The sea urchin family Pourtalesiidae is primarily an abyssal taxon, exhibiting extremely modified morphologies that have emerged as an adaptation for burrowing in soft sediment. Here, we present the first detailed molecular phylogeny of the family Pourtalesiidae. Both morphological and molecular evidence support the establishment of the family Ceratophysidae fam. nov. to accommodate seven former pourtalesiid genera. The name Pourtalesiidae is retained for the group of genera Cystocrepis and Pourtalesia. Based on morphological data, the fossil genus Galeaster is transferred to the monotypic family Galeasteridae fam. nov.. Families Pourtalesiidae and Ceratophysidae are each characterized by a unique pattern of plastron plating. Reconstructions indicate that elongated tests, as well as other adaptations for burrowing, evolved independently in these families. The evolutionary histories of pourtalesiids and ceratophysids are complex and include several instances of increase and decrease in this specialization. Molecular data support the Antarctic origin of Pourtalesiidae and Ceratophysidae, although for the latter the support is limited. The initial dispersal of pourtalesiids from the Antarctic occurred in the northward direction and included distribution of the least specialized forms throughout the eastern Pacific. Broad radiation of the more specialized forms apparently occurred later. The biogeographic history of the family Ceratophysidae is more complex and at present cannot be reconstructed reliably.

中文翻译：

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深海海胆科 Pourtalesiidae Agassiz 1881 和 Ceratophydae fam 的进化和生物地理模式。十一月（海胆总科）

海胆科 Pourtalesiidae 主要是一种深海分类群，表现出极其改变的形态，是为了适应在软沉积物中挖洞而出现的。在这里，我们首次展示了 Pourtalesiidae 科的详细分子系统发育。形态学和分子证据都支持角骺科的建立。十一月可容纳七个前 pourtalesiid 属。 Cystocrepis 属和 Pourtalesia 属的名称保留为 Pourtalesiidae。根据形态学数据，化石属 Galeasteridae 被转移到单一型 Galeasteridae 科。 nov.. Pourtalesiidae 科和 Ceratophydae 科均具有独特的腹甲图案。重建表明，延长的测试以及其他穴居适应性在这些家族中独立进化。普塔莱西科和角足科的进化史很复杂，并且包括该专业化的几个增加和减少的实例。分子数据支持 Pourtalesiidae 和 Ceratophydae 起源于南极，尽管对后者的支持有限。普塔莱西科动物最初从南极洲的扩散发生在向北的方向，包括最不专业的形式分布在整个东太平洋。更专业的形式的广泛辐射显然是后来发生的。角鲫科的生物地理学历史更为复杂，目前无法可靠地重建。