Fig. 1: Anatomical overview of Youti yuanshi.
To anyone who has ever looked at the segmented body of an annelid worm and the segmented body of an insect, particularly in its larval stage, that the latter is really the former with legs and (usually as an adult) wings should be obvious. The same can be said for annelid worms and centipedes and, for that matter, worms with legs and arachnids (spiders, scorpions and mites). But maybe the connection between arachnids and crabs or insects and barnacles is not so obvious, until you look at how the legs work and how they both have an exoskeleton instead of an endoskeleton like the vertebrates.
But then even the primitive ancestors of the vertebrates were segmented like the annelids, as we can see in the spinal column and the way nerves arise from the spinal cord.
But, tell a creationist that a segmented worm evolved into the arthropods, and they'll immediately demand to see the 'transitional' fossil, that they've been fooled into thinking must exist because every generation of every species is obliged to leave a fossil so there is a complete, unbroken record of evolution somewhere, because the Theory of Evolution says so. In fact, a complete, unbroken fossil record of every generation of an evolving species over time would look suspiciously like something other than chance was at work in creating fossils.
So, what we have are the snapshots at random points in time that are left in the geological column, and various dating methods that tell us how old the fossil is. The rest is simple common sense and joining the dots.
And one such snapshot has just been announced by researchers working at Durham University, UK, who have identified a species that is clearly partway between a segmented worm and an early arthropod (euarthropod). The newly-named Youti yuanshi is about the size of a poppy seed and fits neatly into one of creationism's beloved gaps. And, of course, it is exactly what the TOE predicts should have lived, because, as I said, the connection between segmented worms and segmented arthropods is obvious.
What is the Yu’anshan Formation in China and how was it dated, and in the context of a fossil found in it, what is phosphatization? The Yu'anshan Formation, located in China, is part of the well-known Chengjiang Biota and is famous for its exceptional preservation of Early Cambrian fossils. This formation, dating back approximately 518 million years, is situated in Yunnan Province and is a crucial site for understanding early animal life and the Cambrian explosion—a period of rapid diversification of life forms on Earth.The Durham team, from the University's Earth Science, department, co-led by Martin R. Smith and Emma J. Long, worked with Jie Yang and Xiguang Zhang if the Institute of Palaeontology and Yunnan University, China to analyse the tiny fossil. Their findings are published in Nature and are the subject of a brief press release from Durham University:
Dating of the Yu'anshan Formation
The dating of the Yu'anshan Formation has been achieved through a combination of methods:
- Radiometric Dating: This involves determining the age of rock layers by measuring the decay of radioactive isotopes. Specifically, zircon crystals within volcanic ash layers associated with the formation have been analyzed using uranium-lead (U-Pb) dating, providing precise age estimates.
- Biostratigraphy: By examining the fossil content within the formation and correlating it with other well-dated fossil assemblages worldwide, scientists can infer the relative age of the Yu'anshan Formation.
Phosphatization in Fossilization
Phosphatization is a process of fossilization where soft tissues of organisms are preserved by being replaced with phosphate minerals, typically apatite (calcium phosphate). This type of preservation is significant because it can capture fine details of soft-bodied organisms that are rarely fossilized under normal conditions. In the context of a fossil found in the Yu'anshan Formation, phosphatization means that the soft tissues of the organism, such as muscles, organs, and even cellular structures, were replaced by phosphate minerals shortly after the organism's death. This rapid mineralization helps to preserve intricate details that provide valuable insights into the anatomy and biology of early Cambrian life forms. Importance of Phosphatization in the Yu'anshan Formation
- Exceptional Preservation: Phosphatization allows for the exceptional preservation of soft-bodied organisms, which are otherwise not typically found in the fossil record. This provides a more complete picture of the biodiversity and ecological complexity of the Early Cambrian period.
- Insights into Early Life: The detailed preservation of soft tissues enables scientists to study the morphology and development of early animal groups, shedding light on the evolution of complex life forms.
In summary, the Yu'anshan Formation is a key site for understanding early animal evolution due to its well-preserved fossils, which have been dated using precise radiometric techniques. The process of phosphatization plays a critical role in preserving the delicate features of these ancient organisms, offering a rare glimpse into the early history of life on Earth.
Ancient worm fossil solves mystery of how insects and spiders evolved
A new study led by our Earth Sciences department has uncovered an incredibly rare and detailed fossil, named 'Youti yuanshi', that gives a peek inside one of the earliest ancestors of modern insects, spiders, crabs and centipedes.
The fossil preserves the entire internal anatomy of a tiny larva in exceptional quality that represents one of the earliest arthropod ancestors with legs and a complex brain.
Sophisticated biology
This fossil belongs to a group called the euarthropods, which includes modern insects, spiders and crabs.
Despite being no bigger than a poppy seed, the 3D fossil reveals the larva possessed an advanced brain, digestive system, circulatory system and clusters of nerves extending into primitive legs and sensory appendages.
The level of anatomical complexity is remarkable for such an ancient organism.
Evolutionary clues
The fossil helps bridge a key transitional gap in arthropod evolution between simple worm-like ancestors and the successful modern arthropod body plan.
In particular, the fossil's brain anatomy reveals pivotal steps in how the arthropod head and its appendages like antennae, jaws and eyes became segmented and specialised over time from ancestral brain regions.
The researchers highlight that the fossil fills an important gap in our understanding of how the arthropod body plan originated and became so successful during the Cambrian Explosion of life.
This remarkable specimen is housed at Yunnan University in China, where it was originally discovered.
AbstractOf special significance for creationists who will normally show the disingenuous nature of their constant demand for 'transitional forms' by dismissing this sort of fossil as 'not transitional' and still having a gap either side of it, and anyway, based on flawed dating is the fact that the formation it was found in was dated by one of the most accurate and reliable dating methods there is - U-Pb dating of zircons found in volcanic ash. And I have yet to see a refutation of these dating methods that aren't more than mere hand-waving.
The Cambrian radiation of euarthropods can be attributed to an adaptable body plan. Sophisticated brains and specialized feeding appendages, which are elaborations of serially repeated organ systems and jointed appendages, underpin the dominance of Euarthropoda in a broad suite of ecological settings. The origin of the euarthropod body plan from a grade of vermiform taxa with hydrostatic lobopodous appendages (‘lobopodian worms’)1,2 is founded on data from Burgess Shale-type fossils. However, the compaction associated with such preservation obscures internal anatomy3,4,5,6. Phosphatized microfossils provide a complementary three-dimensional perspective on early crown group euarthropods7, but few lobopodians8,9. Here we describe the internal and external anatomy of a three-dimensionally preserved euarthropod larva with lobopods, midgut glands and a sophisticated head. The architecture of the nervous system informs the early configuration of the euarthropod brain and its associated appendages and sensory organs, clarifying homologies across Panarthropoda. The deep evolutionary position of Youti yuanshi gen. et sp. nov. informs the sequence of character acquisition during arthropod evolution, demonstrating a deep origin of sophisticated haemolymph circulatory systems, and illuminating the internal anatomical changes that propelled the rise and diversification of this enduringly successful group.
Superphylum Panarthropoda
Lower stem group to Phylum Euarthropoda10
Youti yuanshi gen. et sp. nov.
LSID.. urn:lsid:zoobank.org:act:28BD6A01-5FDC-40EC-973A-63AEB05328A4.
Etymology. From Pinyin yòutĭ, meaning larva, and yuánshĭ, meaning primitive; reflecting the early developmental stage of the fossil and its bearing on the origin of the euarthropod body plan.
Holotype. YKLP 12387 (Figs. 1–3 and Extended Data Figs. 1–4), recovered by 5% acetic acid digestion of carbonate nodules from black shales of the Yu’anshan Formation (Eoredlichia–Wutingaspis Biozone, approximately late Atdabanian stage, Cambrian Period Series 2, Stage 3), Xiaotan section, Yongshan, Yunnan Province.Diagnosis. Euarthropod with paired glands dorsal to lobopods. Bulbous anterior appendages adjacent to ventral mouth. Perivisceral cavity incompletely partitioned by transverse membranes of connective tissue. Ventrolateral sinuses with serially repeated dorsal lacunae. Prominent dorsal head lobe with paired dorsal projections. Subdivided brain with discrete frontal body.Fig. 1: Anatomical overview of Youti yuanshi.
YKLP 12387. a, External scanning electron microscopy, right side. Damage to posterior epidermis exposes lining of perivisceral cavity, demonstrating blind gut. b, External scanning electron microscopy, left side. c,g–j, Median virtual dissection from X-ray computed tomography (XCT) data (c), showing location of transverse slices intersecting digestive glands (g,i) and transverse membrane (h,j). d, Semi-manual segmentation of internal chambers from XCT data, viewed from the left side. Dorsolateral aspects of the peripheral cavity are omitted for clarity. e,f, Virtual dissection parallel to coronal plane, looking ventrally (e) and dorsally (f), showing digestive glands, pericardial sinus, transverse membranes within perivisceral cavity, and oblique membranes within peripheral cavity. g–j, XCT sections at positions indicated in c at position of digestive glands (g,i) and at position of ventrolateral lacunae and transverse membrane (h,j). g,h, Sections close to the anterior trunk, reflecting segments at late developmental stage. i,j, Sections close to the posterior trunk, showing superior preservation of internal tissue. k, Segmentation of internal chambers from XCT data, viewed from the dorsal perspective at anterior, middle and posterior trunk. Aspects of peripheral cavity are omitted for clarity. a, appendage; cb, central body of brain; db, dorsolateral body of brain; dia, diagenetic grain; dg, digestive gland; dm, dorsal membrane; dp, dorsal projection; dv, dorsal vessel; fb, frontal body of brain; irr, irregular chamber; lig, ligament; om, oblique membrane; pc, pericardial sinus; pph, peripheral cavity; pn, perineural sinus; pv, perivisceral cavity; tm, transverse membrane; vl, ventrolateral sinus; vv, ventral vessel. Scale bars, 200 μm.
Fig. 2: Internal anatomy of Youti yuanshi.
YKLP 12387. a,b, Virtual dissections of dorsolateral trunk, looking posteriad, showing internal structure of tenth (a) and eighth (b) digestive glands, oblique membrane within peripheral cavity and ligaments associated with gut. c, Virtual dissection through 14th digestive gland, looking anteriad, showing connection of digestive glands to dorsal gut. d, Virtual dissection showing blind termination of posterior gut; dashed line marks anterior limit of gut preservation. e–g, Disposition of chambers within trunk appendages, showing extensions of perivisceral and peripheral cavities into appendage. Virtual dissections oriented parallel (e), oblique (f) and subperpendicular (g) to appendages. A, anterior; P, posterior. Colour scheme as in Fig. 1. dgp, digestive gland process; lac, lacuna of the ventrolateral sinus. Scale bars, 100 μm.
Fig. 3: Head structure in Youti yuanshi.
YKLP 12387. a–d, XCT sections from ventral (a,b) to dorsal (c,d) surface of dorsal lobe, showing internal structure of head and trunk. e–j, Transverse XCT sections from anterior (e) to posterior (j) of head. D, dorsal; V, ventral. k–m, Ventral view of head, showing external XCT volume render (k) and segmentation of chambers without (l) and with (m) ventral structures. n, Sublateral view. Colour scheme as in Fig. 1. an, anterior compartment of first appendage; cc, circumpharyngeal connective; co, circumoral ring; e, eye; mm, transverse medial membrane of the central body; po, posterior compartment of first appendage; sp, subpharyngeal gland; µb, microboring. Scale bars, 200 μm.
Preservation. Orsten-type preservation11 typically replicates chitinous cuticle in amorphous apatite; preservation of more labile tissue12 is rare. Concretions within the Yu’anshan Formation are exceptional in preserving non-chitinous material, including coprolites and muscle, at exquisite resolution9,13. This material is often penetrated by post-phosphatization microborings13 with diameters on the scale of 10 µm. Secondary encrustations of diagenetic phosphate, although evident in similar deposits14, are absent. Small grains of diagenetic minerals (Figs. 1f and 2b) are readily identified by their higher X-ray attenuation, which corresponds to a higher greyscale value.
Although the limited material available cannot support a detailed taphonomic model, the high fidelity indicates an early onset of phosphatization, with differential preservation of different tissue types9. In YKLP 12387, preservation is restricted to the integument and connective tissue, leaving behind voids that correspond to the outlines of non-phosphatized tissue.
Smith, M.R., Long, E.J., Dhungana, A. et al.
Organ systems of a Cambrian euarthropod larva. Nature (2024). https://doi.org/10.1038/s41586-024-07756-8
Copyright: © 2024 The authors.
Published by Springer Nature Ltd. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)
The other significant thing for creationists, especially those who have been fooled into thinking the 'Cambrian Explosion' was literally an instantaneous creation of multiple different body plans, and not the gradual evolution of biodiversity of several tens of millions of years, is that this fossil is from the early part of the Cambrian era when this or something very much like it, was the progenitors of several of those body plans.
But then, this is just another piece of evidence for creationists to ignore, lie about or otherwise dismiss, like so much else in the mountains of evidence that creationism is merely an evidence-free superstition, and a source of income for a few rich frauds who have no scruples about fleecing ignorant simpletons.
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