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Ghost lineages!
Topic Started: Jun 21 2017, 06:59 AM (1,828 Views)
Rodlox
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kusanagi
Jul 24 2017, 09:03 AM
n and Tullimonstrum seems to have been a total group craniate nowadays even if other possibilities cannot be rejected out of hand.
turns out, nope, not a craniate.
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kusanagi
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Rodlox
Jul 24 2017, 02:38 PM
kusanagi
Jul 24 2017, 09:03 AM
n and Tullimonstrum seems to have been a total group craniate nowadays even if other possibilities cannot be rejected out of hand.
turns out, nope, not a craniate.
Would you like to expand on that? Admittedly many craniate-type features of Tullimonstrum are consistent with ie. gastropoda, but T, does make good sense as a chordate with a well developed brain compared to the cephalochordates which would place T. somewhere on the craniate line. I do not think T. was a hyperoartian based on assumptions of homologies but it makes most sense as some sort of craniate (yet). As I said there are still problematica but many make more sense than they used to. Remember that if you read a book it tells you a veritable taxonomic roulette of proposed relationships for T. and even that it might be the Loch Ness monster (ghost lineages...) but the plausible list seems narrowed down to just gastropods and craniates at present. Really there needs to be a multi-phylum dataset like Aldridge et al used for the vetulicolidans to test if they are duterostomes.
Edited by kusanagi, Jul 24 2017, 03:21 PM.
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IIGSY
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kusanagi
Jul 24 2017, 02:15 PM
Cyclostomata is an old idea based on developmental data that was rfuted as the progressive loss of cranial elements forsced the reorganisation of skull development in stem gnathostomes. Were cyclostomata monophyletic then even the crownward stem gnathostomes like cephalaspidomorphs would have to be moved out of total group gnathostomes. This is obviously untrue as gnathostomes nest within the cephalaspidomorphs. Hagfish do at least have the genes for vertebrae and both the hagfish and lampreys have the genes neccessary to secrete enamel, but the present state of knowledge is still that hagfish diverged first. As a total group myxinoidea seems to include Palaeospondylus otherwise neither myxinoids nor hyperoartians are definitely pre-Carboniferous. Euphanerops seems to be a stem hyperoartian from the late Devonian and Jamoytius is probably the most stemward of total group gnathostomates which include all of the armoured and scaled agnathans. People like Jarvik talked about a monophyletic cyclostome clade when people still thought caudates might be lungfishes but a lot moved on since then, and it actually is a bit disturbing that many people still treat the molecular evidence as having precedence on this whilst still citing the developmental differences between cyclostome and gnathostome vertebrates as though the evolution of the latter from the former had never been demonstrated by developmental evidence.

https://zoologicalletters.biomedcentral.com/articles/10.1186/s40851-016-0057-0
But hagfish and lampreys share several unique micro-RNAs. Micro RNA are slow evolving and are crucial to relationships. I feel like you underestimate the usefulness of molecular phylogeny.



And since when are vetulicolians khinorhynchs? I have heard of them being arthropods, but khinorhynchs?
Edited by IIGSY, Jul 24 2017, 04:13 PM.
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Nematozoic: After a mass extinction of ultimate proportions, a single species of nematode is the only surviving animal.
Tri-devonian: A devonian like ecosystem with holocene species on three different continents.

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kusanagi
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Jul 24 2017, 03:54 PM
kusanagi
Jul 24 2017, 02:15 PM
Cyclostomata is an old idea based on developmental data that was rfuted as the progressive loss of cranial elements forsced the reorganisation of skull development in stem gnathostomes. Were cyclostomata monophyletic then even the crownward stem gnathostomes like cephalaspidomorphs would have to be moved out of total group gnathostomes. This is obviously untrue as gnathostomes nest within the cephalaspidomorphs. Hagfish do at least have the genes for vertebrae and both the hagfish and lampreys have the genes neccessary to secrete enamel, but the present state of knowledge is still that hagfish diverged first. As a total group myxinoidea seems to include Palaeospondylus otherwise neither myxinoids nor hyperoartians are definitely pre-Carboniferous. Euphanerops seems to be a stem hyperoartian from the late Devonian and Jamoytius is probably the most stemward of total group gnathostomates which include all of the armoured and scaled agnathans. People like Jarvik talked about a monophyletic cyclostome clade when people still thought caudates might be lungfishes but a lot moved on since then, and it actually is a bit disturbing that many people still treat the molecular evidence as having precedence on this whilst still citing the developmental differences between cyclostome and gnathostome vertebrates as though the evolution of the latter from the former had never been demonstrated by developmental evidence.

https://zoologicalletters.biomedcentral.com/articles/10.1186/s40851-016-0057-0
But hagfish and lampreys share several unique micro-RNAs. Micro RNA are slow evolving and are crucial to relationships. I feel like you underestimate the usefulness of molecular phylogeny.



And since when are vetulicolians khinorhynchs? I have heard of them being arthropods, but khinorhynchs?
Too *** right I "underestimate" its usefulness wen it contradicts the other lines of evidence. One is fine with molecular-based arguments if they are backed up with the other lines of evidennce, not simply scouring for one or two potential synapomorphies uniting Afrotheria or such. But one cannot make the argument that molecular phylogenies and the fossil record are usually in agreement, which they are, and then ignore those situations where there is a genuine discord between lines of evidence. Such cases include the supposed clades Afrotheria and Cyclostomata, the placement of brachiozoans as either deuterostomes or spiralians, the mess at the base of the metazoa stemwards of node Bilateria et cetera. Besides you miss the point I made that people still cite developmental characters as evidence for clade Cyclostomata even though this is a disproven hypothesis according to developmental data. Even if molecular data supports the clade the developmntal data does not. You cannot handwavium that laziness or dishonesty about the history of the hypothesis, which comes from lazy attempts at consilience, aka cherry picking, selection bias. Whilst I will not discount molecular data outright I will not be guilty of cherry picking snippets of interest from bodies of data I will not pretend to understand. If there is consilience to be had the lines of evidence will reach it independently without faulty reasoning. Adding molecular frameworks to morphological trees or vice versa is cheating to obtain a preconcieved result.

Yes the vetulicolidans are (probably) closest to kinorhynchs unless you assume questionable organ homologies and the earliest of them like Banffia are the least chordate-like. quite a cautionary tale for Yunnanozoon and Pikaia. The atrium morphology of vetulicolidans is unlike that of urochordates and their anus is in fact terminally placed. Only higher vetulicolidans turn out as tunicate relatives as they move closer to kinorhynchs when basal members of their clade are added to the matrix. As vetulicolida are strongly supported their polyphyly is out of the question. Getting the clade Vetulicolida to return next to tunicates requires more steps or assuming doubtful homologies in fossils. However: "Placement of the vetulicolians in a polytomy with both protostomes and deuterostomes in many of our analyses adds only one step to a position as stem kinorhynchs". All the same they would not be urochordates and kinorhynchs are the most similar living phylum, and if the vetulicolidan fossils do not preserve a tunic they do show something like an ecdysozoan cuticle. So as with the tullimonster and the Ediacaran fronds a phylogenetic placement is not exactly certain yet, but looks vastly more probable now, or at least until better soft tissues preserved actually do confirm a notochord and an endostyle were present after all. And then they will still be a sister group to tunicates that independently evolved a structurally disimilar atrium and had to re-evolve chordate-type gill slits as a reversal.

http://onlinelibrary.wiley.com/doi/10.1111/j.1475-4983.2006.00606.x/full
Edited by kusanagi, Jul 24 2017, 10:01 PM.
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IIGSY
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Oh. Well, lampreys and hagfish do share some morphological features such as a median nostril and pouch shaped gills for what it's worth. Or are these the developmental features you where talking about?
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Punga: A terraformed world with no vertebrates
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ARTH-6810: A world without vertebrates (It's ded, but you can still read I guess)

Potential ideas-
Swamp world: A world covered in lakes, with the largest being caspian sized.
Nematozoic: After a mass extinction of ultimate proportions, a single species of nematode is the only surviving animal.
Tri-devonian: A devonian like ecosystem with holocene species on three different continents.

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kusanagi
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Jul 24 2017, 04:47 PM
Oh. Well, lampreys and hagfish do share some morphological features such as a median nostril and pouch shaped gills for what it's worth. Or are these the developmental features you where talking about?
Cherry picking: lampreys are overall closer to gnathostomes in any cladistic analysis. Example:

Myxini + ((Pteromyzontiformes + Euphanerops) + (Jamoytius + (Anaspida + (Thelodonta + (Pteraspidomorphi + Cephalaspidomorphi)))))

Exact details might differ between analyses but you get the picture. Besides among stem gnathostomes most of them have one external medial nostril. Pouch shaped gills are no biggie either as to determine properly the presence of gill pouches would require soft tissues rarely preserved but "gills of adult cyclostome type and not that found in the ammocete" were identifiable in Jamoytius. That is the gill apparatus of stemward gnathostome ancestorss were cyclostome-type. Jamoytius seems to have a vestigal and displaced annular cartilage suggesting the cyclostome oral apparatus that gave them their name is primitive for all vertebrates. Did stem gnathostomes evolve through neoteny? J. generally resembles an ammocete.

Total group lampreys are present in the Devonian and that of jawed vertebrates in the Silurian. Palaeospondylus may draw back the fossil record of the hagfishes to the Devonian but P. hasn't been included in any cladistic analyses yet. If any such matrix includes euconodonts also then trees ought to be rooted further back than Craniata or Chordata ie. in Pikaia or Yunnanozoon or both given that both are unquestionably outside of crown Chordata but resemble somewhat its LCA.
Edited by kusanagi, Jul 24 2017, 05:31 PM.
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IIGSY
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kusanagi
Jul 24 2017, 05:18 PM
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Jul 24 2017, 04:47 PM
Oh. Well, lampreys and hagfish do share some morphological features such as a median nostril and pouch shaped gills for what it's worth. Or are these the developmental features you where talking about?
Cherry picking: lampreys are overall closer to gnathostomes in any cladistic analysis. Example:

Myxini + ((Pteromyzontiformes + Euphanerops) + (Jamoytius + (Anaspida + (Thelodonta + (Pteraspidomorphi + Cephalaspidomorphi)))))

Exact details might differ between analyses but you get the picture. Besides among stem gnathostomes most of them have one external medial nostril. Pouch shaped gills are no biggie either as to determine properly the presence of gill pouches would require soft tissues rarely preserved but "gills of adult cyclostome type and not that found in the ammocete" were identifiable in Jamoytius. That is the gill apparatus of stemward gnathostome ancestorss were cyclostome-type. Jamoytius seems to have a vestigal and displaced annular cartilage suggesting the cyclostome oral apparatus that gave them their name is primitive for all vertebrates. Did stem gnathostomes evolve through neoteny? J. generally resembles an ammocete.

Total group lampreys are present in the Devonian and that of jawed vertebrates in the Silurian. Palaeospondylus may draw back the fossil record of the hagfishes to the Devonian but P. hasn't been included in any cladistic analyses yet. If any such matrix includes euconodonts also then trees ought to be rooted further back than Craniata or Chordata ie. in Pikaia or Yunnanozoon or both given that both are unquestionably outside of crown Chordata but resemble somewhat its LCA.
I see. Hagfish do have remnants of vertebrae so you could still reasonably call "craniata" vertebrata. But, where does this all this leave Haikouichthys, Myllokunmingia, and Zhongjianichthys?
Edited by IIGSY, Jul 24 2017, 05:35 PM.
Projects
Punga: A terraformed world with no vertebrates
Last one crawling: The last arthropod

ARTH-6810: A world without vertebrates (It's ded, but you can still read I guess)

Potential ideas-
Swamp world: A world covered in lakes, with the largest being caspian sized.
Nematozoic: After a mass extinction of ultimate proportions, a single species of nematode is the only surviving animal.
Tri-devonian: A devonian like ecosystem with holocene species on three different continents.

Quotes


Phylogeny of the arthropods and some related groups


In honor of the greatest clade of all time


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All African countries can fit into Brazil
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kusanagi
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Jul 24 2017, 05:34 PM
kusanagi
Jul 24 2017, 05:18 PM
Insect Illuminati Get Shrekt
Jul 24 2017, 04:47 PM
Oh. Well, lampreys and hagfish do share some morphological features such as a median nostril and pouch shaped gills for what it's worth. Or are these the developmental features you where talking about?
Cherry picking: lampreys are overall closer to gnathostomes in any cladistic analysis. Example:

Myxini + ((Pteromyzontiformes + Euphanerops) + (Jamoytius + (Anaspida + (Thelodonta + (Pteraspidomorphi + Cephalaspidomorphi)))))

Exact details might differ between analyses but you get the picture. Besides among stem gnathostomes most of them have one external medial nostril. Pouch shaped gills are no biggie either as to determine properly the presence of gill pouches would require soft tissues rarely preserved but "gills of adult cyclostome type and not that found in the ammocete" were identifiable in Jamoytius. That is the gill apparatus of stemward gnathostome ancestorss were cyclostome-type. Jamoytius seems to have a vestigal and displaced annular cartilage suggesting the cyclostome oral apparatus that gave them their name is primitive for all vertebrates. Did stem gnathostomes evolve through neoteny? J. generally resembles an ammocete.

Total group lampreys are present in the Devonian and that of jawed vertebrates in the Silurian. Palaeospondylus may draw back the fossil record of the hagfishes to the Devonian but P. hasn't been included in any cladistic analyses yet. If any such matrix includes euconodonts also then trees ought to be rooted further back than Craniata or Chordata ie. in Pikaia or Yunnanozoon or both given that both are unquestionably outside of crown Chordata but resemble somewhat its LCA.
I see. Where does that leave Haikouichthys, Myllokunmingia, and Zhongjianichthys?
Stemwards. And the later Metaspriggina is stemward of crown craniates too. From their combined data Janvier managed to reconstruct the likeliest appearence and function of the first craniates. Tullimonstrum is likeliest evolved from the same grade but specialised in an alternative direction, presuming T. is not a gastropod of some kind as some of the anatomical traits preserved are equivocal.

Palaeospondylus preserves vertebrae if you don't know.
Edited by kusanagi, Jul 24 2017, 05:43 PM.
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kusanagi
Jul 24 2017, 05:41 PM
Insect Illuminati Get Shrekt
Jul 24 2017, 05:34 PM
kusanagi
Jul 24 2017, 05:18 PM
Insect Illuminati Get Shrekt
Jul 24 2017, 04:47 PM
Oh. Well, lampreys and hagfish do share some morphological features such as a median nostril and pouch shaped gills for what it's worth. Or are these the developmental features you where talking about?
Cherry picking: lampreys are overall closer to gnathostomes in any cladistic analysis. Example:

Myxini + ((Pteromyzontiformes + Euphanerops) + (Jamoytius + (Anaspida + (Thelodonta + (Pteraspidomorphi + Cephalaspidomorphi)))))

Exact details might differ between analyses but you get the picture. Besides among stem gnathostomes most of them have one external medial nostril. Pouch shaped gills are no biggie either as to determine properly the presence of gill pouches would require soft tissues rarely preserved but "gills of adult cyclostome type and not that found in the ammocete" were identifiable in Jamoytius. That is the gill apparatus of stemward gnathostome ancestorss were cyclostome-type. Jamoytius seems to have a vestigal and displaced annular cartilage suggesting the cyclostome oral apparatus that gave them their name is primitive for all vertebrates. Did stem gnathostomes evolve through neoteny? J. generally resembles an ammocete.

Total group lampreys are present in the Devonian and that of jawed vertebrates in the Silurian. Palaeospondylus may draw back the fossil record of the hagfishes to the Devonian but P. hasn't been included in any cladistic analyses yet. If any such matrix includes euconodonts also then trees ought to be rooted further back than Craniata or Chordata ie. in Pikaia or Yunnanozoon or both given that both are unquestionably outside of crown Chordata but resemble somewhat its LCA.
I see. Where does that leave Haikouichthys, Myllokunmingia, and Zhongjianichthys?
Stemwards. And the later Metaspriggina is stemward of crown craniates too. From their combined data Janvier managed to reconstruct the likeliest appearence and function of the first craniates. Tullimonstrum is likeliest evolved from the same grade but specialised in an alternative direction, presuming T. is not a gastropod of some kind as some of the anatomical traits preserved are equivocal.

Palaeospondylus preserves vertebrae if you don't know.
Since hagfish have remnants of vertebra and palaeospondylus is definitely a vertebrate, is there any functional difference between vertebrata and craniata? And if tullimonstrum is really a stem craniate, then what is that claw thing? Is that it's mouth? Sorry if I seem ignorant.
Projects
Punga: A terraformed world with no vertebrates
Last one crawling: The last arthropod

ARTH-6810: A world without vertebrates (It's ded, but you can still read I guess)

Potential ideas-
Swamp world: A world covered in lakes, with the largest being caspian sized.
Nematozoic: After a mass extinction of ultimate proportions, a single species of nematode is the only surviving animal.
Tri-devonian: A devonian like ecosystem with holocene species on three different continents.

Quotes


Phylogeny of the arthropods and some related groups


In honor of the greatest clade of all time


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Other cool things


All African countries can fit into Brazil
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kusanagi
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Jul 24 2017, 06:07 PM
kusanagi
Jul 24 2017, 05:41 PM
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Jul 24 2017, 05:34 PM
kusanagi
Jul 24 2017, 05:18 PM
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Jul 24 2017, 04:47 PM
Oh. Well, lampreys and hagfish do share some morphological features such as a median nostril and pouch shaped gills for what it's worth. Or are these the developmental features you where talking about?
Cherry picking: lampreys are overall closer to gnathostomes in any cladistic analysis. Example:

Myxini + ((Pteromyzontiformes + Euphanerops) + (Jamoytius + (Anaspida + (Thelodonta + (Pteraspidomorphi + Cephalaspidomorphi)))))

Exact details might differ between analyses but you get the picture. Besides among stem gnathostomes most of them have one external medial nostril. Pouch shaped gills are no biggie either as to determine properly the presence of gill pouches would require soft tissues rarely preserved but "gills of adult cyclostome type and not that found in the ammocete" were identifiable in Jamoytius. That is the gill apparatus of stemward gnathostome ancestorss were cyclostome-type. Jamoytius seems to have a vestigal and displaced annular cartilage suggesting the cyclostome oral apparatus that gave them their name is primitive for all vertebrates. Did stem gnathostomes evolve through neoteny? J. generally resembles an ammocete.

Total group lampreys are present in the Devonian and that of jawed vertebrates in the Silurian. Palaeospondylus may draw back the fossil record of the hagfishes to the Devonian but P. hasn't been included in any cladistic analyses yet. If any such matrix includes euconodonts also then trees ought to be rooted further back than Craniata or Chordata ie. in Pikaia or Yunnanozoon or both given that both are unquestionably outside of crown Chordata but resemble somewhat its LCA.
I see. Where does that leave Haikouichthys, Myllokunmingia, and Zhongjianichthys?
Stemwards. And the later Metaspriggina is stemward of crown craniates too. From their combined data Janvier managed to reconstruct the likeliest appearence and function of the first craniates. Tullimonstrum is likeliest evolved from the same grade but specialised in an alternative direction, presuming T. is not a gastropod of some kind as some of the anatomical traits preserved are equivocal.

Palaeospondylus preserves vertebrae if you don't know.
Since hagfish have remnants of vertebra and palaeospondylus is definitely a vertebrate, is there any functional difference between vertebrata and craniata? And if tullimonstrum is really a stem craniate, then what is that claw thing? Is that it's mouth? Sorry if I seem ignorant.
To save typing them out Løvtrup's list is on wikipedia on the entry for Craniate. It is not perfect as there is some question as to there is a region in the brain of hagfishes that corresponds to the cerebellum of gnathostomes.

https://link.springer.com/chapter/10.1007/978-94-011-5834-3_29

The hard parts of Palaeospondylus are reckoned as calcified cartilages and similar tissue is seen in the early hyperoarian Euphanerops. The proboscis of Tullimonstrum is probably the mouth yes. T. diverged before the cyclostome grade (if it is a craniate and not a gastropod).

Metaspriggina + Haikouichthys + Myllokunmingia + Zhongjianichthys ?+ Tullimonstrum + ((Myxini ?+ Palaeospondylus) + ((Hyperoartia + Euphanerops) + (Jamoytius + (Anaspida + (Thelodonti + (Pteraspidomorphi + (Galeaspida + ((Osteostraci + Pituriaspida) + (Brindabellaspida + (Antiarchi + (?Wuttagonaspis + (*Petalichthyida + (Acanthothoraciformes + (Arthrodira + (Entelognathus + (Chondrichthyes + Osteichthyes))))))))))))))))

*may be paraphyletic.

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0163157

Thinking about crown gnathostomes after thinking about the cladistian ghost ineage and Jarvik's odd phylogenetic theories which were often fringe even then. Jarvik was one of the few who recognised acanthodians as close to elasmobranchs but his other theories didn't pan out that well - amphibian diphyly within rhipidistia, lungfish without porolepiformes as close to elasmobranchs (dipnoi + holocephali + elasmobranchi + "placodermi"), bichirs as crossopterygians (polypteriformes + actinistia + rhipidistia). But the thing is its easy to make a list of characters shared by primitive sarcopterygians (Dipnoi) and primitive chondrichthyeans (Holocephali) or between even more primitive chondrichthyeans ("acanthodians"), primitive actinopterygians (Cladistia) and tetrapods. Jarvik's views on specific homologies might stand up better, ie. the mammalian ear as a spiracle but, Zhu et al 1999 produce a tree in which Psarolepis, Cheirolepis and Polypterus are all stemward sarcopterygians. They note that "The position of Polypterus calls for further study, and the impact of data sampling and character coding on osteichthyan phylogeny deserves more attention." Quite though later studies including psarolepids and polypteriformes do not recover this result, there is now a question mark replaced over polypteriformes and Cheirolepis. Regardless the polypteriformes are so close to the first bony fish they resemble the LCA despite their late Mesozoic first appearence and still similar to even cartilaginous fishes somewhat. A classic ghost lineage of around 300 million years or so.
Edited by kusanagi, Jul 24 2017, 09:51 PM.
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Is there any diagram reconstructing what the skeleton/skull of tullimonstrum might have looked like?

And when where cambroernids considered close to brachiopods? I always remembered them being ambulocrarians.

And if conodonts aren't particularly close to vertebrates, then where do they fall within chordates?
Projects
Punga: A terraformed world with no vertebrates
Last one crawling: The last arthropod

ARTH-6810: A world without vertebrates (It's ded, but you can still read I guess)

Potential ideas-
Swamp world: A world covered in lakes, with the largest being caspian sized.
Nematozoic: After a mass extinction of ultimate proportions, a single species of nematode is the only surviving animal.
Tri-devonian: A devonian like ecosystem with holocene species on three different continents.

Quotes


Phylogeny of the arthropods and some related groups


In honor of the greatest clade of all time


More pictures


Other cool things


All African countries can fit into Brazil
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kusanagi
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Jul 24 2017, 07:28 PM
Is there any diagram reconstructing what the skeleton/skull of tullimonstrum might have looked like?

And when where cambroernids considered close to brachiopods? I always remembered them being ambulocrarians.

And if conodonts aren't particularly close to vertebrates, then where do they fall within chordates?
Craniate affinity of Tullimonstrum is based on the brain development rather than a skull per se. If T. is a chordate it is not a cephalochordate or a urochordate. Euconodonts are simply a part of a messy Chordata (euconodonta + cephalochordata + urochordata + craniata + Cathaymyrus). Morphological data usually suggest urochordates are the outgroup to cephalochordata + craniata, if so then euconodonts would at least be closer to vertebrate origins than are urochordates. No one has placed the euconodonts in a cladistic analysis with character states corrected that allows them to be anything other than chordates but it is doubtful they are not.

Brachiopods are interpreted as deuterostomes by cladistics using morphological datasets and the lophophore of brachiozoans is not developmentally spiralian because the mesosomal tentacle crowns of hemichordates and brachiozoans share upstream-collecting ciliary bands with monociliate cells unlike those of entoprocts which have tentacles without coelomic canals and with a downstream-collecting ciliary system like that of trochophore larvae as well as the adults of rotifers and "tube worm" annelids (Nielsen). Lophophores cannot possibly be homologous. Though morphological characters do not support Protostomia anything like as strongly as the molecular data this is the only real conflict between the datasets, that brachiozoans share too many traits with ambulacrarians (drawing in the cambroernids which have siilarities to both). Rest of protostomes divide neatly into Spiralia and Ecdysozoa as in molecular trees plus the stray chaetognaths.
Edited by kusanagi, Jul 24 2017, 09:54 PM.
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Rodlox
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Insect Illuminati Get Shrekt
Jul 24 2017, 07:28 PM
Is there any diagram reconstructing what the skeleton/skull of tullimonstrum might have looked like?
I would think that if it was going to be done, those reconstructions would have followed the temporary placement of Tully Monster as a lamprey.

(also, Kusanagi, what did you mean by *** ?)
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"Marsupialless Australia" (what-if) & "Out on a Branch" (future evolution) & "The Earth under a still sun" (WIP)
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kusanagi
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Rodlox
Jul 24 2017, 09:39 PM
Insect Illuminati Get Shrekt
Jul 24 2017, 07:28 PM
Is there any diagram reconstructing what the skeleton/skull of tullimonstrum might have looked like?
I would think that if it was going to be done, those reconstructions would have followed the temporary placement of Tully Monster as a lamprey.

(also, Kusanagi, what did you mean by *** ?)
It is not a lamprey but the critique merely questioned the supposed homologies one by one and corrected the matrix to remove over-optimism in the search for homologies. Incidentally another Mazon Creek problematicum, Typhloesus, also has similarities to gastropods and chordates but in this case it is too different to be either.
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IIGSY
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kusanagi
Jul 24 2017, 09:04 PM
Brachiopods are interpreted as deuterostomes by cladistics using morphological datasets and the lophophore of brachiozoans is not developmentally spiralian because the mesosomal tentacle crowns of hemichordates and brachiozoans share upstream-collecting ciliary bands with monociliate cells unlike those of entoprocts which have tentacles without coelomic canals and with a downstream-collecting ciliary system like that of trochophore larvae as well as the adults of rotifers and "tube worm" annelids (Nielsen). Lophophores cannot possibly be homologous. Though morphological characters do not support Protostomia anything like as strongly as the molecular data this is the only real conflict between the datasets, that brachiozoans share too many traits with ambulacrarians (drawing in the cambroernids which have siilarities to both). Rest of protostomes divide neatly into Spiralia and Ecdysozoa as in molecular trees plus the stray chaetognaths.
Aren't morphological characters more subject to convergent evolution than molecular ones? Because that would mean molecular takes priority when the two come into conflict.

Brachiopods are just one of several groups of protostomes that undergo dueterostome like embryonic development. The molecular data overwhelmingly points to them being protostomes. How do you account for this?
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Punga: A terraformed world with no vertebrates
Last one crawling: The last arthropod

ARTH-6810: A world without vertebrates (It's ded, but you can still read I guess)

Potential ideas-
Swamp world: A world covered in lakes, with the largest being caspian sized.
Nematozoic: After a mass extinction of ultimate proportions, a single species of nematode is the only surviving animal.
Tri-devonian: A devonian like ecosystem with holocene species on three different continents.

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Phylogeny of the arthropods and some related groups


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