Category: Teeth

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Teeth are essential for many animals, as they are used to break down food (and sometimes for other purposes as well). Numerous instances of convergence are related to teeth, and as these hard, calcified structures fossilize well, they can also provide insights into the evolutionary history of extinct groups. The sabre-toothed cats, carnivores with long, dagger-like canines, represent one of the most spectacular tooth-related convergences, as only some of them were actually true cats. The sabre-tooth morphology evolved repeatedly in several groups, even in marsupials! On a rather more peaceful note, ceratopsians and hadrosaurs, dominant plant-eating dinosaurs during the Late Cretaceous, both independently evolved continuous batteries of serrated teeth that occluded at the back of the mouth to shear and slice vegetation. Today, analogues of these dental batteries are found in elephants.

Many interesting (and convergent) tooth specialisations have arisen in fish. Teleosts possess pharyngeal jaws, a second set of jaws in the pharynx that are functionally separate from the oral teeth and can take on different functions, thus allowing a huge diversity of feeding modes. Best known are probably the moray eels, which use their pharyngeal jaws to feed in a way that is strikingly reminiscent of snakes. Pharyngeal jaws can furthermore be modified as crushing tooth plates to eat hard-bodied prey, including molluscs and crustaceans. Such durophagy has arisen several times, for example in the freshwater cichlids and the marine labrids (which show further interesting feeding convergences, for instance the repeated evolution of mechanically fast jaw systems). Several groups of fish employ their oral teeth as crushers, including bony (e.g. pufferfish) as well as cartilaginous fish (e.g. eagle rays and bullhead sharks). In the latter group, this is particularly remarkable, as a suite of morphological and functional adaptations are needed to crush the protective armour of prey with the rather soft cartilaginous jaws.

Reptile dentition is highly instructive, too, and an interesting case is found in those taxa that have adapted to life in aquatic environments. Distinctly specialised teeth and jaws are critical to capturing and processing prey underwater. Despite the taxonomic diversity of aquatic reptiles, however, only three tooth types have been described, presenting us with a clear example of convergent evolution. In contrast, teiids, a group of skink-like lizards, show a stunning diversity of tooth types, from simple, single-cusped teeth to complex, multi-cusped molariforms. These cases provide rich evidence of convergence, within the teiids themselves as well as with distantly related reptile groups and even certain mammals and fish. The dentition of two unusual Early Cretaceous crocodiles, which show complex tooth occlusion, parallels that observed in a group of advanced proto-mammals called tritylodonts. Turtles and lizards of the genus Uromastyx have convergently lost their dentition and adopted specialised beak structures for feeding, which is, of course, reminiscent of birds. More famously, however, certain snakes such as vipers and cobras possess enlarged, hollow venom fangs in the upper jaw. Interestingly, these two groups independently arrived at the same developmental mechanism for formation of their anterior fangs. Venom fangs evolved convergently also outside the snakes, for example in some lizards but even in some mammals, for example solenodons, where the venom-delivering teeth are located in the lower jaw. Curiously, several groups of frogs also possess fangs, but it remains unknown whether they are involved in prey capture or have resulted from sexual selection.

Teeth are, inevitably, subject to wear and various strategies have evolved to deal with this. Of particular interest is the convergent incorporation of zinc to harden the teeth or equivalent structures. This is observed in, for example insects and polychaete annelids.

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Topic Title Teaser text Availablity
Snail eating: an asymmetric diet

Snails may not be everyone's first choice on the menu but several distinct colubrid snakes have evolved expert techniques for gorging on these nutritious gastropods.

Directionally asymmetric feeding in snakes n/a Not Available
Enamel in reptile teeth n/a Not Available

Cichlids are one of the cause celebré of evolution, and rightly so because these freshwater fish show a remarkable diversity and exemplify many key aspects of adaptive radiation. But why so successful? The answer lies in the versatility of the jaws (and yes, they are convergent).

Pufferfish (and inflation)

Pufferfish are some of the most extraordinary fish to have evolved, especially because of their capacity to swallow water and inflate themselves to something like a football. Not only that but some representatives can be deadly to the unwary diner...

Crustacean-trapping teeth in mesosaurs and crabeater seals

The multi-lobed post-canines of Lobodon carcinophagus are a functional analogue to the long, thin cage-like teeth of Mesosaurus, as both cage and prevent the escape of small crustacean prey.

Teeth in aquatic reptiles

Aquatic reptiles tend to display one of three dentition types, well adapted to either seize and slice large vertebrate prey, pierce and gouge slippery fish, or entrap small prey such as crustaceans.

Dental batteries in ceratopsians, hadrosaurs and elephants

The dental batteries or 'pavements' of ceratopsians and hadrosaurs evolved independently, and yet the dentition of several more distantly related animals also converges on their highly adapted tooth form.

Teiid lizard dentition: convergence with other reptiles, mammals and fish

Teiids are skink-like lizards whose members show a stunning diversity of tooth types, providing rich evidence of convergence within the teiids themselves, in distantly related reptile groups and even in certain mammals and fish.

Complex tooth occlusion in notosuchid crocodiles and tritylodonts (proto-mammals)

Two unusual Early Cretaceous crocodiles provide a shining example of convergence, as their dentition parallels that observed in a group of advanced proto-mammals called tritylodonts.

Reptile dentition: convergence on complex occlusion

Some reptiles have transverse chisel-like teeth for slicing, and others have teeth bearing projections ('cusps') that interlock and slice or grind tough food. In each case evolutionary parallels are clear both within and outside the reptiles.

Beak structures in reptiles and birds

Among reptile taxa with beak structures, we find several cases of convergent evolution, for example between turtles, Uromastyx lizards, a number of herbivorous dinosaurs and the tuatara (Sphenodon) of New Zealand.

Venom and venom fangs in snakes, lizards and synapsids

Although the evolution of snake fangs itself provides us with a window on convergence, the presence of fang-like teeth in lizards, therapsids and mammals provides an even broader and more remarkable perspective.

Feeding in snakes and lizards

The Turtle-headed sea snake feeds on small eggs and its feeding shows intriguing similarities to the way lizards forage, and herbivorous mammals graze and browse.

Pharyngeal jaws in teleost fish

One of the great evolutionary breakthroughs in the teleost fish was the conversion of some of the elements that supported the gill bars into a second set of pharyngeal teeth that complemented the oral teeth. See how a fish becomes a snake!

Durophagy (hard prey-eating) in fish

Plenty of animals have an extraordinary capacity to crush hard prey and this has evolved independently many times in the vertebrates. If you suspect it is a durophage, watch your fingers!

Venom in mammals (and other synapsids)

Beware the venomous shrew! Yes, venomous. And convergent on some formidable lizards...

Sabre-toothed cats and marsupials

Marsupials with giant fangs? Yes, not all of the extinct sabre-toothed cats were actually cats…

Cheetahs of Africa and America

The American cheetah (Miracinoyx) is an extinct Pleistocene form, and is strikingly similar to the cheetah (Acinoyx) that formerly had a wide range in the Old World but is today effectively restricted to Africa.

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Zinc in teeth

On land, we find the employment of zinc to reinforce feeding structures in the fangs of spiders, and also in a variety of insect groups.

Trap-jaws in ants

Remarkable trap-jaw structures have evolved independently in various ants.

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Frogs with fangs

Teeth have clearly evolved a number of times, and one of the more interesting curiosities is found in the amphibians, notably in the frogs where several groups have independently evolved fangs.