Nesting at extreme polar latitudes by non-avian dinosaurs

How smart wasT. rex? Testing claims of exceptional cognition in dinosaurs and the application of neuron count estimates in palaeontological research

“…Rather than emerging with theropods, contemporary evidence suggests that endothermy evolved in the ornithodiran stem-lineage or even earlier (Legendre et al, 2016; Benton, 2021; Grigg et al, 2022) and hence was inherited by pterosaurs and dinosaurs. The extensive data supporting the presence of endothermy across Ornithodira has recently been reviewed by Grigg et al (2022) and includes the presence of hair-like, sometimes branched, integumentary structures (Benton et al, 2019; Campione et al, 2020), the efficiency of the ornithodiran respiratory system (Wedel, 2006; Butler et al, 2009; Aureliano et al, 2022; Wang et al, 2023), bone histology and high skeletal growth rates (de Ricqlès et al, 2000; Padian et al 2004; Prondvai et al, 2012; Redelstroff et al 2013; Legendre et al, 2016), paleoenvironmental data (Druckenmiller et al, 2021), models of locomotor costs (Pontzer et al, 2009) and geochemically-derived thermometric findings (Barrick et al, 1996; Dawson et al 2020; Wiemann et al, 2022). Nevertheless, osteohistological evidence suggests that both theropod and non-theropod ornithodiran taxa varied in their growth and associated metabolic rates (Jenkins et al, 2001; Erickson et al, 2009; Redelstroff et al 2013; D’Emic et al, 2023) and a secondary reduction of metabolic rate in some ornithischian groups appears plausible (Padian et al, 2004; Redelstroff and Sander, 2009; Wiemann et al, 2022), albeit still compatible with an endothermic physiology (Grigg et al, 2022).…”

Evidence for heterothermic endothermy and reptile-like eggshell mineralization inTroodon, a non-avian maniraptoran theropod

“…( 19 ) (on one of the specimens also analyzed here) and are comparable with modern birds, suggesting that Troodon possessed the capacity to achieve high metabolic rates, an observation in line with results from previous studies on dinosaur skeletal morphology and bone vascularization ( 41 ), melanosome morphology ( 20 ), mathematical models ( 42 ), and recently discovered metabolism-related biomolecules ( 18 ). In addition, high metabolic rates and endothermic thermoregulation represent the only possible explanation for the perennial residence of troodontid hatchlings at paleolatitudes of 80 to 85°N ( 43 – 45 ). Given the high body temperature indicated by several eggshells, it is possible that Troodon could have used body heat, at least in part, for egg incubation, not inconsistent with the previously hypothesized brooding behavior in Troodon ( 24 ).…”

Early Jurassic origin of avian endothermy and thermophysiological diversity in Dinosauria

“…Sauropodomorphs exhibit a preference for high temperatures, while ornithischians and theropods demonstrate a broader range of thermal landscapes in their evolutionary histories. This divergence in climatic niches likely played a crucial role in shaping the ecological diversity, biogeographic history and success of these groups ( 12 , 17 , 51 , 52 ).…”

“…This adaptation, along with elevated cold tolerance, may have facilitated their continuous persistence at high latitudes and occupation of broader climatic zones (Fig. 3B), ranging from tropical to polar environments ( 12 , 17 , 53 ). Theropods also displayed a wide range of climatic preferences, with some taxa retaining ancestrally warmer and drier niches, while others adapted to cooler and slightly more seasonal conditions.…”

“…That is, species with higher variation in internal temperature that rely on environmental heat for homeostasis ( 7 ). However, recent discoveries [( 12 , 13 )] are challenging this ‘cold-blooded’ environmental, thermally-regulated body temperature paradigm, painting a more nuanced picture. It highlights the emergence – at least within certain dinosaurian subclades (e.g.…”