Closest dinosaur relative

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Closest Dinosaur Relatives: Insights from Recent Research

Introduction to Dinosaur Relatives

Understanding the closest relatives of dinosaurs is crucial for unraveling the evolutionary history of these fascinating creatures. Recent research has provided significant insights into the dinosauriforms, a group that includes the closest relatives of dinosaurs, and their evolutionary traits.

Silesaurids: Non-Dinosaurian Dinosauriforms

Growth Patterns and Osteohistology

Silesaurids, a group of non-dinosaurian dinosauriforms, are among the closest relatives of crown-group dinosaurs. The osteohistology of Sacisaurus agudoensis, a silesaurid from the Late Triassic of Brazil, reveals rapid growth patterns characterized by uninterrupted fibrolamellar bone tissue. This indicates that rapid growth was a trait present early in the dinosauromorph lineage, although silesaurids exhibit simpler vascular arrangements compared to saurischian dinosaurs, suggesting relatively slower growth rates.

Anatomical Features and Phylogenetic Position

Asilisaurus kongwe, another dinosauriform from the Middle Triassic of Tanzania, provides detailed anatomical insights that help clarify the relationships within early dinosaur relatives. Asilisaurus shares several primitive features with archosaurs, such as a crocodylian-like ankle configuration, and is more closely related to Silesaurus opolensis than to true dinosaurs. This suggests high homoplasy and parallel evolutionary trends within Silesauridae and early dinosaurs.

Lagerpetids: Bridging the Gap to Pterosaurs

Morphological and Temporal Proximity

Lagerpetids, a group of cursorial, non-volant dinosaur precursors, have been identified as the sister group to pterosaurs. Recent discoveries of well-preserved cranial remains and associated postcrania demonstrate numerous shared features between lagerpetids and pterosaurs, significantly shortening the morphological and temporal gap between these groups. This finding supports the hypothesis that pterosaurs belong to the avian line of archosaurs and that certain neuroanatomical features related to flight evolved before the actual development of flight capabilities.

Dromaeosaurids: Feathered Relatives of Birds

Feather Morphologies and Evolution

Dromaeosaurids, a group of theropod dinosaurs, are among the closest relatives of birds. The discovery of Zhenyuanlong suni, a large-bodied, short-armed dromaeosaurid from the Early Cretaceous of China, provides evidence of feather morphologies and distribution in these dinosaurs. Zhenyuanlong had large wings with pennaceous feathers on the arms and tail, similar to smaller dromaeosaurids, but potentially lacked vaned feathers on the legs. This discovery adds to the diversity of dromaeosaurids and highlights the complexity of their phylogeny.

Smallest Non-Avian Theropod

Microraptor zhaoianus, another dromaeosaurid from the Early Cretaceous of China, is notable for being smaller than the primitive bird Archaeopteryx. This discovery eliminates the size disparity between the earliest birds and their closest non-avian theropod relatives, providing new insights into the morphological transition to birds. Microraptor's bird-like teeth and unique skeletal features improve our understanding of the evolutionary steps leading to avian characteristics.

Conclusion

The closest relatives of dinosaurs, including silesaurids, lagerpetids, and dromaeosaurids, provide critical insights into the evolutionary history and morphological diversity of early dinosauriforms. These findings highlight the complex evolutionary pathways and the gradual acquisition of traits that eventually led to the rise of true dinosaurs and their avian descendants.