New York, July 12 (IANS): It is likely that some dinosaurs mumbled or cooed with closed mouths, according to a study.
According to the study published in the journal Evolution, researchers highlighted how dinosaurs made sound and also examined the evolution of a specialised way birds emit sound -- closed-mouth vocalisation.
As birds descended from dinosaurs, the study endeavours to understand the origin and evolution of the unique vocal organ of birds and the large array of sounds it can produce.
Closed-mouth vocalisation is the sound that is emitted through the skin in the neck area while the beak is kept closed. To make it, birds typically push air that drives sound production into an esophageal pouch rather than exhaling through the open beak.
To understand when and how closed-mouth vocalisation evolved, researchers used a statistical approach to analyse the distribution of this vocal ability among birds and other reptilian groups.
In total, the researchers identified 52 out of 208 investigated bird species that use closed-mouth vocalisation.
"Looking at the distribution of closed-mouth vocalisation in birds that are alive today could tell us how dinosaurs vocalised," said Chad Eliason, Researcher, University of Texas.
Interestingly, only animals with a relatively large body size (about the size of a dove or larger) use closed-mouth vocalisation behavior.
As dinosaurs are members of the archosaur group and many had large body sizes, it is likely that some dinosaurs made closed-mouthed vocalisations in a manner similar to birds today, perhaps during mating displays.
"Our results show that closed-mouth vocalisation has evolved at least 16 times in archosaurs, a group that includes birds, dinosaurs and crocodiles,” added Eliason.
Researchers, however, are still not certain about how the ancestors of modern archosaurs vocalised. But the occurrence of closed-mouth vocalisation across birds and crocodiles -- the two surviving groups of archosaurs -- indicates that closed-mouth vocalisation can emerge in diverse archosaur species depending on behavioral or environmental circumstances.