A reply to a comment on Lemanis (2020): The ammonite septum is not an adaptation to deep water
A reply to a comment on Lemanis (2020): The ammonite septum is not an adaptation to deep water
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对 Lemanis (2020) 的评论的回复：菊石隔膜不是对深水的适应
DOI：
10.1098/rspb.2021.0068
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Lemanis
中科院分区：
文献类型：
--
作者：
Lemanis
在我去年发表的一篇论文[1]的最近评论中，研究了几个形态参数如何不同地影响菊石壳的强度[2]，评论者提出了两个主要的批评：（1）该论文完全集中在巴克兰模型上，忽略了普法夫模型;（2）模拟的隔膜不够复杂，沿着一些更小的批评。总之，巴克兰和普法夫模型是关于流体静压力如何与隔膜相互作用的两种观点。巴克兰模型指出，更复杂的隔片支撑壳壁免受侧向压力，在评论论文[2]中建模，而Pfaff模型表明，更复杂的隔片提高了最终形成的隔片对来自体腔的静水压力的抵抗力[3，4]。当然，我们没有对体腔进行建模，因此实际上忽略了普法夫模型。值得注意的是，当对Cadoceras中的不同间隔形态进行建模时，基于CT的经验模型的测试与Pfaff模型不一致[5]。此外，包括亚成体Kosmoceras的更复杂的隔膜，在[6]中看到的，并没有证实这一假设;尽管这并没有像评论论文中的巴克兰模型那样在相同程度上解决Pfaff模型。这种批评和由此产生的讨论似乎是出于这样一种想法，即本文的目标是试图模拟和预测一个真实的壳体的失效。事实并非如此;事实上，正如在引言中所解释的，我试图解构真实的壳体的重要形态参数，并单独测试它们对最终结构强度的相对贡献。为了做到这一点，需要创建壳体的简化模型进行比较测试。评论者将这种批评扩展到讨论壳体的哪个部分是最薄弱的，最终得出结论，最终形成的隔膜将是第一个在水压下失效的结构，引用我之前写的一篇论文，查看几个基于CT的壳体模型的FEA结果[5]。然而，重要的是要认识到，无论是被评论的论文还是早期的论文都没有考虑真实的壳体中的哪个结构会首先失效，也没有考虑真实的壳体在水压下如何失效。这个问题将需要一组更复杂的材料特性（尚未完全了解）和验证研究，甚至开始解决。在这两种情况下，所讨论的主题都是隔膜的潜在功能，因此使这段对话稍微有点离题。话虽如此，目前尚不清楚最终隔膜是否是最薄弱的结构。正如鹦鹉螺的内爆实验所指出的，最后的隔膜或虹吸管是第一个失败的结构，但确切的顺序尚不清楚[7]。我的早期论文[5]明确地从模型中排除了虹吸管，因此我们没有评论它。如果虹吸管确实是最弱的结构，根据评论者自己的推理，整个关于隔膜和水深的讨论有点毫无意义。与此讨论相关的是关于不切实际的壁厚的评论。同样，所使用的模型的“不切实际”的结构是所提出的问题所必需的。例如，当试图了解不同的间隔形态如何影响最终结构的强度时，采用具有完全相同参数的不同模型，例如
In a recent comment on a paper I published last year [1], examining how several morphological parameters can differentially influence the strength of an ammonoid shell [2], the commenter makes two major criticisms:(1) the paper focuses entirely on the Buckland model and ignores the Pfaff model; and (2) the modelled septa are not complex enough, along with a few more minor criticisms. In a short summary, the Buckland and Pfaff models are two ideas about how hydrostatic pressure would interact with the septa. The Buckland model states that the more complex septa buttress the shell wall from lateral pressure, modelled in the commented paper [2], while the Pfaff model suggests the more complex septa improve the final-formed septum’s resistance to hydrostatic pressure from the body chamber [3, 4]. It is certainly true we do not model a body chamber and thus effectively ignore the Pfaff model. It is worth noting that tests on CT-based, empirical models are inconsistent with the Pfaff model when modelling different septal morphologies in Cadoceras [5]. Furthermore, including the more complicated septa of a sub-adult Kosmoceras, seen in [6], does nothing to validate this hypothesis; though this does not address the Pfaff model to the same degree as the Buckland model was in the commented paper. This criticism and the resulting discussion seem to be born out of the idea that the goal of this paper was to try to model and predict the failure of a real shell. This is not the case; in fact, as was explained in the introduction, I attempted to deconstruct the important morphological parameters of real shells and individually test their relative contribution to the final structure’s strength. To do this one needs to create simplified models of the shell for comparative testing.The commenter extends this criticism to discuss which part of the shell is the weakest, ultimately coming to the conclusion that the final-formed septum would be the first structure to fail under water pressure, citing an earlier paper I had written looking at FEA results from several CT-based shell models [5]. It is important to recognize however, that neither the paper being commented on nor the earlier paper are looking at which structure in the real shell would fail first nor how a real shell would fail under water pressure. This question would require a more sophisticated set of material properties (which are not fully known) and validation studies to even begin to address. In both cases, the topic being addressed is the potential function of the septa, thereby making this conversation slightly tangential. That being said it is not currently known if the final septum is the weakest structure. As pointed out in the implosion experiments on Nautilus, either the final septum or the siphuncle is the first structure to fail but the exact order is not known [7]. The earlier paper of mine [5] explicitly left out the siphuncle from the models, hence why we did not comment on it. If the siphuncle is indeed the weakest structure, by the commenter’s own reasoning, this entire discussion about septa and water depth is somewhat pointless. Tied to this discussion, is a comment about the unrealistic wall thickness. Again, the ‘unrealistic’structure of the models used is all that is necessary for the questions being asked. For example, when trying to understand how different septal morphologies affect the final structure’s strength, taking different models with the exact same parameters, such
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影响因子：
2.7
作者：
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通讯作者：
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DOI：
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发表时间：
1997
期刊：
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影响因子：
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影响因子：
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作者：
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通讯作者：
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影响因子：
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作者：
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通讯作者：
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DOI：
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发表时间：
2007
期刊：
影响因子：
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作者：
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通讯作者：
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