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January 07, 2013

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Ancient bird’s teeth really stood out

Jan. 7, 2013
Courtesy of the Society of Vertebrate Paleontology
and World Science staff

A newly dis­cov­ered bird of the di­no­saur age, iden­ti­fied from a fos­sil, had some of the most elab­o­rate teeth ev­er seen in a bird, sci­en­tists say.

What makes it all the more in­ter­est­ing, they add, is that this bird flour­ished at a time when oth­er bird spe­cies had al­ready be­gun an ev­o­lu­tion­ary jour­ney to­ward tooth­less­ness.

Sulcavis ge­eorum skull. The scale bar is in in milli­meters. (Pho­to: Ste­pha­nie Abram­o­wicz)

"Maybe dif­fer­ences in di­et played a part" in ex­plain­ing the un­usu­al fea­tures of the spe­cies, said Jing­mai O'­Con­nor of the Uni­vers­ity of South­ern Cal­i­for­nia, lead au­thor of a new study on the find­ings.

Pub­lished in the lat­est is­sue of the Jour­nal of Ver­te­brate Pa­le­on­tol­ogy, the anal­y­sis sug­gests the an­i­mal, called Sul­cavis gee­o­rum, lived on a tough di­et that may have in­clud­ed crabs. The re­search­ers be­lieve the teeth of the new spec­i­men greatly in­crease the known di­vers­ity of tooth shape in early birds, and hints at pre­vi­ously un­rec­og­nized ec­o­log­i­cal di­vers­ity.

The fos­sil hails from the early Cre­ta­ceous era, an es­ti­mat­ed 121-125 mil­lion years ago, from what is now Liao­ning Prov­ince, Chi­na. The bird is be­lieved to a mem­ber of a line­age known as En­an­tior­ni­th­ines, the most nu­mer­ous birds from the time of the di­no­saurs.

Artist's reconstruct­ion of Sul­ca­vis ge­eorum in flight. (Im­age: Ste­pha­nie Abram­o­wicz)

Di­no­saurs—an­ces­tors of the birds—of­ten fea­tured car­niv­o­rous teeth with spe­cial fea­tures for eat­ing meat, the sci­en­tists not­ed. The En­an­tior­ni­th­ines are un­ique among birds in show­ing "min­i­mal" re­duc­tion of these fea­tures, and a wide va­ri­e­ty of "den­tal pat­terns," O'­Con­nor and col­leagues said. Some were even evolv­ing new "den­tal spe­cial­iz­a­tions," he added.

Sul­cavis gee­o­rum was de­scribed as hav­ing strong teeth with grooves on the in­side sur­face, which likely strength­ened the teeth against harder food items. No pre­vi­ous bird spe­cies have pre­served ridges, stria­t­ions, ser­rat­ed edges, or any oth­er form of den­tal "or­na­menta­t­ion" like S. gee­o­rum, the re­search­ers added. 

"We still don't un­der­stand why En­an­tior­ni­th­ines were so suc­cess­ful in the Cre­ta­ceous but then died out," O'­Con­nor said. "This study high­lights again how un­even the di­vers­ity of birds was dur­ing the Cre­ta­ceous. There are many more En­an­tior­ni­th­ines than any oth­er group of early birds, each one with its own ana­tom­i­cal spe­cial­iz­a­tion," added study co-au­thor Lu­is Chi­appe, from the Nat­u­ral His­to­ry Mu­se­um of Los An­ge­les Coun­ty.

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A newly discovered bird from the dinosaur age had some of the most elaborate teeth ever seen in a bird, scientists say. What makes it all the more interesting, they add, is that this bird flourished at a time when other bird species had already begun an evolutionary journey toward toothlessness. “Maybe differences in diet played a part” in explaining the unusual features of the species, identified from a fossil, said Jingmai O’Connor of the University of Southern California, lead author of a new study on the findings. Published in the latest issue of the Journal of Vertebrate Paleontology, the analysis suggests the animal, Sulcavis geeorum, was adapted to a tough diet that may have included crabs. The researchers believe the teeth of the new specimen greatly increase the known diversity of tooth shape in early birds, and hints at previously unrecognized ecological diversity. The fossil hails from the early Cretaceous era, an estimated 121-125 million years ago, from what is now Liaoning Province, China. The bird is believed to a member of a lineage known as Enantiornithines, and the most numerous birds from the the age of the dinosaurs. Dinosaurs – ancestors of the birds – often featured carnivorous teeth with special features for eating meat, the scientists noted. The enantiornithines are unique among birds in showing “minimal” reduction of these features, and a wide variety of “dental patterns,” O’Connor and colleagues said. Some were even evolving new “dental specializations,” he added. Sulcavis geeorum was described as having strong teeth with grooves on the inside surface, which likely strengthened the teeth against harder food items. No previous bird species have preserved ridges, striations, serrated edges, or any other form of dental “ornamentation” like S. geeorum, the researchers added. “We still don’t understand why enantiornithines were so successful in the Cretaceous but then died out,” O’Connor said. “This study highlights again how uneven the diversity of birds was during the Cretaceous. There are many more enantiornithines than any other group of early birds, each one with its own anatomical specialization,” added study co-author Luis Chiappe, from the Natural History Museum of Los Angeles County.