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. 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 35–40 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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