Middle Cambrian ptero-branchs and the question: what is a
graptolite? Lethaia 38: 73-85.
"The explosive radiation of
graptolites in the Paleozoic planktonic ecosystems is known only from the diversity of their tubes.
Nemagraptid
graptolites are a particularly important fossil group for Ordovician biostratigraphy.
Herein we provide new information on the chronostratigraphy of the "Siluro-Devonian" succession in the subsurface of West Texas based on conodonts from a core from the Pegasus field in Midland County, Texas, and a reevaluation of
graptolites originally described by Decker (1942, 1952) from wells in adjoining Crane County.
The use of
graptolites in biostratigraphy is limited in these rocks (Paskevicius 1973, 2011; Mannil 1976).
* Ordovician extinction - It was a time when the earth was dominated by sea creatures such as trilobites, brachiopods, and
graptolites. They were drastically reduced in number during the die out.
The Kentville Formation contains
graptolites and microfossils (Smitheringale 1973; Bouyx et al.
(1985): Conodonts and associated
graptolites from the late Early Devonian of east-central Alaska and western Yukon Territory.
On the distribution of
graptolites in the Dictyonema shale of Estonia and the noncontemporaneity of its different facies.
About 30 species of pterobranch are known to exist today although 380-490 million years ago a group of these animals called
graptolites were common across the prehistoric oceans.