A revised ontogeny of the early Ordovician trilobite Leptoplastides salteri (Callaway, 1877)

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A revised ontogeny of the early Ordovician trilobite Leptoplastides salteri (Callaway, 1877). / Månsson, Kristina; Clarkson, Euan N.K.

I: Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 20.11.2018.

Forskningsoutput: TidskriftsbidragArtikel i vetenskaplig tidskrift

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TY - JOUR

T1 - A revised ontogeny of the early Ordovician trilobite Leptoplastides salteri (Callaway, 1877)

AU - Månsson, Kristina

AU - Clarkson, Euan N.K.

PY - 2018/11/20

Y1 - 2018/11/20

N2 - The ontogeny of the pelturine olenid trilobite Leptoplastides salteri (Callaway, 1877) from the Shineton Shales, Shropshire, England, was first described in 1925 by Frank Raw. Since that time, scanning electron microscopy and other new technologies have revealed many more details of structure, of early developmental stages in particular, than were available to Raw. Whereas protaspides are not preserved and the state of preservation is less than perfect for the smallest meraspides, we have established that the latter had an array of delicate, long thoracic and pygidial spines, as well as paired procranidial spines, which disappear by meraspid degree 8. Raw's reconstructions of early meraspides, and his measurements of the early stages in development, are here amended in the light of new information. Dorsal spines in the adult are much more highly developed than have been documented in any other olenid. The hypostome is preserved in place in several specimens. Initially conterminant (attached to the doublure), it becomes natant (free) in late meraspid to early holaspid stages of development, with its anterior contour fitting exactly to that of the glabella. The ecology of the widespread Leptoplastides is best known from very extensive sections in South America, which provide a useful basis for comparison. It was well adapted to a range of environments, both oxygenated and dysoxic, and is usually the dominant taxon in the biofacies in which it is found.

AB - The ontogeny of the pelturine olenid trilobite Leptoplastides salteri (Callaway, 1877) from the Shineton Shales, Shropshire, England, was first described in 1925 by Frank Raw. Since that time, scanning electron microscopy and other new technologies have revealed many more details of structure, of early developmental stages in particular, than were available to Raw. Whereas protaspides are not preserved and the state of preservation is less than perfect for the smallest meraspides, we have established that the latter had an array of delicate, long thoracic and pygidial spines, as well as paired procranidial spines, which disappear by meraspid degree 8. Raw's reconstructions of early meraspides, and his measurements of the early stages in development, are here amended in the light of new information. Dorsal spines in the adult are much more highly developed than have been documented in any other olenid. The hypostome is preserved in place in several specimens. Initially conterminant (attached to the doublure), it becomes natant (free) in late meraspid to early holaspid stages of development, with its anterior contour fitting exactly to that of the glabella. The ecology of the widespread Leptoplastides is best known from very extensive sections in South America, which provide a useful basis for comparison. It was well adapted to a range of environments, both oxygenated and dysoxic, and is usually the dominant taxon in the biofacies in which it is found.

KW - olenid

KW - Shineton Shales

KW - Shropshire

KW - Tremadoc

KW - Trilobita

U2 - 10.1017/S1755691018000841

DO - 10.1017/S1755691018000841

M3 - Article

JO - Earth and Environmental Science Transactions of the Royal Society of Edinburgh

T2 - Earth and Environmental Science Transactions of the Royal Society of Edinburgh

JF - Earth and Environmental Science Transactions of the Royal Society of Edinburgh

SN - 1755-6929

ER -