| System (period) | Series | Stage (age) | Lower boundary, Ma | |
|---|---|---|---|---|
| Ordovician | Lower | Tremadocian | 485.4±1.9 | |
| Cambrian | Furongian | Stage 10 | ~489.5 | |
| Jiangshanian |  ~494
| |||
| Paibian | ~497
| |||
| Miaolingian | Guzhangian | ~500.5
| ||
| Drumian | ~504.5
| |||
| Wuliuan | ~509
| |||
| Series 2 | Stage 4 | ~514 | ||
| Stage 3 | ~521 | |||
| Terreneuvian | Stage 2 | ~529 | ||
| Fortunian | 538.8±0.2
| |||
| Ediacaran | older | |||
| Subdivisions and "golden spikes" according to IUGS as of September 2023[1] | ||||
The Drumian is a second stage of the Miaolingian series, corresponding to the Drumian age of the Miaolingian epoch. It lasted from approximately 504.5 Ma to around 500.5 Ma (million years ago). It is preceded by the Wuliuan and is followed by the Guzhangian.
It was named after Drum Mountains in Millard County, western Utah, USA.
Definition[]
The GSSP of the Drumian stage was ratified in 2006. The lower boundary is fixed at the base of a dark calcisiltite layer, 62 m above the base of the Wheeler Formation in Drum Mountains, Utah, USA, and related to the first appearance of agnostoid arthropod Ptychagnostus atavus.[2]
Drumian life[]
Active evolution took place in the seas. The fauna of the Drumian is known mainly from Utah, USA, although there are also finds from Canada, Norway and Spain.
An Elrathia fossil
Misszhouia
Tuzoia
Balhuticaris
The seas of that time were dominated by sponges and arthropods. Valospongia, Hintzespongia and many other sponges have been found in the Marjum Formation of Utah.[3] Among arthropods, trilobites reached large numbers and diversity. Various asaphid (Asaphiscus), ptychopariid (Trymataspis, Altiocculus, Utaspis, Elrathia, Modocia), corynexochid (Bathyuriscus, Athabaskiella, Hemirhodon, Olenoides) and olenid (Groenwallia, Andrarina) trilobites inhabited the seas. Nektaspidids (Naraoia, Misszhouia) were originally classified as trilobites, but later they were removed from this group due to such features as the absence of lateral eyes and spines. Agnostids are another group of animals that were originally thought to be trilobites. These are small, eyeless arthropods that probably led a pelagic lifestyle. Many agnostids, including Iniospheniscus, Peronopsis, Utagnostus, Ammagnostus, Hypagnostus, Cotalagnostus, Ptychagnostus etc., are known from the Drumian deposits of Utah. Dytikosicula, a shrimp-like arthropod, probably fed on plankton in the water column. Several arthropods like Branchiocaris and Tuzoia acquired a wide shell that protected them from the large predators. Carnivorous radiodonts, such as Buccaspinea, Pahvantia and Peytoia, have adapted to capturing benthic animals using movable appendages in the front part of the body. Caryosyntrips, another radiodont, possessed anterior appendages that probably functioned like scissors. Balhuticaris, an unusual arthropod with a body of more than 100 segments, was found in Drumian strata of Burgess Shale Formation, Canada.
Other fossils of this age include brachiopods (Acrothele, Prototreta, Linnarssonia, Canthylotreta), eocrinoids (Gogia, Marjumicystis), pterobranchs (Mastograptus) and worms (Scathascolex, Ottoia).
References[]
- ↑ "Latest version of international chronostratigraphic chart". International Commission on Stratigraphy. https://stratigraphy.org/chart#latest-version.
- ↑ "GSSP Table - Paleozoic Era". https://timescalefoundation.org/gssp/index.php?parentid=77.
- ↑ Lucas Del Mouro, Joseph Botting, Jacob Skabelund, Rudy Lerosey-Aubril, Robert R. Gaines, Javier Ortega-Hernández (2022). "Revision of the middle Cambrian (Drumian) sponges from the Marjum Formation of Utah, USA". Conference: 6th International Palaeontological Congress, Khon Kaen, Thailand.