三突起类（Triprojectacites Mtchedlishvili，1961emend. Stanley，1970）是晚白垩世–古新世北半球广泛分布的一类被子植物花粉，具有重要的孢粉植物分区和地层意义。其主要特征是发育突出于体的突起和其末端的沟状萌发器。由于形态复杂多变，该类花粉在度量和描述中存在不少难点，缺少明确而统一的标准，制约了其分类的进展。本文根据对松辽盆地白垩系三突起类标本的萌发器、极性、突起形态和纹饰等分类性状的观察，结合对前人在三突起类描述、分类中存在问题的剖析，提出了一套形态学术语、度量方法和参数。它们不仅能有效避免各种误差、准确反映和描述三突起类花粉的形态特征，而且还适用于不同位置保存的标本，有助于建立这些标本之间的联系，为三突起类花粉分类系统提供了科学合理的形态学度量和描述基础。
Triprojectacites Mtchedlishvili, 1961 emend. Stanley, 1970 is a group of angiosperm pollen with great significance in the Late Cretaceous and Paleocene stratigraphy and palynofloristic biogeography in the Northern Hemisphere. Their extreme complexity in morphology makes it very difficult in measuring and describing these pollen. There has been so far no clear and uniform standard, which as a result hampers the progress on the classification of Triprojectacites. Triprojectacites is diagnosed by three or occasionally four to five projections with colpate apertures, which excludes tricolporate types from this group. The equatorial zone, where projections grow from body, divides the body into two parts, which determine the polarity of the pollen grain(Fig. 1). The initiation area of projections from the body is called the base of projection while the distal part at the opposite direction is called the terminal of projection. Based on the observation of a large number of specimens from the Cretaceous strata in the Songliao Basin, northeastern China, a standard of measuring methodology of Triprojectacites is here proposed. Base Point (B) of projection is defined as the beginning of the endexinous thickening along the projection, which marks the border between projection and body. Similarly, Distal Point (D) of the endexinous thickening represents the base of terminal of a projection. These referring points, together with Tip Point (T) of projection and two poles (P), provide the basis for an accurate implementation of the following measurements (Fig. 7), i. e. length (h)and width (wb) of body, length of distal (h1)and proximal (h2) body, length (lp) and width (w1) of projection, terminal width of projection (w2) and length of endexinous thickening (wt). Based on these measurements, six mathematical indices are designated for evaluating the morphology of body and projection. Length-width ratios of body (Rb) and projection (Rp) can describe the shape of body and projection. Width Index of projection (WI=w1/h) and Length Index of projection (LI=lp/wb) can tell if the projection is robust or not as compared to body. Reduction Rate of projection (Rr) reveals the narrowing gradient from the base towards the terminal of a projection. Polarity Index (PI=h1/h2) shows how much projection is deviated away from the center of the body. The last index has an advantage than previous parameters in that it avoids the interference of the angle and width of projection. With the assistance of the indices above, body can be divided into different types of shapes as cylindrical, ellipsoidal, biconical, or diamond-shaped and projection can be described as slat-like, lingulate, ear-like, or lanceolate. Also, specimens preserved at different position, e.g. in polar view and equatorial view, can be well compared. These description terms and indices and their measurement methodology will provide a significant contribution to the establishment of a scientific and reasonable classification system for Triprojectacites.
中国科学院战略性先导科技专项（XDB 26000000，XDA 20070202）和国家自然科学基金项目（41688103、41872004）资助。