A variety of pits representing symbiotic embedments, sometimes associated with pathological deformation in the host, are known from the skeletons of Paleozoic stalked echinoderms. These structures are well known from multiple genera of crinoids and a limited number of blastozoans but have not previously been described in detail from the skeletons of rhombiferans. This is surprising given the abundance of rhombiferans in certain deposits, the co-occurrence of rhombiferans with frequently infested taxa, including diploporitans, in multiple assemblages, and the morphological similarity between certain rhombiferan taxa and coeval infested crinoids. The common hemicosmitid rhombiferan Caryocrinites Say, 1825 is widespread throughout the middle Silurian of eastern North America and is herein reported to contain symbiotic (potentially parasitic) embedment structures. Specimens were collected from the lower portion of the mudstone lithofacies of the Massie Formation (Wenlock, Sheinwoodian) at the Napoleon quarry of southeastern Indiana, USA. Strong host specificity is indicated by the absence of pits in C. ornatus Say, 1825 and exclusive infestation of a smaller co-occurring species of Caryocrinites. Thecae with embedment structures are consistently smaller than thecae without such structures, with pitted specimens being restricted to a narrow range of thecal heights (20–24 mm). All embedment structures are present only on the proximal portion of thecae, with individual specimens containing between one and 30 pits. No elevated rims or significant swelling were observed on any specimens, and all pits are relatively small (~1 mm in diameter). The presence of symbiotic embedment structures represents an additional example of a crinoid-like aspect to the ecology of Caryocrinites.

中文翻译：

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志留纪石斑岩中的共生嵌入结构（棘皮动物纲、菱形纲、半球纲）

从古生代有柄棘皮动物的骨骼中可以知道代表共生嵌入的各种凹坑，有时与宿主的病理变形有关。这些结构在多个海百合属和有限数量的囊胚动物中是众所周知的，但以前没有从菱形动物的骨骼中详细描述过。这是令人惊讶的，因为某些矿床中菱形动物的丰度，菱形动物与经常感染的分类群（包括双孢类）在多个组合中同时出现，以及某些菱形动物分类群与同时期感染的海百合之间的形态相似性。常见的菱形半粘虫石晶石比如说，1825 广泛分布于北美东部的中志留纪，据报道包含共生（可能是寄生的）嵌入结构。标本采集自美国印第安纳州东南部拿破仑采石场的 Massie 组（Wenlock，Sheinwoodian）泥岩岩相下部。强烈的宿主特异性由在C. ornatus比如说，1825 年和一个较小的同时发生的物种的独家侵染石核石。具有包埋结构的囊始终小于没有这种结构的囊，有凹痕的标本被限制在狭窄的囊高度范围内（20-24 毫米）。所有嵌入结构仅存在于囊的近端部分，单个样本包含 1 到 30 个凹坑。在任何样品上都没有观察到升高的边缘或明显的肿胀，并且所有的凹坑都相对较小（直径约 1 毫米）。共生嵌入结构的存在代表了海百合生态学的另一个例子。石晶石.