A CAMBRIAN MERASPID CLUSTER: EVIDENCE OF TRILOBITE EGG DEPOSITION IN A NEST SITE
A CAMBRIAN MERASPID CLUSTER: EVIDENCE OF TRILOBITE EGG DEPOSITION IN A NEST SITE
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DOI：
10.2110/palo.2018.102
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发表时间：
2019-05
期刊：
影响因子：
1.6
通讯作者：
D. Schwimmer;William M. Montante
中科院分区：
文献类型：
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作者：
D. Schwimmer;William M. Montante
翻译后摘要：最近的证据证实，三叶虫卵生，但是，他们随后的胚胎发育尚未确定。格鲁吉亚西部上寒武统（派比安）Conasauga组的一个106平方厘米的粘土岩标本包含一组超过100个的meraspid三叶虫，其中许多完整的librigenae。这些幼年三叶虫被鉴定为Ausaraspis sp.，多为1.5 ~ 2.0 mm的全长，在同一层面上以多个轴向方向共存。该观察结果以及附加的自由颊表明，该关联不是当前排序的结果。大多数的青少年与确定的胸段计数是meraspid度5，这表明他们孵化penecontemporaneously以下一个单一的鸡蛋沉积事件。此外，它们是紧密组装的，有几个流浪者，这表明幼虫要么留在产卵地点，要么选择性地重新组装为从属，喂养或保护行为。三叶虫的群居行为（“三叶虫集群”）已被频繁报道，但以前只包括holaspid成人或混合年龄的组合。这是首次报道的幼年三叶虫集群和少数报道的集群之一，涉及寒武纪三叶虫。许多解释三叶虫集群行为已被假定，在这里，它提出了幼虫集群鸡蛋沉积在巢址，幼虫聚集可能是归巢的反应。
Abstract: Recent evidence confirms that trilobites were oviparous; however, their subsequent embryonic development has not been determined. A ∼ 6 cm2 claystone specimen from the upper Cambrian (Paibian) Conasauga Formation in western Georgia contains a cluster of >100 meraspid trilobites, many complete with librigenae. The juvenile trilobites, identified as Aphelaspis sp., are mostly 1.5 to 2.0 mm total length and co-occur in multiple axial orientations on a single bedding plane. This observation, together with the attached free cheeks, indicates that the association is not a result of current sorting. The majority of juveniles with determinable thoracic segment counts are of meraspid degree 5, suggesting that they hatched penecontemporaneously following a single egg deposition event. Additionally, they are tightly assembled, with a few strays, suggesting that the larvae either remained on the egg deposition site or selectively reassembled as affiliative, feeding, or protective behavior. Gregarious behavior by trilobites (“trilobite clusters”) has been reported frequently, but previously encompassed only holaspid adults or mixed-age assemblages. This is the first report of juvenile trilobite clustering and one of the few reported clusters involving Cambrian trilobites. Numerous explanations for trilobite clustering behavior have been posited; here it is proposed that larval clustering follows egg deposition at a nest site, and that larval aggregation may be a homing response to their nest.