Ancestry of the Grass Snake (Natrix natrix): Paleontological Evidence
Ancestry of the Grass Snake (Natrix natrix): Paleontological Evidence
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草蛇（Natrix natrix）的祖先：古生物学证据
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发表时间：
1991
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通讯作者：
Z. Szyndlar
中科院分区：
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作者：
Z. Szyndlar
欧洲中新世至近代natricine蛇的颅骨遗骸极有可能证明现存物种Natrix natrix是新近纪物种N. longivertebrata的直系后代。在 N. longivevertebrata-N 中观察到的进化变化。 natrix谱系主要由两种基本颅骨形态模式的逐渐改变组成，而其他颅骨特征保持不变。来自这一假设谱系成员的数据，以及来自其他一些欧洲蛇化石的数据，支持了这样的假设：中新世蛇与其最近的后代在骨骼学上几乎没有什么不同，并提供了额外的间接证据，表明许多现存蛇类属的起源可能发生在古近纪/新近纪边界之前。新爬行动物学家经常怀疑化石记录在蛇系统学和进化研究中的有用性。这种观点源于这样一个事实：大多数蛇化石都是基于孤立的椎骨，这些元素极难解释（例如，McDowell，1987），并且通常缺乏头骨。颅骨元素本身通常不足以推断已灭绝的物种与其现存亲属之间的系统发育关系。同源元素通常很少见，因此特定骨骼中种内变异的重要性不容易解释。在这种情况下，许多先前的研究给出的已灭绝蛇的分类位置通常是基于轻微的表型相似或不同。以这种方式建立的分类群的使用在系统学和系统发育学考虑中并不重要。为了帮助纠正这种情况，有必要根据大量化石遗址的颅骨元素对蛇类分类群进行详细描述。然而，绝大多数有关新近纪蛇的出版物都是对来自单一地点的动物群的描述。基于代表更广泛地理区域和不同地质时代的材料的类群描述很少。许多博物馆都收藏了大量蛇类化石，但蛇类古生物学家的数量却很少。尽管如此，我的调查表明，在许多欧洲新近纪遗址中发现的蛇头骨元素并不像人们普遍认为的那么罕见，至少就本文讨论的遗址而言是这样。本文的主要目的是证明新近纪化石遗迹可能有利于有效重建活蛇的系统发育。最近对现存眼镜蛇属的一项研究清楚地记录了西古北界化石遗迹的有用性（Szyndlar 和 Rage，1990）。现存的欧洲蛇 Natrix natrix 是从其推测的祖先——已灭绝的长颈蛇（N. longivertebrata）（下文将讨论）的后裔，这也许是化石记录所证明的蛇类微观进化的最佳例证之一。 N. longivevertebrata-N的历史。 natrix谱系基于许多分类学上重要的颅骨元素，这些元素来自许多不同时代的欧洲遗址。本文的另一个重要方面是，根据欧洲现有的化石记录，证明中新世物种与其现存后代密切相关，因此，现存蛇类属的起源可能发生在古近纪/新近纪边界之前。
Cranial remains of European middle Miocene-Recent natricine snakes demonstrate with high probability that the living species Natrix natrix is a direct descendant of the Neogene species N. longivertebrata. Evolutionary changes observed in the N. longivertebrata-N. natrix lineage mainly consist of gradual modification of two basicranial morphological patterns, while other skull characters remain invariant. Data from members of this postulated lineage, as well as data derived from some other European snake fossils, support the hypothesis that Miocene snakes differed little from their recent descendants osteologically, and provide additional indirect evidence that the origin of many living ophidian genera may have taken place before the Paleogene/Neogene boundary. The usefulness of the fossil record in studies of snake systematics and evolution is often doubted by neoherpetologists. Such opinions derive from the fact that most fossil snakes are based on isolated vertebrae, elements that are extremely difficult to interpret (e.g., McDowell, 1987), and skull bones are usually lacking. It is also the case that cranial elements in themselves are usually insufficient to infer phylogenetic relationships between extinct forms and their living relatives. Homologous elements are usu- ally rare, and thus the significance of intraspe- cific variation in particular bones cannot be in- terpreted easily. This being the case, the taxonomic position of extinct snakes given in many previous studies has been based on usu- ally slight phenetic similarities or dissimilari- ties; the use of taxa erected in this manner is of little importance in systematic and phyloge- netic considerations. To help rectify this situation, detailed de- scriptions of ophidian taxa based on cranial el- ements from a greater number of fossil sites will be necessary. The overwhelming majority of publications devoted to Neogene snakes, how- ever, consist of descriptions of faunal assem- blages coming from single localities; there are few descriptions of taxa based on materials rep- resenting both wider geographical areas and different geological ages. There are extensive collections of ophidian fossils in many muse- ums, but the number of ophidian paleontolo- gists is small. This situation notwithstanding, my investigations have shown that finds of cra- nial elements of snakes in many European Neo- gene sites are not so rare as has been commonly believed, at least with respect to the sites dis- cussed in this paper. The major aim of the present article is to dem- onstrate that Neogene fossil remains may be advantageous in fruitfully reconstructing the phylogeny of living snakes. The usefulness of West Palearctic fossil remains was documented clearly in a recent study of the extant elapid genus Naja (Szyndlar and Rage, 1990). The de- scent of the living European snake Natrix natrix from its presumed ancestor, the extinct species N. longivertebrata, discussed below, is perhaps one of the best illustrations of ophidian micro- evolution evidenced by the fossil record. The history of the N. longivertebrata-N. natrix lineage is based on numerous taxonomically important cranial elements, coming from many European sites of diverse ages. Another important aspect of this paper is to demonstrate, based on the available fossil record from Europe, that Mio- cene species were closely related to their living descendants and, therefore, that the origin of living ophidian genera may have taken place prior to the Paleogene/Neogene boundary.