scholarly journals Absolute axial growth and trunk segmentation in the early Cambrian trilobite Oryctocarella duyunensis

Paleobiology ◽  
2021 ◽  
pp. 1-16
Author(s):  
Tao Dai ◽  
Nigel C. Hughes ◽  
Xingliang Zhang ◽  
Giuseppe Fusco
Keyword(s):  
Growth Rates ◽  
Early Cambrian ◽  
Phase Growth ◽  
Developmental Patterns ◽  
Cambrian Trilobite ◽  
Determinate Growth ◽  
Western Hunan ◽  
Axial Growth ◽  
Size Data ◽  
Stratigraphic Interval

Abstract A short stratigraphic interval near Bulin in western Hunan (China) yields multiple specimens of the ~514-Myr-old oryctocarine trilobite Oryctocarella duyunensis. Size data obtained from these specimens indicate that, from meraspid degree 1 onward, degrees represent successive instars. Meraspid growth persisted until a terminal stage was reached, providing the first example of determinate growth in trilobites and, notably, in an early Cambrian species. The sample contains three varieties of such terminal stages, recognized as holaspids, with 9, 10, or 11 thoracic segments, respectively. During the meraspid phase, growth rates were not constant in this species. The pattern of growth seen in the Bulin assemblage differs modestly from that reported in the same species from two other localities, attesting to microevolutionary variation in developmental patterns among these collections.

Lower Cambrian acritarchs from northern Spain: the Precambrian-Cambrian boundary and biostratigraphic implications

1992 ◽  
Vol 129 (4) ◽  
pp. 421-436 ◽  
Author(s):  
Teodoro Palacios ◽  
Gonzalo Vidal
Keyword(s):  
Lower Cambrian ◽  
East European Platform ◽  
Early Cambrian ◽  
Eastern Siberia ◽  
Western North America ◽  
Northern Spain ◽  
East European ◽  
Cantabrian Region ◽  
Biostratigraphic Correlation ◽  
Cambrian Trilobite

AbstractAcritarchs are reported from basal Cambrian rock units inthe Cantabrian region of northern Spain that are known to contain archaeocyathan and trilobite faunas. Biostratigraphic correlation of the Iberian sequences with other regions has been hampered by the strong provincialism of these faunas. However, this report of evidently cosmopolitan acritarch taxaestablishes the time equivalence of early Cambrian trilobite faunas from Iberia, Baltoscandia and the East European Platform (EEP). Our data suggest that the detrital deposition of the Lower Cambrian Herreria Formation embraces at least three (and possibly four) Lower Cambrian acritarch zones previously identified in the EEP, eastern Siberia, Baltoscandia, Scotland, Greenland, Svalbard and western North America. The early Cambrian transgression in northern Spain was probably initiated in Talsy times (Schmidtiellus mickwitzi trilobite Zone in Baltoscandia and the EEP), in part corresponding to the Dokidocyathus regularis archaeocyathian Zone of the Middle Tommotian in Siberia.

New material of three-dimensionally phosphatized and microscopic cycloneuralians from the Cambrian Paibian Stage of South China

2017 ◽  
Vol 92 (1) ◽  
pp. 87-98 ◽  
Author(s):  
Yunhuan Liu ◽  
Qi Wang ◽  
Tiequan Shao ◽  
Huaqiao Zhang ◽  
Jiachen Qin ◽  
...  
Keyword(s):  
New Species ◽  
South China ◽  
Early Cambrian ◽  
Late Cambrian ◽  
New Material ◽  
Western Hunan ◽  
Fossil Embryos

AbstractSome rare microscopic cycloneuralians are present in the Cambrian of South China, represented by Eopriapulites and Eokinorhynchus (both early Cambrian), fossil embryos of Markuelia (middle to late Cambrian), and palaeoscolecids (early to late Cambrian). Among them, palaeoscolecids are relatively diverse and abundant. Here, we describe new material of three-dimensionally phosphatized and microscopic cycloneuralians from the Paibian Stage of Wangcun Lagerstätte, western Hunan, South China. New material includes fossil embryos assignable to Markuelia sp., two other types of fossil embryos, and three species of palaeoscolecids, including Dispinoscolex decorus Duan, Dong, and Donoghue, 2012, Schistoscolex hunanensis Duan, Dong, and Donoghue, 2012, and Austroscolex sinensis new species. The palaeoscolecid fragments differ mainly in size and armor of the trunk annuli. Since Eokinorhynchus and Eopriapulites occurred the earliest among the Cambrian cycloneuralians, it is proposed here that: (1) cycloneuralians originated in the Cambrian Fortunian small shelly faunas rather than in the early Cambrian macrobenthos, (2) ancestral cycloneuralians may have simple trunk armor, and (3) Eopriapulites represents an ancestral cycloneuralian.

Change in the phase growth rates in Cu-Si films subjected to ion implantation

1995 ◽  
Vol 74-75 ◽  
pp. 937-940 ◽  
Author(s):  
E.M. Shpilevsky ◽  
M.E. Shpilevsky ◽  
M.A. Andreev
Keyword(s):  
Ion Implantation ◽  
Growth Rates ◽  
Phase Growth ◽  
Si Films

scholarly journals The oldest hyolithids (Cambrian Series 2, Montezuman Stage) from the Iapetan margin of Laurentia

2020 ◽  
Vol 94 (4) ◽  
pp. 616-623
Author(s):  
John S. Peel ◽  
Sebastian Willman ◽  
Steven J. Hageman
Keyword(s):  
Early Cambrian ◽  
The Poor ◽  
Iapetus Ocean ◽  
Cambrian Trilobite ◽  
Laurentian Margin ◽  
North Greenland

AbstractThe recent description of the nevadioid trilobite Buenellus chilhoweensis Webster and Hageman, 2018 established the presence of early Cambrian Montezuman Stage (Cambrian Series 2, Stage 3) faunas in the Murray Shale of Chilhowee Mountain, Tennessee. The description recognized the oldest known age-diagnostic Cambrian trilobite from the Laurentian margin of the former Iapetus Ocean since Buenellus Blaker, 1988 is known otherwise only from the Sirius Passet Lagerstätte on the Innuitian margin of North Greenland. The bivalved arthropods Isoxys chilhoweanus Walcott, 1890 and Indota tennesseensis (Resser, 1938a) have also been described from the Murray Shale, but hyolithids appear to be the dominant body fossils in terms of diversity and abundance. Although poorly preserved, the hyolithids occurring together with Buenellus chilhoweensis are described to improve understanding of the Murray Shale biota. The hyolith assemblages of the Murray Shale and Sirius Passet Lagerstätte are not closely similar, although the poor preservation of both hinders comparison.

Early Cambrian trilobite larvae and ontogeny of Ichangia ichangensis Chang, 1957 (Protolenidae) from Henan, China

1999 ◽  
Vol 73 (1) ◽  
pp. 117-128 ◽  
Author(s):  
Xi-Guang Zhang ◽  
Brian R. Pratt
Keyword(s):  
Lower Cambrian ◽  
Henan Province ◽  
The Other ◽  
Early Cambrian ◽  
Structural Variations ◽  
Simple Body ◽  
Cambrian Trilobite

The Lower Cambrian Shuigoukou Formation of Xichuan, Henan province, China, yielded phosphatized instars belonging to the protolenid Ichangia ichangensis Chang, 1957, and two undetermined taxa. With relatively simple body plans, the three larval forms resemble each other to some extent, and protaspides of I. ichangensis show general similarities to those of the ellipsocephalid Palaeolenus lantenoisi Mansuy. However, their early ontogenetic processes exhibit subtle yet distinct differences. One group of unassigned protaspides possesses a sagittal glabellar furrow and protomarginal spines with branching extremities. The other unassigned protaspides bear especially long genal and protomarginal spines. The detailed preservation of these larvae reveals delicate structural variations that help provide a framework for evaluating relationships among Early Cambrian trilobites.

Field environment studies on lupins. I. Developmental patterns in Lupinus angustifolius L., the effects of cultivar, site and planting time

1975 ◽  
Vol 26 (1) ◽  
pp. 81 ◽  
Author(s):  
MW Perry ◽  
ML Poole
Keyword(s):  
Moisture Stress ◽  
Lupinus Angustifolius ◽  
Floral Initiation ◽  
Growth Phases ◽  
Developmental Patterns ◽  
Field Environment ◽  
Cool Environment ◽  
Determinate Growth ◽  
Lateral Branches ◽  
Western Australian

The development of early (Unicrop) and late (Uniharvest) flowering cultivars of Lupinus angustifolius was studied with eight planting times at two climatically contrasting sites representing the main lupin-producing areas in Western Australia. Differences in time from planting to floral initiation and from initiation to first flower, in duration of flowering, and in time of maturity were measured. The major differences in phasic development between the cultivars for the different planting times and sites were for the period from planting to initiation. This is explained in terms of the known vernalization requirement of Uniharvest. As a consequence, initiation of the two cultivars was closest with midwinter planting in the cool environment and farthest apart with eariy planting at the warmer site. For comparable planting times the differences between cultivars for the period from initiation to first flower were small. Duration of flowering and final maturity were mainly influenced by the definite end to the growing season brought on by moisture stress and high temperatures. Differences in photoperiod exerted little influence on development. Growth of the plant was indeterminate, but the presence of terminal inflorescences on the main axis and branches produced a series of easily identified orders of lateral branches. Inflorescences flowered in sequence, extending the duration of flowering as successively higher orders of laterals were formed. Late planting reduced the length of all growth phases but drastically reduced the duration of flowering. The results are discussed in relation to the Western Australian environment, and it is argued that, in such environments, indeterminate growth has potential adaptive advantage over the determinate growth pattern of the cereals.

Growth and Development of the Wheat Tiller. I. Growth and Form of the Tiller Bud

1975 ◽  
Vol 23 (5) ◽  
pp. 715 ◽  
Author(s):  
RF Williams ◽  
BC Sharman ◽  
RHM Langer
Keyword(s):  
Growth Rates ◽  
Continuous System ◽  
Nitrogen Supply ◽  
Leaf Primordium ◽  
Developmental Morphology ◽  
Developmental Anatomy ◽  
Relative Growth ◽  
Relative Growth Rates ◽  
Axial Growth ◽  
Tiller Bud

The initiation and growth of the tiller bud is described in the context of the developing shoot in wheat. The experimental plants were subjected to two levels of nitrogen supply and to two light intensities so as to diversify the pattern of tiller growth. The descriptions cover properties of tiller bud placement within the shoot, the external developmental morphology, and some aspects of the developmental anatomy of the bud, and of the nodal plexus in relation to growth of the leaf primordium and tiller bud. The results have been integrated in terms of linear relative growth rates in both radial and axial directions. In spite of the mutual constraints imposed within the continuous system, severe gradients in axial growth rates were found to be consistent with the maintenance of the integrity of the system.

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