Graptolites


Also found in: Dictionary, Medical.

graptolites

[′grap·tə‚līts]
(paleontology)

Graptolites

 

(Graptolithina), a subphylum of extinct marine colonial animals of phylum Hemichordata.

Graptolites are known from the Cambrian to the Carboniferous periods; they were most common in the Ordovi-cian. Silurian, and lower Devonian periods. The skeletons of graptolites consisted of chitinous branches formed from little compartments in which the zooids lived. Graptolites were either benthic or planktonic. Planktonic graptolites had a swim bladder filled with gas released by the zooids as a product of their vital processes. There were two classes: Stereostolonata, with hard stolons and functionally varied compartments, and Graptoloidea, without stolons and with uniform compartments. Graptolites are of great importance as index fossils.

REFERENCE

Obut, A. M. “Tip Hemichordata (Gemikhordovye): Podtip Graptolithina (Graptolity).” In Osnovy paleontologii: Iglokozhie, gemikhordovye, pogonofory i shchetinkocheliustnve. Moscow, 1964.

A. M. OBUT

References in periodicals archive ?
Palaeogeographically, the Lower Ordovician graptolites of the studied area are similar to other scattered records occurring in South-Polar Peri-Gondwanan terranes, where the scarcity of Rhabdinopora and other anisograptid graptolites is linked with the extensive development of shallow-water facies dominated by sandstones and green micaceous shales.
Hirnantian (latest Ordovician) graptolites from the upper Yangtze region, China.
Hirnantian mudstones are abruptly but conformably overlain by anoxic black shales with abundant graptolites of the basal Silurian Akidograptus ascensus Biozone (Storch 2006).
However, intercalations of dark grey calcareous mudstone with graptolites are lacking in these marlstones and therefore the sections have an intermediate position between the Riga and Jaani formations.
In Proceedings of the Sixth International Graptolite Conference of the GWG (IPA) and the SW Iberia Field Meeting 1998 of the International Subcommission on Silurian Stratigraphy (ICS-IUGS), Madrid, 1998 (Gutierres-Marco, J.
The upper Wenlock is a dynamic time slice of the Silurian Period, marked by substantial environmental and biotic changes, with especially profound graptolite and conodont extinctions.
The definitions of the series and stages of the Silurian System and their correlation are traditionally based on relatively well developed graptolite zonation.
The presence of early Ordovician (late Tremadocian to early Arenigian) graptolites in the underlying Bright Eye Brook Formation of the Woodstock Group (see above) and Late Ordovician (early Caradocian) graptolites in the overlying Belle Lake Formation of the Meductic Group (see below) restricts the depositional range of the volcanic components (Porten Road, Eel River, and Oak Mountain formations) of the Meductic Group to between early Arenigian and Llanvirnian time.
System Series Stage Age Regional Beds Period Epoch stage SILURIAN PRIDOLI JURA MINIJA Varniai Silale LUDLOW LUDFORDIAN PAGEGIAI DUBYSA GORSTIAN System Series Biozones Period Epoch Graptolites Conodonts SILURIAN PRIDOLI N.
A stepwise extinction during the Mulde Event in the Homerian (Wenlock, Silurian) has been suggested for hemipelagic fauna such as graptolites and conodonts (Jaeger 1991; Jeppsson 1993; Kaljo et al.