closest living ancestor to dinosaurs

Introduction

The closest living ancestors to dinosaurs have been a subject of extensive research, focusing on the evolutionary lineage and characteristics that link modern species to their prehistoric predecessors. This synthesis aims to consolidate findings from multiple research papers to provide a clear understanding of the closest living relatives to dinosaurs.

Key Insights

Primitive Dinosaur Ancestors:
- Eoraptor lunensis, discovered in Argentina, is considered close to the common dinosaurian ancestor, exhibiting features that align it with theropods .
- Herrerasaurus ischigualastensis and Staurikosaurus pricei are among the oldest known dinosaurs, suggesting a rapid divergence from a common ancestor.
Phylogenetic Relationships:
- Early dinosaurs like Pisanosaurus mertii and Panphagia protos from the Ischigualasto Formation, and Staurikosaurus pricei and Saturnalia tupiniquim from the Santa Maria Formation, indicate a Middle Triassic origin inferred from footprint records and sister-group relations to basal dinosauromorphs.
- The diapsid common ancestor (DCA) genome structure, inferred from modern species, suggests a stable genomic organization that predates the emergence of early dinosaurs and pterosaurs.
Miniaturization and Evolution:
- Kongonaphon kely, a tiny ornithodiran from Madagascar, indicates a pronounced miniaturization event near the common ancestor of dinosaurs and pterosaurs, which may have facilitated the origins of flight in pterosaurs and fuzzy integument in both groups.
Developmental Variation:
- Early dinosaurs and their close relatives exhibited high intraspecific variation in postnatal development, a trait that was lost in more derived theropods like Allosaurus and Tyrannosaurus, but this high variation may have contributed to their dominance during the Triassic-Jurassic mass extinction.

Conclusion

The closest living ancestors to dinosaurs are traced back to early theropods and basal dinosauromorphs, with significant evolutionary traits such as miniaturization and high developmental variation playing crucial roles. Eoraptor lunensis and other early dinosaurs from the Triassic period provide key insights into the rapid divergence and evolutionary adaptations that led to the dominance of dinosaurs. The genomic stability observed in the diapsid common ancestor further underscores the deep evolutionary roots shared by modern birds and their prehistoric relatives.

Closest living ancestor to dinosaurs

Summary

Introduction

Key Insights

Conclusion

Sources and full results

Primitive dinosaur skeleton from Argentina and the early evolution of Dinosauria

The discovery of Eoraptor lunensis supports the hypothesis that dinosaurs diverged rapidly at small body size from a common ancestor, with the principal herbivorous and carnivorous lineages present by the middle Carnian.

The origin and early evolution of dinosaurs

Dinosaurs evolved from a common ancestor with birds and Triceratops, with the oldest fossils dating to the Late Triassic.

Reconstruction of the diapsid ancestral genome permits chromosome evolution tracing in avian and non-avian dinosaurs

The diapsid common ancestor had a highly stable genomic structure that contributed to phenotypic diversity and adaptive responses to environmental disruptions, predating the emergence of early dinosaurs and pterosaurs and the evolution of flight.

A tiny ornithodiran archosaur from the Triassic of Madagascar and the role of miniaturization in dinosaur and pterosaur ancestry

The early ornithodirans (Kongonaphon kely) from the Triassic of Madagascar show a miniaturization event near the common ancestor of dinosaurs and pterosaurs, potentially explaining the origins of flight in pterosaurs and fuzzy integu

Anomalously high variation in postnatal development is ancestral for dinosaurs but lost in birds

High intraspecific variation in postnatal development is ancestral for dinosaurs and their closest relatives, but lost in more derived nonavian theropods, potentially contributing to the rise of dinosaur dominance during the Triassic-Jurassic mass extinction.

Increases in sampling support the southern Gondwanan hypothesis for the origin of dinosaurs

A southern Gondwanan origin for dinosaurs remains the most plausible hypothesis, supported by increased taxonomic and geographic sampling and divergent phylogenetic results.

Archaeopteryx and the origin of birds

Archaeopteryx evolved from a small coelurosaurian dinosaur, and modern birds are surviving dinosaurian descendants.

The Complete Skull and Skeleton of an Early Dinosaur

Herrerasaurus ischigualastensis, a primitive theropod, was an agile, bipedal predator in the Upper Triassic Ischigualasto Formation, suggesting the dinosaurian radiation was well under way before they dominated terrestrial vertebrate communities.

The origin and early evolution of birds

Birds evolved from theropod dinosaurs, with many avian features evolving in non-avian theropods for unrelated reasons, and most extant bird orders were not known until the Paleocene or Eocene.

Synchrotron scanning reveals amphibious ecomorphology in a new clade of bird-like dinosaurs

Halszkaraptor escuilliei, a new clade of bird-like dinosaurs, exhibits amphibious ecomorphology, convergent with short-tailed birds, and shows neck hyperelongation for food procurement.

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