Sediment samples of deep marine oceanic ODP boreholes from sites 999 in the Caribbean Sea and 1237 in the Eastern Pacific Ocean covering the period between 6 and 4.5 Ma have been studied with a focus on ceratolith evolution. Orthorhabdus rugosus is a nannolith with three blades (sinistral, median, and dextral) that first appeared during the Serravallian, it is not-birefringent in its stable orientation. It shows a high morphological variability time-interval at the end of the Messinian to the basal Pliocene (5.5 to 5 Ma) during which Ceratolithus (5.484 Ma) evolved. Changes occurred in the sinistral and median blades, whilst the dextral blade was reduced. Ceratolithus finifer n. comb is the first species of the evolutionary line. The nannolith stable position changed during its evolution, resulting in the older forms showing low birefringence and the younger ones moderate to high birefringence in the most stable orientation. Ceratolithus acutus, with an arrowhead shape, Ceratolithus armatus, and the morphologically distinct C. larrymayeri evolved from C. finifer with all three species showing high birefringence. The previous O. rugosus and C. finifer continued. Finally, C. armatus gives rise to C. cristatus. Ceratolithus atlanticus and C. tricorniculatus also evolved from C. finifer. All the species mentioned become extinct during the Pliocene except Ceratolithus cristatus that lives today. Detailed observations permit the analysis of the evolutionary trends of the group, possible mechanisms, patterns, and processes of speciation, and establish new criteria to define the species that, by their relative abundance and short geologic range, have permitted adjustment of biostratigraphic markers for this period.

对来自加勒比海 999 号地点和东太平洋 1237 号地点的深海 ODP 钻孔的沉积物样本进行了研究，涵盖 6 至 4.5 Ma 时期，重点是角藻演化。Orthorhabdus rugosus是一种具有三个叶片（左旋、中旋和右旋）的纳米石体，首次出现于塞拉瓦利亚时期，其稳定方向不是双折射的。它显示了从墨西拿末期到基底上新世（5.5 至 5 Ma）的高形态变异时间间隔，在此期间角锥石属（ Ceratolithus）（5.484 Ma）演化。左侧和中间叶片发生变化，而右侧叶片则减少。Ceratolithus finifer n．梳子是进化线上的第一个物种。纳米石的稳定位置在其演化过程中发生了变化，导致较旧的形式表现出低双折射，而较年轻的形式在最稳定的方向上表现出中等到高的双折射。具有箭头形状的Ceratolithus acutus 、 Ceratolithus armatus和形态独特的C. larrymayeri由C. finifer进化而来，所有三个物种均表现出高双折射。之前的O. rugosus和C. finifer继续存在。最后，C. armatus产生了C. cristatus。Ceratolithus atlanticus和C. tricorniculatus也是由C. finifer进化而来。所有提到的物种在上新世期间都灭绝了，除了今天生活的角角鲸（Ceratolithus cristatus）。详细的观察允许分析该群体的进化趋势、可能的机制、模式和物种形成过程，并建立新的标准来定义物种，通过其相对丰度和较短的地质范围，允许为此调整生物地层标记。时期。