Closest living relatives of dinosaurs

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Closest Living Relatives of Dinosaurs: Birds and Crocodilians

Research consistently identifies birds and crocodilians as the closest living relatives of dinosaurs. Birds are considered the direct descendants of theropod dinosaurs, sharing many anatomical and physiological traits, while crocodilians are the next closest relatives within the broader group Archosauria, which also includes dinosaurs and pterosaurs. Both birds and crocodilians provide important comparative models for understanding dinosaur biology, despite their very different metabolic and anatomical adaptations today 12.

Evolutionary Relationships: Archosauria and Dinosauriforms

Dinosaurs, birds, and crocodilians all belong to the archosaur lineage. Within this group, birds are the only surviving lineage of dinosaurs, specifically derived from small theropod ancestors. Crocodilians, while not dinosaurs themselves, are the closest living outgroup to both birds and dinosaurs, sharing a common ancestor with them before the dinosaur-bird split 12. Fossil and molecular evidence strongly support this evolutionary relationship, with birds and crocodilians forming the two main branches of living archosaurs .

Dinosaur Precursors and Extinct Close Relatives

Fossil discoveries of dinosauriforms, such as silesaurids and Asilisaurus kongwe, help clarify the evolutionary steps leading to true dinosaurs. These extinct forms are not direct ancestors of modern birds or crocodilians but represent close relatives that share many skeletal features with early dinosaurs. Detailed anatomical studies of these precursors reveal a mix of primitive and derived traits, highlighting the complex evolutionary history of the dinosaur lineage 34.

Implications for Dinosaur Biology

Comparisons with birds and crocodilians have been crucial for reconstructing dinosaur physiology, metabolism, and behavior. For example, while modern birds are warm-blooded and highly active, crocodilians are cold-blooded and have different respiratory systems. Dinosaurs likely exhibited a range of metabolic strategies, with some showing bird-like features and others more similar to crocodilians . These comparisons help paleontologists infer how dinosaurs may have lived, grown, and interacted with their environments.

Conclusion

In summary, birds are the closest living relatives of dinosaurs, directly descending from theropod ancestors, while crocodilians are the next closest relatives within the archosaur group. Both provide essential insights into dinosaur evolution and biology, and fossil discoveries of dinosauriforms further illuminate the evolutionary path from early archosaurs to modern birds 1234.

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Most relevant research papers on this topic

Dinosaur Physiology: Were Dinosaurs Warm‐blooded?

Dinosaurs were likely ectothermic, with lower metabolic rates than modern mammals or birds, but could maintain high body temperatures through behavioral or inertial thermoregulation due to favorable Mesozoic climate conditions.

2013·

1citation

·W. J. Hillenius

N COMMEN Detecting Dinosaur DNA

The DNA sequence from Cretaceous bone fragments suggests a possible dinosaur, but its phylogenetic relationship with birds and crocodilians remains unclear.

2008·

0citations

·Marc et al.

The Anatomy of Asilisaurus kongwe, a Dinosauriform from the Lifua Member of the Manda Beds (~Middle Triassic) of Africa

This study provides the first complete anatomy of Asilisaurus kongwe, a dinosauriform from the Middle Triassic Manda Beds of Tanzania, revealing its unique skull and plesiomorphic features, suggesting high homoplasy and parallel trends within Silesauridae and early dinosaur lineages

2019·

43citations

·S. Nesbitt et al.

Osteohistology of the silesaurid Sacisaurus agudoensis from southern Brazil (Late Triassic) and implications for growth in early dinosaurs.

The Late Triassic silesaurid Sacisaurus agudoensis shows rapid growth in its limb bones, supporting the idea that rapid growth occurred early in the dinosauromorph lineage.

2019·

9citations

·Fábio H Veiga et al.

Digestibility of dinosaur food plants revisited and expanded: Previous data, new taxa, microbe donors, foliage maturity, and seasonality

Dinosaur herbivores found living relatives of Araucariaceae and Equistaceae highly digestible, while fern taxa were inconsistent, with season, leaf maturity, and rumen fluid donor not influencing digestibility.

2023·

2citations

·Mariah M. Howell et al.

Enigmatic dinosaur precursors bridge the gap to the origin of Pterosauria

Lagerpetids are the sister group of pterosaurs, shortening the temporal and morphological gap between the oldest and closest relatives, and strengthening the evidence that pterosaurs belong to the avian line of archosaurs.

Rigorous JournalHighly Cited

2020·

101citations

·M. Ezcurra et al.

A Dome-Headed Stem Archosaur Exemplifies Convergence among Dinosaurs and Their Distant Relatives

A new Triassic stem archosaur demonstrates convergence among dinosaurs and their distant relatives, highlighting early exploration of morphospace in the Triassic Period.

2016·

57citations

·M. Stocker et al.

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.

Highly Cited

2016·

70citations

·C. Griffin et al.

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, combining bipedalism with forelimb proportions for swimming, and convergent with short-tailed birds.

Very Rigorous JournalHighly Cited

2017·

124citations

·A. Cau et al.

The first dinosaur from the Jurassic Aliança Formation of northeastern Brazil, west Gondwana: a basal Neotheropoda and its age and paleobiogeographical significance

Theropod dinosaurs from the Middle-Late Jurassic Aliança Formation of Brazil are closer related to basal neotheropods like Dilophosaurus wetherilli, suggesting their survival during the Middle-Late Jurassic period.

2022·

8citations

·Leonardo M. De Oliveira et al.

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