牙形类原颚齿刺属的分类、谱系和分带的再研究

详细研究了牙形类原颚齿刺属的分类、谱系和分带，重点研究了Protognathodus collinsoni—Pr. kockeli演化谱系。齿杯口面光滑无饰的Pr. meischneri形态型2演化为齿杯口面只有1个瘤齿的Pr. collinsoni, 后者的口面瘤齿可以发育在外齿杯或内齿杯。长期以来，一直认为Pr. kockeli 是由Pr. collinsoni直接演化而来，但齿杯口面仅具1个瘤齿的Pr. Collinsoni难以直接演化为齿杯口面具3个以上瘤齿的Pr. Kockeli。理论上，二者之间应当还存在具2个瘤齿的过渡型分子，在演化上缺失了一个中间环节。众所周知，泥盆纪末期曾发生过一次全球性海平面下降事件（D-C事件），导致绝大多数晚泥盆世生物灭绝，只有少数生物躲过D-C事件幸存下来，直到早石炭世最早期才开始复苏，而后辐射演化。全球的资料表明，这些残存下来的生物的演化谱系几乎均被D-C事件打断，牙形类原颚齿刺属和管刺属（Siphonodella）的演化谱系也不例外，问题的关键在于应当找到被D-C事件打断的演化谱系的节点。原颚齿刺属演化谱系中被打断的节点正是Pr. collinsoni—Pr. kockeli支系，表明Pr. kockeli首次出现的位置是难以确定的，因此该种的首次出现不能用来定义泥盆—石炭系界线。相反，Pr. kuehni的首次出现可以用来定义泥盆—石炭系界线，因为其首次出现与Siphonodella sulcata的首次出现基本同时。根据原颚齿刺属各种的演化关系和地层分布，泥盆—石炭系界线地层可识别出6个牙形类带，即下meischneri带、上meischneri带、collinsoni带、待命名带、kockeli带和kuehni带，各带基本以带名种的首次出现来定义其底界（待命名带除外）。

Restudy on the speciation, phylogeny and zonation of genus Protognathodus (conodonts)

This paper deals with the speciation, phylogeny and zonation of Protognathodus (conodonts) in details and puts more attention to the Pr. collinsoni-Pr. kockeli lineage in particular. Pr. meischneri Morphotype 2 with no node give rise to Pr. collinsoni by developing a single node orally either on the outer cup or on the inner cup, and then Pr. collinsoni with a single oral should gives rise to an unknown form with 2 oral nodes, rather than directly to Pr. kockeli with one row of oral nodes on each side of the cup respectively. It is obvious that there might be a missing link between Pr. collinsoni and Pr. kockeli. In addition, the Pr. collinsoni-Pr. kockeli lineage is clearly interrupted by the D-C event, and the first occurrence of Pr. kockeli should be after the event. Thus, the Devonian-Carboniferous boundary could not be defined by the first appearance of Pr. kockeli. According to their evolutionary relationship and stratigraphic distribution, six zones can be roughly recognized: the Lower meischneri zone, the Upper meischnei zone, the collinsoni zone, the unknown zone, the kockeli zone and the kuehni zone. We prefer placing Devonian-Carboniferous boundary (DCB) at the base of the kuehni zone to placing DCB at the base of the kockeli zone, because the base of the kuehni zone is consistent with the base of the sulcata zone.