From Newsgroup: sci.bio.paleontology

The split between synapsids (us) and sauropsids (reptiles) has generally though to have happened in the Carboniferous ~350 Mya. New trackways
found in Australia suggests that the split occurred in the Devonian,
about 35-40 My earlier.

https://www.nature.com/articles/s41586-025-08884-5

Earliest amniote tracks recalibrate the timeline of tetrapod evolution

Abstract
The known fossil record of crown-group amniotes begins in the late Carboniferous with the sauropsid trackmaker Notalacerta1,2 and the
sauropsid body fossil Hylonomus1,2,3,4. The earliest body fossils of crown-group tetrapods are mid-Carboniferous, and the oldest trackways
are early Carboniferous5,6,7. This suggests that the tetrapod crown
group originated in the earliest Carboniferous (early Tournaisian), with
the amniote crown group appearing in the early part of the late
Carboniferous. Here we present new trackway data from Australia that
challenge this widely accepted timeline. A track-bearing slab from the
Snowy Plains Formation of Victoria, Taungurung Country, securely dated
to the early Tournaisian8,9, shows footprints from a crown-group amniote
with clawed feet, most probably a primitive sauropsid. This pushes back
the likely origin of crown-group amniotes by at least 35rCo40 million
years. We also extend the range of Notalacerta into the early
Carboniferous. The Australian tracks indicate that the amniote
crown-group node cannot be much younger than the Devonian/Carboniferous boundary, and that the tetrapod crown-group node must be located deep
within the Devonian; an estimate based on molecular-tree branch lengths suggests an approximate age of early Frasnian for the latter. The
implications for the early evolution of tetrapods are profound; all stem-tetrapod and stem-amniote lineages must have originated during the Devonian. It seems that tetrapod evolution proceeded much faster, and
the Devonian tetrapod record is much less complete, than has been thought.

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From Newsgroup: sci.bio.paleontology

On 5/14/25 17:01, erik simpson wrote:

The split between synapsids (us) and sauropsids (reptiles) has generally though to have happened in the Carboniferous ~350 Mya.-a New trackways
found in Australia suggests that the split occurred in the Devonian,
about 35-40 My earlier.

https://www.nature.com/articles/s41586-025-08884-5

Earliest amniote tracks recalibrate the timeline of tetrapod evolution

Abstract
The known fossil record of crown-group amniotes begins in the late Carboniferous with the sauropsid trackmaker Notalacerta1,2 and the
sauropsid body fossil Hylonomus1,2,3,4. The earliest body fossils of crown-group tetrapods are mid-Carboniferous, and the oldest trackways
are early Carboniferous5,6,7. This suggests that the tetrapod crown
group originated in the earliest Carboniferous (early Tournaisian), with
the amniote crown group appearing in the early part of the late Carboniferous. Here we present new trackway data from Australia that challenge this widely accepted timeline. A track-bearing slab from the
Snowy Plains Formation of Victoria, Taungurung Country, securely dated
to the early Tournaisian8,9, shows footprints from a crown-group amniote with clawed feet, most probably a primitive sauropsid. This pushes back
the likely origin of crown-group amniotes by at least 35rCo40 million
years. We also extend the range of Notalacerta into the early
Carboniferous. The Australian tracks indicate that the amniote
crown-group node cannot be much younger than the Devonian/Carboniferous boundary, and that the tetrapod crown-group node must be located deep
within the Devonian; an estimate based on molecular-tree branch lengths suggests an approximate age of early Frasnian for the latter. The implications for the early evolution of tetrapods are profound; all stem-tetrapod and stem-amniote lineages must have originated during the Devonian. It seems that tetrapod evolution proceeded much faster, and
the Devonian tetrapod record is much less complete, than has been thought.

So

Some fish have scales

All living amphibians do not have sales

Some reptiles have scales

Some mammals have hair

So

What was the scale, hair, feather situation for these vertebrates?


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From Newsgroup: sci.bio.paleontology

On 5/21/25 11:58 AM, x wrote:

On 5/14/25 17:01, erik simpson wrote:

The split between synapsids (us) and sauropsids (reptiles) has
generally though to have happened in the Carboniferous ~350 Mya.-a New
trackways found in Australia suggests that the split occurred in the
Devonian, about 35-40 My earlier.

https://www.nature.com/articles/s41586-025-08884-5

Earliest amniote tracks recalibrate the timeline of tetrapod evolution

Abstract
The known fossil record of crown-group amniotes begins in the late
Carboniferous with the sauropsid trackmaker Notalacerta1,2 and the
sauropsid body fossil Hylonomus1,2,3,4. The earliest body fossils of
crown-group tetrapods are mid-Carboniferous, and the oldest trackways
are early Carboniferous5,6,7. This suggests that the tetrapod crown
group originated in the earliest Carboniferous (early Tournaisian),
with the amniote crown group appearing in the early part of the late
Carboniferous. Here we present new trackway data from Australia that
challenge this widely accepted timeline. A track-bearing slab from the
Snowy Plains Formation of Victoria, Taungurung Country, securely dated
to the early Tournaisian8,9, shows footprints from a crown-group
amniote with clawed feet, most probably a primitive sauropsid. This
pushes back the likely origin of crown-group amniotes by at least
35rCo40 million years. We also extend the range of Notalacerta into the
early Carboniferous. The Australian tracks indicate that the amniote
crown-group node cannot be much younger than the
Devonian/Carboniferous boundary, and that the tetrapod crown-group
node must be located deep within the Devonian; an estimate based on
molecular-tree branch lengths suggests an approximate age of early
Frasnian for the latter. The implications for the early evolution of
tetrapods are profound; all stem-tetrapod and stem-amniote lineages
must have originated during the Devonian. It seems that tetrapod
evolution proceeded much faster, and the Devonian tetrapod record is
much less complete, than has been thought.

So

Some fish have scales

All living amphibians do not have sales

Some reptiles have scales

Some mammals have hair

So

What was the scale, hair, feather situation for these vertebrates?

Actually, as John Harshman has pointed out, some caecilians (living amphibians) do have scales. The earliest body fossils are from the Carboniferous, and display keratinized (scaly) skin. The Devonian
trackways are just trackways, and the only thing we can say about them
is they had claws (unlike amphibians). The tracks appear to have been
made by sauropsids, I don't know how you could tell synapsids and
sauropsids apart without body fossils, and even then they were probably
very similar.

The earliest unambiguous fossil hair is much later, but therapids ~290
MYa show evidence of whiskers.
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From Newsgroup: sci.bio.paleontology

On 5/14/25 8:01 PM, erik simpson wrote:

The implications for the early evolution of tetrapods are profound; all stem-tetrapod and stem-amniote lineages must have originated during the Devonian. It seems that tetrapod evolution proceeded much faster, and
the Devonian tetrapod record is much less complete, than has been thought.

right - you think we know all we need to from a few dozen fossils
covering more than 100 million years of evolutionary life?
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From Newsgroup: sci.bio.paleontology

On 5/24/25 12:37 PM, Popping Mad wrote:

On 5/14/25 8:01 PM, erik simpson wrote:

The implications for the early evolution of tetrapods are profound; all
stem-tetrapod and stem-amniote lineages must have originated during the
Devonian. It seems that tetrapod evolution proceeded much faster, and
the Devonian tetrapod record is much less complete, than has been thought.

right - you think we know all we need to from a few dozen fossils
covering more than 100 million years of evolutionary life?

We'll probably never have all we need to understand all the details, but
these recent findings certainly help the overall picture.
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