Scleromochlus and the early evolution of Pterosauromorpha

Foffa, Davide; Dunne, Emma; Nesbitt, Sterling J.; Butler, Richard J.; Fraser, Nicholas C.; Brusatte, Stephen L.; Farnsworth, Alex; Lunt, Daniel J.; Valdes, Paul J.; Walsh, Stig; Barrett, Paul M.

doi:10.1038/s41586-022-05284-x

Cited by 21 publications

(63 citation statements)

References 49 publications

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“…[ 75 ] and Foffa et al . [ 31 ], and the second, alternative tree, termed ‘Ezcurra tree’ was based on recent work by Ezcurra [ 76 ], Garcia et al . [ 77 ] and Müller & Garcia [ 78 ].…”

Section: Methodsmentioning

confidence: 99%

“…However, throughout their evolutionary history, the two archosaurian clades Avemetatarsalia and Pseudosuchia explored a multitude of different locomotor modes [21][22][23][24][25][26][27], including multiple occurrences of bipedalism, such as their independent acquisition in pseudosuchians (i.e. poposaurids and shuvosaurids) and Postosuchus, and in Avemetatarsalia perhaps in lagerpetids and pterosauromorphs, such as Scleromochlus [9,10,[28][29][30][31]. The abundant fossil record of archosaurs facilitates detailed studies of their morphological and locomotor evolution [2,21,[31][32][33].…”

Section: Introductionmentioning

confidence: 99%

“…poposaurids and shuvosaurids) and Postosuchus, and in Avemetatarsalia perhaps in lagerpetids and pterosauromorphs, such as Scleromochlus [9,10,[28][29][30][31]. The abundant fossil record of archosaurs facilitates detailed studies of their morphological and locomotor evolution [2,21,[31][32][33]. However, the exact timing and frequency of the emergence of a more upright gait and bipedalism remain contentious [2,10,21,[25][26][27]31,34,35].…”

Section: Introductionmentioning

confidence: 99%

“…The abundant fossil record of archosaurs facilitates detailed studies of their morphological and locomotor evolution [2,21,[31][32][33]. However, the exact timing and frequency of the emergence of a more upright gait and bipedalism remain contentious [2,10,21,[25][26][27]31,34,35].…”

Section: Introductionmentioning

confidence: 99%

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Quantitative biomechanical assessment of locomotor capabilities of the stem archosaur Euparkeria capensis

2023

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Birds and crocodylians are the only remaining members of Archosauria (ruling reptiles) and they exhibit major differences in posture and gait, which are polar opposites in terms of locomotor strategies. Their broader lineages (Avemetatarsalia and Pseudosuchia) evolved a multitude of locomotor modes in the Triassic and Jurassic periods, including several occurrences of bipedalism. The exact timings and frequencies of bipedal origins within archosaurs, and thus their ancestral capabilities, are contentious. It is often suggested that archosaurs ancestrally exhibited some form of bipedalism. Euparkeria capensis is a central taxon for the investigation of locomotion in archosaurs due to its phylogenetic position and intermediate skeletal morphology, and is argued to be representative of facultative bipedalism in this group. However, no studies to date have biomechanically tested if bipedality was feasible in Eupakeria . Here, we use musculoskeletal models and static simulations in its hindlimb to test the influences of body posture and muscle parameter estimation methods on locomotor potential. Our analyses show that the resulting negative pitching moments around the centre of mass were prohibitive to sustainable bipedality. We conclude that it is unlikely that Euparkeria was facultatively bipedal, and was probably quadrupedal, rendering the inference of ancestral bipedal abilities in Archosauria unlikely.

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“…[ 75 ] and Foffa et al . [ 31 ], and the second, alternative tree, termed ‘Ezcurra tree’ was based on recent work by Ezcurra [ 76 ], Garcia et al . [ 77 ] and Müller & Garcia [ 78 ].…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Quantitative biomechanical assessment of locomotor capabilities of the stem archosaur Euparkeria capensis

2023

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“…Relatively complete fossil ankle specimens will provide a valuable resource in detailing evidence of network-based functional trade-offs. In future applications, the data-based perspectives presented here may provide new evidence for discriminating ancestral archosaur ankle function and hind limb posture [e.g., Euparkeria (Chatterjee, 1982;Cruickshank, 1979;Demuth et al, 2020;Sullivan, 2007Sullivan, , 2010Thulborn, 1980)], inferring foot posture in crocodylian-line taxa [e.g., Poposaurus, Hallopus (Farlow et al, 2014;Gauthier et al, 2011;Parrish, 1987;Schachner et al, 2020)], debates on pterosaur ankle function and terrestrial locomotor capabilities (Foffa et al, 2022;Hutchinson, 2006;Padian, 2008;Padian, 2017), and exploring reversals such as secondarily quadrupedal taxa [e.g., ornithischians and sauropods (Barrett & Maidment, 2017;Carrano, 2005)].…”

Section: Inner Workings Of the Alligator Ankle Offer A Network-based ...mentioning

confidence: 99%

Inner workings of the alligator ankle reveal the mechanistic origins of archosaur locomotor diversity

Turner

Gatesy

2022

Journal of Anatomy

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Major transformations in the locomotor system of archosaurs (a major clade of reptiles including birds, crocodiles, dinosaurs, and pterosaurs) were accompanied by significant modifications to ankle anatomy. How the evolution of such a complex multijoint structure is related to shifts in ankle function and locomotor diversity across this clade remains unclear and weakly grounded in extant experimental data. Here, we used X-ray Reconstruction of Moving Morphology to reconstruct skeletal motion and quantify the sources of three-dimensional ankle mobility in the American alligator, a species that retains the ancestral archosaur ankle structure. We then applied the observed relationships between joint excursion and locomotor behaviors to predict ankle function in extinct archosaurs. High-resolution reconstructions of Alligator skeletal movement revealed previously unseen regionalized coordination among joints responsible for overall ankle rotation. Differences in joint contributions between maneuvers and steady walking parallel transitions in mobility inferred from the ankle structure of fossil taxa in lineages with more erect hind limb postures. Key ankle structures related to ankle mobility were identified in the alligator, which permitted the characterization of ancestral archosaur ankle function. Modifications of these structures provide morphological evidence for functional convergence among sublineages of bird-line and crocodylian-line archosaurs. Using the dynamic insight into the internal sources of Alligator ankle mobility and trends among locomotor modes, we trace anatomical shifts and propose a mechanistic hypothesis for the evolution of ankle structure and function across Archosauria.

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Braincase and neuroanatomy of the lagerpetid Dromomeron gregorii (Archosauria, Pterosauromorpha) with comments on the early evolution of the braincase and associated soft tissues in Avemetatarsalia

Bronzati,

Langer,

Ezcurra

et al. 2023

The Anatomical Record

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The anatomy of the braincase and associated soft tissues of the lagerpetid Dromomeron gregorii (Archosauria: Avemetatarsalia) from the Late Triassic of the United States is here described. This corresponds to the first detailed description of cranial materials of Lagerpetidae, an enigmatic group of Late Triassic (c. 236–200 Million years ago) animals that are the closest known relatives of pterosaurs, the flying reptiles. The braincase of D. gregorii is characterized by the presence of an anteriorly elongated laterosphenoid and a postparietal, features observed in stem‐archosaurs but that were still unknown in early members of the avian lineage of archosaurs. Using micro‐computed tomography (CT‐scan data), we present digital reconstructions of the brain and endosseous labyrinth of D. gregorii. The brain of D. gregorii exhibits a floccular lobe of the cerebellum that projects within the space of the semicircular canals. The semicircular canals are relatively large when compared to other archosauromorphs, with the anterior canal exhibiting a circular shape. These features of the sensory structures of D. gregorii are more similar to those of pterosaurs than to those of other early avemetatarsalians. In sum, the braincase anatomy of D. gregorii shows a combination of plesiomorphic and apomorphic features in the phylogenetic context of Archosauria and suggests that the still poorly understood early evolution of the braincase in avemetatarsalians is complex, with a scenario of independent acquisitions and losses of character states.

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Scleromochlus and the early evolution of Pterosauromorpha

Cited by 21 publications

References 49 publications

Quantitative biomechanical assessment of locomotor capabilities of the stem archosaur Euparkeria capensis

Quantitative biomechanical assessment of locomotor capabilities of the stem archosaur Euparkeria capensis

Inner workings of the alligator ankle reveal the mechanistic origins of archosaur locomotor diversity

Braincase and neuroanatomy of the lagerpetid Dromomeron gregorii (Archosauria, Pterosauromorpha) with comments on the early evolution of the braincase and associated soft tissues in Avemetatarsalia

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