What's the closest relative to a dinosaur
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Closest Relatives to Dinosaurs: Insights from Recent Research
Silesaurids: Non-Dinosaurian Dinosauriforms
Silesaurids as Dinosaur Precursors
Silesaurids, a group of non-dinosaurian dinosauriforms, are considered the closest relatives to crown-group dinosaurs. The osteohistology of Sacisaurus agudoensis, a Late Triassic silesaurid from Brazil, reveals rapid growth patterns similar to early dinosaurs, although they lack the complex vascular arrangements seen in saurischian dinosaurs. This suggests that silesaurids had relatively slower growth rates compared to most Dinosauria. The detailed anatomy of Asilisaurus kongwe, another silesaurid from the Middle Triassic of Tanzania, further supports the close relationship between silesaurids and early dinosaurs, highlighting high homoplasy and parallel trends within Silesauridae and early dinosaur lineages.
Dromaeosaurids: Feathered Dinosaur Relatives
Dromaeosaurids and Avian 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 significant insights into feather evolution. This species had large wings with pennaceous feathers on the arms and tail, similar to smaller dromaeosaurids, indicating a complex evolutionary history of feather development among these theropods.
Lagerpetids: Sister Group to Pterosaurs
Lagerpetids and Pterosaur Origins
Recent studies have identified lagerpetids, a group of cursorial, non-volant dinosaur precursors, as the sister group to pterosaurs. This relationship is supported by numerous synapomorphies across the entire skeleton, which bridge the morphological gap between the oldest pterosaurs and their closest relatives. This finding suggests that certain neuroanatomical features related to flight in pterosaurs evolved before the development of powered flight, highlighting the evolutionary innovations within this lineage.
Dinosaur Footprints: Evidence from the Triassic
Triassic Trackways and Dinosaur Evolution
Footprint records from the Middle to Late Triassic provide additional evidence of dinosaur and close relative activity. Tracks from the Los Rastros Formation in Argentina, characterized by tridactyl digitigrade pes and well-developed claws, suggest the presence of derived dinosauriforms, including potential early dinosaurs, by at least the Middle Triassic. These ichnological findings complement body-fossil records and help trace the early evolutionary history of dinosaurs.
Conclusion
The closest relatives to dinosaurs include silesaurids, dromaeosaurids, and lagerpetids, each providing unique insights into the evolutionary pathways leading to the rise of dinosaurs. Silesaurids exhibit growth patterns and anatomical features that closely align with early dinosaurs, while dromaeosaurids offer a glimpse into the evolution of feathers and avian characteristics. Lagerpetids, as the sister group to pterosaurs, highlight the shared evolutionary traits that predate the development of flight. Together, these findings enrich our understanding of the complex evolutionary history of dinosaurs and their closest relatives.
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