Graviportality in large quadrupedal dinosaurs and mammals + tetrapod skull-neck boundary + Upper Devonian tetrapod tracks from Ireland

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

Some recent papers:

Free pdf:

Donald R. Prothero, Kristin I. Watmore, and Ed Welsh (2025)
What is graviportality? Interspecific limb allometry in large quadrupedal dinosaurs and mammals
Lucas et al., 2025, Fossil Record 10. New Mexico Museum of Natural History and Science Bulletin 100: 189--196
https://www.researchgate.net/publication/394114954_WHAT_IS_GRAVIPORTALITY_INTERSPECIFIC_LIMB_ALLOMETRY_IN_LARGE_QUADRUPEDAL_DINOSAURS_AND_MAMMALS


It is well known that limb bones must grow more robust allometrically as animals become larger, because mass increases as a power of three while most dimensions, such as limb length, only show linear increase in size. This has been documented across a wide range of mammals of body sizes from shrews to elephants. But it should be especially pronounced in graviportal mammals, which are on the larger end of the body size range, with the most robust pillar-like limbs, such as elephants, rhinos, hippos, and most large quadrupedal dinosaurs. We tested this hypothesis using measurements of the humerus, femur, and tibia in nine groups of graviportal mammals (proboscideans, rhinos, hippos, pigs, tapirs, hyracodonts, camelids, bovids, and entelodonts) which exhibit a wide range of body sizes, as well as three groups of large quadrupedal dinosaurs (ceratopsians, ankylosaurs, and stegosaurs). As predicted, nearly all the interspecific slopes of body size increase were negatively allometric, with larger members of the group having disproportionately more robust limbs than the smallest members. Not all these slopes were significantly removed from isometry at the 95% confidence level, but it is striking that nearly all the slopes showed negative allometry, with only one or two exceptions.

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Free pdf:

Dana E. Korneisel & Hillary C. Maddin (2025)
Review of the tetrapod skull–neck boundary: implications for the evolution of the atlas–axis complex
Biological Reviews (advance online publication)
doi: https://doi.org/10.1111/brv.70053
https://onlinelibrary.wiley.com/doi/10.1111/brv.70053

Free pdf:
https://onlinelibrary.wiley.com/doi/epdf/10.1111/brv.70053


This review describes variation in modern and fossil occiput–atlas–axis complex anatomy of total group Tetrapoda with the aim of documenting the range of structural variation throughout their evolutionary history to establish grounds for comparison of the complex between tetrapod clades. This review reveals that every modern tetrapod has an atlas with morphology unique to its vertebral column that articulates to the skull, composed, typically, of paired neural arch halves and an intercentrum. Maximally complex tetrapod atlantes articulate to paired proatlas halves and are composed of paired neural arch halves, an intercentrum, and a pleurocentrum. The centra may occur as left and right halves but are most often singular elements in adults. Lissamphibians often have an interglenoid tubercle extending anteriorly from their atlas centrum. Stem tetrapods develop a specialised second cervical vertebra, the axis, most often distinguished from its posterior neighbours by an anteriorly oriented odontoid process contributing to the skull–neck joint. An axis is retained in nearly all subsequently diverging tetrapod clades, except for lissamphibians and their closest relatives. Exemplar fossil taxa reveal patterns of atlas–axis evolution throughout the tetrapod lineage. Here, synthesis of osteological data from extinct and extant taxa provides a basis for hypotheses of skull–neck boundary evolution in tetrapods. For example, convergent trends towards fewer separate components in adult tetrapod atlas–axis complexes, except in crocodylians and rhyncocephalians, are illuminated. Further insights into the development of the atlas and axis may help support or refute these hypotheses and will contribute to a more complete understanding of the origin of observed variation.

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Free pdf:

Kenneth T. Higgs & Patrick A. Meere (2024)
Tetrapod trackways from the Upper Devonian St. Finan's Sandstone Formation, southwest Kerry, Ireland
Irish Journal of Earth Sciences 42: 97-118
DOI: https://doi.org/10.1353/ijes.2024.a935022
https://muse.jhu.edu/pub/423/article/935022

Free pdf:
https://muse.jhu.edu/pub/423/article/935022/pdf

Tetrapod trackways are described for the first time from the Upper Devonian St. Finan's Sandstone Formation at Tooreen in St. Finan's Bay, southwest County Kerry. The St. Finan's Sandstone Formation is a 1,240m thick sandstone-dominated sequence that occurs in the middle part of the continental Old Red Sandstone Munster Basin succession. The trackways comprise 140 imprints that show variable depth and shape. This variability is attributed to changes in the firmness of the substrate and water depth along the length of the trackways. One of the trackways preserves an imprint with possible five-digit impressions and another displays a tapered elongated depression that is tentatively interpreted as a tetrapod body impression. Analysis of three trackways indicates they were made by a population of similar-sized tetrapods (just under 1m in length) that moved by lateral sequence walking. The trackways are preserved in a current-rippled and parallel-laminated sandstone sequence that was deposited on a flood plain bordering a river channel margin. A spore assemblage obtained from a mudstone within the trackway-bearing sequence is assigned to the Rugospora bricei - Cymbosporites acanthaceus BA Biozone, which biostratigraphically dates the trackway as Upper Devonian (mid Frasnian) in age. The Tooreen tetrapod trackways are very similar in size, spatial arrangement and palaeoenvironment to those recorded from the older Middle Devonian (Givetian) Valentia Slate Formation that occur nearby on Valentia Island. This new evidence extends the geographic and geological range of these ichnological datasets and provides a better understanding of the early stages of colonisation of continental (terrestrial) environments by Devonian tetrapods.

[Mike Taylor]

According to the first paper, Loxodonta africana has a humerus 858 mm in length and 2694.12 mm in diameter. I am sceptical.

(There are a lot more typos in the data table. That was just the one that caught my eye.)

-- Mike.

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