Morphological trends across the Norian/Rhaetian boundary within Late Triassic conodonts in western Canada: implications for protracted paleoenvironmental disturbance preceding the end-Triassic mass extinction

IF 2.6 2区 地球科学 Q2 BIODIVERSITY CONSERVATION
Paleobiology Pub Date : 2023-12-04 DOI:10.1017/pab.2023.30
Jerry Z. X. Lei, Martyn L. Golding, Jon M. Husson
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引用次数: 0

Abstract

The Late Triassic conodont species Mockina ex gr. carinata and Mockina ex gr. englandi were exceptionally prevalent among the marine fauna of the Panthalassan realm from the middle Norian through to the Rhaetian. Leading into the complete extinction of conodonts near the Triassic/Jurassic boundary, a significant turnover event occurred in conodont fauna across the Norian/Rhaetian boundary (NRB), with the pectiniform elements of common Rhaetian genera from Tethys exhibiting minimal or absent platforms. This intergeneric trend of platform reduction is not as evident in Panthalassa, where these genera are very rare, but morphometric analyses of M. ex gr. carinata and M. ex gr. englandi specimens from across the Canadian Cordillera demonstrate that comparable shifts in morphology occurred intraspecifically in Panthalassa across the NRB, confirming the global extent of these trends. Pectiniform elements of M. ex gr. carinata display a sequential reduction of platform width from the middle Norian to late Norian to Rhaetian, whereas pectiniform elements of M. ex gr. englandi display a reduction of platform width only from the late Norian to Rhaetian. Specimens of both species that have a mid-platform length to breadth ratio greater than 3:1 are restricted to the Rhaetian. Specimens from the Kennecott Point section on Haida Gwaii, British Columbia, demonstrate that this morphological shift occurred somewhat later than other biostratigraphic proxies for the NRB. The global trend of platform width reduction in many conodont pectiniform elements may reflect a change in primary diet away from hard food sources, perhaps suggesting some degree of carbonate biomineralization suppression beginning around the NRB. This interpretation would support CO2 outgassing as the causal mechanism of the environmental disturbance at the NRB and identify the NRB as a significant turning point for Late Triassic ecosystems, marking the beginning of a protracted, multiphase end-Triassic mass extinction.
加拿大西部晚三叠世牙形刺中横跨Norian/Rhaetian边界的形态趋势:对三叠纪末大灭绝前持续的古环境扰动的影响
晚三叠世牙形刺物种Mockina ex gr. carinata和Mockina ex gr. englandi在中诺里亚到雷提亚的泛地中海王国的海洋动物群中特别普遍。在三叠纪/侏罗纪边界附近的牙形刺完全灭绝之前,在Norian/Rhaetian边界(NRB)的牙形刺动物群中发生了一次重大的更替事件,来自Tethys的常见Rhaetian属的pectinform元素显示出很少或没有平台。这种台地减少的属间趋势在Panthalassa中并不明显,因为这些属在那里非常罕见,但对加拿大科迪勒拉地区的M. ex gr. carinata和M. ex gr. englandi标本的形态测量学分析表明,在整个NRB的Panthalassa中,形态上的类似变化发生在种内,证实了这些趋势的全球范围。m.ex gr. carinata的pectinform元素表现出中诺里亚-晚诺里亚-雷蒂亚的台地宽度递减,而m.ex gr. englandi的pectinform元素只表现出晚诺里亚-雷蒂亚台地宽度递减。这两个物种的标本中平台的长度与宽度比大于3:1仅限于雷蒂亚。来自不列颠哥伦比亚省海达瓜伊的Kennecott Point剖面的标本表明,这种形态转变发生的时间比其他生物地层代用物要晚。许多牙形石果胶状元素的平台宽度减少的全球趋势可能反映了原始饮食从硬食物来源的变化,可能表明在NRB周围开始某种程度的碳酸盐生物矿化抑制。这一解释将支持二氧化碳脱气作为北海带环境扰动的因果机制,并将北海带确定为晚三叠纪生态系统的一个重要转折点,标志着一场旷日持久的、多阶段的三叠纪末期大灭绝的开始。
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来源期刊
Paleobiology
Paleobiology 地学-古生物学
CiteScore
5.30
自引率
3.70%
发文量
38
审稿时长
>12 weeks
期刊介绍: Paleobiology publishes original contributions of any length (but normally 10-50 manuscript pages) dealing with any aspect of biological paleontology. Emphasis is placed on biological or paleobiological processes and patterns, including macroevolution, extinction, diversification, speciation, functional morphology, bio-geography, phylogeny, paleoecology, molecular paleontology, taphonomy, natural selection and patterns of variation, abundance, and distribution in space and time, among others. Taxonomic papers are welcome if they have significant and broad applications. Papers concerning research on recent organisms and systems are appropriate if they are of particular interest to paleontologists. Papers should typically interest readers from more than one specialty. Proposals for symposium volumes should be discussed in advance with the editors.
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