https://europepmc.org/backend/ptpmcrender.fcgi?accid=PMC5664179&blobtype=pdf

I picked up this article sometime ago, intending to read it, but something came up, and I just "rediscovered" i while cleaning up directories. It's the most comprehensive yet study of the phylogeny of ctenophores, and pretty solidly supports Ctenophora as the sister group of all other metazoa. Another notable result is that a number of "traditional" recognized groups are most likely polyphyletic, and a general re-examination of the total group is in order.

Abstract:

Ctenophora, compromising approximately 200 described species, is an important lineage for understanding metazoan evolution and is of great ecological and economic importance. Ctenophore diversity includes species with unique colloblasts used for prey capture, smooth and
striated muscles, benthic and pelagic lifestyles, and locomotion with ciliated paddles or muscular propulsion. However, ancestral states of traits are debated and relationships among many lineages are unresolved. Here,
using 27 newly sequenced ctenophore transcriptomes, publicly available
data, and methods to control systematic error we establish the placement of Ctenophora as the sister group to all other animals and refine phylogenetic relationships within ctenophores.
Molecular clock analyses suggest modern ctenophore diversity originated approximately 350MYA ± 88 MY, conflicting with previous hypotheses of approximately 65 MYA. We recover Ctenophores, or comb jellies, have successfully colonized nearly every marine environmentand can be key species in marine food webs1–6. For example, invasive ctenophores have
caused dramatic fisheries collapses by voraciously preying on native fish larvae and thei food, resulting in the economic loss of millions of US dollars to impacted areas4. Understanding morphological and life history diversity of ctenophores in a comparative context is essential for our knowledge of ctenophore and metazoan diversification as a whole7. Ctenophores have received considerable attention in regard to debate about whether
they are the sister group to all other animals3,5,8–11, but relationships within Ctenophora has been the focus of only limited research3,12,13..
Putative ctenophore fossils date back to the Ediacaran period14 with substantial morphological diversity being present in the Cambrian15,16. All ctenophores possess smooth muscles, and at least one genus,
Euplokamis, has striated muscles17. Most ctenophores possess tentacles (Fig.. 1), but species in the genus Ocyropsis lose tentacles as adults18 and
beroids lack them throughout their life cycle (Fig. 1)1,6. Many species are pelagic, but some are benthic or semi-benthic as adults and can have a relatively flattened body and lose the ciliary comb rose that otherwise characterize the phylum6,19 (Fig. 1). Relationships among
ctenophore lineages remain poorly resolved as past phylogenetic analyses have either had too few taxa to recover broad evolutionary patterns3 or resulted in weak support for the deepest nodes, likely resulting from the use of only one or two genes12,13. Past researchers12,13 have also hypothesized that Ctenophora has undergone a bottleneck in
species diversity, possibly as recently as 65 MYA. However, the age of crown group ctenophores has yet to be estimated with molecular dating methods. Here, we sequenced 27 transcriptomes from species across most of the known phylogenetic diversity of Ctenophora. New sequence data were combined with 10 ctenophore and 50 non-ctenophore publicly
available transcriptomes (Supplementary Tables S1, S2) to clarify the phylogenetic placement of Ctenophora11,20–22. Thus, we performed analyses to determine appropriate outgroups and ctenophore placement among other metazoans using more ctenophore taxa than previous studies3,5,9–11,20 (Supplementary Table S2).

On 4/8/23 19:36, erik simpson wrote:
> Ctenophora, compromising approximately 200 described species, is an important lineage for understanding metazoan evolution and is of great ecological and economic importance.

A whole need Genera to cause me nightmares when I swim in Coney.

>Molecular clock analyses suggest modern ctenophore diversity originated
approximately 350MYA ± 88 MY, conflicting with previous hypotheses of
approximately 65 MYA<

that is a HUGE difference.

On Saturday, April 8, 2023 at 7:03:23 PM UTC-7, Popping Mad wrote:
> On 4/8/23 19:36, erik simpson wrote:
> > Ctenophora, compromising approximately 200 described species, is an important lineage for understanding metazoan evolution and is of great ecological and economic importance.
> A whole need Genera to cause me nightmares when I swim in Coney.
> >Molecular clock analyses suggest modern ctenophore diversity originated
> approximately 350MYA ± 88 MY, conflicting with previous hypotheses of
> approximately 65 MYA<
> that is a HUGE difference.

It is indeed. They do produce the arguments. Most of the previous ctenophore analyses were
of much more limited data sets. This is likely to be controversial for quite some more time. The
idea that sponges represent the most "primitive" form of metazoa life has been around for a while.

On 4/8/23 23:46, erik simpson wrote:
> idea that sponges represent the most "primitive" form of metazoa life has been around for a while.

to get stuck on something that is so much guesswork is pure ego.

On 4/8/23 23:46, erik simpson wrote:
> They do produce the arguments. Most of the previous ctenophore analyses were
> of much more limited data sets.

Jut based on the phenology and simplicity of these creatures, it is a
huge leap to have placed them as late as the Cenozoic for the entire
lineage.

On Sunday, April 9, 2023 at 2:32:43 PM UTC-7, Popping Mad wrote:
> On 4/8/23 23:46, erik simpson wrote:
> > They do produce the arguments. Most of the previous ctenophore analyses were
> > of much more limited data sets.
> Jut based on the phenology and simplicity of these creatures, it is a
> huge leap to have placed them as late as the Cenozoic for the entire
> lineage.

Agreed. I was surprised (shouldn't have been) at the diversity of extant ctenophores, but
the existence of even greater diversity in the Paleozoic suggests something terrible happened.
Sure enough, it did, so the earlier data (poorly constained as it is) still looks more convincing.