Extreme neck elongation evolved despite strong developmental constraints in bizarre Triassic reptiles—implications for neck modularity in archosaurs

Royal Society Open Science, Journal Year: 2024, Volume and Issue: 11(5)

Published: May 1, 2024

The Triassic radiation of vertebrates saw the emergence modern vertebrate groups, as well numerous extinct animals exhibiting conspicuous, unique anatomical characteristics. Among these, members Tanystropheidae (Reptilia: Archosauromorpha) displayed cervical vertebral elongation to an extent unparalleled in any other vertebrate. Tanystropheids were exceptionally ecologically diverse and had a wide spatial temporal distribution. This may have been related their neck anatomy, yet its evolution functional properties remain poorly understood. We used geometric morphometrics capture intraspecific variation between vertebrae comprising column among early archosauromorphs, trace evolutionary history these animals. Our results show that series reptiles can be divided into modules corresponding those extant achieved through somite shift thoracic regions, without presacral count increase—contrary crown archosaurs. suggests peculiar developmental constraint strongly affected tanystropheids. data obtained just at base archosauromorph phylogenetic tree are crucial for further studies on modularity columns not only reptile groups but well.

Language: Английский

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Permissive and instructiveHoxcodes govern limb positioning

bioRxiv (Cold Spring Harbor Laboratory), Journal Year: 2024, Volume and Issue: unknown

Published: July 19, 2024

Abstract The positioning of limbs along the anterior-posterior axis varies widely across vertebrates. mechanisms controlling this feature remain to be fully understood. For over 30 years, it has been speculated that Hox genes play a key role in process but evidence supporting hypothesis largely indirect. In study, we employed loss- and gain-of-function gene variants chick embryos address issue. Using approach, found Hox4/5 are necessary insufficient for forelimb formation. Within expression domain, Hox6/7 sufficient reprogramming neck lateral plate mesoderm form an ectopic limb bud, thereby inducing formation anterior normal field. Our findings demonstrate program depends on combinatorial actions these genes. We propose during evolutionary emergence neck, provide permissive cues throughout region, while final position is determined by instructive mesoderm. Impact statement Elucidation code defining provides novel insights patterning integration vertebrate column structure positioning. Classification Development --- developmental biology

Language: Английский

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Permissive and instructive Hox codes govern limb positioning

Published: Oct. 14, 2024

The positioning of limbs along the anterior-posterior axis varies widely across vertebrates. mechanisms controlling this feature remain to be fully understood. For over 30 years, it has been speculated that Hox genes play a key role in process but evidence supporting hypothesis largely indirect. In study, we employed loss- and gain-of-function gene variants chick embryos address issue. Using approach, found Hox4/5 are necessary insufficient for forelimb formation. Within expression domain, Hox6/7 sufficient reprogramming neck lateral plate mesoderm form an ectopic limb bud, thereby inducing formation anterior normal field. Our findings demonstrate program depends on combinatorial actions these genes. We propose during evolutionary emergence neck, provide permissive cues throughout region, while final position is determined by instructive mesoderm.

Language: Английский

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Permissive and instructive Hox codes govern limb positioning

Published: Oct. 14, 2024

The positioning of limbs along the anterior-posterior axis varies widely across vertebrates. mechanisms controlling this feature remain to be fully understood. For over 30 years, it has been speculated that Hox genes play a key role in process but evidence supporting hypothesis largely indirect. In study, we employed loss- and gain-of-function gene variants chick embryos address issue. Using approach, found Hox4/5 are necessary insufficient for forelimb formation. Within expression domain, Hox6/7 sufficient reprogramming neck lateral plate mesoderm form an ectopic limb bud, thereby inducing formation anterior normal field. Our findings demonstrate program depends on combinatorial actions these genes. We propose during evolutionary emergence neck, provide permissive cues throughout region, while final position is determined by instructive mesoderm.

Language: Английский

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Unique internal anatomy of vertebrae as a key factor for neck elongation in Triassic archosauromorphs

Zoological Journal of the Linnean Society, Journal Year: 2024, Volume and Issue: 202(3)

Published: Oct. 14, 2024

Abstract The Triassic was a key period in the evolution of vertebrates, and reptiles particular, giving rise to plethora successful lineages, some which are still extant. One groups that flourished during early Mesozoic were tanysaurians (Archosauromorpha: Tanysauria). They had elongate neck vertebrae genera reached extreme proportions. Here, we provide first comprehensive description internal structure these extraordinary elements, focusing on famously bizarre Tanystropheus. Through computed tomography sectioning, able reveal intriguing features comparable those seen pterosaurs birds. However, contrary what see pneumatic bones, cervicals contain singular voluminous cavity. This results cylindrical vertebrae, likely provided durability, while contributing less weight neck. These insights relevant for better understanding unique anatomy among tetrapods, evolved as result very strict selection particular function. Importantly, our findings demonstrate major modifications not derived avemetatarsalians (pterosaurs dinosaurs), but more widespread reptiles.

Language: Английский

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