The ontogeny of<i>Ellipsocephalus</i>(Trilobita) and systematic position of Ellipsocephalidae

Laibl, Lukáš; Fatka, Oldřich; Budil, Petr; Ahlberg, Per; Szabad, Michal; Vokáč, Václav; Kozák, Vladislav

doi:10.1080/03115518.2015.1034968

Cited by 11 publications

(14 citation statements)

References 41 publications

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“…There are several issues with the definition of the new species. First, the morphology of the genal spine changes remarkably during ontogeny (Chatterton, 1980;Chatterton & Speyer, 1997;Park & Choi, 2009;Laibl et al 2015) and differences in the position of eyes can be an effect of taphonomic compression (see Hughes & Rushton, 1990 for detailed explanation). Second, genal spines in Moroccan trilobites are often artificially modified by local collectors (Gutiérrez-Marco & García-Bellido, 2018).…”

Section: Methodsmentioning

confidence: 99%

Large trilobites in a stress-free Early Ordovician environment

et al. 2020

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Understanding variations in body size is essential for deciphering the response of an organism to its surrounding environmental conditions and its ecological adaptations. In modern environments, large marine animals are mostly found in cold waters. However, numerous parameters can influence body-size variations other than temperatures, such as oxygenation, nutrient availability, predation or physical disturbances by storms. Here, we investigate trilobite size variations in the Lower Ordovician Fezouata Shale deposited in a cold-water environment. Trilobite assemblages dominated by small- to normal-sized specimens that are a few centimetres in length are found in proximal and intermediate settings, while those comprising larger taxa more than 20 cm in length are found in the most distal environment of the Fezouata Shale. Drill core material from distal settings shows that sedimentary rocks hosting large trilobites preserved in situ are extensively bioturbated with a high diversity of trace fossils, indicating that oxygen and nutrients were available in this environment. In intermediate and shallow settings, bioturbation is less extensive and shallower in depth. The rarity of storm events (minimal physical disturbance) and the lack of predators in deep environments in comparison to shallower settings would also have helped trilobites attain larger body sizes. This highly resolved spatial study investigating the effects of numerous biotic and abiotic parameters on body size has wider implications for the understanding of size fluctuations over geological time.

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Section: Methodsmentioning

confidence: 99%

Large trilobites in a stress-free Early Ordovician environment

et al. 2020

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“…; Laibl et al . ). Certainly, it is difficult to accept that the expanded front of the Ellipsocephalus glabella, its lack of a preglabellar field, long palpebral lobes and whole even‐width of the spineless cephalic border are elements of a Fortey's () ptychopariid, especially those of Agraulos ceticephalus .…”

Section: Systematic Palaeontologymentioning

confidence: 97%

Agraulos ceticephalusand other Cambrian trilobites in the subfamily Agraulinae from Bohemia, Newfoundland and Wales

Fletcher

2017

Papers in Palaeontology

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The Cambrian trilobite Agraulos ceticephalus Barrande, first described from Bohemia, is the type species for the genus and subfamily Agraulinae. That subfamily is here regarded as a ptychoparioid grouping in the family Solenopleuridae, characterized by prominently punctate cephala. In Bohemia, it occurs with, and is related to, specimens of the genus Skreiaspis Růžička, differing mainly in their glabellar shapes and cephalic borders. More‐complete descriptions of their type species are based largely on undistorted museum topotypes and supplementary specimens of ceticephalus collected from Avalonian Newfoundland and Wales. With such information and the use of Photoshop, a reinterpretation of the original tectonically‐distorted syntypes of ‘A. longicephalus’ from Wales indicates that those specimens cannot be differentiated from ceticephalus. Consequently, Hicks’ species may be regarded as a junior synonym. Additional information derived from recent Welsh collections concerns the hypostome–rostral plate relationship of ceticephalus and the recognition of a ventral plate lying beneath the rostral plate. Non‐syntype Welsh material, subsequently assigned to ‘longicephalus’, includes specimens of A. lewisi sp. nov. with a prominent occipital spine, relatively long genal spines and upstanding thoracic axial spines. Other species of Agraulos occur in Newfoundland, viz., affinis, socialis, ‘sp. nov. 1’ and ‘sp. nov. 2’, marked by differences in their anterior cephalic borders, occipital rings and ornamented thoracic axes. Two species of Skreiaspis, viz., punctatissimus sp. nov and ‘S. sp. nov. 1’ are recognized in the Newfoundland succession along with two other agraulines, Skehanos quadrangularis Whitfield and ‘Agraulinae gen. nov.’ To demonstrate the significant differences between the biometrics of the external surfaces and their inner parietal moulds/casts, and those of meraspid–holaspid cranidial growth stages between 0.10 and 2.9 cm sagittal length, a suite of A. socialis cranidia intermixed with some other Newfoundland agraulines of comparable size is illustrated.

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“…Further complications are present within the palaeolenids of the Guanshan Biota as the validity of P. douvillei and P. "lantenoisi" has been debated: authors have suggested that they were unable to confidently differentiate P. "lantenoisi" and P. douvillei when thoracic tergites numbers are not definitive (Hu et al, 2013). Conversely, P. longispinus is likely a valid taxon as there are a robust second thoracic tergite and hypertrophied spines on meraspid and holaspid specimens (Laibl et al, 2015). To this end, while P. longispinus is accounted for, M. deprati, P. douvillei, and P. "lantenoisi" need to be explored.…”

Section: Species Considered Relevant Notesmentioning

confidence: 99%

Geometric morphometric assessment of Guanshan trilobites (Yunnan Province, China) reveals a limited diversity of palaeolenid taxa

Zhao¹,

Liu²,

Bicknell³

2020

Palaeontol Electron

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The Guanshan Biota is a typical Burgess Shale-type Cambrian-aged Lagerstätte with diverse trilobites. As such, the taxonomy of trilobites from the Guanshan Biota, especially the palaeolenid group, has been the focus of research over the last decade. To develop this research, we present a geometric morphometric analysis of cranidial shape in 60 specimens from three sections of the Guanshan Biota from the Wulongqing Formation (Cambrian Series 2, Stage 4), Yunnan Province, South China. We show that cranidia of Megapalaeolenus deprati and Palaeolenus douvillei occupy distinct regions of morphospaces and that P. douvillei and P. "lantenoisi" occupy the same region of morphospace. Combined with qualitative observation on the thorax, P. "lantenoisi" is here considered a junior synonym of P. douvillei. Megapalaeolenus deprati is still considered valid and is distinguished from P. douvillei by its rounded glabella, longer palpebral lobes, shorter ocular ridges, and more developed posterolateral projections. Its pleural spines are more curved, and pleural lobes are markedly wider than P. douvillei. These results highlight that the supposed diversity of palaeolenid taxa in lower Cambrian deposits need reconsideration, potentially using similar morphometric methods.

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The ontogeny ofEllipsocephalus(Trilobita) and systematic position of Ellipsocephalidae

Cited by 11 publications

References 41 publications

Large trilobites in a stress-free Early Ordovician environment

Large trilobites in a stress-free Early Ordovician environment

Agraulos ceticephalusand other Cambrian trilobites in the subfamily Agraulinae from Bohemia, Newfoundland and Wales

Geometric morphometric assessment of Guanshan trilobites (Yunnan Province, China) reveals a limited diversity of palaeolenid taxa

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