Krause D W, Carlson S J
Scan Electron Microsc. 1986(Pt 4):1591-607.
The enamel ultrastructure of multituberculate mammals has been sampled extensively and studied intensively and is better known than for any other group of early mammals. The enamel of the earliest multituberculates, those of the Late Triassic-Early Jurassic suborder Haramiyoidea and the Late Jurassic-early Early Cretaceous suborder Plagiaulacoidea, is "preprismatic." With only two exceptions, all Late Cretaceous and early Tertiary genera of multituberculates examined have prismatic enamel. Prisms are either small with circular (complete) boundaries or large with arc-shaped (incomplete) boundaries. There is a remarkably consistent relationship between enamel ultrastructural type and subordinal taxa in that small, circular prisms are usually found within the suborder Ptilodontoidea and large, arc-shaped prisms are usually found in the suborder Taeniolabidoidea and in six Late Cretaceous-Early Tertiary genera of indeterminate subordinal status. Research currently in progress suggests that both small, circular prisms and large, arc-shaped prisms are homologous in all multituberculates in which they occur, with one exception. Neoliotomus, a taeniolabidoid, appears to have evolved small, circular prisms independently. In addition, it appears that large, arc-shaped prisms represent the primitive condition in multituberculates with prismatic enamel, not small, circular prisms as has been proposed previously.
多瘤齿兽类哺乳动物的釉质超微结构已被广泛采样并深入研究，相比其他任何早期哺乳动物群体，我们对其了解得更多。最早的多瘤齿兽类，即晚三叠世-早侏罗世的副目哈氏兽亚目（Haramiyoidea）和晚侏罗世-早白垩世的副目斜纹齿兽亚目（Plagiaulacoidea）的釉质是“棱柱前期的”。在所有已研究的晚白垩世和早第三纪多瘤齿兽类属中，仅有两个例外，其余均具有棱柱形釉质。棱柱要么小且边界呈圆形（完整），要么大且边界呈弧形（不完整）。釉质超微结构类型与亚目分类单元之间存在显著一致的关系，即小的圆形棱柱通常见于梳趾兽亚目（Ptilodontoidea），大的弧形棱柱通常见于带齿兽亚目（Taeniolabidoidea）以及六个晚白垩世-早第三纪亚目地位不确定的属。目前正在进行的研究表明，但有一个例外，在所有出现小的圆形棱柱和大的弧形棱柱的多瘤齿兽类中，这两种棱柱都是同源的。带齿兽类的新尼奥托姆斯（Neoliotomus）似乎是独立演化出了小的圆形棱柱。此外，似乎大的弧形棱柱代表了具有棱柱形釉质的多瘤齿兽类的原始状态，而非如先前所提出的小的圆形棱柱。
