Late Cretaceous sturgeons (Acipenseridae) from North America, with two new species from the Tanis site in the Hell Creek Formation of North Dakota
Late Cretaceous sturgeons (Acipenseridae) from North America, with two new species from the Tanis site in the Hell Creek Formation of North Dakota
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DOI：
10.1017/jpa.2022.81
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发表时间：
2022-10
影响因子：
1.4
通讯作者：
E. Hilton;L. Grande
中科院分区：
文献类型：
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作者：
E. Hilton;L. Grande
摘要。尽管白垩纪被广泛认为是北美淡水鱼类区系发生重大进化转变的时期，但这一时期的化石记录却非常糟糕，主要由碎片和孤立的骨骼成分组成。本文所讨论的鲟形目以及一些极其罕见的硬骨鱼是例外。在此，我们描述了来自北达科他州晚白垩世海尔克里克组塔尼斯遗址的两种保存完好的新种鲟鱼（鲟科）。模式标本和参考材料保存在一种松散固结的基质中。†先备鲟（Acipenser praeparatorum n. sp.）有多个身体化石（包括头部和相对完整的颅后遗骸）以及一个完整的、三维保存的头骨和胸带标本作为代表。该分类群可根据鳃盖骨成分的特征（鳃条骨极高且窄）进行鉴别。第二个物种，†不等鲟（Acipenser anisinferos n. sp.），由一个部分保存的头骨作为代表，可通过相对较长的眶前区域（即吻部）以及头骨顶部骨骼上没有刺状棘来鉴别。大多数已知的白垩纪鲟鱼化石仅由无法鉴别的碎片遗骸（即骨板和胸鳍棘）或保存不佳的部分骨骼（例如†原铲鲟）所代表，†原始鲟和†近鲟（均为单型）是罕见的例外。因此，新发现的塔尼斯化石让我们难得一见鲟科在鲟形目系统发育历史的关键时期的进化情况，并表明该类群在进化早期具有显著的形态和分类多样性。
Abstract. Although the Cretaceous is widely regarded as a time of great evolutionary transition for the freshwater fish fauna of North America, the fossil record of this period is notoriously poor, consisting mostly of fragments and isolated skeletal elements. Exceptions include the acipenseriforms, discussed in this paper, and some exceedingly rare teleosts. Here we describe two new species of well-preserved sturgeons (Acipenseridae) from the Tanis site in the Late Cretaceous Hell Creek Formation of North Dakota. The type and referred materials were preserved in a loosely consolidated matrix. †Acipenser praeparatorum n. sp. is represented by multiple body fossils (including the head and relatively complete postcranial remains) and a specimen of an intact, three dimensionally preserved skull and pectoral girdle. This taxon can be diagnosed based on features of the opercular elements (exceptionally tall and narrow branchiostegal). The second species, †Acipenser anisinferos n. sp., is represented by a partially preserved skull, and can be diagnosed by a relatively elongate preorbital region (i.e., snout) and the absence of thorn-like spines on the skull roofing bones. Most known sturgeon fossils from the Cretaceous are represented only by undiagnosable fragmentary remains (i.e., scutes and pectoral-fin spines) or poorly preserved partial skeletons (e.g., †Protoscaphirhynchus), with †Priscosturion and †Anchiacipenser (both monotypic) being rare exceptions. Therefore, the newly discovered Tanis fossils give a rare glimpse into the evolution of Acipenseridae at a critical time in the phylogenetic history of acipenseriforms, and suggest significant morphological and taxonomic diversity early in the evolution of this group.