MORPHOTYPE MATTERS: AN EXPERIMENTAL ANALYSIS OF THE MORPHOLOGICAL FIDELITY OF GASTROPOD STEINKERNS

IF 1.5 4区 地球科学 Q2 GEOLOGY
Palaios Pub Date : 2024-07-24 DOI:10.2110/palo.2023.041
ERYNN JOHNSON, Miranda MARGULIS-OHNUMA, Thomas J. Smith, Susan H. Butts, Christina Lutz, Derek E.G. Briggs
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Abstract

Gastropods are commonly preserved as steinkerns (internal casts), a mode of fossilization that leads to loss of external morphological features. This loss of information is problematic for taxonomic identification and ecological inference in evaluating assemblages where original shell material is not preserved. We seek to quantify how closely gastropod steinkerns represent the morphology of their original shells. We investigated this relationship experimentally by fabricating steinkerns in silicone from modern gastropod shells and comparing their geometry to that of the shells we used to create them. In addition to recording traces of ornamentation such as ribs and spines, we used a theoretical morphospace framework to evaluate the fidelity of shell-coiling parameters in steinkerns. Our results show that some morphotypes reflect their taxonomic identification more accurately than others, indicating that steinkern fidelity is highly variable. Experimental steinkerns consistently cluster less reliably by morphotype than their original shell counterparts. Additionally, we find that shell thickness is an important factor in determining steinkern fidelity. The fidelity of the high-spired Duplicaria duplicata, for example, is significantly lower than the average value for the morphotypes investigated whereas the fidelity of planispiral Haplotrema concavum and open-coiling Epitonium is significantly higher, a trend related to shell thickness. Thus, taxonomic identification and subsequent analyses, such as community composition, of steinkern assemblages must recognize this differential fidelity to counter preservational biases.
形态类型很重要:对腹足纲 steinkerns 形态保真度的实验分析
腹足纲动物通常以内部铸件(steinkerns)的形式保存,这种化石模式会导致外部形态特征的丧失。在评估未保存原始贝壳材料的集合体时,这种信息的缺失会给分类鉴定和生态推断带来问题。我们试图量化腹足类沉积物与其原始贝壳形态的密切程度。我们用硅胶制作了现代腹足类贝壳的沉降片,并将其几何形状与我们用来制作沉降片的贝壳的几何形状进行了比较,从而通过实验研究了这种关系。除了记录肋骨和棘刺等装饰物的痕迹外,我们还使用了一个理论形态空间框架来评估沉降片中贝壳卷曲参数的保真度。我们的研究结果表明,一些形态类型比其他形态类型更准确地反映了它们的分类鉴定,这表明石龙子的保真度变化很大。与原壳对应物相比,实验沉箱按形态类型聚类的可靠性较低。此外,我们还发现,贝壳厚度是决定隐翅虫保真度的一个重要因素。例如,高螺旋形的杜父鱼(Duplicaria duplicata)的保真度明显低于所调查形态类型的平均值,而平螺旋形的Haplotrema concavum和开螺旋形的Epitonium的保真度则明显较高,这一趋势与外壳厚度有关。因此,对石龙子集合体进行分类鉴定和群落组成等后续分析时,必须认识到这种不同的保真度,以消除保存上的偏差。
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来源期刊
Palaios
Palaios 地学-地质学
CiteScore
2.80
自引率
12.50%
发文量
40
审稿时长
6 months
期刊介绍: PALAIOS is a monthly journal, founded in 1986, dedicated to emphasizing the impact of life on Earth''s history as recorded in the paleontological and sedimentological records. PALAIOS disseminates information to an international spectrum of geologists and biologists interested in a broad range of topics, including, but not limited to, biogeochemistry, ichnology, paleoclimatology, paleoecology, paleoceanography, sedimentology, stratigraphy, geomicrobiology, paleobiogeochemistry, and astrobiology. PALAIOS publishes original papers that emphasize using paleontology to answer important geological and biological questions that further our understanding of Earth history. Accordingly, manuscripts whose subject matter and conclusions have broader geologic implications are much more likely to be selected for publication. Given that the purpose of PALAIOS is to generate enthusiasm for paleontology among a broad spectrum of readers, the editors request the following: titles that generate immediate interest; abstracts that emphasize important conclusions; illustrations of professional caliber used in place of words; and lively, yet scholarly, text.
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