Andrej Spiridonov's avatar

Andrej Spiridonov

@andrejpaleo.bsky.social

711 followers 1118 following 335 posts

Professor of paleontology and Earth systems at Vilnius University. My interests are: theoretical paleontology, evolution, geology, stratigraphy, philosophy of biology and geology, climate at scales great and small.
twitter.com/AndrejSpiridon4

Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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"We find significant proportions of S-type granite in the Hadean Jack Hills zircon as far back as 4.24 Ga. These proportions exhibit regular variations in supercontinent-like cycles...This suggests that...plate tectonics were active since the Hadean..."
www.pnas.org/doi/10.1073/...
🧪 ⚒️ #Geology

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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This is not the alien spawn but a Jurassic Kimmeridgian oyster Actinostreon. Małogoszcz quarry, Holy Cross Mountains, Poland.

🧪 ⚒️ #Geology #Paleobio #EvoBio

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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Jesus wants you to study macroevolution. Sign showing the location of the oldest tetrapod tracks in the Zachelmie quarry, Holy Cross Mountains, Poland.
🧪 ⚒️ #Geology #Paleobio #EvoBio

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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Late Cretaceous dinosaur isotopic paleobiology and some evidence for omnivory of troodontid dinosaurs.
pubs.geoscienceworld.org/gsa/gsabulle...

🧪 ⚒️ #Geology #Paleobio #EvoBio

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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"Here we link the history of Phanerozoic O2 and CO2 concentrations... We emphasize that spatially resolved coupled redox and fossil evidence may be key to understanding feedbacks between the biosphere and the geosphere... and limits on habitability"
academic.oup.com/nsr/article/...
🧪 ⚒️ #Geology

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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Nonlinearities, history, long-memory matters not only in evolution (as we shown here doi.org/10.1017/pab.... ) but also in the dynamics of mega-climate:
"these features originate from nonlinearities and initial state dependence in carbon cycle behavior"
doi.org/10.1073/pnas...
🧪 ⚒️ #Geology

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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Interesting paper showing functional shift from mandible to trunk in elephants:
elifesciences.org/articles/90908
How these radical switches in gross functional morphology happen? Is it some kind of tipping nonlinear shift?
🧪 ⚒️ #Geology #Paleobio #EvoBio

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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Innovation vs diversity:
"Stability hypothesis: selection against phenotypic novelty enhances species diversifcation by strengthening dispersal limitation.
Novelty hypothesis: selection for phenotypic novelty impedes species diversifcation by weakening dispersal limitation."🧪
doi.org/10.1093/jeb/...

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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We would like to thank @bethanyjallen.bsky.social and several anonymous colleagues for especially useful feedbacks. 
 9/9

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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The HespDiv was tailored explicitly for the purpose of revealing spatial hierarchical nature of past and present biotas — The Bretskyan hierarchy. The theory of which we with @nilese.bsky.social published earlier this year. 
doi.org/10.1017/pab....
8/9

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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The hespdiv ‘R’ package in which the method family is implemented, also allows the explicit spatial Monte Carlo testing of the significance of split-curves. The regions which concentrate more sub-sampled runs are obviously more probably to have significant paleo-barriers. 7/9

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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To show the potential of the approach, we’ve analyzed the Paleobiology Database Miocene fossil record of mammals from the contiguous USA. The approach revealed a spatially complex structure with west-northwest separated from the rest of the bioregion being the first-order structure 6/9

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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The procedure can be done recursively until the stopping rule is satisfied. This procedure gives you a spatial hierarchy of sub-setting polygons which is accompanied by a more usual visualization form —the cluster diagram 5/9

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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Here we use a geometric approach when geographic convex hull of localities (or an area defined by other means) is subdivided by optimally separating regions by their maximal dissimilarity split-lines or nonlinear functions 4/9

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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This makes problem of finding the best split infinitely more complex: instead of point on a line you can have infinite variety of lines or curves fragmenting plane into contiguous polygons 3/9

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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In its essence the machine learning hespdiv algorithm performs CART-like (Classification and Regression Trees) hierarchical subdivision, just with a crucial difference, that this subdivision is done not in 1D feature space but in the 2D real geographical space. 2/9

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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I’m excited to share our new article published in “Palaeontology" presenting HespDiv family of methods for the spatially constrained hierarchical subdivision and clustering developed by brilliant PhD candidate @liudasdaumantas.bsky.social
doi.org/10.1111/pala... 
1/9 
🧪 ⚒️ #Geology #Paleobio #EvoBio

1 replies 3 reposts 10 likes

Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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"Abundant carbon was identified on Mercury... the formation of a solid inner core caused diamond to crystallize from the cooling molten core and formation of a diamond layer becoming thicker with time."

www.nature.com/articles/s41...
🧪 ⚒️ #Geology #Astronomy

0 replies 1 reposts 2 likes

Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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Interesting article on the dynamics of culture-climate co-evolution:
"For slow resource recovery time scales and in the absence of climate forcing, the model predicts a long-term global population collapse."
royalsocietypublishing.org/doi/pdf/10.1...
🧪 ⚒️ #Geology #Paleobio #EvoBio

0 replies 9 reposts 9 likes

Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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Geo-Red Queen modulated the GABI? "...temperature change, particularly cooling, triggered mammal dispersals during the GABI. On the other hand, we found the extinction rate in South America to be caused by warming."
link.springer.com/article/10.1...
🧪 ⚒️ #Geology #Paleobio #EvoBio

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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Soviet climatologist and pioneer of the physical climatology Mikhail Budyko was essentially a prophet, 52 years ago. He predicted kind of things we observing now—the dramatic decrease of the Arctic Sea Ice, and possibly complete collapse in 2050s.
agupubs.onlinelibrary.wiley.com/doi/abs/10.1...

0 replies 5 reposts 8 likes

Reposted by Andrej Spiridonov

Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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Architectural geology of Edinburgh. Beautiful laminations on the sandstone accentuated by the weathering. If sandstone was mined locally it should be of Devonian or Carboniferous age.

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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At the University of Edinburgh Futures Institute. With a range of experts we will dwell on the nature of extinctions.

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Reposted by Andrej Spiridonov

Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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Please read the 🌟 excellent 🌟 thread on our just published in TREE article on the Punctuated Evolution - a conceptual generalization of Punctuated Equilibria at different levels and kinds of evolutionary systems 👇
🧪 ⚒️ #Geology #Paleobio #EvoBio

0 replies 4 reposts 11 likes

Reposted by Andrej Spiridonov

Dr. Julian Lozos's avatar Dr. Julian Lozos @seismogenic.bsky.social
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⚒️🧪 Updated vedur.is fissure location map 2:05 PM Iceland time.
Also in this update:
Fissure is 3.4 km long. Lava flowed 1 km to the west in the first 45 min of the eruption. Lava flow is mostly southward now. Flow rate is 1000 cubic km/second.
Source (in Icelandic): www.vedur.is/um-vi/fretti...

2 replies 10 reposts 29 likes

Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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I'm using some, but it surely unneeded in many kinds of biological research. Similarly as deep knowledge of quarks is unneeded in many kinds of chemistry research.

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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This coordinated depletion corresponds to the “time anomalous” episode dected by us www.sciencedirect.com/science/arti... in the taxonomic records of conodonts and brachiopods, which were also dominanted exactly in the same post-Lau interval by unusuall (in temporal context) taxa.
8/8

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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Moreover, during the Lau Event itself graptolites disappear completely from the record, which the diversity of phytoplankton also drops sharply with the emergence of super-dominance of disaster taxon Leiosphaeridia spp. 7/8

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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Apparently the local diversity of the phytoplankton was directly correlated with the diversity of graptolites, which points to their coupled ecological and evolutionary responses to the climate variability. 6/8

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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The abundance variability of plankton components was driven by the ~ 1.0 Ma cyclicity. This periodicity was detected earlier in the variability of the d18O. We interpreted this as related to the 1.2 Ma modulation of the obliquity changes of the Earth's rotational axis 5/8

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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We confirmed so called “disaster taxon” status of a sphaeromorphs Leiosphaeridia spp., and determined that their dominance during extinction or stress intervals is achieved due to their higher resistance in comparison to other acritarch/green algae. 4/8

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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Here we quantitatively studied the base of the food web—phytoplankton, acritarchs and some groups of the zooplankton using different approaches, including #Recurrence_plots which were used in revealing the coordination of diversity dynamics of the phytoplankton and graptolites 3/8

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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The Lau Event witnessed significant extinction and replacement of graptolites, conodonts. It resulted in so called “time anomalous facies", and it was associated with the highest amplitude positive stable carbon isotopic ratio excursion of the Phanerozoic Eon. 2/8

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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Molecular systematics approach? 😅

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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"•Organism shape and size had the greatest influence on mixing patterns
•Mixing could have influenced the distribution of water column resources like oxygen •Ediacaran communities may have contributed to the ventilation of the oceans"

www.cell.com/current-biol...

🧪 ⚒️ #Geology #Paleobio #EvoBio

0 replies 3 reposts 8 likes

Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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Interesting study using recurrence plots investigated multiple transitions from wet to dry periods in Africa: "Together with events of extreme wetness at the end of the transition, these droughts form a pronounced climate “flickering”.."
www.nature.com/articles/s41...
🧪 ⚒️ #Geology #Paleobio #EvoBio

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Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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This is fundamental for geology, and terrestrial habitability. Climate caused cratons:
"Generation of sedimentary rocks enriched in heat-producing elements...resolves a long-standing question of why many cratons were stabilized in the Neoarchaean period"
www.nature.com/articles/s41...
🧪 ⚒️ #Geology

1 replies 1 reposts 12 likes

Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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Does anyone know what is the current conventional interpretation of this Tr-J boundary layer?
doi.org/10.1371/jour...
Is there a support for asteroid impact, or regular giant landslide-related tsunami, or of tectonic or volcanic explosion-related tsunami/ies? 2/2

1 replies 2 reposts 2 likes

Andrej Spiridonov's avatar Andrej Spiridonov @andrejpaleo.bsky.social
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Giant British ichthyosaurs are exciting, but in the same paper, hear me out, they mentioned:
"The stratigraphic horizon present immediately above the level of both finds represents a period of cataclysm with extensive seismite and tsunamite rocks"
doi.org/10.1371/jour...
🧪 ⚒️ #Geology #Paleobio 1/2

1 replies 3 reposts 10 likes