Dbk: Created page with "'''Base''': The base of the zone is immediately below the first appearance of the inoceramid bivalve ''Mytiloides'', which is approximately coincident with the top of the ''N...."

2013-09-26T12:01:23Z

Created page with "'''Base''': The base of the zone is immediately below the first appearance of the inoceramid bivalve ''Mytiloides'', which is approximately coincident with the top of the ''N...."

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'''Base''': The base of the zone is immediately below the first appearance of the inoceramid bivalve ''Mytiloides'', which is approximately coincident with the top of the ''N. juddii'' ammonite zone (Mortimore & Pomerol, 1996).

'''Top''': The top of the zone is coincident with the top of the highest occurrence of common ''Mytiloides'' shell fragments, below the appearance of ''Terebratulina lata'' (the index of the next youngest zone). However, there is a small gap between the highest acme of ''Mytiloides'' and the lowest occurrence of ''T''. ''lata'' (Mortimore & Pomerol, 1996).

'''Range of index''': ''Mytiloides'' has a sporadic range through most of the Turonian, making the nomenclature of this earliest Turonian zone quite inappropriate. As currently understood, the ''Mytiloides'' spp. Zone equates with that part of the early Turonian range of ''Mytiloides'' below the entry of ''Terebratulina lata'', in which various species and subspecies of this inoceramid are abundant. As so defined, ''Mytiloides'' ranges throughout the ''Mytiloides'' spp. Zone.

'''Key fauna''':
{| class="Wikitable"
| Annelida: || ''Filograna avita''
|-
| Brachiopoda: || ''Orbirhynchia cuvieri''
|-
| ||large terebratulid brachiopods
|-
| Bivalvia: || ''Mytiloides puebloensis''
|-
| ||'' M. hattini''
|-
| ||'' M. labiatus''
|-
| ||'' M. mytiloides (abundant)''
|-
| Ammonoidea:||''Fagesia'' sp.
|-
| ||''Lewesiceras peramplum''
|-
| ||''Mammites nodosoides''
|-
| ||''Metasigaloceras rusticum''
|-
| ||''Pseudaspidoceras spp.''
|-
| ||''Watinoceras aff. amaduriensis''
|-
| ||''W.devonense''
|-
| Crinoidea: || ''Roveacrinus communis''
|-
| Echinoidea: || ''Hemiaster minimus''
|}
'''Faunal abundance & preservation''': Fragmentary ''Mytiloides'' shells are abundant through the greater part of the zone, mostly preserved in pinkish calcite. There are local acmes of ''Filograna avita'' and ''Roveacrinus communis''.

'''Bio-markers''': ''Mytiloides hattini'' and ''M. puebloensis'' characterise the lower part of the zone, at which level there is also the lowest of two Turonian acmes of the micro-crinoid ''Roveacrinus communis''. A unique acme occurrence of the serpulid ''Filograna avita'', encrusting ''Mytiloides'' shells, occurs just above the middle of the zone (Gale, 1996).

'''Age''': Early Turonian
[[category:Standard zonation | 014]]

Mytiloides spp. Zone - Revision history

Dbk: Created page with "'''Base''': The base of the zone is immediately below the first appearance of the inoceramid bivalve ''Mytiloides'', which is approximately coincident with the top of the ''N...."