The last known freshwater coelacanths: New Late Cretaceous mawsoniid remains (Osteichthyes: Actinistia) from Southern France
The last known freshwater coelacanths: New Late Cretaceous mawsoniid remains (Osteichthyes: Actinistia) from Southern France
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DOI：
10.1371/journal.pone.0234183
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发表时间：
2020-06-05
期刊：
影响因子：
3.7
通讯作者：
Valentin, Xavier
中科院分区：
文献类型：
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作者：
Cavin, Lionel;Buffetaut, Eric;Valentin, Xavier
腔棘鱼是一种标志性的鱼类，今天由一个单一的海洋属代表。中生代时，这一类群的类型稍多样化，晚白垩世时在海相和陆相环境中都有代表。在这里，我们描述了在法国南部（奥德省、罗讷河口省、埃罗省和瓦尔省）从早期坎帕尼亚期到早期马斯特里赫特期的几个化石地点发现的最后一批淡水腔棘鱼的孤立头骨。该样本不允许区分不同的物种，所有材料都被称为Axelrophthys megadromos Cavin，Valentin，Garcia，最初描述于法国南部的文塔布伦。建议对颅骨进行重建。以前未被认识的功能进行了描述，包括部分后顶骨部分的头骨，悬骨和下颌骨。新的数据证实了该物种的归属mawsoniids，更具体地说，Axelrophilthys。一个分支分析评分新的字符状态提供了一个类似的拓扑结构比以前的分析，即A。megadromos与Axelrophthys arararipensis和Lualabaea lerichei（分别来自巴西的早白垩世和刚果民主共和国的晚侏罗世的两个物种）一起被置于多分体中。A. megadromos似乎已被限制在淡水环境中，相反，最古老的西方冈瓦纳代表的家庭，能够生活在半咸水和海洋沃茨。A. megadromos是mawsoniids的最后一个代表，它在欧洲的出现可能是白垩纪发生的一次西冈瓦纳的扩散事件的结果。根据现有的资料，毛松类在马斯特里赫特中期灭绝，即在白垩纪末大灭绝之前。但是，这个家族的化石记录最近才在晚白垩世欧洲沉积物中被发现，随着进一步的发现，它在地理和地层上的范围可能会扩大。
Coelacanths are iconic fishes represented today by a single marine genus. The group was a little bit more diversified in the Mesozoic, with representatives in marine and continental environments in the Late Cretaceous. Here we describe isolated skull bones of the last know freshwater coelacanths found in several fossil sites from the Early Campanian to the Early Maastrichtian of Southern France (in the Departments of Aude, Bouches-du-Rhone, Herault, and Var). The sample does not allow distinguishing different species, and all material is referred to Axelrodichthys megadromos Cavin, Valentin, Garcia originally described from the locality of Ventabren in Southern France. A reconstruction of the skull is proposed. Previously unrecognized features are described, including parts of the postparietal portion of the skull, of the suspensorium and of the mandible. The new data confirm the assignation of the species to the mawsoniids, and more specifically to Axelrodichthys. A cladistic analysis scoring new character states provides a similar topology than a previous analysis, i.e. A. megadromos is placed in a polytomy with Axelrodichthys araripensis and Lualabaea lerichei, two species from the Early Cretaceous of Brazil and from the Late Jurassic of the Democratic Republic of the Congo, respectively. A. megadromos appears to have been restricted to freshwater environments, to the contrary of oldest Western Gondwanan representatives of the family that were able to live in brackish and marine waters. A. megadromos is the last representative of the mawsoniids and its occurrence in Europe is probably the result of a dispersal event from Western Gondwana that happened somewhen in the Cretaceous. Based on the available data, the mawsoniids went extinct in the mid-Maastrichthian, i.e. before the end-Cretaceous mass extinction. But it is possible that the fossil record of this family, which has been only recently recognized in Late Cretaceous European deposits, will geographically and stratigraphically widen with further discoveries.