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[魚類] 中級會員
 
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白堊紀「反鳥」體型小如知更鳥 利齒卻可粉碎獵物堅甲
白堊紀「反鳥」體型小如知更鳥 利齒卻可粉碎獵物堅甲
考古學家最近在中國大陸遼寧省發現一組前所未有的化石遺跡，這是一種生活在距今1億2500萬至1億2100萬年前，屬於白堊紀早期的「反鳥亞綱」鳥類，學名為Sulcavis geeorum。牠們雖然體型嬌小，但銳利牙齒代表「專業化」的食性，與現代鳥類的喙部有很大不同。
Sulcavis geeorum是鳥類的原始祖先，在這次發現的化石標本中，可以看到牠們在牙齒的內側表面還有明顯凹槽，這個特殊構造能夠強化研磨、咀嚼功能，甚至幫助牠們粉碎帶有厚重堅甲的獵物，像是昆蟲、螃蟹等。
古生物學家歐康納(Jingmai O'Connor)表示，過去從未在史前鳥類的身上觀察到類似的牙齒構造；到了中生代時期，鳥類還演化到連牙齒都沒了。他還說，只能推測在白堊紀時期，這類「反鳥」的牙齒為生存競爭帶來很大的成功。
原文網址: 白堊紀「反鳥」體型小如知更鳥 利齒卻可粉碎獵物堅甲 | ETtoday新奇新聞 | ETtoday 新聞雲 http://www.ettoday.net/news/20130108/149807.htm#ixzz2HRJcYwXy
英文版本
First Fossil Bird With Teeth Specialized For Tough Diet
Beak shape variation in Darwin's finches is a classic example of evolutionary adaptation, with beaks that vary widely in proportions and shape, reflecting a diversity of ecologies. While living birds have a beak to manipulate their food, their fossil bird ancestors had teeth. Now a new fossil discovery shows some fossil birds evolved teeth adapted for specialized diets.
A study of the teeth of a new species of early bird, Sulcavis geeorum, published in the latest issue of the Journal of Vertebrate Paleontology, suggests this fossil bird had a durophagous diet, meaning the bird's teeth were capable of eating prey with hard exoskeletons like insects or 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.
Photograph of Sulcavis geeorum skull, a fossil bird from the Early Cretaceous (120 million-years-ago) of Liaoning Province, China with scale bar in millimeters.
Sulcavis geeorum is an enantiornithine bird from the Early Cretaceous (121-125 million years ago) of Liaoning Province, China. Enantiornithine birds are an early group of birds, and the most numerous birds from the Mesozoic (the time of the dinosaurs). Sulcavis is the first discovery of a bird with ornamented tooth enamel. The dinosaurs – from which birds evolved – are mostly characterized by carnivorous teeth with special features for eating meat. The enantiornithines are unique among birds in showing minimal tooth reduction and a diversity of dental patterns. This new enantiornithine has robust teeth with grooves on the inside surface, which likely strengthened the teeth against harder food items.
This is a photograph of Sulcavis geeorum, a fossil bird from the Early Cretaceous (120 million-years-ago) of Liaoning Province, China with scale bar in millimeters.
No previous bird species have preserved ridges, striations, serrated edges, or any other form of dental ornamentation. "While other birds were losing their teeth, enantiornithines were evolving new morphologies and dental specializations. We still don't understand why enantiornithines were so successful in the Cretaceous but then died out – maybe differences in diet played a part." says Jingmai O'Connor, lead author of the new study.
"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." offers study co-author Luis Chiappe, from Natural History Museum of Los Angeles County.
Founded in 1940 by thirty-four paleontologists, the Society now has over 2,000 members representing professionals, students, artists, preparators, and others interested in VP. It is organized exclusively for educational and scientific purposes, with the object of advancing the science of vertebrate paleontology.
The Journal of Vertebrate Paleontology
The Journal of Vertebrate Paleontology (JVP) is the leading journal of professional vertebrate paleontology and the flagship publication of the Society. It was founded in 1980 by Dr. Jiri Zidek and publishes contributions on all aspects of vertebrate paleontology.
For complimentary access to the full article after the embargo period, visit: http://www.tandfonline.com/toc/ujvp20/current
The article appears in the Journal of Vertebrate Paleontology 33(1), published by Taylor and Francis
Citation: O'Connor, J.K., Y. Zhang, L. M. Chiappe, Q. Meng, L. Quanguo, and L. Di. 2013. A new enantiornithine from the Yixian formation with the first recognized avian enamel specialization. Journal of Vertebrate Paleontology 33(1):1-12.
照片來源 : http://nanopatentsandinnovations ... ird-with-teeth.html
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