>>While Hesperornithoides wasn’t a flier, the dinosaur may represent one of the earliest known forerunners of modern birds, helping to piece together a part of the evolutionary tree that remains incomplete.
From related dinosaurs, Hartman and colleagues are confident that Hesperornithoides was extensively feathered. And in terms of skeletal anatomy, the dinosaur has traits that are associated with the origin of flight in other dinosaurs. Hesperornithoides has a curved wishbone, an important site of muscle attachment for arm muscles that were used for flight in early birds, as well as a particular wrist bone called the semilunate carpal that allowed for bird-like folding of the hand under the arm.<<
>>Other experts are not entirely sure about how Hesperornithoides fits into the greater raptor family tree. It may hop to another branch with future analysis, as there is a great deal of uncertainty regarding how closely related these dinosaur species are to one another, Brusatte says. Birds certainly evolved from dinosaurs like Hesperornithoides, but experts have yet to reach a consensus on which species of ancient raptors are closest to this fascinating evolutionary origin story.
“Maybe Hesperornithoides is the type of animal that birds directly evolved from,” Brusatte says, meaning the dinosaur wasn’t the ancestor of the first birds but gives us a look at that ancestor’s body plan. Or perhaps the dinosaur was one of many bird-like dinosaurs that are near the origin of avians but not direct ancestors. Debate will continue, Brusatte says, but “if birds evolved from a Hesperornithoides-like animal, then that means they probably evolved from running, ground-living animals.”<<
