Many still think dinosaurs were massive reptilian creatures, and Hollywood certainly reinforced those ideas in popular dinosaur movies like Jurassic Park. Nevertheless, modern science continues to unveil how dinosaurs were probably nothing like what we've envisioned for years.
Instead, oodles of fossil evidence point to the idea that dinosaurs were more bird-like than originally thought. Many exhibited bird-like plumage and some were even beaked instead of toothed; it would be an understatement to say that dinosaurs laid the groundwork for the plethora of modern birds and beaked animals in existence today.
While the latest theories seem simple enough to understand based on fossil evidence, one lingering question continues to baffle scientists: how exactly did dinosaurs transition from having razor-sharp carnivorous teeth to bird-like beaks?
In a new study published in the Proceedings for the National Academy of Sciences (PNAS), an international team of researchers led by Shou Wang from the Capital Normal University in Beijing believe they might have discovered an important key to unlocking the secrets behind this question.
In search of answers, the researchers probed various dinosaur jawbones with CT scans to understand their internal structures. On the inside, traces of blood vessel and nerve canals, and bone-generating cell pits tell an interesting story about the dinosaurs' mouth structure and how it changed over time.
While searching the contents of a Limusaurus jawbone, the team discovered that although there were no teeth at the front of the jaw, there was evidence for teeth formation previously. As it would seem, the dinosaurs were probably born with a mouth full of teeth early in life, but lost some or all of them and developed a bird-like beak as they aged.
Worthy of note, the genetic mechanisms responsible for beak development also happen to suppress tooth formation. As time went on, these mechanisms kicked into overdrive and jump-started keratin-based beak growth earlier in life. Eventually, dinosaurs emerged from their eggs as hatchlings with beaks rather than teeth.
Gene BMP4 seems to play a vital role in this behavior, and evidence is all around us today. Several animal species, including birds, turtles, and whales have keratin beaks instead of teeth, or some hybrid between the two.
A continued analysis performed in this study showed that many of today's beaked creatures might have had teeth at one point, similarly to the story behind Limusaurus. While many animals don't have full-blown beaks, they do exhibit partial beaks covering the snout, known as a caruncle. Other creatures have hybrids between the two. In all cases, it seems similar mechanisms are behind the beak development.
While BMP4 helps tell a striking story about beak development in toothed dinosaurs and many modern animals, the researchers also propose that it may not be the only mechanism at work here. More research is needed to understand beak development in animals across the board. Nevertheless, the study lays the groundwork for how dinosaurs slowly transitioned from toothed babies to beaked babies.
Studying dinosaurs is never simple because of the limited fossil record we have to go by, but this is just one of the hurdles that can make searching for answers fun.