Tellinidae is one of the most diverse families in Brazilian coastal areas, comprising nine subfamilies, one of which is Macominae. These species are known for their morphological similarities, which make their identification difficult. To minimize such difficulties, taxonomists have sought methods or tools, such as the use of geometric morphometric data, to study the continuous characteristics which are often observed subjectively and are not measurable. Almost thirty right valves were chosen from five of the most representative Macominae species: Austromacoma biota Arruda & Domaneschi, 2005, Austromacoma constricta (Bruguière, 1792), Psammotreta brevifrons (Say, 1834 in Say 1830–1834), Psammotreta cleryana (d’ Orbigny, 1846 in d’ Orbigny 1834–1847), Macoploma tenta (Say, 1834 in Say 1830–1834). The geometric morphometric data were based on the fourteen landmarks of each internal valve, performed by TPSDig, and the morphometric and statistical analyses, carried out with MorphoJ, were Procrustes analysis, Procrustes Anova, principal components analysis, discriminant function analysis, and regression analysis. Permutations and Goodall’s F test with bootstrap were performed in the R software package. All the analyses divided the studied species into two groups based on the external shape of their shells: oval-trigonal or elongated. The variation of the external shape of the shell is related to the life habits of the bivalve, with the elongated shells lying inclined in the substrata, and the oval-trigonal shells lying horizontally, facilitating deposit-feeding habits. The pallial sinus shape and position of the adductor muscle scar also helped differentiate species of each group, relating them to the bivalve anatomy. Psammotreta cleryana and P. brevifrons exhibited remarkably similar shapes, and a broader population study is needed to differentiate between these two species.

Tellinidae是巴西沿海地区最多样化的家庭之一，包括9个亚科，其中一个是Macominae。这些物种以其形态相似性而闻名，这使其难以鉴定。为了使这种困难最小化，分类学家寻求了方法或工具，例如使用几何形态数据，以研究通常在主观上观察到且无法测量的连续特征。从五个最具代表性的马科蝇种类中选出了近三十个右瓣：Austromacoma biota Arruda＆Domaneschi，2005年，Austromacoma constricta（Bruguière，1792年），Psammotreta brevifrons（Say，1834年，Say 1830–1834年），Psammotreta cleryana（d'Orbigny，1846年在d'Orbigny 1834-1847年），Macoploma tenta（说，1834年在Say 1830-1834年）。几何形态学数据基于每个内部阀门的14个界标，由TPSDig执行，而使用MorphoJ进行的形态学和统计分析为Procrustes分析，Procrustes Anova，主成分分析，判别函数分析和回归分析。排列与古道尔F引导程序测试是在R软件包中进行的。所有分析都根据其壳的外部形状将研究物种分为两组：卵形三角形或细长形。壳的外部形状的变化与双壳类动物的生活习性有关，其中细长的壳在基质中倾斜，卵形的三角形壳在水平方向倾斜，这有利于沉积物的饲养。内收肌疤痕的睑窦形状和位置也有助于区分每个组的物种，将它们与双壳类解剖联系起来。Psammotreta cleryana和P. brevifrons表现出非常相似的形状，需要进行更广泛的种群研究以区分这两个物种。