Ker­mit is re­lated to this mon­ster?

An­ces­tors of mod­ern frogs had thou­sands of teeth — and fangs

Waterloo Region Record - - LOCAL - Michelle McQuigge

TORONTO — Canadian re­searchers say they’ve found ev­i­dence that the an­cient an­ces­tors of mod­ern-day frogs were once keen preda­tors with thou­sands of teeth to help de­vour their prey.

The team from the Univer­sity of Toronto ex­am­ined fos­sils of an­i­mals be­lieved to have evolved into the am­phib­ians peo­ple are fa­mil­iar with to­day.

The fos­sils, be­lieved to be 289 mil­lion years old, show that frogs, sala­man­ders and other am­phib­ians have evolved sig­nif­i­cantly over time.

While mod­ern frogs have sev­eral small teeth lin­ing the edges of their mouths, their pre­de­ces­sors’ jaws were much more men­ac­ing.

The an­cient an­ces­tors, known as dis­sorophoids, boasted thou­sands of tiny hooked teeth through­out the roof of their mouths, as well as large fangs meant to sink into their prey.

Se­nior re­searcher Robert Reisz says the find­ings raise in­trigu­ing ques­tions about the way the species has evolved over the mil­len­nia.

“It’s an in­ter­est­ing mys­tery,” Reisz said in an in­ter­view. “It takes a lot of en­ergy to make these teeth, and it may have been that they were not needed in the changeover from these an­cient ter­res­trial preda­tors to frogs and sala­man­ders.”

Reisz said the per­fectly pre­served fos­sils were dis­cov­ered in caves lo­cated in Ok­la­homa along­side thou­sands of other bones.

He said the caves acted as nat­u­ral traps for an­i­mals of the pe­riod and helped main­tain their re­mains in ex­cel­lent con­di­tion over the cen­turies.

Reisz said the pre­served skull of a dis­sorophoid gave re­searchers a de­tailed look at the in­side of the mouth.

The teeth that pre­vail in present-day frogs were still in ev­i­dence, but Reisz said the rest of the mouth bore lit­tle re­sem­blance to to­day’s am­phib­ians.

They found thou­sands of tiny teeth not only em­bed­ded in the bone on the roof of the mouth, but also in the soft tis­sue that cov­ers the palate.

“They’re very cool and very in­ter­est­ing be­cause they all point back­wards,” he said. “They’re hooked ... and they would have prob­a­bly just stuck out of the skin of the roof of the mouth, so they would be like tiny, tiny lit­tle grap­pling hooks that would al­low for the food to go down the gul­let, but would pre­vent it from mov­ing out of the mouth.”

Re­searchers ini­tially spec­u­lated that the hooked ob­jects were den­ti­cles, which are tooth-like projections that don’t have char­ac­ter­is­tics of real teeth.

But Reisz and his team an­a­lyzed the projections and found that they matched the def­i­ni­tion of ac­tual teeth. They all fea­tured pulp cav­i­ties, an enamel cov­er­ing, and the hard, cal­cium-heavy ma­te­rial known as den­tine that com­prises the main part of proper teeth.

Reisz said the an­i­mals would have been re­plac­ing these teeth ev­ery few months.

Mod­ern-day am­phib­ians are car­ni­vores that pri­mar­ily sur­vive on in­sects and other an­i­mals, but Reisz said the find­ings sug­gest their an­ces­tors were “pretty ef­fec­tive lit­tle preda­tors” in a dif­fer­ent class from the crea­tures that suc­ceeded them. The power of the small teeth would have been en­hanced by larger fangs ideal for sink­ing into un­sus­pect­ing prey, he added.

Reisz said the next step of the re­search is to in­ves­ti­gate how the process of re­plac­ing the teeth took place in the an­cient dis­sorophoids, as well as to probe rea­sons why the teeth in the roof of the mouth are nowhere to be found in to­day’s am­phib­ians.

BRIAN ENGH, THE CANADIAN PRESS

The Early Per­mian dis­sorophid Ca­cops dis­plays its fear­some den­ti­tion as it preys on the hap­less rep­tile Cap­torhi­nus in this hand­out il­lus­tra­tion.

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