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Revision of the trace fossil Megagrapton Książkiewicz, 1968 with focus on Megagrapton aequale Seilacher, 1977 from the lower Eocene of the Lesser Caucasus in Georgia
Geological Quarterly ( IF 1 ) Pub Date : 2022-06-24 , DOI: 10.7306/gq.1640
Alfred Uchman, Zurab Lebanidze, Tamar Beridze, Nino Kobakhidze, Koba Lobzhanidze, Sophio Khutsishvili, Rusudan Chagelishvili, Davit Makadze, Kakha Koiava, Nino Khundadze

Megagrapton Książkiewicz, 1968 is a characteristic deep-sea trace fossil belonging to the group of graphoglyptids and mostly preserved as a network of irregular meshes in hypichnial semirelief. So far, eleven ichnospecies have been distinguished under this ichnogenus, though commonly on weak evidence. The so-far poorly known ichnospecies Megagrapton aequale Seilacher, 1977 is described here on the basis of the numerous, newly discovered specimens from deep-sea siliciclastic deposits of the Bolevani Subsuite (lower Eocene) in the Lesser Caucasus of Georgia, together with other collections and published examples. A neotype of this ichnospecies is designated and the diagnosis emended. M. aequale occurs in lower Cambrian to upper Miocene deep-sea turbiditic deposits, mostly in the Paleogene. It is characterized by relatively small, variable meshes, which have mostly irregular sub-pentagonal, sub-hexagonal or sub-heptagonal shapes that are variable in size and are bordered by curved or straight semicircular ridges. It has been mistaken for Paleodictyon, which forms regular hexagonal nets. Paleodictyon imperfectum Seilacher, 1977 is included in M. aequale as the ichnosubspecies M. a. imperfectum, which is characterized by relatively thin bordering ridges. After critical analysis of all ichnospecies, only M. irregulare Książkiewicz, 1968, M. submontanum (Azpeitia Moros, 1933), and M. aequale are recommended for further use. These are distinguished on the basis of the prevailing morphology of the meshes, irrespective of large differences in morphometric parameters within the ichnospecies. Irredictyon chaos Vialov, 1972 is included in M. irregulare as the ichnosubspecies M. i. chaos, which is characterized by relatively thick bordering ridges. Megagrapton is interpreted as a cast of a subsurface open burrow network with a few connections to the sea floor. The burrows probably functioned as a trap for small organisms (ethological subcategory irretichnia).




中文翻译:

1968 年修订的痕迹化石 Megagrapton Książkiewicz,重点是 1977 年来自佐治亚州小高加索下始新世的 Megagrapton aequale Seilacher

Megagrapton Książkiewicz,1968 年是一种特征性的深海痕迹化石,属于图文类,大部分保存为半浮雕中的不规则网格网络。到目前为止,已经在这个 ichnogenus 下区分了 11 种 ichnospecies,尽管通常证据不足。迄今为止鲜为人知的ichnospecies Megagrapton aequale Seilacher, 1977 在这里描述的基础是来自佐治亚州小高加索地区 Bolevani Subsuite(下始新世)深海硅质碎屑沉积物的大量新发现的标本,以及其他收藏品并发布示例。这种鱼种的一个新类型被指定并修正了诊断。M. aequale产于寒武统下寒武统至上中新统深海浊积岩沉积物中,主要分布在古近纪。它的特点是相对较小、多变的网格,其大多具有不规则的亚五边形、亚六边形或亚七边形,其大小可变,并以弯曲或笔直的半圆形脊为界。它被误认为是形成规则六边形网的Paleodictyon。Paleodictyonfectum Seilacher, 1977 被包括在M. aequale作为 ichnosubspecies M. a. 不完美的,其特征是相对较薄的边界脊。在对所有 ichnospecies 进行批判性分析后,只有M.regulare Książkiewicz, 1968, M. submontanum (Azpeitia Moros, 1933) 和建议进一步使用M. aequale 。这些是根据网格的主要形态来区分的,而不管 ichnospecies 内形态测量参数的巨大差异。I rredictyon chaos Vialov, 1972作为 ichnosubspecies M. i. 包含在 M.regulare 中。混沌,其特点是相对较厚的边界脊。Megagrapton被解释为地下开放洞穴网络的铸件,与海底有一些连接。洞穴可能充当了小生物的陷阱(行为学亚类irretichnia)。


更新日期:2022-06-24
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