Archosaur aerobic metabolic rates and endothermy evidence from long bone blood flow rates + Bartassochersis, new turtle from Triassic of France (free pdfs)

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

New papers:

Free pdf:

Roger S. Seymour, Case Vincent Miller, Qiaohui Hu, Martin D. Ezcurra, Sterling J. Nesbitt, Marc E. H. Jones, Susannah C. R. Maidment, Daniela Schwarz, Eric W. Wilberg, Nicolás E. Campione & Gordon Grigg (2026)
Blood flow rates to long bones of archosaurs reveal high aerobic metabolic rates and endothermy throughout most of their evolutionary history
Paleobiology (advance online publication)
DOI: https://doi.org/10.1017/pab.2026.10110
https://www.cambridge.org/core/journals/paleobiology/article/blood-flow-rates-to-long-bones-of-archosaurs-reveal-high-aerobic-metabolic-rates-and-endothermy-throughout-most-of-their-evolutionary-history/A12DA2D6DD15CDAF4619AB253462B5B5


The origin and evolution of endothermy among Archosauria are uncertain because living species are represented by two lineages: ectothermic crocodylians (Pseudosuchia) and endothermic birds (Avemetatarsalia). Endothermy is characterized by high metabolic rates (tachymetabolism) and a physiological ability to control body temperature (thermoregulation), partly by using heat generated within the body. Ectothermy is characterized by low metabolic rates (bradymetabolism) and behavioral body temperature regulation. Levels of metabolic rate can be indirectly assessed by measuring the size of primary nutrient foramina of long bones. Foramen radius is related to blood flow rate (˙Q) into the bone, which supports growth, repair, and remodeling of bone tissue that increase in more active vertebrates. Extant endothermic mammals are known to have profoundly higher ˙Q than extant ectothermic reptiles of the same body size. This study measures nutrient foramen minor radius, mid-shaft circumference, and length of femora of archosaur fossils, focusing on the earliest lineages. It reports ˙Q and body mass for 81 extinct archosauriform taxa and compares the data allometrically with extant endothermic and ectothermic vertebrates. The extinct archosauriforms yield generally higher ˙Q  values than occur in extant mammals and non-varanid reptiles. The study indicates that tachymetabolic archosauriforms dominated the Mesozoic from the Triassic onward. Their high basal metabolic rates produced heat potentially used for thermoregulation. With few exceptions, both Pseudosuchia and Avemetatarsalia exhibit high ˙Q values from the Triassic to the Cretaceous. Avemetatarsalians apparently remained endothermic until the present, while some tachymetabolic pseudosuchians became bradymetabolic relatively recently, as evident in extant crown crocodylians.

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Free pdf:

Bartassochersis lopezi gen. et sp. nov.

Tomasz Szczygielski, Fanny Celestin, Sylvain Adnet & Guillaume Guinot (2026)
Triassic turtles of France: the first European Rhaetian stem turtle taxon (clades Testudinata, Proterochersidae)
Swiss Journal of Palaeontology 145: 851-879.
doi: https://doi.org/10.3897/sjp.145.198341
https://sjp.pensoft.net/article/198341/list/9/


The earliest turtles (clade Testudinata) are known from the Norian (middle Late Triassic) and soon after their appearance they became speciose and widespread. However, their record in the later part of the Late Triassic (Rhaetian) remains very scarce. Herein, we present the first European representatives of the clade from that age. Bartassochersis lopezi gen. et sp. nov. from the Rhaetian Formation of France is recovered here as a proterochersid and presents a number of unique, autapomorphic characters, hinting at the previously unknown morphological diversity of stem turtles in the latest Triassic. This landscape is supplemented by a find of an indeterminate, but probably remarkably small-bodied species from the ‘Grès infraliasiques’ Formation. Previously uncharted regions and latest Triassic strata of Pangaea may, therefore, still hide unknown testudinates.

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[Gregory Paul]

Dr Bob was right. 

GSPaul

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[Jody]

this is a very interesting paper. the evolutionary history of archosaurs gets more interesting with each new discovery.

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[Jody]

the turtle paper is also interesting