Avian time tree + avian quadrate morphology and possible new clade (free pdf)

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

New avian papers:

Free pdf:

Santiago Claramunt, Catherine Sheard, Joseph W. Brown, Gala Cortés-Ramírez, Joel Cracraft, Michelle M. Su, Brian C. Weeks & Joseph A. Tobias (2025)
A new time tree of birds reveals the interplay between dispersal, geographic range size, and diversification
Current Biology (advance online publication)
doi: https://doi.org/10.1016/j.cub.2025.07.004
https://www.sciencedirect.com/science/article/pii/S096098222500870X
https://www.cell.com/current-biology/fulltext/S0960-9822(25)00870-X

Free pdf:
https://www.cell.com/action/showPdf?pii=S0960-9822%2825%2900870-X


Highlights

We assembled a new time-scaled phylogenetic tree of the world’s birds
Dispersal ability increases range size but has minimal effects on speciation rates
Small geographic ranges are associated with high speciation rates
High speciation rates produce a reduction in geographic range size

Summary

The spatial and temporal dynamics of biodiversity are shaped by complex interactions among species characteristics and geographic processes. A key example is the effect of dispersal on geographical range expansion and gene flow, both of which may determine speciation rates. In this study, we constructed a time-calibrated phylogeny of over 9,000 bird species and leveraged extensive data on avian traits and spatial occurrence to explore the connections between dispersal, biogeography, and speciation. Phylogenetic path analyses and trait-dependent diversification models reveal that geographic range size is strongly associated with the hand-wing index, a proxy for wing aspect ratio related to flight efficiency and dispersal ability. By contrast, we found mixed evidence for the effect of dispersal on diversification rates: dispersive lineages show either slightly higher speciation rates or higher extinction rates. Our results therefore suggest that high dispersal ability increases range expansion and turnover, perhaps because dispersive lineages expand into islands or other geographically restricted environments and have lower population sizes. Our results highlight the nuanced and interconnected roles of dispersal and range size in shaping global patterns of avian diversification and biogeography and provide a richly sampled phylogenetic template for exploring a wide array of research questions in macroecology and macroevolution.


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Free pdf:

Gerald Mayr (2025)
A Derived Morphology of the Quadrate May Support a Previously Unrecognized Major Higher-Level Clade of Neoavian Birds
Journal of Morphology 286(8): e70070
doi: https://doi.org/10.1002/jmor.70070
https://onlinelibrary.wiley.com/doi/10.1002/jmor.70070

Free pdf:
https://onlinelibrary.wiley.com/doi/epdf/10.1002/jmor.70070

The avian quadrate plays a critical role in cranial kinesis, but few comparative studies exist of its morphological variation across higher-level taxa. The present paper surveys the occurrence of a markedly concave articular facet of the condylus medialis. It is detailed that this feature, for which the term trochlea lateralis is introduced, may represent an apomorphy of a higher-level clade that includes the Aequornithes (gaviiforms, procellariiforms, suliforms, pelecaniforms, and allies), Phaethontimorphae (tropicbirds, sunbittern, and kagu), Mirandornithes (flamingos and grebes), and Gruiformes (cranes and allies). Like many other morphological characters, the occurrence of the trochlea lateralis shows homoplasy. However, at least one analysis of sequence data found a clade including the aforementioned four taxa, the interrelationships of which are not conclusively resolved in other studies. A trochlea lateralis is present in birds with different cranial morphologies and feeding adaptations, so that its occurrence often seems to have a phylogenetic (shared common ancestry) rather than a functional origin. The morphology of the condylus medialis of the quadrate may also bear on the affinities of some fossil taxa, such as the early Eocene Halcyornithidae and Messelasturidae, in which a trochlea lateralis is present.

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[Gregory Paul]

Is there a general term for how during ontogeny juveniles of a given species start out similar in form, and then may become more anatomically variable with maturity? 

GSPaul

[David Fastovsky]

You're describing von Baer's Law.

On Wed, Jul 30, 2025 at 4:43 PM 'Gregory Paul' via Dinosaur Mailing Group <DinosaurMa...@googlegroups.com> wrote:

Is there a general term for how during ontogeny juveniles of a given species start out similar in form, and then may become more anatomically variable with maturity? 

GSPaul

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[Jura]

I would say that this sounds like a variation of heterochrony.

[Jacqueline Silviria]

Well, yes, von Baer believed that postnatal individual development usually goes from more general to more specific (mostly universal), and therefore most recapitulation is non-terminal addition (rarely true if ever, same with Haeckelian recapitulation/terminal addition). But I think GSP was asking about postnatal intrapopulational variation increasing at more mature stages relative to embryos. That would accord well with “diversification” in embryonic developmental hourglasses, which at a gene regulatory level is typically attributed to positive selection on pattern enhancers

Incidentally, I was going to ask about the “ontogenetic auxillary principle” (assume growth in the absence of contrary evidence) teased by Aiden Younk a few weeks back. Thomas Carr (pers. comm.) claims it’s at least analogous to Hennig's auxiliary principle as reformulated by Farris and de Laet (given the most parsimonious tree, assume synapomorphy in the absence of contrary evidence/homplasy); presumably he will outline the connection in more detail in an upcoming manuscript. I fail to see how it is different from the standard epigenetic, transformationist view of ontogeny that superseded strict preformationism in the 19th century. Nor do I see how this is a justification for “cladistic ontogeny” because the same assumption could apply to any other methods that posits ontogeny is hierarchically structure. Nor do I think it answers the question of whether it is a logical necessity that ontogeny needs to be hierarchically structured.

Jacqueline S. Silviria

she/her/hers

The Last King of the Jungle

Department of Earth & Space Science
University of Washington
Seattle, WA, USA
jsi...@uw.edu, sympan...@gmail.com

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[Gregory Paul]

Looks like my question has not been answered. 

My question is very specific. It refers only to ontogenetic events WITHIN A GIVEN SPECIES, not to evolutionary patterns. 

What is the technical term for what I undestand is the norm. Young juveniles in a species are pretty similar in aatomical form, and either remain that all the way to adults (horses), or divergence occurs with maturity (humans, lions). This does not seem to be Von Baers Law or heterochrony. 

While I am at it, does the reverse occur? Lots of anatomical variation in juveniles of a given species that is lost until the adults are uniform in morphology. If so, what is the technical term for that? 

GSPaul

[Franco Sancarlo]

Developmental hourglass ?

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[Jaime Headden]

> My question is very specific. It refers only to ontogenetic events WITHIN A GIVEN SPECIES, not to evolutionary patterns. 

Your original question was "Is there a general term for how during ontogeny juveniles of a given species start out similar in form[?]"

It follows that this is a comparative ontogeny question, so it reads like one. "Why are all juveniles triangular-headed but get boxy when they mature?" Unless you're asking why two lizards from the same clutch end up growing up to look [more or less] identical to one another?

Cheers,

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Jaime A. Headden

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

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

[Andreas Johansson]

He’s about when juveniles of a given species are very similar to one another but adults of that species less so. 

—
Andreas Johansson

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[Gregory Paul]

Why is this so hard to understand? 

My question from the start clearly was specific to specific species, it did not indicate comparative ontogeny between species. Had it done so I would have said so. 

The question is, what is what is or are the technical terms when young juveniles of a given species are very similar to one another, and adults of that particular species remain similar (as per horses - I have cited examples), OR when the adults are highly divergent (as per humans, lions). 

I am suspecting there are no technical terms for what is the standard situation, but I want to see if I have missed it or them. 

GSPaul

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[Jura]

Well, if we are keeping it strictly intraspecies then you are just talking about sexual dimorphism. Though, I suspect that this is still not what you are aiming for.

[The Dinosaur Heretic]

Maybe I’m reading Greg’s question wrong, but is he not just discussing individual variation? Or are we looking more in the realms heterochrony, i.e. paedomorphosis/peramorphosis?

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[Jacqueline Silviria]

I did my best to answer this by referencing “hourglass" and “spinning top” models for development. Is anything still unclear?

If it makes you feel better, my question on OAP hasn’t been answered at all.

Jacqueline S. Silviria

she/her/hers

The Last King of the Jungle

Department of Earth & Space Science
University of Washington
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jsi...@uw.edu, sympan...@gmail.com

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[Jacqueline Silviria]

Developmental hourglass models can be traced to at least Duboule (1994) based on ideas articulated by Müller & Dallas (1869), His (1868) and Keibel (1906);  Irie & Kuratani (2014) and Richardson (2021) provide updated historical reviews.

Basically the models explicitly accounts for heterochrony and is thus an antidote to “Haeckelian recapitulation explains anything”. The classic model under phylogenetic embryological perspective posits that eukaryotic embryos of different populations* exhibit greater disparity (“divergence”) at earlier stages of prenatal development, prior to converging on a more conserved “phylotypic” stage shortly before birth. After birth, postnatal development involves (re)diversification and thus increased disparity between adults of the respective populations due to heterochronic processes. This is in contrast to the funnel models of Haeckel and von Baer, in which embryos simple become more divergent as they mature without ever undergoing a phylotypic stage, therefore any differences ontogeny between populations are simply terminal or non-terminal addition.

Of course, in real-world interpopulation comparisons, and especially intrapopulational comparisons, in the classic hourglass model is not always upheld. Richardson et al. (1997; see also Richardson, 2021) and Drost (2017) have noted the geometry of the “hourglass” is highly variable and most organisms do not conform to a simple pattern. Drost specifically notes animals tend to have conservation midway through embryogenesis rather than the later “phylotypic” period and then again in postnatal ontogeny when metamorphosis is involved; whereas plants may have multiple periods of phenotypic conservation within embryogenesis and during and/or after germination.  Therefore, numerous other geometries for ontogeny, such as "spinning-tops" or "inverted hourglasses” (cf. Müller & Dallas, 1869; Richardson, 1999; Bininda-Emonds et al., 2003), are possible.

The spinning-top model is exactly what GSP describes: within a population, variation due to heterchrony increases at some stage of postnatal development before becoming decreasing with maturity.  It is of note because it is arguably the default assumption of Ontogenetic Sequence Analysis (OSA; Colbert & Rowe, 2008; Griffin & Nesbitt, 2016), provided evenly large sampling and realistic character coding of semaphoronts; since the network is double-rooted to both the least mature semaphoront at the base and the most mature semaphoront at the crown, any variation in character states will show “bloat” at some point before the . (Whether OSA as traditionally practiced is a reproducible, viable alternative to Brochu-Carr “cladistic ontogeny" is a separate issue; my view is that it is not, and that is not necessarily a blanket defense of Brochu and Carr.)

*To avoid further quarrels on species concepts, population is used here in an operational, statistical sense.

Jacqueline S. Silviria

she/her/hers

The Last King of the Jungle

Department of Earth & Space Science
University of Washington
Seattle, WA, USA
jsi...@uw.edu, sympan...@gmail.com

ResearchGate profile

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[Dawid Mazurek]

"Is there a general term for how during ontogeny juveniles of a given species start out similar in form, and then may become more anatomically variable with maturity?"

I would say, it's always the case. The genome doesn't change with ontogeny, but the older the organism is, the bigger are the effects of environment on growth.