Ontogenetic Development of an Exceptionally Preserved Devonian Cartilaginous Skeleton
Ontogenetic Development of an Exceptionally Preserved Devonian Cartilaginous Skeleton
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DOI：
10.1002/jez.b.21441
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发表时间：
2012-01-15
影响因子：
2.2
通讯作者：
Smith, Moya Meredith
中科院分区：
文献类型：
--
作者：
Johanson, Zerina;Kearsley, Anton;Smith, Moya Meredith
软骨脊椎动物的骨骼很少留下化石记录，除非矿化。在这里，我们报告突出保存软骨分化的早期阶段，目前在泥盆纪脊椎动物古脊椎动物。在大型古脊椎动物标本中，软骨基质中主要是增大的肥大细胞间隙（腔隙），每个间隙由薄的矿化基质限定，其中磷和钙共存。这与活的软骨内软骨相当，其中细胞肥大和基质矿化标志着骨形成之前细胞生长和分裂的个体发育过程的结束。来自古椎龙小型个体的新信息表明，骨骼主要由未矿化的有机基质组成，只有很少的肥大细胞空间，这些仅发生在每个元素的中心区域。只有在这里，周围的基质才开始矿化，与较大的标本不同的是，在这些早期阶段，磷占主导地位，几乎没有钙。这反映了通过肥大细胞周围的磷酸盐积累，以及随后软骨基质中钙的增加，对活组织中矿化的细胞控制。这些特征总是与软骨内骨的发育有关，但在古椎龙的骨骼中，这种骨骼从未发育过。到目前为止，这种骨骼状态在脊椎动物中是独一无二的，有两种可能的解释：要么是软骨内骨发育的后期阶段在古脊椎动物中已经消失，要么是在逐步获得矿化骨骼的过程中，这些后期阶段尚未进化。J. Exp. Zool.（Mol. Dev. Evol.）318：50-58，2012. (C)2011 Wiley Periodicals，Inc.
Cartilaginous vertebrate skeletons leave few records as fossils, unless mineralized. Here, we report outstanding preservation of early stages of cartilage differentiation, present in the Devonian vertebrate Palaeospondylus gunni. In large specimens of Palaeospondylus, enlarged, hypertrophic cell spaces (lacunae) are dominant in the cartilage matrix, each defined by thin mineralized matrix, where phosphorus and calcium co-occur. This is comparable to living endochondral cartilage, where cell hypertrophy and matrix mineralization mark the end of an ontogenetic process of cell growth and division before bone formation. New information from small individuals of Palaeospondylus demonstrates that the skeleton comprises mostly unmineralized organic matrix with fewer hypertrophic cell spaces, these occurring only in the central regions of each element. Only here has the surrounding matrix begun to mineralize, differing from the larger specimens in that phosphorus is dominant with little associated calcium at these earlier stages. This reflects cellular control of mineralization in living tissues through phosphate accumulation around hypertrophic cells, with later increase in calcium in the cartilaginous matrix. These features are always associated with endochondral bone development, but in the Palaeospondylus skeleton, this bone never develops. This skeletal state is thus far unique among vertebrates, with two alternative explanations: either later stages of endochondral bone development have been lost in Palaeospondylus, or, in a stepwise acquisition of the mineralized skeleton, these late stages have not yet evolved. J. Exp. Zool. (Mol. Dev. Evol.) 318:50-58, 2012. (C) 2011 Wiley Periodicals, Inc.