| 单词 | placoid |
| 例句 | Shark teeth likely evolved from the jagged scales that cover their skin, called placoid scales. Fundamentals of Biology 2015-01-01T00:00:00Z The fossils discovered include 134 teeth, 61 vertebrae, 23 placoid scales and fragments of calcified cartilage, researchers said in a statement. Massive 91M-year-old shark species with in utero 'cannibalistic behavior' discovered 2019-11-19T05:00:00Z An important feature is the complete absence of all trace of the calcified placoid plates which are so characteristic of the Elasmobranchii. Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 8 "Cube" to "Daguerre, Louis" 2012-01-31T03:00:17.257Z The remains of fish are as yet confined to the upper part of the Silurian series; but some of these belong to placoid fish, which occupy a high grade in the scale of organization. Principles of Geology or, The Modern Changes of the Earth and its Inhabitants Considered as Illustrative of Geology A singular species, rare, but easily recognized by its peculiar, placoid scales, large and firmly embedded in the peridial wall. The North American Slime-Moulds A Descriptive List of All Species of Myxomycetes Hitherto Reported from the Continent of North America, with Notes on Some Extra-Limital Species But one of the most remarkable weapons of the period was the sting of the Pleuracanthus, another great placoid of the age of gigantic fishes. The Testimony of the Rocks or, Geology in Its Bearings on the Two Theologies, Natural and Revealed The skin of the dog-fish is closely set with pointed tooth-like scales, the placoid scales, and these are continued over the lips into the mouth as teeth. Text Book of Biology, Part 1: Vertebrata As to whether they represent the remnant of a once present system of epidermal scales, which may have preceded the coating of placoid elements in the evolution of the vertebrate, there is no evidence. Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 8 "Cube" to "Daguerre, Louis" 2012-01-31T03:00:17.257Z Many years before, several observers—J. Müller, Williamson, and Steenstrup—had been struck with the resemblance existing between the placoid scales and the teeth of Elasmobranch fishes. Form and Function A Contribution to the History of Animal Morphology It is the same with the cutaneous teeth or placoid scales of the Selachii. The Evolution of Man — Volume 2 Besides the teeth there perhaps remain relics of the placoid scales in the anatomy of the higher vertebrata, in the membrane bones. Text Book of Biology, Part 1: Vertebrata How placoid scales may have given rise to these structures will be understood by considering such a bone as the vomer of the frog. Text Book of Biology, Part 1: Vertebrata |
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