https://www.cell.com/current-biology/fulltext/S0960-9822(24)00669-9#%20

A reeaximanation Of Pikaia gracilens leads to a reorganization of stem
chordates, including ventucolians as stem chordates, and adjusted
positions of yunnaozoans and Amphioxus.

I'd include the abstract, but it's graphical.

On 6/12/24 9:35 AM, erik simpson wrote:
> https://www.cell.com/current-biology/fulltext/S0960-9822(24)00669-9#%20
>
> A reeaximanation Of Pikaia gracilens leads to a reorganization of stem
> chordates, including ventucolians as stem chordates, and adjusted
> positions of yunnaozoans and Amphioxus.
>
> I'd include the abstract, but it's graphical.
>
Might as well put in the summary, which is more or less an abstract:

Our understanding of the evolutionary origin of Chordata, one of the
most disparate and ecologically significant animal phyla, is hindered by
a lack of unambiguous stem-group relatives. Problematic Cambrian fossils
that have been considered as candidate chordates include vetulicolians,1
Yunnanozoon,2 and the iconic Pikaia.3 However, their phylogenetic
placement has remained poorly constrained, impeding reconstructions of
character evolution along the chordate stem lineage. Here we reinterpret
the morphology of Pikaia, providing evidence for a gut canal and,
crucially, a dorsal nerve cord—a robust chordate synapomorphy. The
identification of these structures underpins a new anatomical model of
Pikaia that shows that this fossil was previously interpreted upside
down. We reveal a myomere configuration intermediate between amphioxus
and vertebrates and establish morphological links between Yunnanozoon,
Pikaia, and uncontroversial chordates. In this light, we perform a new
phylogenetic analysis, using a revised, comprehensive deuterostome
dataset, and establish a chordate stem lineage. We resolve vetulicolians
as a paraphyletic group comprising the earliest diverging stem
chordates, subtending a grade of more derived stem-group chordates
comprising Yunnanozoon and Pikaia. Our phylogenetic results reveal the
stepwise acquisition of characters diagnostic of the chordate crown
group. In addition, they chart a phase in early chordate evolution
defined by the gradual integration of the pharyngeal region with a
segmented axial musculature, supporting classical
evolutionary-developmental hypotheses of chordate origins4 and revealing
a “lost chapter” in the history of the phylum.

On 6/12/24 9:35 AM, erik simpson wrote:
> https://www.cell.com/current-biology/fulltext/S0960-9822(24)00669-9#%20
>
> A reeaximanation Of Pikaia gracilens leads to a reorganization of stem
> chordates, including ventucolians as stem chordates, and adjusted
> positions of yunnaozoans and Amphioxus.
>
> I'd include the abstract, but it's graphical.
>
Interesting that Pikaia is now reconstructed as having no post-anal tail
and possibly no notochord.

On 6/14/24 10:36 AM, John Harshman wrote:
> On 6/12/24 9:35 AM, erik simpson wrote:
>> https://www.cell.com/current-biology/fulltext/S0960-9822(24)00669-9#%20
>>
>> A reeaximanation Of Pikaia gracilens leads to a reorganization of stem
>> chordates, including ventucolians as stem chordates, and adjusted
>> positions of yunnaozoans and Amphioxus.
>>
>> I'd include the abstract, but it's graphical.
>>
> Interesting that Pikaia is now reconstructed as having no post-anal tail
> and possibly no notochord.
The identification of vetulicolians as stem chordates is also new to me.
Amazing what the inversion of Pikaia has done!