Quantifying intra- and interspecific variability in trilobite moulting behaviour across the Palaeozoic

Jin

et al. 2021

LET

It is important to understand moulting behaviours in trilobites through different growth stages. Most studies have focused on patterns of moulting in trilobites based on a few exuviae. The present study is based on 177 disarticulated specimens of Arthricocephalites xinzhaiheensis from the Balang Formation (Cambrian Series 2, Stage 4, Guizhou Province, South China). The abundance of disarticulated assemblages allows the distinction between carcasses and exuviae to be made with confidence and enables a detailed exploration of moulting behaviours. About 96.6% of exuviae of both meraspides and holaspides of Ar. xinzhaiheensis show a disarticulated cranidium characterizing Henningsmoen's configuration. The trilobites commonly used the cephalic sutures and cephalothoracic joint for moulting, involving lateral rotation or inversion of the cranidium to create a wide exuvial gape. Only one specimen displays the Somersault configuration characterized by an overturned lower cephalic unit and the data also show that trilobites employing the cephalic sutures to create an anterior exuvial gape are rare in holaspides. Though some specimens are similar to Salter's configuration with an inverted cephalon with respect to the thoracopygon, the specimens show closed cephalic sutures and thus dissociated or inverted cephala are likely to represent disturbed carcasses. Several other species of oryctocephalid trilobites display Henningsmoen's configuration indicating that exuviation by disarticulated cranidium to enlarge the exuvial gape was prevalent in the family from Cambrian Series 2 Stage 4 to the succeeding Wuliuan Stage of the Miaolingian Series.

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Moulting in the Cambrian oryctocephalid trilobiteArthricocephalites xinzhaiheensisfrom Guizhou Province, South China

Jin

et al. 2021

LET

“…Two specimens of Ogygopsis klotzi with abnormalities were identified. Both specimens lack free cheeks and are therefore examples of axial shield moults (Daley and Drage, 2016;Drage et al, 2018;Drage, 2019). Complete specimen.…”

Section: Gabriellus Kierorummentioning

confidence: 99%

Injured trilobites within a collection of dinosaurs: Using the Royal Tyrrell Museum of Palaeontology to document Cambrian predation

Bicknell¹,

Holland²

2020

Palaeontol Electron

Biomineralised exoskeletons of trilobites are ideal for recording abnormalities, documenting injuries from failed attacks, and understanding predation in the fossil record. The illustration of new injured Cambrian-aged trilobites is particularly important for elucidating aspects of early Paleozoic predator-prey systems and identifying groups that were targets of this early predation. We document six new abnormal trilobite specimens from the Royal Tyrrell Museum of Palaeontology, including the first evidence for injuries on the corynexochid trilobite Hemirhodon amplipyge. These new data highlight the importance of museum collections in uncovering unique and informative specimens for studies of predation on early animals.

New records of injured Cambrian and Ordovician trilobites

2022

Records of abnormal fossil arthropods present important insight into how extinct forms responded to traumatic damage and developmental complications. Trilobites, bearing biomineralized dorsal exoskeletons, have arguably the most well-documented record of abnormalities spanning the Cambrian through the end-Permian. As such, new records of malformed, often injured, trilobites are occasionally identified. To further expand the documentation of abnormal specimens, we describe malformed specimens of Lyriaspis sigillum Whitehouse, 1939, Zacanthoides sp. indet., Asaphiscus wheeleri Meek, 1873, Elrathia kingii (Meek, 1870), and Ogygiocarella debuchii (Brongniart, 1822) from lower Paleozoic deposits. In considering these forms, we propose that they illustrate examples of injuries, and that the majority of these injuries reflect failed predation. We also considered the origin of injuries impacting singular segments, suggesting that these could reflect predation, self-induced damage, or intraspecific interactions during soft-shelled stages. Continued examination of lower Paleozoic trilobite injuries will further the understanding of how trilobites functioned as prey and elucidate how disparate trilobite groups recovered from failed attacks.