Paddlefish and Sturgeon (Chondrostei: Acipenseriformes: Polyodontidae and Acipenseridae) from Lower Paleocene Deposits of Montana, U.S.A.
Paddlefish and Sturgeon (Chondrostei: Acipenseriformes: Polyodontidae and Acipenseridae) from Lower Paleocene Deposits of Montana, U.S.A.
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来自美国蒙大拿州下古新世沉积物的白鲟和鲟鱼（软骨鱼：鲟鱼目：多齿鱼科和鲟鱼科）
DOI：
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发表时间：
2020
影响因子：
1.4
通讯作者：
G. Wilson
中科院分区：
文献类型：
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作者：
A. Murray;D. Brinkman;D. Demar;G. Wilson
摘要：美国蒙大拿州联合堡组图洛克段的古新世沉积物产出了几件†多齿铲颌鱼（Polyodon tuberculata）的新标本，该分类群此前已在该地层中被描述过，同时还产出了一种新的鲟鱼（鲟科）属种。三件†多齿铲颌鱼的新标本使我们能够修订并确认此前报道的正模标本的特征，以及描述在之前已知的单一标本中未保存的其他特征。例如，我们观察到：（1）左右后颞骨覆盖左右顶骨并在中线相接；（2）后颞骨有一个深的腹侧凸缘；（3）副蝶骨向后延伸得比顶骨更远。新的鲟鱼体型相当小，且保存不佳。它可以通过一系列特征组合与所有其他鲟科鱼类区分开来，这些特征包括：带有强烈中脊的风筝形背骨板、形状从菱形到不规则形状的侧骨板、臀鳍后面的一个大三角形骨板以及覆盖尾骨的众多小菱形鳞片。它无法归入任何目前已知的属，在此被命名为†恩格达利奇鱼（Engdahlichthys milviaegis），新属新种。
ABSTRACT Paleocene deposits of the Tullock Member of the Fort Union Formation, Montana, U.S.A., have yielded several new specimens of †Polyodon tuberculata, a taxon previously described from the formation, as well as a new genus and species of sturgeon (Acipenseridae). The three new specimens of †P. tuberculata allow us to revise and to confirm previously reported features of the holotype, as well as to describe other features that were not preserved in the single specimen previously known. For example, we observe that (1) the left and right posttemporals overlie the left and right parietals to meet in the midline, (2) the posttemporal has a deep ventral flange, and (3) the parasphenoid extends farther posteriorly than the parietals. The new sturgeon is fairly small, and not well preserved. It can be distinguished from all other acipenserids by a combination of features, including kite-shaped dorsal scutes bearing a strong median ridge, lateral scutes that vary in shape from rhomboid to irregularly shaped elements, a large triangular scute behind the anal fin, and numerous small rhomboid scales covering the caudal skeleton. It cannot be included in any currently known genus and is here named †Engdahlichthys milviaegis, gen. et sp. nov.