New Discovery of Rhyncholites and Conchorhynchs (Cephalopod Jaw Elements) from the Upper Cretaceous Mount Laurel Formation of Delaware

IF 1.1 3区环境科学与生态学 Q3 BIODIVERSITY CONSERVATION

American Museum Novitates Pub Date : 2023-05-10 DOI:10.1206/3998.1

Amane Tajika, N. Landman, Hiromichi Koyasu, A. Broussard, Lian C. Anderson, Kenji Ikuno

{"title":"New Discovery of Rhyncholites and Conchorhynchs (Cephalopod Jaw Elements) from the Upper Cretaceous Mount Laurel Formation of Delaware","authors":"Amane Tajika, N. Landman, Hiromichi Koyasu, A. Broussard, Lian C. Anderson, Kenji Ikuno","doi":"10.1206/3998.1","DOIUrl":null,"url":null,"abstract":"ABSTRACT Rhyncholites and Conchorhynchs are the calcitic elements of upper and lower jaws of cephalopods, respectively. Rhyncholites and conchorhynchs occur in relatively high abundance and are widely distributed, with a long geological range, extending from the Triassic to the Miocene. While rhyncholites and conchorhynchs are relatively common in Europe, there are only a few reports from North America. Here, we document 24 specimens of rhyncholites and 12 specimens of conchorhynchs from the Upper Cretaceous Mount Laurel Formation in Delaware. The specimens were found in isolation and, thus, identifying the taxon to which the rhyncholites and conchorhynchs belong is difficult. However, the Cretaceous nautilid Eutrephoceras occurs in the same formation, suggesting that the rhyncholites and conchorhynchs may belong to this taxon. We performed a morphometric analysis of these structures based on linear measurements. Our results reveal that some morphological parameters in rhyncholites are correlated with size. Additionally, our specimens exhibit high intraspecific variation, which may have been overlooked in previous studies.","PeriodicalId":55527,"journal":{"name":"American Museum Novitates","volume":"2023 1","pages":"1 - 20"},"PeriodicalIF":1.1000,"publicationDate":"2023-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"American Museum Novitates","FirstCategoryId":"93","ListUrlMain":"https://doi.org/10.1206/3998.1","RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"BIODIVERSITY CONSERVATION","Score":null,"Total":0}

引用次数: 0

Abstract

ABSTRACT Rhyncholites and Conchorhynchs are the calcitic elements of upper and lower jaws of cephalopods, respectively. Rhyncholites and conchorhynchs occur in relatively high abundance and are widely distributed, with a long geological range, extending from the Triassic to the Miocene. While rhyncholites and conchorhynchs are relatively common in Europe, there are only a few reports from North America. Here, we document 24 specimens of rhyncholites and 12 specimens of conchorhynchs from the Upper Cretaceous Mount Laurel Formation in Delaware. The specimens were found in isolation and, thus, identifying the taxon to which the rhyncholites and conchorhynchs belong is difficult. However, the Cretaceous nautilid Eutrephoceras occurs in the same formation, suggesting that the rhyncholites and conchorhynchs may belong to this taxon. We performed a morphometric analysis of these structures based on linear measurements. Our results reveal that some morphological parameters in rhyncholites are correlated with size. Additionally, our specimens exhibit high intraspecific variation, which may have been overlooked in previous studies.

查看原文本刊更多论文

特拉华州上白垩纪劳雷尔山组Rhyncholites和Conchorhynchs（头足类颚元素）的新发现

Rhyncholites和Conchorhynchs分别是头足类动物上下颚的钙化元素。Rhyncholites和conchorhynchs的丰度相对较高，分布广泛，地质范围长，从三叠纪一直延伸到中新世。虽然钩吻岩和海螺在欧洲相对常见，但只有少数来自北美的报道。在这里，我们记录了特拉华州上白垩纪劳雷尔山组的24个流纹岩标本和12个海螺标本。这些标本是孤立发现的，因此，很难确定钩虫和海螺属的分类单元。然而，白垩纪的鹦鹉螺Eutrephoceras出现在同一个地层中，这表明钩虫和海螺可能属于这个分类单元。我们基于线性测量对这些结构进行了形态计量学分析。我们的研究结果表明，流纹岩中的一些形态参数与大小有关。此外，我们的标本表现出很高的种内变异，这在以前的研究中可能被忽视了。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

求助全文

约1分钟内获得全文求助全文

来源期刊

American Museum Novitates 环境科学-动物学

CiteScore

3.00

自引率

6.70%

发文量

审稿时长

>36 weeks

期刊介绍： The Novitates (Latin for "new acquaintances"), published continuously and numbered consecutively since 1921, are short papers that contain descriptions of new forms and reports in zoology, paleontology, and geology.