Evolution of shell morphology and suture complexity in Paleozoic prolecanitids, the rootstock of Mesozoic ammonoids
Evolution of shell morphology and suture complexity in Paleozoic prolecanitids, the rootstock of Mesozoic ammonoids
复制标题
中生代菊石的砧木——古生代prolecanitids的壳形态和缝合线复杂性的演化
DOI：
10.1017/s0094837300019709
复制
发表时间：
1997
期刊：
影响因子：
2.7
通讯作者：
D. M. Work
中科院分区：
文献类型：
--
作者：
W. Saunders;D. M. Work
菊石目构成了一个相对较小（43属，~250种）但分布范围较长的谱系（下石炭-三叠纪，~ 1.08亿年），它们勉强地在P/T演化中幸存下来，并提供了所有晚中生代菊石的来源。早菊石类是晚古生代菊石类中的一个小类，它与同时代的菊石类有很大的区别，包括：（1）壳的几何形状（W-D-S）的长期渐变;（2）形态空间是迄今为止所研究的古生代菊石类中最强的限制;（3）平均缝合复杂性增加8倍（4）壳的几何形状、壳和间隔的厚度与缝合线的复杂性之间有很高的相关性;（5）短体腔，因此，高孔径方向;（6）照相机液体可能用于浮力控制的迹象;（7）平均寿命为1470万年的属。相比之下，在上石炭纪的角石类中，这似乎与缝合线的复杂性无关。普罗卡尼提人表现出一种普遍的趋势，即增加缝合线的复杂性（在整个分支以及分支内部和超过90%的祖先-后代属中），从而为驱动复杂性趋势提供了一个理由。普罗卡尼特类的独特性使人怀疑它们和它们的中生代后代角闪岩和菊石是否严格类似于古生代的角闪岩。
The ammonoid order Prolecanitida constitutes a relatively small (43 genera, ~250 species) but long-ranging lineage (Lower Carboniferous—Triassic, ~108 m.y.), which narrowly survived the P/Tr extinctions and provided the stock from which were derived all later Mesozoic ammonoids. Prolecanitids were a minority among Late Paleozoic ammonoids, which were dominated by the Goniatitida, and showed many features that set them far apart from their contemporaries, including (1) long-term, gradual changes in shell geometry (W-D-S); (2) the most strongly constrained morphospace of any Paleozoic ammonids examined to date; (3) an eight-fold increase in mean suture complexity (three times that of Pennsylvanian goniatitids); (4) high correlations between shell geometry, shell and septal thickness, and suture complexity; (5) short body chambers and, as a consequence, high aperture orientations; (6) indications that cameral liquid may have been used for buoyancy control; and (7) a genus longevity that averaged 14.7 m.y. compared with 5.7 m.y. in Upper Carboniferous goniatitids, and that appears to have been unrelated to suture complexity. Prolecanitids showed a pervasive tendency to increase suture complexity (in the clade as a whole as well as within subclades and in more than 90 percent of ancestor-descendant genera), thus arguing a case for a driven complexity trend. The uniqueness of the prolecanitids calls into question whether they and their Mesozoic descendants, ceratites and ammonites, were strictly analogous to Paleozoic goniatites.