstrates diverse body organization in Palaeozoic wingless insects. Together, these stem-group fossils represent the earliest uncontested insects and partly reconcile the incongruence between molecular clock estimates and the fossil record. The unusual abdominal gill-like appendages of Chosha suggest a semiaquatic mode of life in at least some stem-insects and revise our understanding of the assembly of insect morphological organization.

Tihelka, E., Vásquez, C., Engel, M.S. et al. Amphibious stem-insect sheds light on colonization of land. Nature (2026). https://doi.org/10.1038/s41586-026-10961-2

© 2026 Springer Nature Ltd.
Reprinted under the terms of s60 of the Copyright, Designs and Patents Act 1988.

The importance of Chosha praecursor is not that it supplies every missing stage in the origin of insects, nor that it can be identified as the direct ancestor of anything alive today. Its importance is that it possesses the predicted evolutionary mixture: an insect-like thorax, reproductive structures and terminal filaments combined with ancestral abdominal limbs suited to a partly aquatic existence. It shows that the familiar insect body plan was assembled progressively, while early branches of the lineage experimented with different combinations of inherited structures.

It also illustrates why gaps in the fossil record cannot honestly be treated as evidence that evolution did not occur. The fossil had already been collected; it had simply been misidentified and overlooked for four decades. Only new questions, careful comparison and improved imaging revealed its significance. As further specimens are discovered or old collections are re-examined, yesterday’s allegedly unbridgeable gaps repeatedly become today’s increasingly detailed evolutionary transitions.

Nothing in this discovery suggests the sudden appearance of insects as a completed design. Instead, it records descent with modification: existing appendages being retained, repurposed or lost as populations adapted to the boundary between water and land. There was no predetermined destination called “the modern insect”. There were only organisms surviving and reproducing in their immediate environments, with some evolutionary branches disappearing and one eventually giving rise to the enormously successful six-legged crown group.

Nor can a 324-million-year-old semi-aquatic stem insect be accommodated within a recent creation followed by a single global flood. It occurs in its appropriate Carboniferous geological and ecological setting, among organisms belonging to that remote period rather than mixed indiscriminately with modern life. Once again, the evidence presents the orderly consequences of deep time, common ancestry and evolutionary change, while creationism offers only denial of the evidence and an ever-shrinking appeal to what has not yet been found.

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