Solnhofen avialans likely all Archaeopteryx (free pdf)

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

A new paper:

Free pdf:

Jingmai O’Connor & Jesús Marugán-Lobón (2026)
Evaluating variation in Solnhofen avialans
Biology Letters 22(3): 20250601
doi: https://doi.org/10.1098/rsbl.2025.0601
https://royalsocietypublishing.org/rsbl/article/22/3/20250601/481026/Evaluating-variation-in-Solnhofen-avialans


As the oldest known fossil bird, Archaeopteryx is pivotal to the study of avian origins. Fifteen avialan fossils have been described from the Upper Jurassic Solnhofen Limestones, 14 of which have been referred to Archaeopteryx. Recently, this sample has been hypothesized to include archaeopterygids, non-archaeopterygid avians and anchiornithines, although interpretations concerning newly erected non-archaeopterygid avialans have not been critically examined, and currently, there is no taxonomic consensus. Morphometrics, as a powerful tool for understanding variation within a sample, can recognize non-random patterns that can support taxonomic hypotheses. Here, we analyse linear skeletal measurements from all Solnhofen avialans and compare them to the non-avian avialan Anchiornis. Results strongly suggest all Solnhofen avialans belong to a single taxon conforming to a growth curve. If more than one taxon is represented within the sample, these taxa are proportionately indistinguishable when growth is considered. Results also indicate that, while the forelimb becomes proportionately longer with increasing maturity, the opposite pattern is observed in Anchiornis, supporting interpretations that anchiornithines are non-volant. We examine the validity of the genera Ostromia and Alcmonavis and argue that purported diagnostic features do not provide robust support for their distinctiveness. Our results suggest that all known Solnhofen avialans represent Archaeopteryx.
===

[Tim Williams]

Quick thoughts, in no particular order:

* I really like the hypothesis that _Archaeopteryx_ gets longer forelimbs as it gets older (and therefore larger), whereas _Anchiornis_ gets longer hindlimbs.  Plus, in the authors' words, "Compared to _Archaeopteryx_, sampled _Anchiornis_ specimens show much greater proportional variation, not falling along a tight regression like _Archaeopteryx_ (figure 1) and also observed in _Confuciusornis_ [41]. We suggest this is also the result of locomotor

differences, in which the proportions of the volant _Archaeopteryx_ (and _Confuciusornis_) are more constrained by the biomechanics of aerodynamic locomotion."  This rings true to me.  I wonder where _Microraptor_ falls out.  Since it's quite likely that it could fly, it should be more like _Archaeopteryx_/_Confuciusornis_ than _Anchiornis_.

All this provides further support for _Anchiornis_ being non-volant (i.e., did not glide and did not fly), and that its pennaceous plumage was not aerodynamic.  This is supported by a raft of recent studies.  The disagreement now is over whether _Anchiornis_ is secondarily flightless.

* Defining Aves as a node-based clade that includes the common ancestor of _Archaeopteryx_ and _Passer_ and all its descendants makes sense.  It conforms to historical usage.  (The name Ornithes was previously proposed for this _Archaeopteryx_-based clade, but sadly never really took off - no pun intended.)  

I gather that Avialae is defined here as a stem-based clade that includes crown birds (Neornithes) but not _Deinonychus_.  Under certain topologies, Avialae and Aves would have the same content (and Aves would get priority).  And if _Archaeopteryx_ turns out to be a deinonychosaur, then Avialae would be a less inclusive clade inside Aves.

* If _Ostromia_ and _Alcmonavis_ are indeed referable to _Archaeopteryx_, then they add to the long tally of junior synonyms:

Objective junior synonyms: _Griphosaurus_ Wagner, 1862; _Griphornis_ Woodward, 1862.

Subjective junior synonyms: _Archaeornis_ Petronievics, 1917; _Jurapteryx_ Howgate, 1984; _Wellnhoferia_ Elzanowski, 2001; _Ostromia_ Foth and Rauhut, 2017; _Alcmonavis_ Rauhut, Tischlinger, and Foth, 2019.

--
You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingG...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CAMR9O1%2Bz2CJMMBg9cmtbYtbo3vYoWUwh%3DLvJb%2BGpnQSoRQncSQ%40mail.gmail.com.

[Mickey Mortimer]

"Defining Aves as a node-based clade that includes the common ancestor of _Archaeopteryx_ and _Passer_ and all its descendants makes sense."

But that's not what PhyloCode decided, and if we're not following them for phylogenetic definitions, it's just anarchy.

"Under certain topologies, Avialae and Aves would have the same content (and Aves would get priority)"

Can't happen since one is node-based and the other stem-based. Even if Archaeopteryx is the earliest branching avialan known, Aves would still be a separate, less inclusive clade than Avialae.

As a lumper, I like the basic conclusion (and Alcmonavis does resolve within Archaeopteryx in the Lori matrix, though Ostromia does not). But I do wonder why so few Anchiornis were used. Where's 41HIII 0404 and 0415 (Guo et al., 2018), BMNHC Ph 828 (Li et al., 2010) and YFGP-T5199 (Lindgren et al., 2015)? And if an argument is "Anchiornis specimens cluster distinctly and separately from all Solnhofen avialans, including the Haarlem specimen which clusters with other Archaeopteryx, indicating that morphometrics do not support the hypothesis that Ostromia represents a distinct taxon and a non-avian anchiornithine avialan", then Aurornis, Eosinopteryx, Serikornis and Caihong should have been included because these results only support that the Haarlem specimen (Ostromia) isn't Anchiornis, not that it isn't an anchiornithine.  I'd also be curious to see where Fujianvenator and Baminornis go.

Mickey Mortimer

[Tim Williams]

Mickey Mortimer <therizino...@gmail.com> wrote:

> "Defining Aves as a node-based clade that includes the common ancestor of _Archaeopteryx_ and _Passer_ and all its descendants makes sense."
>
> But that's not what PhyloCode decided, and if we're not following them for phylogenetic definitions, it's just anarchy.

Nevertheless, there is currently inconsistency in how Aves is applied: crown group (per PhyloCode) vs the "_Archaeopteryx_ node".  So something isn't working.

When defining Aves as the crown group, Clarke &c recognized that "None of the uses of the name Aves is optimal in all respects. Exclusion of _Archaeopteryx lithographica_ from Aves is disruptive given that this species was included in that taxon by many authors for more than 150 years".  

> "Under certain topologies, Avialae and Aves would have the same content (and Aves would get priority)"
>
> Can't happen since one is node-based and the other stem-based. Even if Archaeopteryx is the earliest branching avialan known, Aves would still be a
> separate, less inclusive clade than Avialae.

In theory.  But in practice we can only work with the taxa we have.  As clades, it is possible for Avialae and Aves to include the same known taxa, and not be synonymous.

[Mickey Mortimer]

"So something isn't working."

That would be papers like this one not following the PhyloCode. I'm no fan of e.g. Archosauromorpha being  (Gallus gallus + Alligator mississippiensis + Mesosuchus browni + Trilophosaurus buettneri + Prolacerta broomi + Protorosaurus speneri) instead of what PhyoCode defines as Pan-Archosauria, but I changed The Theropod Database to reflect it. Just takes some humility.

Mickey Mortimer

[Gregory Paul]

Putting the classic Archie specimens in one genus makes sense. Possibility of multiple species is quite high because of the variation, and the specimens span from the middle to the late Kimmeridgian, about 2 million years. Sorting it all out is difficult because of small sample, and damage and missing parts in the fossils. 

The big problem is Alcomonavis. The central finger base is very broad, a classic avian feature for firmly anchoring the primaries otherwise not seen until sinornithosaurs. That breadth being due to crushing is a stretch. And it is late appearing. 

GSPaul

[Scott Hartman]

Sigh - there is zero good reason to not go with the crownclade defintion of Aves. It's clearly what Linnaeus intended, which should be reason enough. It's also the Phylocode definition, and the history of Archaeopteryx studies are littered with misinterpretations where authors tried to pull crown-clade assumptions down to the "first bird."

| > "Exclusion of _Archaeopteryx lithographica_ from Aves is disruptive given that this species was included in that taxon by many authors for more than 150 years".  

Sure, but it's wrong. Reclassifying Pluto as a dwarf planet was disruptive to the designation of it being called a planet, but scientists should be able to adapt as more information comes out. There is absolutely nothing special about the "birdiness" of Archaeopteryx, the name was due to both an accident of history, and it occuring in a time period when cultural inertia made it impossible to comprehend feathered non-birds. We know better now, so we should use the more useful definition that also happens to match the original definition of Aves, and the most important modern phylogenetic taxonomy revision.

-Scott

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/296632706.483105.1774615027718%40mail.yahoo.com.

--

Scott Hartman, PhD
Teaching Faculty III 

Department of Integrative Biology

UW-Madison
(608) 620-4030
www.skeletaldrawing.com

[Tristan Stock]

Have to agree heavily with Mickey and Scott here. Trying to preserve an outdated conception of a clade is never a good look, and a crown definition better represents the original descriptions of various groups by Linnaeus, who was not particularly concerned with fossil taxa nor had any way to know about the myriad of Mesozoic toothed forms of birds we know about today.

Why do we preserve the very loose Archaeopteryx-rooted definition that is younger than the Linnaeus model just because “it’s been used for 150 years?” Greeks and Romans had a loose definition of bird that broadly matched the Linnaeus definition, and those were used for hundreds to thousands of years. They have a way longer-running precedent. Not to mention all the other historical cultures on Earth with their own definitions of bird that also better match the crown definition. None of these people knew about Archaeopteryx, Hesperornis, etc.

This also feels like a uniquely made-up bird paleontology problem. Please correct me if I’m unaware, but nobody seems to be fighting desperately to preserve a definition of Mammalia that keeps things like tritylodontids in the crown, despite ~120 years of similar literature baggage. Archaeopteryx is an important taxon, but if Anchiornis was discovered and described before Archaeopteryx as the “first bird”, would people be arguing for a definition that must include the Yanliao and Jehol Taxa? What if it was Microraptor? Most people that work on birds do not concern themselves with the taxonomic placement of fossil stem taxa, and a “crown” definition like this just makes it more awkward for the majority of ornithological work.

Just my 2 cents.

- Tristan

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CAN5CYQ3_jDfmuTEgR6X%2B0iTtih3twGmbGbuUdjEGQ0bK5GmtQw%40mail.gmail.com.

[Jerry Harris]

>> Sigh - there is zero good reason to not go with the crownclade defintion of Aves. It's clearly what Linnaeus intended

Honestly, I think this is horse hockey (to quote Col. Potter). Linnaeus and most people in Linnaeus' time were unaware of fossils, and everyone was unaware of their meaning in an evolutionary sense. Linnaeus stuck with extant organisms because that's all he knew about. If Linnaeus had been aware of Archaeopteryx, I am quite certain that he would've happily placed it into his Aves, although certainly in it's own family within that. Being of a typological mind, he would've seen the feathers and placed it with all other birds, and he probably would've done the same for the various other pennaraptoran theropods, and maybe more.

I'm not saying that using a crown-clade definition for Aves isn't viable or useful; only that the justification for doing so as "that's what Linnaeus wanted" is crappy. Linnaeus very unfortunately left us with a classification system that, in light of the current state of the fossil record and the understanding of evolution, requires drawing totally arbitrary lines between groups. 

On a personal note, I despise the "Linnaean names should be restricted to crown clades only" logic—I think it is drawing arbitrary lines in a poor places. I liked it much better when the arbitrary line for "bird & non-bird" was at Archaeopteryx, the arbitrary line between "croc & non-croc" was at the Protosuchus level (now Crocodyliformes), and the arbitrary line between "mammal & non-mammal" was somewhere around the Morganucodon & Sinoconodon level (now Mammaliformes). 

I think the "crown-clade only" folks did scientific communication a real disservice—I am not certain that this was a consideration in their deliberations and decisions at all. Here we are 30-ish years after the "crown-clade concept" really began to take hold, and it's still really a pain in the ass to try to talk to people, and especially to teach students, that Archaeopteryx isn't a bird, docodonts and such aren't mammals, and Goniopholis and such aren't crocs, and that there are bird-like, mammal-like, and croc-like things that don't fall into those categories. Does using crown clade definitions bring a form of stability? Of course, but so would drawing the lines anywhere else, such as where they had been for 120+ years since the discovery of Archaeopteryx. Do I teach these things the right way? Mostly, yes, except when being correct is far too time consuming, and then I'll just call Archaeopteryx and everything crownward of that Aves because it's a LOT easier for non-scientists to grasp, and a LOT less time-consuming to explain. In this respect, I agree with O'Connor et al in trying to severely limit what can be a non-avian avialan, and return Archaeopteryx, Confuciusornis, enantiornithians, etc. to their status as birds.

Now comes the "just move the application of 'bird' to Avialae and problem solved!" arguments. So the logic behind that is: we can arbitrarily redefine common words, but not scientific ones? If Linnaeus intended his names to apply only to crown clades, then "bird" has to stick with "Aves"—it's hypocritical to think one of those words is malleable and moveable and the other isn't. 

Am I biased by my understanding of "bird," "croc," and "mammal" from my pre-PhyloCode days? Almost certainly.

Now get off my lawn, you young whippersnappers!

[Meig Dickson]

Look, speaking as a paleornithologist, at the end of the day: it's arbitrary. 

All of these are names that we give to concepts in nature in order to communicate about them, nothing more, nothing less. To act as if they reflect some sort of fundamental reality is just silliness. 

The truth is, the entire total-group Aves are all, by definition, more like modern birds than like any other group of living Sauropsids. That's what Avemetatarsalia is. Sure, no one looking at an Aphanosaur would say "Bird!", but your average uniformed shmuck seeing a Microraptor would. 

The problem with insisting on Avialae as the definition of "bird" is that it ignores the nuance and allows historical bias to take precedence over nomenclatural clarity. We only think of Archaeopteryx as the first "bird" because we have been calling it that for centuries. But there are other Avialans older than Archaeopteryx, and more to the point, the non-avialan dinosaurs most closely related to Archaeopteryx are almost as birdy as it is - and the nuanced differences in that birdiness would not have mattered if some non-neornithine dinosaurs had made it to the modern day. They would have been grouped with birds. 

The only points in that spectrum that aren't arbitrary cutoffs are Avemetatarsalia and Neornithes. Everything in between is just us picking a particular feature and going "THAT'S what makes a bird a bird!" But to the feathered weirdos of the Yixian, the differences were not worth mentioning. They were all small, feathered, agile dinosaurs, and many - but not all - could fly. We could have decided long bony tails were the cutoff and count Confuciusornis but not Archaeopteryx, but we didn't. 

And before someone comes in with "flight is a non-arbitrary start point", I will simply point out how much flight is lost in many groups of birds and, thanks to the discoveries of species such as Yi qi, was clearly evolved in a complex and non-linear manner in stem-avians. Furthermore, given the consensus that Pterosaurs belong in Avemetatatarsalia, I don't think "flight" is the hill one wants to die on, here. 

Finally, the fact that only crown-avians (ignore Qinornis) survived the end-Cretaceous extinction points to Neornithes as a clear cutoff for "bird". Not because of Linnaeus - that would still be letting the biases of the past influence scientific progress - but because it turns "bird" into a category that means, specifically, those Avemetatarsalians that survived into the Cenozoic. The end. That isn't arbitrary, it's a dramatic event in Avemetatarsalian evolution that changed the course of it forever. 

You can call any animal more closely related to modern birds than to modern crocodilians a "bird" if you want to. And I enjoy saying Argentinosaurus is the largest bird, not only to mess with people, but because the traits that enabled gigantism in sauropods also enabled flight in birds. But at the end of the day, there is a single cutoff point: what survived the end-Cretaceous. And for that, the answer is Neornithes, and Neornithes alone. 

~ Meig 

Meig Dickson

PhD Student, Houde & Orr Labs

Paleobiology, Department of Biological Sciences

New Mexico State University

---

From: dinosaurma...@googlegroups.com <dinosaurma...@googlegroups.com> on behalf of Jerry Harris <dino...@gmail.com>
Sent: Friday, March 27, 2026 10:15
To: Dinosaur Mailing Group <dinosaurma...@googlegroups.com>
Subject: Re: [DMG] Solnhofen avialans likely all Archaeopteryx (free pdf)

 

WARNING This email originated external to the NMSU email system. Do not click on links or open attachments unless you are sure the content is safe.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/befae264-7b48-4e84-854e-b5d2febb5954n%40googlegroups.com.

[Scott Hartman]

I have to respectfully disagree Jerry,

While of course Linnaeus didn't know about fossils, surely defining his taxa based on "how he might have defined them if he had more knowledge" is a fools errand? And we've long kept Linnaen-era names while rejecting the system, so why would that impact his systematic definitions and not others?

Obviously your personal preference is your own, but I fundamentally reject the idea that crown-clades negatively impact outreach and education. Like many of you I've done outreach at all ages and educational levels, and teach for a living. In my case it's almost entirely evolution-based courses, including an undergraduate course on dinosaurs twice a year, and I've never found difficult to explain that Archaeopteryx isn't a bird. In my experience it often results in thoughtful questions about what it means to name groups of organisms. What is confusing is why if Archaeopteryx is a bird Anchiornis or Microraptor aren't. Once the definition is no longer based on objective knowledge (we know crown-clade inferences apply plesiomorphically to all members), you are instead using degree of perceived similarity (or picking one historical name argument event over another). 

I would counter that superficial similarity ("is it birdy enough, or croc-like enough?")-style definitions actually harm students' understanding of evolution and the fossil record. Any clade in a well-sampled part of the tree will have outgroup OTUs that look very much like basal members within that clade - how else could it work? Stretching a clade defintion to cover all taxa someone feels are "enough like the crown" just results in moving the defintion to where there's a sufficiently large gap in the fossil record for now, which turns systemmatics into a clade-of-the-gaps system.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/befae264-7b48-4e84-854e-b5d2febb5954n%40googlegroups.com.

[Gregory Paul]

Jerry has a point. 

Take prosauropods. There is not entry for this major group in Wikipedia. Only as a subset among the clunky jargon termed sauropodomorphs. Meanwhile crown sauropods get their own big entry. Thecodonts that I grew up with are pretty much gone, while crown dinosaurs exist. This leaves archosaurs that are not dinosaurs a vaque collection of groups most folks have no idea what they are. Meanwhile therapsids which now include mammals does get a Wiki entry, but the crown mammals are oddly barely there. Now pterosaurs that are not crown pterodactyloids are nonpterodactyloids. 

All this is real pain to explain to nonexperts to whom it comes across as those paleoelites not caring about making the scheme easy for outsiders understand, as per other professional fields such as law. And by the way if you want to kill sales of your book on sauropodomorphs title it after that, I not being dumb named by book Sauropods and Prosauropods. 

Grade is very real. Battlecruisers are not battleships, even through there is some overlap. Cumulus clouds are not cumulonimbus although the boundary between them is arbitrary. Crown groups are themselves arbitrary because they are accidents of being named here in the Holocene, or were the last members of a clade to have gone extinct, leaving clades that did not make it to the end of the clade or to today in the taxonomic lurch for no good scientific reason. 

Prosauropods. Sauropodomorphs that are not sauropods. Thecodonts are archosauromorphs that are not in the dinosaur or pterosaur clades -- thus crocs are the last thecodont group which is like way cool man, and helps explain to people what they biologically represent. Nonpterodactyloids are good old rhamphorhynchoids -- which I just found has a Wiki entry:) 

When Archie was put at the base of Aves that was a big advance because it was the scientific community acknowledging evolution!!! Which has been dropped for a reason that does not seem necessary. 

I was rolling my eyes on over recognizing crown clades from the start. Partly because the paleoexperts were failing to realize how disruptive it would be to the lay public. It is a major problem in my field guides, using the phylocode is often not viable in those. 

BTW I have a way to explain birds being dinosaurs to people. They often ask what that means. I say are bats flying mammals? They say yes. I then say birds are flying dinosaurs. I always see the aha realization of the explanation in their eyes. 

GSPaul

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/befae264-7b48-4e84-854e-b5d2febb5954n%40googlegroups.com.

[Henry Thomas]

Since when have extant crocs been considered "thecodonts"? Every time I've seen that terminology used, it's been specifically for the nebulous extinct grade of mostly-Triassic reptiles from which dinosaurs and crocs descended (or, rarely, including both).

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/885617931.570433.1774631336748%40mail.yahoo.com.

[Scott Hartman]

Greg raises an interesting point, but my answer would be: By all means if you find prosauropod is easier to explain it to non-scientists, than do so! There's no phylogenetic conflict, because it's not a formal name. Likewise, just use near-bird or proto-bird if you want to convey how close some non-avian is to birds. Easy to do, easy to understand, and if you aren't teaching formal nomenclature there's no need for the same degree of terminological precision. I just try to avoid misusing formal names, as that creates a mess that future educators have to clean up. FWIW, in secondary education and college courses I've found that "croc-line" and "bird/dinosaur-line" work just fine for explaining non-croc/non-dinosaur archosaurs with minimal explanation, and it's more precise than referring to Aphanosaurus as a thecodont.

But Aves is a clade with a formal definition. It was given that definition centuries ago, and it was re-affirmed by modern phylogenetic systemmatics (Phylocode). The rest of the fears around removing Archaeopteryx from Aves sound like all the hand-wringing of people who were concerned that Pluto not being classified as a planet were going to harm astronomy outreach, when the answer was just to teach it and explain why. People want to learn about these things, it's ok to take the time to teach them where appropriate, and to use non-formal names when you need shortcuts.

I also use the bat/birds and mammals/dinosaurs analogy all the time (it's really useful!). But I don't see how moving Archaeopteryx out of Aves makes it any less about evolution? Acknowledging there have been multiple clades of progressively more bird-like flying dinosaurs prior to reaching the crown is literally nothing but evolution.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CAC4cqEWbWPD6Lvk7_K-yPTs8if8GD6r8Zh9R5aabtohNkA8PtQ%40mail.gmail.com.

[Gregory Paul]

Used to be the norm. Check books etc up to the 60s/70s/80s. You like many do not know your not so distant paleohistory LoL.  

GSPaul

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CAC4cqEWbWPD6Lvk7_K-yPTs8if8GD6r8Zh9R5aabtohNkA8PtQ%40mail.gmail.com.

[Meig Dickson]

It's almost like the science and standards around science communication have changed in the past 30 years or something. 

Meig Dickson

PhD Student, Houde & Orr Labs

Paleobiology, Department of Biological Sciences

New Mexico State University

---

From: 'Gregory Paul' via Dinosaur Mailing Group <DinosaurMa...@googlegroups.com>
Sent: Friday, March 27, 2026 12:11
To: dinosaurma...@googlegroups.com <dinosaurma...@googlegroups.com>

Subject: Re: [DMG] Solnhofen avialans likely all Archaeopteryx (free pdf)

WARNING This email originated external to the NMSU email system. Do not click on links or open attachments unless you are sure the content is safe.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/1822497840.594228.1774635094766%40mail.yahoo.com.

[Scott Hartman]

On Fri, Mar 27, 2026 at 1:11 PM 'Gregory Paul' via Dinosaur Mailing Group <DinosaurMa...@googlegroups.com> wrote:

Used to be the norm. Check books etc up to the 60s/70s/80s. You like many do not know your not so distant paleohistory LoL.  

Come on Greg, I know we're arguing different sides here, but I grew up reading dinosaur books from the 60s, 70s and 80s. Phylogenetric nomenclature has changed for good reasons, however we each want to square the circle of teaching the subject to non-specialists.

[Thomas Yazbek]

Yeah, they're an extinct "ancestral stock"/grab-bag in most older writings. I actually am glad Thecodontia is deprecated, because its membership was very murky. Pelycosauria, Prosauropoda are much better paraphyletic grades to continue talking about, since their membership & definition have never been in as much doubt for quite a long time (maybe not including multiple crown groups helps?). 

BTW, on the same thread, historical linguistics has no trouble using phylogenetic trees that involve paraphyletic stages...I wonder if they have the same problems explaining how Vulgar Latin is the parent of many modern languages?

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CAC4cqEWbWPD6Lvk7_K-yPTs8if8GD6r8Zh9R5aabtohNkA8PtQ%40mail.gmail.com.

[Thomas Yazbek]

You just barely beat me to making the same point, except better, Greg. 

It seems trivial, but this *is* actually of supreme importance. Trust in science is at an all-time low. Paleontology of course is a relatively minor science, but it's still science, and if you give certain parts of the public an inch of elitist obscurantism, they will take a mile. 

TY

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/885617931.570433.1774631336748%40mail.yahoo.com.

[Thomas Yazbek]

I'm sympathetic to Jerry's points. The concepts are simple enough, but taught poorly, and more importantly are irrelevent & uninteresting to most humans, even those who deal with animals or even fossils. High school & possibly undergrad bio classes in the US are likely to be outdated/inadequate at teaching the modern ways we classify life.

Intuitively, we categorize things (e.g. ourselves) based on traits *and/or* genealogy based on context. Sometimes, as in biology, the former way is deceiving, like when a full-blooded German baby is adopted by Scottish parents - he talks, looks, acts like a Scotsman, but for those who know his true family tree, we are seeing a metaphor of convergent evolution (something that of course tripped up many pre-Darwin, pre-cladistics taxonomists). I somehow doubt all teachers are using these simple metaphors.

Scientists are just understandably cautious & lazy. Easier to anchor Aves on the rock-solid Neornithes to make it simple & avoid trouble, nevermind the effects it might have on science communication/education. To me, it's perfectly simple & effortless to separate the colloquial 'bird' from the actual definition of clade Aves, just like how it's effortless to understand the concept of informal grades like pelycosaurs or prosauropods. 

I actually think the phobia around continuing to use grade names is quite unnecessary, since the cacophonia crisis in paleo is already a 5-alarm fire (my opinion) - if some authors still use "pelycosaurs" with scare quotes, do we need to use the mouthful "non-mammalian synapsids" in popular writings? We all know what 'pelycosaur' means - a science-curious high school student probably can too. 

TY

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/befae264-7b48-4e84-854e-b5d2febb5954n%40googlegroups.com.

[Gregory Paul]

While paleo science is not like say medical, or climatological, or physics (Jack McIntosh wanted to study dinosaurs in the late 40s, but was steered into physics), it is a very popular science among the public, starting with children for whom it is often their intro to science. 

GSPaul

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CAPySu-W0ifwDcSdefJb3iEnDHNivdkL%3D0yy_8zTGf7C%2B35FUOA%40mail.gmail.com.

[Jerry Harris]

>> While of course Linnaeus didn't know about fossils, surely defining his taxa based on "how he might have defined them if he had more knowledge" is a fools errand?

It may well indeed be, but it's equally foolish (in the sense of presuming to know what he might have thought) to assert that he intentionally wanted to restrict Aves to crown-group birds. We can't know either way, so treating one of those possibilities as fact and the other as fiction, or one as poorly supported and the other as well supported, is fallacious. Ultimately, Linnaeus' classification system only grouped things for the sake of convenience, not because he wanted to discover or track evolutionary patterns, though he did want to understand the mind of God and the (popular at the time) Scala Naturae.

>> And we've long kept Linnaen-era names while rejecting the system, so why would that impact his systematic definitions and not others?

Some names, sure; others (e.g., Pisces) we did not (and for good reasons). And some of Linnaeus' names (e.g., Amphibia, Primates) could also have been restricted to crown clades, but haven't been—for example, as far as I know, everyone still considers various traditional plesiadapiforms (purgatoriids, micromomyids, etc.) to be primates even though they're not in the crown group. I don't know why Aves, Crocodylia, and Mammalia were considered special and specifically considered "crown-group only" in this regard. We've been selective and, really, arbitrary about what to discard, what to keep, and how to use what was kept. And as long as we're being arbitrary, why is historical usage considered inferior to presumptions of what Linnaeus wanted? That was also an arbitrary decision. And lastly, we happily discarded Linnaeus' character-based definitions, too—we repurposed his names in a completely different way. Why keep the names at all, then? Historical consistency. And yet historical consistency is rejected as a reason to keep Aves where it was for 120+ years at Archaeopteryx. It's strange to me how many modern systematists have contorted themselves to justify what, in the end, were/are arbitrary decisions rather than just admit that the decisions were/are arbitrary. Being arbitrary doesn't make them useless or pointless or otherwise not good. Restricting Aves to the crown group may well be useful, but it's still an arbitrary decision, especially in light of that we had a perfectly good name (Neornithes) for the crown group that had been in use for 100 years before the arbitrary decision was made to discard it and force Aves into a new and confusing position.

>> What is confusing is why if Archaeopteryx is a bird Anchiornis or Microraptor aren't.

See, that's what I find easy to explain: because the line is drawn arbitrarily. Historically, of course, the lines looked like they were nice and clean and various animals (reptiles on one hand, birds on the other) were readily distinct to even casual observers. New discoveries, including Archaeopteryx, began to muddy that picture, of course. The line has to be drawn SOMEWHERE, and it just happens to fall between anchiornithids and Archaeopteryx, arbitrarily. That's a lot easier to explain and understand than show people restorations of enantiornithians and have to explain why they're not birds.

>> you are instead...picking one historical name argument event over another.

Yes I am. ALL these arguments are historically based. The decision to keep using Linnaean names at all was based on wanting to keep some sort of historical consistency (and yes, some did argue that discarding all existing Linnaean names and starting naming things over from scratch based on monophyly was the best idea). I'm not saying that history is the best basis for making such decisions; I'm only pointing out that using history as a reason for making one taxonomic decision and rejecting it for another decision is hypocritical. Yes, of course, decisions have to be made at some point so we have a baseline to work from; I'm just saying that I personally think restricting names such as Aves, Crocodylia, and Mammalia to the crown groups was not the best decision that could have been made from a historical point of view. And yes, that's my bias.

 >> Any clade in a well-sampled part of the tree will have outgroup OTUs that look very much like basal members within that clade - how else could it work? Stretching a clade defintion to cover all taxa someone feels are "enough like the crown" just results in moving the defintion to where there's a sufficiently large gap in the fossil record for now, which turns systemmatics into a clade-of-the-gaps system.

This is all true. But even Linnaeus inherently programmed names in gaps as part of his system. Aves was a class, like Reptilia and Mammalia, because of a metaphorically assumed degree of difference from everything else (birds were as distinct from reptiles as reptiles are from mammals, and reptiles are as distinct from mammals as mammals are from birds, and so on). That was the point of his ranking system. There wasn't anything extant that was partly reptile-ish and partly bird-ish to fit into the gap between Reptilia and Aves. His whole classification system revolves around the perception of gaps. In light of the increasingly good fossil record, that's a problem, and presumably yet another aspect of his system that we've chosen to try to discard.

The argument boils down to: Aves was used only for the crown group for 130ish years because fossils were unknown during that time, and Aves was a line drawn just below Archaeopteryx for roughly the same amount of time after Archaeopteryx was discovered. Which history should take precedence? That, too, is an arbitrary decision. It's a little weird to me to say that one possible interpretation of Linnaeus' intent is correct while discarding most everything else of his. You apparently prefer arbitrarily choosing that first historical period; I arbitrarily prefer choosing the second. And that's perfectly fine; I don't think poorly of you in any way for choosing that. I just think that we had a great and useful (albeit Linnaean) classification system in place with Aves below Archaeopteryx and Neornithes for the crown that had been in use for a really long time until Gauthier took it upon himself to say "No, that sucks because here's what I'm assuming Linnaeus wanted."

[Thomas Richard Holtz]

Tristan writes:

>This also feels like a uniquely made-up bird paleontology problem. Please correct me if I’m unaware, but nobody seems to be fighting desperately to preserve a definition of Mammalia that keeps things like tritylodontids in the crown, despite ~120 years of similar literature baggage

In fact, this most definitely DID happen with other cases of crown-group vs. classic-group definitions. There was some resistance to Mammaliaformes vs. Mammalia, Crocodyliformes vs. Crocodylia, and Archosauriformes vs. Archosaur. Most of these didn't last long, though, with the exception of the archosaur case: in 1999 Benton coined Avesuchia for crown-group archosaurs, and kept Archosauria in its relatively traditional position of proterochampsids, erythrosuchids, euparkeriids, and the crown: https://royalsocietypublishing.org/rstb/article-abstract/354/1388/1423/19479/Scleromochlus-taylori-and-the-origin-of-dinosaurs?redirectedFrom=fulltext 

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CAAwX0VwRneFs0W4E95BMjO4AjO06Z3SD3ZD%3DfinCh1uNCCC%3DRw%40mail.gmail.com.

--

Thomas R. Holtz, Jr.
Email: tho...@umd.edu         Phone: 301-405-4084
Principal Lecturer, Vertebrate Paleontology

Office: CHEM 1225B, 8051 Regents Dr., College Park MD 20742

Dept. of Geological, Environmental, and Planetary Sciences, University of Maryland
http://www.geol.umd.edu/~tholtz/

Phone: 301-405-6965
Fax: 301-314-9661              

Faculty Director, Science & Global Change Program, College Park Scholars

Office: Centreville 1216, 4243 Valley Dr., College Park MD 20742
http://www.geol.umd.edu/sgc
Fax: 301-314-9843

Mailing Address: 

                        Thomas R. Holtz, Jr.
                        Department of Geological,

                            Environmental, and Planetary Sciences
                        Building 237, Room 1117

                        8000 Regents Drive
                        University of Maryland
                        College Park, MD 20742-4211 USA

[Tim Williams]

Gregory Paul' via Dinosaur Mailing Group <DinosaurMa...@googlegroups.com> wrote:

>Take prosauropods.

Please.

I don't understand the rationale for lumping "prosauropods" together.  They are 'defined' by what they lack relative to sauropods. The "prosauropods" can include taxa from _Eoraptor_ and _Buriolestes_ through _Plateosaurus_ and _Massospondylus_ to _Aardonyx_ and _Melanorosaurus.  Collectively, the "prosauropods" document the evolution from small obligate bipeds to massive obligate quadrupeds - at which point it's difficult to delineate them from true sauropods.  

> There is not entry for this major group in Wikipedia. Only as a subset among the clunky jargon
> termed sauropodomorphs.

Unlike beautifully mellifluous names like "baso-eutyrannosaur" and "aveairfoilans" that have appeared in certain books.

Terms like Sauropodomorpha might be clunky.  But the intention of phylogenetic taxonomy is to provide clarity and resolution on the interrelationships of taxa - hence nested clades like  Sauropodomorpha, Sauropodiformes, and Sauropoda.  I personally prefer massopod to sauropod; but sauropod is too entrenched to change now.)

> Meanwhile crown sauropods get their own big entry.

Note that "crown" is applied to a clade that includes the common ancestor of all living members of a group and all of its descendants.  

 
> Thecodonts that I grew up with are pretty much gone, while crown dinosaurs exist.

I'm surprised that anyone laments the passing of the term "thecodont".  Thecodontia was a wastebasket, into which all sorts of archosaur bits and bobs were tossed, along with curios like _Longisquama_ and _Sharovipteryx_.  Thecodontia was a convenient term that hid what little was known about archosaur relationships at the time (including the origins of crocodilians, pterosaurs, birds, and dinosaurs - the last two thought to have separate origins).

Just as obfuscatory were other 'primitive' paraphyletic groups like Sauriurae, Condylarthra, Prototheria, Agnatha, Apterygota, etc etc.  Also not missed.

> This leaves archosaurs that are not dinosaurs a vaque collection of groups most folks have no
> idea what they are.

A  "vaque collection of groups most folks have no idea what they are" is exactly what Thecodontia used to be.   

> When Archie was put at the base of Aves that was a big advance because it was the scientific
> community acknowledging evolution!!! Which has been dropped for a reason that does not seem
> necessary.

Here I'm inclined to agree.  This is why I prefer Aves as the "_Archaeopteryx_ node" rather than the crown group.  This debate over the definition of Aves is essentially a tug-of-war over which historical paradigm should get priority: Linnaean or Darwinian.  I side with Darwinian.

> BTW I have a way to explain birds being dinosaurs to people. They often ask what that means. I say are bats flying mammals? They say yes. I then say birds are flying dinosaurs. I always see the

> aha realization of the explanation in their eyes.

Yes, it's an excellent analogy.  It's just a shame the fossil record hasn't yet produced an _Archaeopteryx_ equivalent for bats.

[Mickey Mortimer]

I think this thread has done a good job of showing that phylogenetic definitions are ultimately subjective, so will never be resolved via arguments. Everything being said here about Aves has been rehashed over the past forty years. So given that the entire point of phylogenetic nomenclature is stability, we need to agree upon an arbitrary set of rules and governing body just as zoologists did with the ICZN. And the only thing even remotely like that now or in the foreseeable future is the PhyloCode.

So WHY would anyone choose to keep squabbling over this issue with no objective best answer until most of the proponents of one side are dead when we could have stability now if everyone just agreed to get on the same page? The PhyloCode has Articles 22.6 to 22.8 to address changes in definition in case you disagree with the current ones. But surely no one prefers the anarchy of everyone just choosing what definition they like and wasting paper space with a list of definitions those particular authors are using?  This is truly a case where egos are "why we can't have good things."

Mickey Mortimer

[Russell Engelman]

> This also feels like a uniquely made-up bird paleontology problem. Please correct me if I’m unaware, but nobody seems to be fighting desperately to preserve a definition of Mammalia that keeps things like tritylodontids in the crown, despite ~120 years of similar literature baggage.

This absolutely does happen in mammalian paleontology, you just don’t hear about it because mammalian and dinosaur paleontologists tend to run in separate circles. This is actually much more a problem for mammal (and fish) paleontology because we have many more extant groups to worry about rather than just considering how things are positioned relative to modern birds and crocodiles.

To use one example, the group I work on — the Sparassodonta — used to be classified as marsupials. The group containing sparassodonts and their allies (Pucadelphyida) appears to be part of a broader radiation that occurred when metatherians dispersed to South America right around the K-Pg boundary, and represent an evolutionary relevant grouping that contains virtually all Cenozoic metatherians (whereas the Mesozoic forms and the handful of Cenozoic stragglers in the Northern Hemisphere are basal). By this point in time the marsupial body plan was well-established and sparassodonts would be biologically indistinguishable from any crown marsupial in terms of general appearance or physiology.

However, because sparassodonts happened to branch off just barely before opossums did and had the bad luck to die out maybe 1 to 2 million years before the present day, they are classified as stem metatherians and “marsupial” does not refer to that nice neat group that includes the South American/Australian Cenozoic metatherian radiation. This makes it very awkward to talk about sparassodonts, especially with laypeople, and often causes people to ask very silly questions like “Did sparassodonts lay eggs? I know they’re not considered to be marsupials anymore so does that mean they laid eggs?” Believe it or not, that’s not even an isolated example but something I’ve seen repeatedly be asked.

The same issue occurs with Mammalia as a whole. Evidence is increasingly suggesting that the typical mammalian body plan (e.g., extensive hair, milk production, diphyodonty) was mostly assembled in a rapid burst of morphological evolution that happened around 220 million years ago. There is a fairly stark morphological divide between “traditional” mammals like Morganucodon and more stemward cynodonts like tritylodonts. Originally everyone was pretty fine with drawing the line for mammals around Morganucodon, but with the advent of crown clades now some people advocate for restricting the definition to the most recent common ancestor of monotremes and therians and calling everything else a mammaliaform or something.

This actually causes more problems down the line because while we know how monotremes and therians are related to one another due to genetics, we actually don’t have a good idea of how these various extinct groups fit into this broader picture and thus who is in the crowd and who is in the stem. We can vaguely point to several groups like eutriconodonts and dryolestoids that seem to be more on the therian line of things, and we have some things that seem to be stem-monotremes (ausktribosphenidans), but with things like haramyidans, euharamiyidans, multituberculates, docodonts, and gondwanatheres it’s anyone’s guess where they go. Adding to this the actual split between crown and stem mammals is based solely on genetic evidence. Genetic data suggests it probably happened somewhere in the middle Jurassic but there’s almost no data to suggest what that ancestor would’ve looked like and if you had a time machine I would bet that you probably couldn’t reliably tell whether a very basal crown mammal was on the crown or the stem; The definition is purely semantic rather than biological. On top of that, there aren’t really any true synapomorphies that diagnose crown mammals relative to other mammaliaforms, many of the features that are shared between monotremes and therians like fully detached inner ear bones appear to have evolved independently between the two groups.

So yeah, a lot of mammal paleontologists hate it and much like Archaeopteryx most of us just conveniently ignore that "mammal" is supposed to only refer to the last common ancestor of platypodes and people and go with the traditional definition simply because it makes it easier to explain to people what exactly we are looking at and why it matters in terms of the broad scheme of things.

> On a personal note, I despise the "Linnaean names should be restricted to crown clades only" logic—I think it is drawing arbitrary lines in a poor places...

There’s actually other cases that are even worse than this. I always like to point out the example of Meiolaniiformes as an example of just how badly restricting crown group definitions to extant taxa can get. Meiolaniiformes are a group of turtles that, as far as we can tell, seem to be really, really basally positioned within the clade. They also survived really, really recently, I think there are carbon-dated meolaniid remains from New Caledonia that date to the third century A.D. and they survived long enough for humans to encounter them (and wipe them out). But, because they are no longer living there are considered stem turtles rather than crown turtles.

 

Or, consider that the most recent data on dasyuromorphian marsupials recover thylacines is outside the clade of numbats + dasyurids. Do we consider thylacines “stem dasyuromorphians”? They became extinct before the advent of cladistic methodology but they were known to Western science for about 120 years before they actually went extinct.

 

I pointed this discrepancy out to someone once and their argument was “we should only consider something belonging to the stem or crown group if it was alive at the time it was discovered by Western science”. Which seems like a really myopic and problematic way to go about doing things.

> I think the "crown-clade only" folks did scientific communication a real disservice—I am not certain that this was a consideration in their deliberations and decisions at all. Here we are 30-ish years after the "crown-clade concept" really began to take hold, and it's still really a pain in the ass to try to talk to people, and especially to teach students, that Archaeopteryx isn't a bird, docodonts and such aren't mammals, and Goniopholis and such aren't crocs, and that there are bird-like, mammal-like, and croc-like things that don't fall into those categories.

100% agree. The point of taxonomic nomenclature is twofold: to describe the underlying architecture of the tree of life and to give us the tools to communicate with one another about patterns observed in nature. This “architecture” does not just mean branching order but also biological and ecological information. In many cases we want terms to be able to describe organisms with similar features, even if they aren’t explicitly monophyletic. For example, most ornithischian paleontologists recognize the utility in contrasting “iguanodontians” with hadrosaurs, even though everyone is aware “iguanodontians” are a non-monophyletic group. Or consider Stuart Sumida’s recent review of “pelycosaur-grade synapsids”. While it’s clear pelycosaurs are not monophyletic they are still so similar to one another in terms of morphology and likely paleobiology than either therapsids or non-synapsid reptiliomorphs it’s most effective to talk about them as a (non-monophyletic) group. As long as people are aware of what’s being talked about and it’s clear that referring to a group colloquially does not equal relatedness that’s fine.

 

Or how about “non-avian dinosaurs”. Everyone understands birds are nested deep, deep within dinosaurs but no one has a problem thinking that a hadrosaur and a tyrannosaur are going to be more similar to one another than a pigeon in many aspects of their biology, evolutionary history, ecology, taphonomy, etc., due to factors like birds generally being smaller than all other non-avian dinosaurs, volancy, and the fact that non-avian dinosaurs were wiped out in the K-Pg extinction. There are going to be some awkward gray areas like Archaeopteryx and other non-avian deinonychosaurians, but you can mostly put things into the two boxes. If there wasn’t value in distinguishing between the two groups no one would use the term “non-avian dinosaur” at all, even though at this point virtually everyone agrees that birds are just a form of dinosaur.

 

This is something that Linnaeus had in mind when he proposed his classification because he explicitly grouped together things that we know today are not closely related but filled roughly similar ecological roles and had loosely similar morphology (e.g., classifying sloths with primates, viverrids with mustelids in the first Systema Naturae. This isn’t to argue we should be grouping species non-cladistically but to highlight biological similarity is an important component in how terminology is used. Arguing that Linnaeus would not have classified Archaeopteryx as a bird is kind of a non sequitur because Linnaeus died 100 years before the first specimen of Archaeopteryx was actually discovered and one could very well argue he would’ve classified it as a bird because that’s how most scientists treated it back in the days of Linnaean taxonomy.

 

The problem is the way distinctions between crown groups and stem groups are made nowadays it doesn’t actually help science communication and in my experience watching how the general public have used (and abused) this idea is primarily utilized by the “uhm acktually” types who want to sound smarter than everyone else by pulling out some technicality that doesn’t actually help the ideas that are trying to be communicated. If you’ve ever seen that Futurama joke about “actually, the [spider aliens] are actually more closely related to our elephants than are spiders”, you know exactly what I’m talking about. The difference isn’t relevant 99% of the time, and I’ve frequently seen it confuse people who don’t really understand the difference between stem and crown groups. A good example of this is the one I gave above about “did sparassodonts lay eggs?” Sharks are a particularly bad case of this, where a lot of paleo-shark fans like to argue online and in-person that ctenacanths, cladoselachians, xenacanths, and hybodonts aren’t sharks because one researcher in the field really promoted that idea in sci comm, but in reality most shark paleontologists call all these forms “sharks” because they are ecologically and functionally similar and only distinguish between crown sharks (neoselachians) and more basal forms where necessary. For the most part they don’t seem to have a problem with treating chimaeras and rays as weird, mutant sharks the same way dinosaur paleontologists treat birds as just another branch of dinosaurs.

 

One could argue that the failure of the general public to think in terms of cladistic methodology, but the problem is human beings generally don’t think this way. When you tell someone “Archaeopteryx isn’t a bird, it’s a non-avian avialaean”, they don’t interpret it as “it’s not a bird but it’s slightly more basal on the family tree and doesn’t have all the features of modern birds” they interpret it as “it’s not a bird, it’s some other thing”. And unfortunately even trying to teach them a cladistic mindset is difficult long term because unless there a student in a field that regularly uses phylogenetics (which doesn’t even include all of biology, to be frank, I know a lot of doctors and most don’t even understand that E. coli is supposed to be a scientific name), they are going to forget about it as soon as they leave the classroom because such a mindset doesn’t have many applications in their daily life. It just doesn’t work in terms of science communication, especially in terms of trying to get across to the lay public exactly what something is.

 

And that’s not getting into the really weird cases where I’ve seen people argue things like “Mesohippus or even Equus simplicidens aren’t horses, they’re stem equids because they're outside the MRCA of modern Equus”, which just completely confuse people who are trying to wrap their heads around horse evolution. Like yes, they're not in the crown, but calling them "not horses" just makes things kind of ridiculous. Equus simplicidens is a one-toed, hypsodont horse that just happens to be from the Pliocene, why call it something majorly different?

It’s really frustrating because despite this long rant I actually prefer the simplicity and elegance of cladistic methodology, and I'm not trying to argue for freaking phenetics, but the way cladistic terminology gets misused so often makes things worse rather than better. The entire point of cladistics was to put some rigor into taxonomy rather than get in pointlessly semantic slap fights over whether some group should be at a family (-idae) or superfamily (-oidea) rank, but in many cases all it's doing is creating new semantic arguments. It gets really difficult because many biologically meaningful, monophyletic groups that your average person would recognize as "a thing" do not easily map onto the crown versus stem dichotomy because of extinctions, which is an accident of history more than reflecting actual patterns of relatedness and divergence (and in the case of "we should only consider something extant if it was alive when [mostly] European scientists discovered it" opens up a can of worms). Similarly, I understand the I should just do what I value in recognizing the difference between stem groups and crown groups, especially when talking about genetic data or soft tissue features that can’t easily be established in fossils, but the way these concepts are used in many cases only makes science communication worse, rather than more effective.

> BTW I have a way to explain birds being dinosaurs to people. They often ask what that means. I say are bats flying mammals? They say yes. I then say birds are flying dinosaurs. I always see the aha realization of the explanation in their eyes.

That's the way I always try to frame it, as well/

[Gregory Paul]

Almost all naming systems have arbitrary boundaries, including taxonomy, there cannot be a truly rigorous biological naming system and the Phylocode is not such. 

Thecodontia is not a wastebasket if it is technically defined as monophyletic clade with an offshoot that is excluded -- archosauriformes sans avemetatarsalians. There you go. Does not include drepanosaurs or Sharivopteryx, those not being archosauriformes it seems.

Nor is variation in the group all that extensive. All thecodonts are sort of lizard-croc like things with short, stout, straight necks, long low slung bodies, long tails and femoral heads that are not inturned. A pretty consistent grade. 

Much less variable than say ungulates that range from Eohippus to blue whales. Or ornithischians that include lesothosaurs, stegosaurs, pachycephalosaurs, protoceratopsids, ceratopsids, lambeosaurs. 

But with the grade free Phylocode scheme the once classic thecodont Euparkeria now has no named greater group to belong to, it vaguely being a basal archosauriform. Same for the classic big thecodonts, the erythrosuchids. How about the most basal thecodonts, the proterosuchids? 

For awhile the two surviving archosaur groups were birds which are dinosaurs and that gives folks a basic idea of what they are about, and crocs which were thecodonts and gave folks a fair idea of what they were about. Nowadays crocs are obscure crurotarsi and pseudosuchians which are just a modest portion of the basal archosaurs -- unlike birds being part of a very great group -- and even excludes the archosaurs most like crocs, the phytosaurs. Doing that is broadly similar to telling people that birds are theropods without mentioning the dinosaurs thing. Technically correct, but not good for public outreach and edification.  

Eliminating Thecodontia was not scientific. It should have been retained with modern clade plus grade techniques as outlined above. Sinking Thecodontia was part of the fashion of excluding grade, which is a real biological factor. Which has been irregularly applied, which is also unscientific. 

In my field guides iguanodonts are iguanodontoids excluding hadrosauromorphs. Entirely scientific scheme that readers can better grasp onto than having the first be basal iguanodontoids. 

The is a way to solve this particular problem. It's called academic freedom over official rigidity. The Phylocode was set up by a set of cladists who think all should conform with a radical and unnecessarily rigid system in which if a taxon is not a crown group it should not e tagged as a member of group simply by what it is, but in part awkwardly by what it is not. As per Plateosaurus is a basal or nonsauropod sauropodomorph, rather than a prosauropod. 

The way to solve it is simply reform the Phylocode to allow groups that are monophyletic but not crown to have an upper cut off. Thus thecodonts, prosauropods, iguanodonts, rhamphorhynchoids, etc., etc. If others wish to say basal-archosauriformes, -sauropodomorphs, -iguanodontoids, non-pterodactyloids then they can do that. 

Advising that if one wants to use say thecodonts instead of basal archosauriformes, and to heck with the Phylocode is not an adequate option. It is controversial and can raise practical objections, such as how a book is titled and the groups in it named. Cannot use the names in technical studies.  

It is funny how the vast majority of the enormously diverse clade is often referred to by saying what it is not, nonavian dinosaurs when birds are just a wee subset. Although I do it myself on occasion. 

GSPaul

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/f4879ce2-fb50-4e3c-988c-270af79615fbn%40googlegroups.com.

[Thomas Yazbek]

Russell makes a lot of good points. I hope it was cathartic to unload that righteous rant.

I wish more laypeople understood how much of a revolution it's been since the 80s. It seems like the popular understanding is that scientists are just guessing or "eyeballing" relationships, rather than using powerful computational tools to evaluate phylogenetic hypotheses (often based on molecules, which are more mysterious than morphology). 

Unfortunately, while the level of precision has increased dramatically, the public is mostly unaware of this, and Wikipedia becoming dominant as an info source is terrible because it gets way too technical, confusing people. There seems to be less reflection than there should be on the part of both academics & popularizers about whether people can understand the gist of the research.

Even I have had trouble with the crown/stem group definition - "crown group" is occasionally used like how Greg Paul did earlier referring to "crown sauropods", and this seems like a perfectly intuitive concept - 'stem' just refers to taxa more closely related to the 'crown group' than to some other crown-y group. It's just an extension of the usual definition where crown groups refer to extant groups. 

I am absolutely sure that we have lost something that used to exist in sci-comm. Modern science communicators need to balance precision & accuracy with the need to actually keep the audience on board. FWIW, I do think the orthodox crown-stem concept has value, but I think communicators have gone overboard in throwing out perfectly good paraphyletic grades.

TY

--

You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingG...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/d1211dba-38a3-4324-ae40-ce3ce79fb381n%40googlegroups.com.

[John D'Angelo]

To suggest that Linnaeus in any way intended Aves to be restricted to the crown group is patently absurd, because he had no such concept. We cannot say for sure that Linnaeus would have considered Archaeopteryx a bird, because he never knew of it, but the fact remains that it was pretty much universally accepted as such by everyone who knew of it for over a century, except by the rare few who rejected the notion it had anything to do with birds at all. The notion that Archaeopteryx, or any other animal, could be an animal that flew on feathered wings homologous to those of birds without being a bird itself is certainly a far newer concept. If Archaeopteryx isn't a bird by this reasoning, then the platypus and echidna are not mammals, as they also fall outside the crown clade of all organisms included in the taxon by Linnaeus.

The origin of powered flight in pennaraptoran theropods was certainly a major evolutionary transition, and it so happens that that transition lines up well with the traditional, common-sense notion of a bird as an animal with feathered wings. Why is it any more arbitrary to associate the definition of Aves with this transition than the crown group or total group, the scopes of which are mere accidents of extinction? Archaeopteryx’s position as the "first bird" has doubtlessly been strengthened by its historical significance, but as it so happens, it remains the strongest candidate for the basalmost known taxon with a capability for powered flight homologous to that of crown-group birds.

An analogous situation to the definition of Aves is the definition of Tetrapoda, as both groups represent major radiations resulting from a locomotory shift. The attempt to restrict Tetrapoda to the crown group seems to have largely failed (despite Phylonyms); most recent papers on tetrapod origins use the traditional apomorphy-based definition of Tetrapoda, not the crown-based definition. The crown-clade redefinitions of Amniota and Mammalia may have stuck in part because both clades are named for characters that have extremely poor preservation potential and are difficult to prove occurred in any members of the stem group.

There are some major differences between the ICZN and the PhyloCode in terms of how they serve taxonomic stability. By the time the ICZN came into effect, the system of taxonomic nomenclature it represented had existed for over a century and long been widely accepted, and the ICZN served only to codify and standardize many of the practices that people had already been doing for several decades. In contrast, when the first draft of the PhyloCode was released, modern phylogenetic nomenclature was little more than a decade old and had only achieved partial acceptance—and indeed even today it has still only achieved partial acceptance, as Greg has pointed out, and there are still several areas, particularly some groups of fossil invertebrates, where a purely clade-based system of higher taxonomy is not practical and has not been widely adopted. So the PhyloCode is going beyond simply codifying already established practices. The fact that it is trying to enforce by fiat controversial redefinitions such as restricting Aves to only a subset of the clade of animals that fly on feathered wings, or Tetrapoda to only a subset of the clade of four-legged vertebrates, only serves to discredit it IMHO.

A major problem with the PhyloCode is that it is attempting to regulate usage in a way that the ICZN does not. The ICZN does not contain rules about when to recognize a species, how a species should be defined, or what the scope of a species should be. In contrast, the PhyloCode does try and set in stone the scope of every clade name, in my opinion to its detriment. A key difference is that it is desirable—and indeed, the goal—to name every species, while it is not useful or even feasible to name every clade.

There is a one-to-one correspondence between nameable species and species worth naming, and to a first approximation any specimen of any organism belongs to exactly one species. This means that any species is uniquely identifiable simply by giving an example of a specimen of that species, which is the point of the principle of typification. When a taxonomist names a species and assigns a type specimen, they are essentially saying "this is a name for the species that this specimen is." The principal problem of species taxonomy—actually delimiting species—is entirely a matter of scientific hypothesis testing that the ICZN has no authority over; the ICZN is a fairly limited set of rules of how to formally apply a name to a newly recognized species and how to resolve conflicts if multiple names are applied to the same species.

In contrast, any given specimen belongs to a great many clades, far more than are ever worth naming. In fact, there are far more clades than species, as it is perfectly possible to identify a clade within a species. As one of the purposes of higher taxonomy is to be able to simplify the vast diversity of life into broad strokes for the ease of communication, it is inevitably necessary that the number of clades in active use to be far lower than the number of theoretically nameable clades, even if you ignore clades that are more granular than the species level. You can't name every clade, nor should you want to, so the matter of which clades to name, and what their scope should be, becomes a far greater concern. And this is precisely the thing that the PhyloCode is trying to shut down all room for debate on. The PhyloCode does provide some room for emending phylogenetic definitions, but unlike the ICZN, where petitions to the Commission are a relatively rare situation arising from certain edge cases, emendations to phylogenetic definitions are clearly a regular part of phylogenetic taxonomy. It is very easy to define a clade badly, as the entire history of phylogenetic nomenclature up to this point has demonstrated, and the potential for taxonomic instability arising from an ill-conceived phylogenetic definition is great—consider Rinconsauria, for example, which depending on the phylogenetic analysis can contain anywhere from two titanosaur species to all of them.

--

You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingG...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/d1211dba-38a3-4324-ae40-ce3ce79fb381n%40googlegroups.com.

[Henry Thomas]

Euparkeria, erythrosuchids, proterosuchids, etc. still have a greater group they belong to - Archosauriformes. It just also happens to include Avemetatarsalia. If Avemetatarsalia is to be excluded from a "Thecodontia" based on perceived difference from the "low-slung, short-necked lizard-croc" bauplan - what of upright-standing rauisuchians, long-legged crocodylomorphs like Hesperosuchus, or the bipedal, long-necked and toothless Effigia? All of those are on the croc line and none match that description of a "thecodont". Conversely, how different are early avemetatarsalians like Teleocrater from it? "Non-X Y" is a mouthful but it is at least objective - if X is a subclade of Y, there must be members of Y that are not in X - and can be applied equally across the board of life.

(Also, "crown" terminology is intended to apply to groups with extant members only. "Crown-birds" exist (Neornithes), but "crown-sauropods" do not because no sauropods are extant.)

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/1248048120.785193.1774731446796%40mail.yahoo.com.

[Jaime Headden]

Mickey Mortimer wrote:

>  But surely no one prefers the anarchy of everyone just choosing what definition they like and wasting paper space with a list of definitions those particular authors are using?  This is truly a case where egos are "why we can't have good things."

*cough* Paul Sereno.

--

You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingG...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/07b43b3f-5f2a-4878-97c5-3fe8ba709160n%40googlegroups.com.

--

Jaime A. Headden

The Bite Stuff: http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth" - P. B. Medawar (1969)

[Mickey Mortimer]

Jaime Headden wrote- "*cough* Paul Sereno."

Of course. But Taxon Search still says 

"1.0 Paul C. Sereno 11/7 2005"

So that died over two decades ago. But papers keep being published using PhyloCode's rules and registration, so we have the potential to all agree and let things be good. "But I don't like PhyloCode because of blah blah blah!" Oh, so are you going to set up your own rival code and gain comparable support based on that objection? No? Well you're not helping then, and what's the saying about the enemy of the good being the perfect? Just go with the flow, people!

As an aside, this topic is unrelated to vernacular names like bird or croc. Non-avian birds can be a thing and non-crocodylian crocs as well.  When you say "croc", the general public isn't even going to think alligators, caimans and gavials count because they have no clue a greater Crocodylia exists that includes a Crocodylidae with actual crocodiles. Just like I can say Birgeria is a fish without Pisces being a thing. Is Archaeopteryx a bird? Eh, depends on your priors. Is Object X big? Depends on the priors. We don't need an objective definition of "big" to use the word.

But seriously, if you have a philosophical objection to the PhyoCode but still want to use phylogenetic nomenclature, what do you think not following it will grant you?

Mickey Mortimer

[Gregory Paul]

Missing the point. Telling regular folks that Euparkeria is an archosauriform is about as informative as telling them that birds are archosauriformes. Instead we tell them birds are dinosaurs, and that puts them in a specific phylogenetic position that is informative. Putting Euparkeria and crocs in thecodonts serves the same relationship location function. 

There are very few thecodonts that do not fit the basic pattern (which does not include lack of an erect gait, it does includes lack of an inturned femoral head to do it). There is much less variation in thecodonts than in dinosaurs, ornithischians, mammals, ungulates.

GSPaul

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CAC4cqEWDNcCpsJpB7_GPcwAhJZH1o4bR62LZy7OvoZcH4OLJ%3DA%40mail.gmail.com.

[Tim Williams]

Meig Dickson via Dinosaur Mailing Group <DinosaurMa...@googlegroups.com> wrote:

> Finally, the fact that only crown-avians (ignore Qinornis) survived the end-Cretaceous extinction points to Neornithes as a clear cutoff for "bird".

I'm going off on a tangent here, but Lithornithidae is another possible exception, if they are outside crown Aves (e.g., Clarke & Chiappe, 2001; Livezey and Zusi 2007; Hartman et al. 2019; also Chen et al., 2025 has some very useful comments).  (Although Hartman &c also found that _Lithornis_ being a palaeognath only required five more steps).

The possibility has also been raised (but AFAIK not yet taken any further) that certain "bizarre" Cenozoic birds like Pelagornithidae, Dromornithidae, and Gastornithidae might be outside the crown clade, based on the interpretation that the neognathous palate is primitive for crown birds (Benito et al., 2022).  This is tied to the view that the 'paleognathous' palate is problematic (which I assume is meant by "an anachronistic conceptual wastebasket"); and so perhaps the Palaeognathae is not a natural group.  If lithornithids are stem-palaeognaths (e.g., Nesbitt and Clarke 2016; Worthy et al. 2017; Mayr & Kitchener, 2025), their position in crown Aves might also be tenuous.

> You can call any animal more closely related to modern birds than to modern crocodilians a "bird" if you want to. And I enjoy saying Argentinosaurus
> is the largest bird, not only to mess with people, but because the traits that enabled gigantism in sauropods also enabled flight in birds.

Excellent point.  On that, I recall that many years ago George Olshevsky proposed using the name Ornithes ("birds") for all dinosaurs and their closest relatives - essentially the same as Pan-Aves.  I don't think this was formally published.  

Martyniuk (2012) later proposed the name Ornithes for the node-based clade that contains the most recent common ancestor of _Archaeopteryx_ and modern birds and all of its descendants.  So Aves swapped out for Ornithes for the "_Archaeopteryx_ node".   

> But at the end of the day, there is a single cutoff point: what survived the end-Cretaceous. And for that, the answer is Neornithes, and Neornithes
> alone.

The name Neornithes has a convoluted history.  Although it came to be applied to the crown group (Walker, 1981), this was not the original intention.  Gadow (1892) subdivided "Class Aves" into two subclasses, which he named Archornithes (sic) (for _Archaeopteryx) and Neornithes (for all other birds, including Hesperornithidae), as one-on-one replacements for the names Saururae and Ornithurae, which he didn't like