Bat limb proportions evolution + proboscidean limb long bone morphology + eutherian gestation evolution + Prophaethon waltonensis, new Eocene bird species

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

Some recent non-dino papers:

Andrew Orkney, David B. Boerma & Brandon P. Hedrick (2024)
Evolutionary integration of forelimb and hindlimb proportions within the bat wing membrane inhibits ecological adaptation
Nature Ecology & Evolution (advance online publication)
doi:  https://doi.org/10.1038/s41559-024-02572-9
https://www.nature.com/articles/s41559-024-02572-9


Bats and birds are defined by their convergent evolution of flight, hypothesized to require the modular decoupling of wing and leg evolution. Although a wealth of evidence supports this interpretation in birds, there has been no systematic attempt to identify modular organization in the bat limb skeleton. Here we present a phylogenetically representative and ecologically diverse collection of limb skeletal measurements from 111 extant bat species. We compare this dataset with a compendium of 149 bird species, known to exhibit modular evolution and anatomically regionalized skeletal adaptation. We demonstrate that, in contrast to birds, morphological diversification across crown bats is associated with strong trait integration both within and between the forelimb and hindlimb. Different regions of the bat limb skeleton adapt to accommodate variation in distinct ecological activities, with flight-style variety accommodated by adaptation of the distal wing, while the thumb and hindlimb play an important role facilitating adaptive responses to variation in roosting habits. We suggest that the wing membrane enforces evolutionary integration across the bat skeleton, highlighting that the evolution of the bat thumb is less correlated with the evolution of other limb bone proportions. We propose that strong limb integration inhibits bat adaptive responses, explaining their lower rates of phenotypic evolution and relatively homogeneous evolutionary dynamics in contrast to birds. Powered flight, enabled by the membranous wing, is therefore not only a key bat innovation but their defining inhibition.

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News:

A comparison of bat and bird wings reveals their evolutionary paths are vastly different

https://phys.org/news/2024-11-comparison-bird-wings-reveals-evolutionary.html

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Free pdf:

Camille Bader, Arnaud Delapré, Ursula B. Göhlich & Alexandra Houssaye (2024)
Diversity of limb long bone morphology among proboscideans: how to be the biggest one in the family
Papers in Palaeontology 10(6): e1597
doi: https://doi.org/10.1002/spp2.1597
https://onlinelibrary.wiley.com/doi/10.1002/spp2.1597

Free pdf:
https://onlinelibrary.wiley.com/doi/epdf/10.1002/spp2.1597


From its first small representatives to its later giant species, the Order Proboscidea evolved increasingly large forms. Limb long bones are heavily affected by shifts in body mass, and this is especially true in proboscideans, in which an increase in body mass is associated with a reorientation of the limb into the parasagittal plane, reducing the need for strong musculature. We investigated shape variation in the six long bones elements of the limb of extant and extinct proboscideans with regard to body mass evolution in this lineage. To do so, we used three-dimensional geometric morphometrics and qualitative comparisons to describe shape variability. Our analysis indicates that the shift from a flexed posture to a columnar one results in reorientations of articular surfaces in the six bones, and a decrease in robustness, thus reducing bending stresses on the bones. We also identify two main morphotypes among graviportal proboscideans: one (MA) corresponding to bones with a thin diaphysis and narrow epiphyses, as in deinotheres and elephantids, and the other (MB) to bones with a large diaphysis and wide epiphyses, seen in gomphotheres and mammutids. Both morphotypes are observed in species of similar mass, indicating that adaptation to high body weight support has been achieved in two different ways among proboscideans, and that once acquired, it remains fixed within the taxon.

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Free pdf:

Thodoris Danis and Antonis Rokas (2024)

The evolution of gestation length in eutherian mammals
Proceedings of the Royal Society B: Biological Sciences 291(2033): 20241412
doi: https://doi.org/10.1098/rspb.2024.1412
https://royalsocietypublishing.org/doi/10.1098/rspb.2024.1412

Free pdf:
https://royalsocietypublishing.org/doi/epdf/10.1098/rspb.2024.1412


Eutherian mammals exhibit considerable variation in their gestation lengths, which has traditionally been linked to variation in other traits, including body mass and lifespan. To understand how gestation length variation, including its association with body mass and lifespan variation, changed over mammalian evolution, we conducted phylogeny-informed analyses of 845 representative extant species. We found that gestation length substantially differed in both whether and how strongly it was associated with body mass and lifespan across mammals. For example, gestation length was not associated with lifespan or body mass in Chiroptera and Cetacea but was strongly associated only with body mass in Carnivora. We also identified 52 evolutionary shifts in gestation length variation across the mammal phylogeny and 14 shifts when we jointly considered variation of all three traits; six shifts were shared. Notably, two of these shifts, both positive, occurred at the roots of Cetacea and Pinnipedia, respectively, coinciding with the transition of these clades to the marine environment, whereas a negative shift occurred at the root of Chiroptera, coinciding with the evolution of flight in this clade. These results suggest that the relationship between gestation length and the two other traits has varied substantially across mammalian phylogeny.

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Free pdf:

Prophaethon waltonensis sp. nov.

 
Gerald Mayr & Andrew C. Kitchener (2024)
A new species of the Prophaethontidae (Aves, Phaethontiformes) from the early Eocene London Clay
Historical Biology (advance online publication)
doi: https://doi.org/10.1080/08912963.2024.2418895
https://www.tandfonline.com/doi/full/10.1080/08912963.2024.2418895

Free pdf:
https://www.tandfonline.com/doi/epdf/10.1080/08912963.2024.2418895



We report new specimens of the stem group phaethontiform Prophaethon from the early Eocene London Clay of Walton-on-the-Naze (Essex, UK). The two partial skeletons are distinctly smaller than a previously described record of Prophaethon from this locality, which was assigned to P. shrubsolei. Even though some extant aquatic birds show a pronounced sexual dimorphism in size, this is considered unlikely to explain the size disparity of the Prophaethon fossils from Walton-on-the-Naze and the new specimens are here described as P. waltonensis, sp. nov. The distal end of the humerus of the new species differs from that of other Phaethontiformes in the presence of a small but well-defined processus supracondylaris dorsalis. With regard to this feature, it shows a resemblance to the humerus of the Procellariiformes, which is unexpected in light of the recently proposed hypothesis that the sister taxon of the Phaethontiformes are the terrestrial Eurypygiformes. Finally, we comment on prophaethontid remains from the late Paleocene of Kazakhstan, which were assigned to the taxa Zhylgaia Nessov, 1988 and Tshulia Nessov, 1988. We synonymise the latter with the former taxon and also consider it possible that Zhylgaia Nessov, 1988 is a junior synonym of Prophaethon Andrews, 1899.

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