Rosa Rubicondior: Creationism Refuted - Blood suckers Were Around Long Before Creationist Frauds - Leeches are 200 Million Years Older Than We Thought

Tuesday, 7 October 2025

Creationism Refuted - Blood suckers Were Around Long Before Creationist Frauds - Leeches are 200 Million Years Older Than We Thought

Rare fossil reveals ancient leeches weren’t bloodsuckers | UCR News | UC Riverside

Artist's reconstruction of the ancient Macromyzon siluricus leech.

EK Chan.

Unlike creationist frauds, leeches haven’t always been blood-sucking parasites. Around 473 million years ago, they were probably marine predators preying on small creatures.

It had previously been assumed that leeches evolved around 150–200 million years ago, but this fossil, found in the Waukesha biota — a geological formation in Wisconsin —might more than double that timeline to 473 million years, if confirmed. This extended timescale makes sense, as the complex adaptations required for a blood-sucking lifestyle would have had longer to evolve. However, the classification is disputed and may be an example of convergent evolution. This fossil shows the large posterior sucker that modern leeches still possess, but lacks the anterior suctorial mouthparts used by leeches today to pierce their victims’ skin and suck blood.

The fossil was discovered by researchers from Ohio State University, but was initially unrecognised for what it was until it was identified by Karma Nanglu, a palaeontologist with the University of California, Riverside, during the early pandemic years. Nanglu collaborated with researchers from the University of Toronto, the University of São Paulo, and Ohio State University on a paper describing the fossil, which is now published in PeerJ.

Here’s a detailed overview of (1) the Waukesha Biota and (2) what we know (and still only partly know) about the evolutionary history of leeches (Hirudinea) and their relationships within Annelida and allied clades.

The Waukesha Biota (Brandon Bridge Lagerstätte)

Geological and paleontological setting

The Waukesha Biota (also called the Waukesha Lagerstätte or Brandon Bridge fauna) is an exceptionally preserved fossil assemblage from the early Silurian, roughly 437 million years ago. [1]
It lies within the Brandon Bridge Formation, in southeastern Wisconsin (including Waukesha County and Franklin, Milwaukee County). [2]
Sedimentologically, the specimens are found in very finely laminated mudstone and dolomite. The deposits are thin (on the order of decimetres) and are interpreted as having formed in a sedimentary trap near an erosional scarp in a shallow marine setting. [2]
The depositional environment is thought to have been a shallow marine lagoon or tidal flat, possibly with restricted circulation or periodic anoxia (oxygen-poor intervals). These factors, combined with microbial activity and rapid burial, helped preserve soft-bodied organisms and lightly sclerotised fossils rarely preserved elsewhere. [3]
The taphonomy (fossil‐preservation processes) is complex: some organisms were washed into the trap from more open water; others may have lived nearby. The presence of microbial mats or micro‐entombment processes is invoked to explain the fine detail and preservation of soft tissues. [3]

Biotic composition and significance

One reason Waukesha is important is that it offers a snapshot of early Silurian life including many soft-bodied or lightly preserved taxa that are usually lost in older rocks. [1]

Some of the taxa include:

Algae: Non-calcified dasycladalean algae (e.g. the genus Jimaodanus) are known, demonstrating that not only mineralised organisms were present. [2]
Sponges (Porifera): Very rare in the site, but one specimen is recorded. [2]
Hemichordates and Graptolites: As part of the planktonic or sessile components, with Desmograptus, Dictyonema, etc. [2]
Worms and vermiform animals: A diversity of polychaetes (segmented marine worms), annelid forms, and “worms” whose affinities are uncertain. [2]
Arthropods: Various arthropods are present, including trilobites (fairly abundant), lesser-known or enigmatic arthropods (e.g. Parioscorpio venator), thylacocephalans, and unclassified bivalved forms. [1]
A putative leech / stem-hirudinean: A key specimen is Macromyzon siluricus, an annulated worm which some interpret as a stem-group leech rather than a true modern leech. [2]

Because soft-bodied fossils are so rarely preserved in the Silurian, the Waukesha Biota gives researchers a chance to test hypotheses about early metazoan diversity, morphological experimentation, and lineage divergence that otherwise are invisible in the rock record. [1]

However, note that assignments of certain fossils (especially the putative leech) remain controversial. Some authors suggest the annulated worm previously thought to be a leech might represent an unrelated lineage (e.g. within Cycloneuralia). [4]

In summary: the Waukesha Biota is one of the rare Silurian Lagerstätten that preserves soft‐bodied and lightly sclerotised organisms, expanding our view of early marine ecosystems and providing possible data points for early annelid/arthropod evolution.

Evolutionary history of leeches and their relationships to other annelids

Below is a structured summary of what is fairly well established, what is inferred or debated, and where open questions remain.

Basic taxonomy and classification

Annelida is the phylum of “segmented worms,” including polychaetes (marine segmented worms), oligochaetes (earthworms, aquatic worms), and leeches (Hirudinea / Hirudinoidea) among other clades.
Within Annelida, there is a subgroup Clitellata (the “clitellate” worms) characterized by, among other features, the presence of a clitellum — the glandular segment involved in cocoon formation for reproduction. Leeches belong to this group (or near it). [5]
The clitellates include both oligochaetes (e.g. earthworms) and hirudinoids (leech-like worms). Some other more obscure groups (e.g. branchiobdellids, the “crayfish worms”) are sometimes considered closer to leech relatives. [6]

So the broad picture is: within Annelida, a lineage led from more “primitive” polychaetes to clitellates, and then from clitellates to leech‐like forms.

Key morphological and developmental innovations in leech lineage

Several features distinguish leeches from many other annelids. Some evolutionary-developmental studies have tried to reconstruct how these features might have arisen. [5]

Some of these features include:

Suckers / attachment organs

Leeches characteristically bear anterior and posterior suckers, which help in attachment (to hosts or substrates).
In stem or early leech forms, the development of a posterior sucker is considered more primitive; the anterior piercing mouthparts evolved later in specialized parasitic lineages. [5]

Loss of chaetae (bristles / setae)

Many annelids (especially polychaetes) bear chitinous setae or chaetae; leeches generally lack them (or have greatly reduced ones). The transition likely involved suppression or loss of chaetae during evolution. [5]

Loss or modification of internal septa

Annelid bodies are compartmentalized by septa (walls between segments). Leeches often show reduced septation, modifications, or loss of certain divisions, accommodating internal morphological changes (e.g. fusion of segments, functional specialization). [5]

A fixed number of segments

Many leech species have a constant or restricted number of body segments (rather than flexibility). This contrasts with many other annelids that show growth or variable segment counts. The evolutionary fixation of segmentation is thought to have been part of the leech lineage’s developmental constraints. [5]

Parasitic / hematophagy adaptations in some lineages

The transition to blood-feeding (hematophagy) in leeches is a derived condition. It requires morphological adaptations such as piercing jaws or proboscises, anticoagulants, specialized feeding behavior, and mechanisms to digest blood.
Hematophagy likely evolved multiple times independently in leech lineages (i.e. not from a single ancestral blood-sucking leech). This is supported by phylogenetic evidence showing blood-feeding groups are interspersed rather than monophyletic. [7]

Fossil record of leeches and stem-group evidence

The fossil record for leeches is sparse, especially because they are soft-bodied and seldom preserved. Nevertheless, a few key findings inform hypotheses about their history:

There are some known leech fossils from the Permian (around 266 million years ago) that are more securely assignable to leech-like annelids. [4]
The newly described Macromyzon siluricus, from the Waukesha Biota (Wisconsin, early Silurian), is interpreted by some authors as a stem-group leech (i.e. on the branch leading to leeches but not within the crown-group). It lacks full blood-feeding adaptations, and thus represents a more primitive stage. [2]
Phylogenetic analyses place Macromyzon as sister (or near) to extant leeches, but not within the group of modern leeches, making it a valuable calibration point for timing divergence. [8]
However, the assignment of older fossils (e.g. the annulated worm in Waukesha) as true leeches is debated. Some paleontologists argue for alternative affiliations (e.g. in Cycloneuralia) because the evidence is fragmentary. [4]

Thus, while the Waukesha fossil potentially pushes back the stem-lineage of leeches quite early, one must treat such assignments cautiously.

Phylogenetic relationships and divergence times

Putting together molecular phylogenetic work, developmental biology, and limited fossils gives a rough sketch of the leech / annelid tree:

The polychaetes are considered the ancestral or basal annelid condition: marine, segmented worms with well-developed chaetae, often many segments. [4]
The branch that led to Clitellata (including both oligochaetes and leech-like forms) likely involves the adaptation to more terrestrial or freshwater environments, reduction in larval stages, and direct development (bypassing trochophore larval forms). [9]
Within Clitellata, divergence led to oligochaetes and then to hirudinoids (leech-like lineages). Some phylogenies show that branchiobdellids (crayfish worms) are closely related to or nested among hirudinoids, though their exact relationship is debated. [6]
Among true leeches (Hirudinea), multiple clades exist (freshwater leeches, terrestrial leeches, blood-feeding vs non-blood-feeding lineages). Mitochondrial phylogenies and molecular data have been used to try to resolve the internal tree. [10]
Regarding divergence times: molecular clock estimates have varied, but many earlier works placed the origin of leeches in the Mesozoic (150–200 Ma). But stem-group fossils like Macromyzon suggest that the lineage may have deeper roots (Silurian or before). [4]

One phylogeny (from a review figure) shows major leech subgroups in relation to Clitellata and polychaetes, illustrating how leech lineages branch off after the transition from polychaetes to clitellates. [9]

Open questions, challenges, and caveats

Because leeches are rarely fossilised, their deep history is largely reconstructed from molecular data combined with scant stem-group fossils, which introduces uncertainty.
The Macromyzon specimen is singular and enigmatically preserved; its assignment to the leech stem lineage is plausible but not universally accepted.
Whether some annulated fossils from Silurian deposits represent true leeches or convergent forms remains under debate.
The evolution of blood-feeding (hematophagy) in leeches appears to have happened multiple times independently, complicating inferences about ancestral states.
The developmental transitions (e.g. suppression of chaetae, segment fixation, loss of septa) are inferred from extant developmental genetics rather than well-preserved fossils, so hypotheses remain tentative

It is also described in a University of California, Riverside news release by Jules Bernstein.

Rare fossil reveals ancient leeches weren’t bloodsuckers
A newly described fossil reveals that leeches are at least 200 million years older than scientists previously thought, and that their earliest ancestors may have feasted not on blood, but on smaller marine creatures.

The fossil leech compared with a modern leech. Double arrows = large caudal sucker used for attachment, single arrows = body annulations.

Andrew J Wendruff/Otterbein University/ Takafumi Nakano/Kyoto University.

This is the only body fossil we’ve ever found of this entire group.

Karma Nanglu, senior author
University of California, Riverside, CA, USA.

[Karma Nanglu] collaborated with researchers from the University of Toronto, University of São Paulo, and Ohio State University on a paper describing the fossil, which is now published in PeerJ.

Roughly 430 million years old, the fossil includes a large tail sucker — a feature still found in modern leeches — along with a segmented, teardrop-shaped body. But one important feature isn’t found in this fossil: the forward sucker that many of today’s leeches use to pierce skin and draw blood.

This absence, along with the fossil’s marine origin, suggests a very different early lifestyle for the group known as Hirudinida. Rather than sucking blood from mammals, reptiles, and other vertebrates, the earliest leeches may have roamed the oceans, consuming soft-bodied invertebrates whole or feeding on their internal fluids.

Blood feeding takes a lot of specialized machinery. Anticoagulants, mouthparts, and digestive enzymes are complex adaptations. It makes more sense that early leeches were swallowing prey whole or maybe drinking the internal fluids of small, soft-bodied marine animals.

Karma Nanglu.

Previously, scientists believed leeches emerged about 150–200 million years ago. That timeline has now been pushed back by at least 200 million years, thanks to the fossil found in the Waukesha biota, a geological formation in Wisconsin known for preserving the bodies of soft tissue animals that usually decay before fossilization.

Artist's reconstruction of the ancient Macromyzon siluricus leech.
EK Chan

Preserving a leech fossil is no small feat. Leeches lack bones, shells, or exoskeletons that are most easily preserved over millions of years. Fossils like this require exceptional circumstances to preserve, often involving near-immediate burial, a low-oxygen environment, and unusual geochemical conditions.

A rare animal and just the right environment to fossilize it — it’s like hitting the lottery twice.

Karma Nanglu.

The fossil came to light during a broader study of the Waukesha site by researchers at Ohio State University, who are co-authors on this paper. Though initially unrecognized for what it was, the specimen caught Nanglu’s eye during the early pandemic years.

He consulted with leech specialists, including lead author Danielle de Carle of the University of Toronto, and the group worked together to confirm its identity. They were ultimately convinced they’d found a leech because of the tail sucker and the clear body segmentation, which is a combination only found in leeches.

Today’s leeches are found in freshwater, saltwater, and even on land. Their feeding behaviors are equally diverse, from scavenging to predation to parasitic blood feeding. But understanding their origin has been difficult because soft-bodied animals rarely leave fossils.

Nanglu, who studies creatures rarely found in the fossil record, said the find is part of a larger effort to trace the early history of complex life, and to challenge assumptions about the past.

We don’t know nearly as much as we think we do. This paper is a reminder that the tree of life has deep roots, and we’re just beginning to map them. It’s a beautiful specimen, and it’s telling us something we didn’t expect.

Karma Nanglu.

Publication:
de Carle D, Iwama RE, Wendruff AJ, Babcock LE, Nanglu K. 2025.
The first leech body fossil predates estimated hirudinidan origins by 200 million years.
PeerJ 13: e19962 https://doi.org/10.7717/peerj.19962

The first leech body fossil predates estimated hirudinidan origins by 200 million years
Danielle de Carle, Rafael Eiji Iwama, Andrew J. Wendruff, Loren E. Babcock, Karma Nanglu.

Abstract

Clitellata is a major annelid clade comprising oligochaetes (e.g., earthworms) and hirudineans (e.g., leeches). Due to their scant fossil record, the origins of clitellates, particularly Hirudinea, are poorly known. Here, we describe the first leech body fossil, Macromyzon siluricus, gen. et sp. nov., from the Brandon Bridge Formation (Waukesha Lagerstätte). This fossil, which is preserved in exceptional detail, possesses several hirudinean soft-tissue synapomorphies–including a large sucker at the posterior end and sub-divided segments–and phylogenetic analyses resolve Macromyzon siluricus as a stem leech. Its age, 437.5–436.5 Ma, is consistent with early age estimates for the origin of clitellates, and predates molecular-clock-based estimates of hirudinidan origins by at least 200 million years. These findings suggest that the earliest true leeches were marine and that, contrary to prevailing hypotheses, were unlikely to have fed on vertebrate blood.

Introduction
Annelida, a speciose and morphologically disparate phylum within the animal group Lophotrochozoa, possesses a fossil record stretching back to the Cambrian. This consists primarily of polychaetes, non-biomineralized examples of which are recorded from deposits of exceptional fossil preservation such as the Burgess Shale in British Columbia, Canada (Conway Morris, 1979; Nanglu & Caron, 2018); Sirius Passet (Buen Formation) in North Greenland (Conway Morris & Peel, 2008); and both the Chengjiang (Maotianshan Shale) and Guanshan Formation biotas of South China (Liu et al., 2015; Han et al., 2019). The fossil record of scolecodonts (polychaete jaw elements) indicates that the first major polychaete radiation occurred during the Ordovician (Hints & Eriksson, 2007).

These fossils, in conjunction with novel modes of analysis and more robust molecular datasets (Parry et al., 2016; Weigert & Bleidorn, 2016.1; Nanglu & Caron, 2018), are helping to clarify some of the broad phylogenetic interrelationships among annelids; however, the origins of the major annelid clade Clitellata (earthworms, leeches, and their relatives) remain uncertain. In part, this is due to the uncertain phylogenetic placement of Clitellata (Weigert & Bleidorn, 2016.1), but, a more significant impediment is the exceedingly poor published fossil record of clitellates (Parry, Tanner & Vinther, 2014; Bomfleur et al., 2015.1). This paucity is unsurprising given that clitellate anatomy consists almost entirely of non-biomineralized tissue. Taphonomic studies have shown that polychaetes decay rapidly post-mortem: only their sclerotized jaws possess high decay resistance (Briggs & Kear, 1993). Although branchiobdellidans and some leeches possess hardened jaws, these structures are absent in the vast majority of clitellates, which reduces the likelihood that they will fossilize under most aqueous depositional circumstances.

Clitellata comprises roughly one-third of all extant annelid species, and they can be found in nearly every conceivable habitat on Earth (Sawyer, 1986; Martin et al., 2008.1; Sket & Trontelj, 2008.2). The group is characterized by the possession of a clitellum, a glandular region in the anterior part of the body which secretes a cocoon into which eggs are deposited (Sawyer, 1986). They are readily distinguished from other annelids by their lack of parapodia, the reduction or lack of chaetae, and the presence of certain autapomorphic internal reproductive characteristics (Brinkhurst, 1982; Rouse & Fauchald, 1995; Westheide, 1997). Clitellates are generally split into two groups: the paraphyletic Oligochaeta (earthworms and their relatives), and Hirudinea (Branchiobdellida, the crayfish worms; Acanthobdellida, the hook-faced fish worms; and Hirudinida, the true leeches) (Tessler et al., 2018.1; Erséus et al., 2020).

Today, clitellates are of great ecological, economic, and evolutionary importance. Non-hirudinean clitellates are among the most important ecosystem engineers in aquatic and terrestrial sedimentary environments (Lavelle et al., 1997.1), and hirudinean taxa fill a broad diversity of ecological niches as parasites, commensal symbionts, predators, and disease vectors (Sawyer, 1986; Martin et al., 2008.1). With the acquisition of a caudal sucker, and reduction of the clitellum, chaetae, and internal segmentation, hirudineans represent a unique annelid body plan (Purschke et al., 1993.1). Furthermore, acanthobdellidans and leeches represent a novel radiation of parasitic annelids, and as a result, the latter have been used as medical tools for thousands of years, continuing to the present day. Based primarily on morphological evidence and ancestral state estimation, most authors have converged on the hypothesis that the earliest clitellates were freshwater organisms, but the precise timing of the transition to a terrestrial habitat is not known (Manum, Bose & Sawyer, 1991; Rousset et al., 2008.3; Erséus et al., 2020).

Shcherbakov et al. (2020.1) provided a comprehensive summary of the clitellate fossil record, which largely consists of poorly preserved oligochaetes; these authors do not recognize any leech body fossils. A specimen putatively labelled (but not formally described) as “?Leech” by Mikulic, Briggs & Kluessendorf (1985a) and cited by Briggs (1991.1) lacks necessary characteristics that are diagnostic of leeches (de Carle, 2022), and has since been referred to the Cycloneuralia (Braddy, Gass & Tessler, 2023). Exceptionally preserved leech cocoons have been documented in deposits dating to the Triassic (Manum, Bose & Sawyer, 1991; Bomfleur et al., 2012; Steinthorsdottir, Tosolini & McElwain, 2015.2). These fossil cocoons, which have been categorized into four distinct genera, exhibit a range of morphologies, all of which are consistent with Hirudinea (Manum, Bose & Sawyer, 1991; McLoughlin et al., 2016.2). Beyond this, it is difficult to associate any particular cocoon morphology with a corresponding hirudinean taxon. Cocoon building is ubiquitous within Hirudinea–and Clitellata more broadly–indicating that this behaviour predates, or at least coincides with, the origins of the clade (Manum, Bose & Sawyer, 1991; Bomfleur et al., 2012). Although cocoon morphology is consistent within some higher-order hirudinean taxa (e.g., Hirudinidae, Erpobdellidae, Glossiphoniidae), little information is available regarding the cocoons produced by other groups (e.g., Branchiobdellida). Spermatozoa consistent with those of extant Branchiobdellida have been preserved within some of these cocoons dating to the Eocene of Antarctica (Bomfleur et al., 2015.1; McLoughlin et al., 2016.2). Ultimately, however, owing to the variability in the cocoons and spermatozoa of extant hirudineans (Bomfleur et al., 2015.1; McLoughlin et al., 2016.2), we are left with little definitive insight into the evolution, ecology, and anatomy of the animals that produced these trace fossils.

The scant fossil record of Clitellata leaves a number of questions unresolved. Although molecular clocks have been used to estimate divergence times for Clitellata, Hirudinea, and true leeches (e.g., Edgecombe et al., 2011; Erwin et al., 2011.1; Erséus et al., 2020), a dense sampling of fossil calibration points is needed to infer divergence times precisely and accurately (Warnock, Yang & Donoghue, 2017). A better understanding of early clitellate history would elucidate the timing of important evolutionary events including terrestrialization, development of the hirudinean body plan, and the origins of parasitism.

Here, we report the first fossil leech from the lower Brandon Bridge Formation (Silurian: Llandovery, Telychian) of Wisconsin, USA. The Brandon Bridge biota is diverse, including the remains of biomineralizing, non-biomineralizing and lightly biomineralizing organisms (Mikulic, Briggs & Kluessendorf, 1985a, Mikulic, Briggs & Kluessendorf, 1985.1b; Wendruff et al., 2020.2a, 2020.3b). This array of anatomies with varying taphonomic potentials includes even the most labile tissues found in leeches and other non-sclerotized animals (Briggs, 1991.1; Briggs & Kear, 1993; Saleh et al., 2020.4). The exceptionally preserved form described herein shows evidence of synapomorphic hirudinean characters–including a large caudal sucker and segments sub-divided into annuli–and does not bear hallmarks of other vermiform taxa, such as palaeoscolecids. This new species allows for a re-evaluation of the timing of clitellate origins, as well as new consideration of ancestral hirudinean ecology.

Figure 1: Macromyzon siluricus gen. et sp. nov. from the Lower Brandon Bridge Formation (Waukesha Lagerstätte), Silurian (Llandovery: Telychian), Waukesha, Wisconsin, USA.
(A) Holotype specimen UWGM 7056. (B) Schematic of the external morphology of Macromyzon siluricus based on the holotype. (C) Detail of the anterior region, dorsal view, showing sexannulate segments with annuli numbered; black arrows indicate putative tubercles. (D) Schematic of the anterior region showing tubercles in light grey and sexannulate segments with annuli numbered. (E) Schematic of segmentation pattern for M. siluricus. Green borders indicate extant Hirudinida introduced for comparison: (F) Ventral view of Myxobdella sinanensis (Zoological Collection of Kyoto University, specimen KUZ Z1794); photo by T. Nakano. (G) Schematic of Haementeria lutzi (dorsal view) with inset showing the species’ segmentation pattern. This specimen is deposited in the collections of the Museum of Zoology of the University of São Paulo (MZUSP 0026). Abbreviations: Ca, caudal sucker; S, segment; Tu, tubercles; Tu?, putative tubercles (metameric circular organs). White arrow indicates mid-body torsion, the point of torsion is shown in blue on schematics; breakage in the specimen is indicated in dark grey. Detail of starred features is shown in Figs. 2A, 2B.

DOI: 10.7717/peerj.19962/fig-1

Figure 2: Comparison of caudal suckers (green arrows) in Macromyzon and extant Hirudinea.
(A) Detail of the caudal sucker in Macromyzon siluricus, whole specimen shown in Fig. 1A. (B) Detail of the caudal sucker in the hirudiniform leech Myxobdella sinanensis (Zoological Collection of Kyoto University, specimen KUZ Z1794), whole specimen shown in Fig. 1F. (C) Cladogram showing relationships between taxa represented in this figure. (D) Branchiobdellidan species Cambarincola aff. okadai (left; National Museum Cardiff, specimen NMW.Z.2014.004) and Triannulata magna (right; Museum National d’Histoires Naturelles, specimen MNHN-HEL656); photos by James et al. (2015.3) and Parpet & Gelder (2020.5). (E) Full body (top) and scanning electron micrograph (bottom) of the acanthobdellidan Acanthobdella peledina; images by P. Swiątek. (F) The oceanobdelliform leech Pterobdellina vernadskyi; photo by Utevsky, Solod & Utevsky (2021). (G) The glossiphoniiform leech Torix sp. (Zoological Collection of Kyoto University, specimen KUZ Z4325); photo by T. Nakano. (H) The hirudiniform leech Haemadipsa japonica (Zoological Collection of Kyoto University, specimen KUZ Z4324); photo by T. Nakano.

DOI: 10.7717/peerj.19962/fig-2

Figure 3: A selection of palaeoscolecids for comparative purposes, refuting any affinity between Macromyzon and vermiform ecdysozoans.
(A) An undescribed palaeoscolecid from Waukesha showing a toughened, plate-like arrangement of the cuticle and scleritome. (B) Another undescribed palaeoscolecid from Waukesha, with tightly packed, regularly arranged, dome-shaped sclerites. A and B demonstrate that diagnostic palaeoscolecid characters readily preserve at Waukesha, and thus their absence in Macromyzon is not a function of taphonomy. (C) A specimen of Wronascolex antiquus from García-Bellido, Paterson & Edgecombe (2013), the most convincing possible palaeoscolecid moult known due to the breakage (white arrow) at the midline; however, the authors acknowledge that this is not a surety. (D) A close-up on a piece of the scleritome of Hadimopanella showing interlocking articulation of the sclerites. The sclerites of palaeoscolecids in general are unlike the more labile tubercles found in leeches and Macromyzon in particular; photo by Topper et al. (2010).

DOI: 10.7717/peerj.19962/fig-3

de Carle D, Iwama RE, Wendruff AJ, Babcock LE, Nanglu K. 2025.
The first leech body fossil predates estimated hirudinidan origins by 200 million years.
PeerJ 13: e19962 https://doi.org/10.7717/peerj.19962

Copyright: © 2025 The authors.
Published by PeerJ, Inc. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

This discovery not only rewrites the timeline for leech evolution but also helps clarify their place within the broader annelid family tree. Leeches belong to the clitellate annelids, alongside earthworms, all of which share a common ancestor that long predated the emergence of vertebrates. The early Silurian *Macromyzon siluricus* therefore represents an ancestral form that had not yet evolved the specialised anatomy and physiology needed for parasitism.

Finding such a creature in the Waukesha Biota also underlines the scientific importance of Lagerstätten — rare fossil deposits that preserve soft-bodied organisms. Without these exceptional sites, much of Earth’s early animal history would remain invisible, since creatures like leeches leave almost no trace in the ordinary fossil record.

What this specimen demonstrates is that leeches had a long evolutionary head start, giving natural selection ample time to refine the complex mechanisms required for a blood-feeding lifestyle, so, a blood-sucking parasitic lifestyle predated that of creationist cult leaders by hundereds of millions of years. It is a story of gradual adaptation, not sudden design — the opposite of what creationists would have us believe. Once again, the rocks and the fossils speak for evolution, not fabrication.

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