What a Tiny Jaw From Greenland Shows About the Origin of Molars
Scientists have described the earliest known example of dentary bone with two rows of cusps on molars and double-rooted teeth. The new findings offer insight into mammal tooth evolution, particularly the development of double-rooted teeth.
A fossil jaw about 2 centimeters long, found in eastern Greenland and about 215 million years old, has the oldest known molar-like teeth with two roots and two rows of cusps. It belongs to a small, shrew-like animal named Kalaallitkigun jenkinsi, a close relative of the first mammals. Engineering tests in the same 2020 study suggest that two roots help a tooth withstand the stress of biting, which may be one reason complex chewing teeth and divided roots evolved together.
What question were the researchers asking?
Mammals chew in a way most other animals do not. Our upper and lower back teeth meet precisely, and their broad crowns grind food. Close relatives of early mammals were already experimenting with tooth shape in the Late Triassic period. One group, the haramiyidans, had molar-like teeth with two rows of cusps suited to a more plant-based diet. Where that pattern came from was unclear.
What did they find?
The team, led by Tomasz Sulej of the Polish Academy of Sciences and Grzegorz Niedźwiedzki of Uppsala University, described the lower jaw of Kalaallitkigun jenkinsi, an animal about the size of a large mouse.
Its molar-like teeth have two rows of cusps on the crown.
Each of those teeth has two roots.
The crown shape sits between two known groups: the insect-eating morganucodontans and the haramiyidans. This suggests the haramiyidan pattern grew out of the simpler morganucodontan tooth.
The researchers also built computer models of single-rooted and double-rooted teeth and tested them with a method engineers use to study stress in structures (finite element analysis). Teeth with two roots handled stronger forces, like those of upper and lower teeth meeting, better than teeth with one root.
What are the limits?
The study rests on a single small jaw, so the picture may change as more fossils are found. The engineering models show what two roots can do mechanically. They cannot prove why divided roots first appeared.
What does this have to do with your teeth?
Your own molars carry the same basic design. Lower molars usually have two roots and upper molars usually have three, with broad crowns built for grinding. That root anatomy matters in everyday dentistry. It affects how a tooth handles chewing forces, how a root canal is planned and how a molar is removed or replaced. Fossils like this one show how long that design has been in use.
For another look at how teeth evolved, see our post on shark teeth and human dental biology. If you have a question about a molar of your own, start with a dental examination.
Sources
Sulej T, Krzesiński G, Tałanda M, et al. The earliest-known mammaliaform fossil from Greenland sheds light on origin of mammals. Proc Natl Acad Sci U S A. 2020;117(43):26861-26867. doi:10.1073/pnas.2012437117. Retrieved via PubMed.
Uppsala University. Press release on the Greenland mammaliaform jaw (October 2020).
About the author. CJ Henley, DMD, is a general dentist in Jacksonville whose practice focuses on cosmetic and restorative dentistry, dental implants and dental care around head and neck cancer. Meet Dr. Henley.
CJ Henley, DMD, PA · 3675 Hendricks Avenue, Jacksonville, FL 32207 · 904-398-1549
Updated October 2026.
What to Know Before Getting Dental Veneers
Dental veneers are thin, custom-made shells that dentists can place on the front of the teeth to improve their appearance. Veneers can hide stained, chipped, and uneven teeth.
Dental veneers are thin shells, usually ceramic, bonded to the front of teeth to change their color, shape or size. They can give a lasting change to a smile, but preparing teeth for them usually removes some enamel, so they're a long-term commitment. Before deciding, it helps to know whether a more conservative option would reach your goal and what veneers need over the years.
What can veneers change?
Veneers cover the front surface and biting edge of a tooth. They can help with:
Teeth that are chipped, worn or uneven in length
Color that whitening doesn't change, such as some deep stains
Small gaps or minor irregularities in shape
Teeth that look too small for the smile
Veneers don't move teeth, fix a bite problem or replace missing teeth. They also need healthy teeth and gums underneath.
Are veneers the same as crowns?
No. Veneers mainly cover the front of a tooth. Crowns cover the whole tooth and are usually recommended when a tooth has a large filling, a fracture or a root canal. A tooth without enough sound enamel may not hold a veneer well.
What are veneers made of?
Ceramic (porcelain) veneers are made by a dental laboratory. They resist staining and reflect light much like enamel.
Composite veneers are tooth-colored resin shaped directly on the tooth. They usually need less preparation and cost less, but they stain and chip more easily and need more upkeep.
Our dental veneers page explains how we approach ceramic veneers.
Are veneers reversible?
Usually not. Most ceramic veneers need some enamel removed so they don't look bulky. Once that enamel is gone, the tooth will always need a veneer or other covering. Some cases need very little or no preparation, depending on the tooth's position and the planned shape. Ask how much preparation is proposed and why.
How long do veneers last?
Ceramic veneers have a good track record. A systematic review of 13 clinical studies estimated that about 89 percent of ceramic veneers were still in service after a median of 9 years. Chipping or fracture was the most common problem. How long yours last depends on your bite, whether you grind your teeth, your gum health and how you care for them.
Should I compare veneers with bonding, whitening or aligners?
Yes. Each solves a different problem.
Teeth whitening changes the color of natural teeth without removing anything. If you plan to whiten, do it first so veneers can be matched to the new shade.
Composite bonding can handle selected small chips and gaps with little or no preparation.
Clear aligners move teeth. If crowding is the main concern, aligning the teeth first often means less tooth reduction for veneers, or no veneers at all.
What does the process involve?
Consultation and records. We talk about what you'd like to change and take photographs and an impression or scan.
Design and trial. A mock-up or temporary version of the new shape can let you see the change and adjust it before anything is final.
Preparation. The teeth are numbed and shaped as needed. Temporary veneers may be placed.
Placement. The laboratory makes the final veneers. I check the fit, color and bite before bonding them.
How do you care for veneers?
Brush twice a day and clean between your teeth daily. The veneer won't decay, but the tooth around it can.
Don't bite fingernails, ice, pens or packaging with your front teeth.
If you clench or grind, wear a night guard.
Keep regular cleanings and examinations so the edges and gums can be checked.
What should I ask at a veneer consultation?
What concerns can this plan address?
How much enamel will be removed?
How does my bite affect the recommendation?
Would a more conservative option meet my goal?
What maintenance and future replacement should I expect?
Can I see relevant examples of your work?
Does insurance cover veneers?
Insurance rarely covers veneers placed for appearance alone. We are an out-of-network practice. We can help you understand how to use your benefits. You are responsible for amounts your plan does not pay.
Discuss veneer options in Jacksonville
At CJ Henley, DMD, on Hendricks Avenue near San Marco, you can talk about the change you want and compare cosmetic dentistry options. Bring photographs that show what you like about your current smile and what you hope to change. See examples of our work on the before and after page, contact the office or call 904-398-1549.
Sources
Morimoto S, Albanesi RB, Sesma N, Agra CM, Braga MM. Main clinical outcomes of feldspathic porcelain and glass-ceramic laminate veneers: a systematic review and meta-analysis of survival and complication rates. Int J Prosthodont. 2016;29(1):38-49. doi:10.11607/ijp.4315 (retrieved via PubMed)
American Dental Association, MouthHealthy. Veneers.
About the author. CJ Henley, DMD, is a general dentist in Jacksonville whose practice focuses on cosmetic and restorative dentistry, dental implants and dental care around head and neck cancer. Meet Dr. Henley.
CJ Henley, DMD, PA · 3675 Hendricks Avenue, Jacksonville, FL 32207 · 904-398-1549
Updated October 2026.