Duncan McIlroy

@dmcediacaran

Ediacaran palaeobiologist at Memorial University of Newfoundland. Working on beautiful fossils in Newfoundland & UK alongside amazing students/colleagues with strong local community partnerships to support GeoEducation GeoConservation & ethical GeoTourism

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Duncan McIlroy@dmcediacaran· 1d

We had not long before realized that the holotype of Charniodiscus was likely furled like a wind-sock in life, then on death the branches folded out. The new lighting showed that this specimen was a (tectonically shortened) C. procerus showing the same body plan. you can read about it for free…

sequential taphonomic explanation of branch orientations in the holotype of Charniodiscus concentricus

holotype specimen of Charniodiscus concentricus with branches false coloured

Duncan McIlroy@dmcediacaran· 1d

Happy #FossilFriday! this week I am sharing a couple of images of the same fossil. #Charniodiscus procerus from the #Ediacaran at Mistaken Point in #Newfoundland. this specimen was alway enigmatic and difficult to classify until one day we saw it in late Fall light & its architecture popped out …

Charniodiscus procerus from the D Surface at Mistaken point.
plaster cast is ideal lighting

same specimen but with different lighting

Duncan McIlroy@dmcediacaran· 8d

And a bonus second #FossilFriday post mainly because I am just back from the field working on a new site here in #Newfoundlamd which today yielded its first complex #Ediacaran fossils #Hadryniscala and #Charniodiscus sp. There’s nothing like finding new Ediacaran fossils. The potential is great!!

leaf like fossil with central axis on a brown rusty surface. Confirms most closely with Charniodiscus

strap like fossil of hadryniscala just above a concentric disc (tectonically compressed) on a rusty brown bedding surface with many cracks

Duncan McIlroy@dmcediacaran· 8d

This #FossilFriday we look between the beautiful #Rangeomorph, #Arboreomorph #Ediacaran macrofossils of #Newfoundland where there is an abundance of (presumed microbial) filaments that provide evidence for 1) the structure of the surrounding microbe dominated seafloor & 2) sub-matground gas buildup

bedding surface covered in thin filaments in a range of widths some possibly radiating from a small crater-like depression. The circular features are pits generated by sub-matground buildup of methane-rich gas from degradation of buried organic matter. base of a diskless rangeomorph to the top right.

Duncan McIlroy@dmcediacaran· 15d

Happy #FossilFriday with a depiction of the newest #rangeomorph genus #Aninoides which is only known from the #Ediacaran of #Newfoundland & my attempt at depicting it on the microbe-dominated seafloor along with #Charniodiscus procerus lurk. This painting didn’t make the cut for our paper.

leaf-like fossil cast of Aninoides coombsorum showing the long first order branches typical of the genus.

Digital painting showing a pinkish #aninoides coombsorum in the foreground surrounded by microbial matgrounds with two Charniodiscus with procumbent stems and upright frondose portions lurking at the edge of the field of view.

Duncan McIlroy@dmcediacaran· 17d

I searched high and low for these images of frond-like chevron marks for comparison with similar structures from the #Ediacaran #Dongpo Biota. too late for our paper doi.org/10.1016/j.pr... @hyperpycnal.bsky.social but here they are anyway. #Fermeuse Formation, Bonavista Pen. Newfoundland

chevron shaped markings on a siltstone bed

$frond like chevron marks on a bedding plane cut by joints and fractures$

Duncan McIlroy@dmcediacaran· 22d

In the #Ediacaran the UK & #Newfoundland were geographically close & share some faunal elements including Primocandelabrum. Tho’ Charnwood Forest “Primo”specimens have #Rangeomorph branches. Charnwood is currently being considered as a possible UNESCO #Geopark so here’s a UK “Primo” on #FossilFriday

my panting depicting the rangeomorph branching of Primocandelabrum boyntoni with the biserial rangeomorph branches arising from bifurcating limbs

photograph of a Primocandelabrum showing a basal anchoring disc and thick stem with thick limbs arising from the top of the stem
the limbs bifurcate at least once before the most distal branches have biserial rangeomorph branches in a range of orientations consistent with having fallen over before burial

Duncan McIlroy@dmcediacaran· 29d

This #FossilFriday I’m sharing a lovely#Ediacaran Hiemalora from Conception Bay North #Newfoundland. A rather atypically wiggly one. They are most likely holdfasts of something, but it’s a bit of a mystery what. They are known from about 570Ma to 550Ma This one is from the Trepassey-Fermeuse Fmn.

sunburst like Hiemalora with small central disc on a bedding surface with indeterminate circular features (?shafts) scale is in cm.

Duncan McIlroy@dmcediacaran· Jul 10

Happy Fossil Friday! This weeks offering is news that the Inner Meadow site is now 774 sq ft. comparable to the main E -Surface at Mistaken Point & much more diverse. We also found the first convincing #Hadryniscala which has small lateral bars on a strap like form a bit like a seaweed.

The inner meadow fossil site showing the size of the excavation and preparation for making of a silicone mold (plasticene dams). The site is on private land with no public access for now (but watch this space)

bedding surface with a narrow strip of darker (wet) surface highlighting the position of a specimen of Hadryniscala about 6cm wide, which has broad lateral bars on an otherwise strap-like form. In life it might have been a bit like some modern macroalgae

Duncan McIlroy@dmcediacaran· Jul 3

Happy #FossilFriday!! Today is brought to you by superposition of #Ediacaran fossils. Throughout Avalonia the genera that lie atop other frondose organisms are Arborea & Primocandelabrum. Fractofusus overgrow ivesheadiomorph necromass but #rangeomorpha like Charnia and Trepassia never overlie other

Stem of a “Primocandelabrum” emerging from a small disc (top right) lying atop a factually branching elongate leaf-like Trepassia with base bottom right and handled towards the top left. Image is retrodeformed approximately

Duncan McIlroy@dmcediacaran· Jun 26

Happy #FossilFriday from the #Ediacaran of #InnerMeadow. This week i would like to share something newly uncovered & new to the site large deep disks, and the charniid #Rangeomorphs Trepassia sp and Charnia gracilis lying next to one another as they have for 551 million years. What a privilege!

large deep basal (probably holdfast) disk of an unknown irganism. Dish shaped and concentric ally ringed. Finger for scale with battered fingernail.

$two elongated broadly leaf shaped rangeomorph fractal-like organisms trepassia is top with rangeomorph branches at variable angles, and charnia gracilis below with all branches at similar acute angles to the axis the smooth shiny bits are glacially polished Field of view is about 20cm$

Duncan McIlroy@dmcediacaran· Jun 19

The highlight for me from my work clearing at #InnerMeadow was this complete #Beothukis mistakensis. There’s only 4 or so complete specimens known of this #Ediacaran rangeomorph. It is almost identical to the holotype that we published on in 2020. We interpret it as growing along the seafloor.

leaf like (spatulas) fossil on a bubbly bedding surface

Duncan McIlroy@dmcediacaran· Jun 16

today at #InnerMeadow was mainly spent splitting erratics in the holes in the surface that were too large to carry. I channeled skills of my forebears who were coal miners and stone masons in the north of England. The satisfaction of splitting the boulders with hand tools was very satisfying!

split boulder at inner meadow with chisel.

Duncan McIlroy@dmcediacaran· Jun 12

I’m a bit late to #FossilFriday today as I’m in the field (literally) clearing at Inner Meadow. But how about a lovely Charnia gracilis to be getting on with. From #InnerMeadow of course.

Duncan McIlroy@dmcediacaran· Jun 5

Happy #FossilFriday which is this week brought to you from the #Ediacaran MUN Surface in @discoverygeoparknl.bsky.social . The exceptional preservation that characterizes that surface is well seen in this ? #culmofrons. A #rangeomorph with branches showing only one 1/2 of the biserial form.

Duncan McIlroy@dmcediacaran· Jun 2

I had a fun day out yesterday in @discoverygeoparknl.bsky.social sharing the #Ediacaran fossils of Capelin Gulch & the Johnson Discovery Surface with delegates from GAC-MAC 2026 in St. John’s. Great discussions on the rocks & the snow even held off for us! Thanks to all leaders delegates!

geologists looking at fossils on 560 million year old seafloor in Little Catalina Discovery geopark

Duncan McIlroy@dmcediacaran· May 29

This #FossilFriday is brought to you courtesy of the lively new #Ediacaran #rangeomorph Aninoides coombsorum named by @simonrosse.bsky.social. Currently only known from the 551Ma Inner Meadow Lagerstätte in Newfoundland. Same age as the youngest White Sea type biotas in Australia, Russia etc.

Duncan McIlroy@dmcediacaran· May 22

Happy #fossilfriday from the #Ediacaran at #InnerMeadow at 551Ma it is the youngest known example of the “Avalon Assemblage” (equivalent to the youngest “White Sea Assemblage”). The field season is underway here in NL. We continue to remove soil & fossiliferous rocks from over the fossil surface.

the excavation at inner meadow the white rock surface is covered by soil full of rocks some of which contain Ediacaran fossils

$An Ediacaran Trepassia from the soil overlying the fossil surface at Inner Meadow. The specimen is slightly glacially polished but the fractal-like 1/2-leaf shaped branches are well preserved$

Duncan McIlroy@dmcediacaran· May 15

Happy #FossilFriday from the #Ediacaran at #InnerMeadow. I’ve been focussing on removing boulders and soil the last couple of weeks but this beauty popped out. It is a scan of the natural cast of the base of a large #Aninoides

Duncan McIlroy@dmcediacaran· May 8

I feel like posting a #notafossil for #FossilFriday necessitates posting a fossil too. Yesterday Helena and i did some clearing at #InnerMeadow. Mainly just removing the thick soil & not getting down to new fossils until the end of day when the surface was wet and light flat (so no 📷) but we did..

graduate student Heléna getting down to the fossil surface with the hose at inner meadow

disc and leaf shaped fossils from inner meadow

Duncan McIlroy@dmcediacaran· May 8

Happy #FossilFriday from the late +Ediacaran where I (disappointedly) want to share the most remarkable pseudofossils I have ever seen. This beautiful #conulariid or protechinurus like thing (bottom) and 2 longitudinal striated tube/like things are all sub glacial scratch marks.

scratch marks like tubular fosskils with chatter marks and grooves

Duncan McIlroy@dmcediacaran· May 1

As tempting as it is to spend all my time in the field at Inner Meadow. This week i went on an Ediacaran adventure up the Bay de Verde Pen. with @jeffontherock.bsky.social looking at the post #KotlinCrisis interval at beautiful sites on the barrens. Access is more open after devastating fires last…

a mixture of concentric disks and rows of chambers on an Ediacaran bedding plane rock surface

Duncan McIlroy@dmcediacaran· Apr 29

weird branching burrows or borings in a mudstone branching is commonly orthogonal to the long axes. Burrow/boring width is about 0.25mm

Duncan McIlroy@dmcediacaran· Apr 29

has anyone seen one of these before? It is in a Newfoundland #Ediacaran mudstone found with @jeffontherock.bsky.social today. It looks a bit like beetle boring in wood. Maybe @ichnologist.bsky.social has seen something like it. burrows on the same bed are positives, this is a negative feature.

Duncan McIlroy@dmcediacaran· Apr 17

I’ve been a bit remiss with #FossilFriday (teaching palaeontology for the first time since 2005). The ground is thawing here and we have had a couple of field days already so here is a newly uncovered A. spinosa and a Primocandelabrum sp. to enjoy from our #Ediacaran #InnerMeadow lagerstatte.

A bedding surface with lots of little holes (gas bubbles formed beneath a microbial mat) and a pointy ended frond of Arborea spinosa with a large disc (bottom) and a above us a bushy/tree-shaped frond of Primocandelabrum, also with basal holdfast disc

Duncan McIlroy@dmcediacaran· Apr 6

and also other bubbly surfaces including the previously described “bubble trains” at “Spaniards Bay” and Crocker Cove. Nagi concludes that they likely represent bubbles of gas trapped beneath matgrounds, possibly produced by methanogenic bacteria decomposing buried matgrounds.

detail of the InnerMeadow fossil surface with abundant negative hemispherical “bubbles” and a specimen of a vermiform (worm-like) fossil of #Uncus

Duncan McIlroy@dmcediacaran· Apr 6

In the latest of our string of papers on the new #Ediacaran Inner Meadow Lagerstätte here is an account of the distinctive bubble like textures (paywalled sorry but $$) doi.org/10.1111/sed.... or ask for a copy :-). Recently graduated MSc student Nagi Chida worked on the textures at…, #InnerMeadow

negative bubbly textures with millimetric aggregations of bubbles either in strips or widespread on Ediacaran bedding planes. Some of which have exceptionally preserved fossils of soft-bodied organisms

Duncan McIlroy@dmcediacaran· Mar 20

Something a bit different this #FossilFriday a fossil i’ve had on my desk for a while now. This is a Cambrian member of the Coronatae, undescribed, from western Newfoundland that I found way back in 2017 (I think).

Duncan McIlroy@dmcediacaran· Mar 13

Yet another new #FossilFriday paper! This time just me, but building on work from the MUN Paleobiology Crowd over a number of years. This OA paper outlines the lines of evidence used to determine mode of life of the #Ediacaran #Rangeomorpha. Always careful and objective we work with one

$reconstruction of the seafloor at Inner Meadow with matgrounds and leaf like fractal Charnia brasieri in inferred life position (c)duncan mcilroy$

$reconstruction of Avalofractus abacus in life position a fractal like upright frond (c)duncan mcilroy$

$Possible Avalofractus abacus from Mistaken Point an originally upright fractal like frond$

$Charnia brasieri with a Trepassia sp. at its top both are fractal like stemless forms trepassia is narrow, brasieri is broad and leaf like$

Duncan McIlroy@dmcediacaran· Mar 6

Pascal’s PhD involves describing this rich biota along with a new date hopefully coming at the same time later this year. The rest of the biota are mainly Mistaken Point type fossils but not quite as well preserved though much closer to St. John’s! and free to read here: doi.org/10.1017/S001...