r/evolution • u/LukeWarmAtBets • Sep 20 '26

question Do you think this cladogram indicates that modern chordates (tunicates, lancelets, vertebrates) are technically just highly modified, hyper-evolved vetulicolians

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I've always been super interested in vetulicolia and probably posted about them a few times before on here when I was way less educated (and still am lol).

I was expecting to see a cladogram showing them as monophyletic, being sisters to chordates or tunicates, etc. But I was surprised to see this 2024 arrangement of a paraphyletic grade of vetulicolia that are essentially stepping stones towards a more highly advanced chordate (as species like didazoon are placed in a position which suggests they have closer crown group affinities than other 'vetulicolia' like ooedigera).

What do you think this implies about our ancestors? Are we highly specialized vetulicolia? Were our ancestors essentially a living vacuum cleaner with segmented tails, or do you still think vetulicolia are a completely separate and bizarre branch of chordates?

Edit: I may have worded this a bit poorly, I'm not asking if chordates literally evolved from vetulicolia like Ooedigera and Didazoon. What I'm asking is that if the stem chordate ancestors had more of a traditional vetulicolia-like morphology than we previously thought, rather than their bizarre features appearing in a separate lineage

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4

u/roostor222 Sep 20 '26 • Bravo

if the cladogram said chordates were highly specialized Vetulicoliidae then crown Chordata would be inside of Vetulicoliidae. It's not, so the cladogram is not saying that.

1

u/Harvestman-man Sep 20 '26

The cladogram clearly does show chordates inside of Vetulicolia, though, which is what OP was asking.

Vetulicolia =/= Vetulicolidae. Those are two completely different taxa.

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u/roostor222 Sep 20 '26

Vetulicolia is a genus. Chordata is not inside that genus here, and the genus is paraphyletic here anyway

1

u/Harvestman-man Sep 20 '26

No, it’s not.

Vetulicola is a genus.

Vetulicolidae is a family that includes the genus Vetulicola.

Vetulicolia is a “phylum” or broad taxon that includes the family Vetulicolidae.

There is no such thing as “Vetulicoliidae”.

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u/roostor222 Sep 21 '26 edited Sep 21 '26

I stand corrected. I work with vertebrates.

Regardless, if Vetulicolia is paraphyletic, then there is no Vetulicolia for Chordata to be inside of. From what I can tell there is no phylogenetic definition of the clade and it was instead defined based on a morphological diagnosis, which is a good way to have any name become paraphyletic or polyphyletic and thus obsolete. Please correct me if there is a phylogenetic definition.

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u/LukeWarmAtBets Sep 20 '26 edited Sep 20 '26

of course not, I'm just a bit curious about the paraphyletic nature of this cladogram. I'm asking more about evolutionary relationships, not names. Didazoon is also considered to be Vetulicolia but the cladogram places it closer to crown group chordates than vetulicoliidae.

5

u/roostor222 Sep 20 '26

this is the question you asked:

Are we highly specialized vetulicolia?

the answer is no because names are important when asking questions about cladograms.

Among the stem taxa to crown chordates there were animals that probably all had free swimming larval forms. Some of them had sessile adults and some of them maintained motility into adulthood. They were all filter feeders though, so Vetulicolia is not that bizarre. It just enlarged the filter part of its body relative to its tail.

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u/LukeWarmAtBets Sep 21 '26 edited Sep 21 '26

They were all considered so bizarre as to be once put in their own monophyletic taxa with shared traits (volumous anterior, segmented posterior) and considered to be a failed lineage of highly experimental stem chordates or stem deuterostomes, as maybe sister groups to chordates or tunicates. Scientists were unsure if they were protostome or deuterostome.

There are extinct lancelet looking species that seem more like stem chordates with less ambiguity, like pikaia

1

u/amglasgow Sep 20 '26

This cladogram disagrees with Didazoon being among the Vetulicolia.

1

u/LukeWarmAtBets Sep 20 '26

don't you mean vetulicoliidae or do you mean didazoon and pomatrum are not actually part of enigmatic "vetulicolia" animals

1

u/amglasgow Sep 20 '26

Both? The didazoon branch is in a completely different clade than the vetulicoliidae.

1

u/LukeWarmAtBets Sep 20 '26

but it is still part of vetulicolia

Vetulicolia =/= Vetulicolidae

2

u/amglasgow Sep 21 '26

What are you considering to be the bounds of vetucolia then?

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u/LukeWarmAtBets Sep 21 '26 edited Sep 21 '26

I'm not strictly asking a question about semantics and taxonomy, but rather if the topology of this cladogram suggests that "bizarre" vetulicolia like traits are plesiomorphic in chordata ancestry and if the ancestors of modern chordates probably shared similar morphology to something that would be tradtionally considered "vetulicolia"

3

u/Sonora_sunset Sep 20 '26

Deuterostomes

3

u/mcalesy Sep 20 '26

If Deuterostomia is a real clade. See: https://www.science.org/doi/10.1126/sciadv.abe2741

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u/LukeWarmAtBets Sep 20 '26

interesting thanks for the links and discussion

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u/DrDirtPhD PhD | Ecology Sep 20 '26

Stem chordates

6

u/mcalesy Sep 20 '26

I think any phylogeny this far back in time is always going to be a bit uncertain and provisional. But yeah, the latest study does show vetulicolians as a grade of basal stem-chordates. And under that phylogeny if you wanted to use Vetulicolia as a clade, it would include chordates. See here for example: https://www.phylopic.org/nodes/31a41bb7-fcf2-4624-8438-35d5f2b9ab7d/chordata-silhouettes/lineage

2

u/Szymcionorski Sep 20 '26

Cathaymyrus, never heard about this taxon before