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The mysterious ‘Tully Monster’ fossil just got more mysterious

#1
C C Offline
https://theconversation.com/the-mysterio...ous-126531

EXCERPT: . . . Every now and again, scientists discover fossils that are so bizarre they defy classification, their body plans unlike any other living animals or plants. Tullimonstrum (also known as the Tully Monster), a 300m-year-old fossil discovered in the Mazon Creek fossil beds in Illinois, US, is one such creature.

At first glance, Tully looks superficially slug-like. But where you would expect its mouth to be, the creature has a long thin appendage ending in what looks like a pair of grasping claws. Then there are its eyes, which protrude outward from its body on stalks. Tully is so strange that scientists have even been unable to agree on whether it is a vertebrate (with a backbone, like mammals, birds, reptiles and fish) or an invertebrate (without a backbone, like insects, crustaceans, octopuses and all other animals).

[...] The body plan of the Tully Monster is so unusual in it’s entirety that it will greatly expand the diversity of of whatever group it ultimately belongs to, changing the way we think about that group of animals. ... 2016 research argued the animal should be grouped with vertebrates because its eyes contain pigment granules called melanosomes, which are arranged by shape and size in the same way as those in vertebrate eyes.

But our research shows that the eyes of some invertebrates such as octopus and squid also contain melanosomes partitioned by shape and size in a similar way to Tully’s eyes, and that these can also be preserved in fossils... (MORE - details)


https://www.youtube-nocookie.com/embed/frnio8eSFyk
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#2
Yazata Offline
This is really fascinating, thanks for posting it CC.

Here's what Wikipedia has to say about it

https://en.wikipedia.org/wiki/Tullimonstrum

I don't know anything about it, but just from looking at the (apparently very good) Wikipedia article, and at what Google Scholar dredged up, I get the impression that these have been known for sixty years, but only are known from one location (in Illinois) and from one point in time (~300-350 million years ago). But having said that, many fossil examples of them have been found (hundreds) so they are definitely real and really existed (if only briefly in a limited geographical area). They were small things, apparently aquatic bottom feeders, ranging from 3 inches to about a foot long. Their mouths were on peculiar stalks which they presumably stuck into crevices to get at the little things hiding there. And their eyes were on stalks too, which presumably watched and controlled what the mouth was doing. They are the official Illinois state fossil!

They have received a low level of attention for years from paleontologists, but there's only a small and speculative literature about them. (Google scholar only found 178 scholarly publications about Tullimonstrum.) The big question is what their evolutionary affinities are and which existing group of animals they are members of, if any. Were they sea slugs (molluscs)? Were they arthropods? Were they primitive chordates? Or were they something more obscure, related to one of the many small and obscure worm phyla that still exist today? Or are they representatives of some unique lineage of their own that died out? There have apparently been many speculations but nothing solid, and these things have therefore become one of the many minor mysteries of biology.

Then in 2016 there was a burst of news about them in the popular science press. Supposedly the mystery had been solved! The Tully monsters were vertebrates! (Even if they had no vertebra or bones, they belonged to the same general evolutionary group.) Supposedly.

The reason was the eye pigments thing, and the claim that Tully monsters had eye pigments that only vertebrates have.

So that seems to be the context of the news that CC is reporting. The new claim seems to be that the same eye pigments are sometimes found in invertebrates too. Which dramatically weakens the supposed vertebrate affinities trumpeted so loudly in 2016.

Tully monster is a vertebrate! (2016)

https://www.researchgate.net/profile/Jam...28d470.pdf

No it isn't! (2017)

https://ora.ox.ac.uk/objects/uuid:aafebb...al+article

Lots more could be said about how this might arguably illustrate the weakness of phylogenetics based on perceived phenotypic synapomorphies. But that's typically all that paleontology has available. What's really needed are intact sequencible DNA samples of these kind of extinct animal types so that a a genomic analysis could be done, but that's impossible.
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#3
C C Offline
(Nov 15, 2019 05:16 PM)Yazata Wrote: . . . Lots more could be said about how this might arguably illustrate the weakness of phylogenetics based on perceived phenotypic synapomorphies. But that's typically all that paleontology has available. What's really needed are intact sequencible DNA samples of these kind of extinct animal types so that a a genomic analysis could be done, but that's impossible.

Tully might have even been a lingering survivor from some bizarre, unrecognized phylum of the experimental Cambrian Explosion (or even before that era). With any other members of its unknown category largely going extinct early on. Somewhat unconsidered because of survivorship bias and confidence in that rank-level of the current taxonomic system being complete.

Tully supposedly has structure which could be "interpreted as a notochord" (but there's uncertainty about that), which could slot it under chordata (that subsumes vertebrates). But that might be parallel evolution, another notochord-ish imposter like the stomochord of hemichordates. More than thirty other recognized phyla it could contend for a place in, though.
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#4
Zinjanthropos Offline
People don’t believe me when I say science has discovered fossils with evidence of melanosomes and that it’s thought the colours of past animal life may be extracted from them. Very cool science IMO.

Never knew States also have official fossils.
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