Ordovisium Tengah

Ordovisium Tengah merupakan kala kedua dari periode Ordovisium yang dimulai pada 470 juta tahun lalu, hingga 458.4 juta tahun lalu^[1]. Dimulainya kala ini ditandai dengan munculnya spesies conodont, Baltoniodus triangularis^[2]

^ "Geologic TimeScale Foundation - Stratigraphic Information". timescalefoundation.org. Diakses tanggal 2021-12-27.
^ "GSSP Table - Paleozoic Era". Geologic TimeScale Foundation. Diakses tanggal 24 November 2012. Note: there is an apparent typo in the article referenced; they give the coordinates as "a latitude of 30°51’37.8"N and a longitude of 110°22’26.5"E", but their map and location description better corresponds to 30°51’37.8"N 111°22’26.5"E.

[1] "Geologic TimeScale Foundation - Stratigraphic Information". timescalefoundation.org. Diakses tanggal 2021-12-27.

[GSSP_Table_-_Paleozoic_Era-2] "GSSP Table - Paleozoic Era". Geologic TimeScale Foundation. Diakses tanggal 24 November 2012. Note: there is an apparent typo in the article referenced; they give the coordinates as "a latitude of 30°51’37.8"N and a longitude of 110°22’26.5"E", but their map and location description better corresponds to 30°51’37.8"N 111°22’26.5"E.

[1]

[2]