What, precisely, makes a tusk a tusk? And how did they happen? New research by U.S. paleontologists sheds light on both of these concerns.
Several animal species today have tusks. From elephants to walruses, nevertheless, something they all share is that theyre mammals. This wasnt always the case, new research study reveals. The history of tusks, according to a group of paleontologists at Harvard University, the Field Museum, the University of Washington, and Idaho State University began with an ancient relative of mammals that lived prior to the age of the dinosaurs.
Left side of the skull of a dicynodont Dolichuranus fossil used in the study. The tusk shows up at the lower left. Image credits: Ken Angielczyk.
Those family members were dicynodont (significance “two canine teeth), a species that shared a few of the qualities of mammals however also reptiles– including sporting a turtle-like beak.
Tooth or tusk?
Apart from the findings of this research study, the teams classification of exactly what makes up a tusk and how theyre different from routine teeth is more broadly applicable to other types. In specific, it gives us insight into the different tasks these structures are suggested to serve.
” For this paper, we had to define a tusk, due to the fact that its a surprisingly uncertain term,” said lead author Megan Whitney, a postdoctoral scientist at Harvard University and a UW doctoral alum, in a news release. “Enamel-coated teeth are a various evolutionary strategy than dentine-coated tusks. Its a compromise.”
The authors more report on some adaptations dicynodonts had to go through to enable the advancement of true tusks. These consist of flexible ligaments connecting the tusks to their jaws, and a minimized general rate of tooth replacement. The roots of their tusks were hollow, as well, to enable fresh dentine to be continually included in time.
For this research study, the team defined tusks as being teeth not covered in enamel (i.e. theyre totally made of dentine), that extend out past an animals mouth, and keep growing throughout the persons life time. They worked with thin slices cut out from the teeth of several fossil species in order to figure out when tusks initially appeared.
Its presence likewise avoids teeth from growing continuously, as tusks do. Animals with tusks utilize them for rooting or combating through the ground, so theyre much more exposed to harm than teeth. Because tusks grow back, harmful or losing a tusk isnt a death sentence.
An example of a true tusk in the dicynodont Lystrosaurus, with a hollow pulp cavity in its root where fresh dentine would have been created. Image credits Megan Whitney.
” Tusks have developed a variety of times, that makes you wonder how– and why? We now have good data on the physiological changes that needed to take place for dicynodonts to progress tusks,” stated co-author Christian Sidor, a UW teacher of biology and a curator at the UWs Burke Museum of Natural History & & Culture. “For other groups, like walruses or warthogs, the jury is still out.”
The enamel layer on this Diictodon caniform (the colorful ring on the cross-section) makes it look like teeth more than tusks. Image credits Megan Whitney.
Given that tusks grow back, harmful or losing a tusk isnt a death sentence.
What, exactly, makes a tusk a tusk? For this study, the team defined tusks as being teeth not covered in enamel (i.e. theyre entirely made of dentine), that extend out past an animals mouth, and keep growing throughout the individuals lifetime. According to the findings, some dicynodont teeth were indeed tusks. Another essential tip that were looking at the first evolution of tusks was that the earlier dicynodont types just showed teeth, whereas tusks started making an appearance amongst the later types to arise in this clade.
The majority of the dicynodont fossils analyzed in this study were discovered in Tanzania and Zambia. Theyre presently stored in a variety of museums in the U.S., and are arranged to be gone back to the National Museum of Tanzania and the Livingstone Museum in Zambia after the conclusion of the research project.
Dicynodonts lived from 270 to 201 million years back, approximately, so theyre quite ancient animals. As a group, they were extremely varied, varying in size from a rat to a modern-day elephant. They got their name from the 2 distinct teeth in their upper jaws, teeth which were the focus of this research study.
” We were able to reveal that the very first tusks belonged to animals that came before contemporary mammals, called dicynodonts,” stated co-author Ken Angielczyk, a curator at the Field Museum in Chicago. “Despite being exceptionally odd animals, there are some things about dicynodonts– like the evolution of tusks– that inform us about the mammals around us today.”
According to the findings, some dicynodont teeth were indeed tusks. Another crucial tip that were looking at the first development of tusks was that the earlier dicynodont species only showed teeth, whereas tusks started making an appearance amongst the later species to occur in this clade.
The study “The advancement of the synapsid tusk: insights from dicynodont therapsid tusk histology” has been released in the journal Proceedings of the Royal Society B.