Terrestrial and Aquatic Mollusks of the Eocene Kishenehn Formation, Middle Fork Flathead River, Montana
Terrestrial and Aquatic Mollusks of the Eocene Kishenehn Formation, Middle Fork Flathead River, Montana
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蒙大拿州中福克弗拉特黑德河始新世 Kishenehn 地层的陆地和水生软体动物
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发表时间：
2014
期刊：
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通讯作者：
K. Constenius
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文献类型：
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作者：
H. G. Pierce;K. Constenius
蒙大拿州西北部和不列颠哥伦比亚省东南部的基申恩组是北美最丰富多样的非海洋软体动物化石组合之一。本文记述了始新世中期至中新世早期陆栖和水生腹足类76个分类单元，其中41个为新记录种。本文报道了在基什内恩盆地最南端始新世中期地层最古老部分的发现。沿着平头河中叉从这个地区的露头已经产生了超过1400个标本，其中62个分类群（37陆生，25水生）进行了鉴定。其中8个是新种，9个在其他地方描述过，但以前没有在该地层中报道过。根据古环境亲缘关系，动物群可分为三个组。第一组是一个残存的热带潮湿动物群，存在于盆地水道，其现代类似物生活在加勒比海和中美洲和南美洲。第二组是亚热带半干旱动物群，其现代类似物分布于墨西哥湾北岸，横跨美国南部和北方墨西哥，至加州南部和巴哈半岛。第三组是一个潮湿的，暖温带动物群，从盆地东部的山脉和沉积在扇三角洲和湖泊边缘设置。这些软体动物类群的现代类似物在美国中东部很常见。这些气候不同的化石软体动物群的不寻常的共存是一个大的古地形起伏，也许大于2000米，存在于谷底和山脉之间的表现。以下分类群在此由资深作者（HGP）描述为新种：双壳类：Sphaeriidae- Sphaerium lentum，Pisidium triangulatum.腹足纲：Proserpinellidae- Tozerpina elsae;扁螺科- Obeliscus scalplockensis;扁螺科- Ferrissia circus，Rhodacmaea crepida，Omalodiscus spira;扁螺科- Physella olive;和一个新亚种：腹足纲：Pupillidae- Pupilla hebes sinistra。
ABSTRACT The Kishenehn Formation of northwest Montana and southeast British Columbia hosts one of the most prolific and diverse assemblages of fossil nonmarine mollusks in North America. More than 76 taxa, of which 41 are newly described species, of middle Eocene to early Miocene terrestrial and aquatic gastropods have been collected and described. This paper reports on the discoveries made in the oldest part of the formation that is middle Eocene in age in the southernmost part of the Kishenehn Basin. Outcrops along the Middle Fork of the Flathead River from this area have yielded over 1400 specimens from which 62 taxa (37 terrestrial, 25 aquatic) were identified. Of these, eight are new species and nine were described elsewhere but were not previously reported in the formation. In terms of paleoenvironmental affinities, the fauna are divisible into three groups. Group I is a relict tropical wet fauna, existing in basinal waterways whose modern analogs live in the Caribbean and Central and South America. Group II is a subtropical, semi-arid fauna with modern analogs ranging from the north coast of the Gulf of Mexico, across the southern United States and northern Mexico to southern California and the Baja Peninsula. Group III is a humid, warm temperate fauna that was transported from mountains east of the basin and deposited in fan-delta and lake-margin settings. Modern analogs of these molluscan taxa are common in the east-central United States. The unusual coexistence of these climatically disparate groups of fossil mollusks is a manifestation of the large paleotopographic relief, perhaps greater than 2000 m, that existed between the valley floor and the mountains. The following taxa are described herein by the senior author (HGP) as new species: Bivalvia: Sphaeriidae- Sphaerium lentum, Pisidium triangulatum. Gastropoda: Proserpinellidae- Tozerpina elsae; Subulinidae- Obeliscus scalplockensis; Planorbidae- Ferrissia circus, Rhodacmaea crepida, Omalodiscus spira; Physidae- Physella olive; and one new subspecies: Gastropoda: Pupillidae- Pupilla hebes sinistra.