| System (period) | Series | Stage (age) | Lower boundary, Ma | |
|---|---|---|---|---|
| Neogene | Miocene | Aquitanian | 23.03 | |
| Paleogene | Oligocene | Chattian |  27.82
| |
| Rupelian | 33.9
| |||
| Eocene | Priabonian | 37.71
| ||
| Bartonian | 41.2 | |||
| Lutetian | 47.8
| |||
| Ypresian | 56.0
| |||
| Paleocene | Thanetian | 59.2
| ||
| Selandian | 61.6
| |||
| Danian | 66.0
| |||
| Cretaceous | Upper | Maastrichtian | older | |
| Subdivisions and "golden spikes" according to IUGS as of September 2023[1] | ||||
The Thanetian is a third and upper stage of the Paleocene series, corresponding to the Thanetian age of the Paleocene epoch. It lasted from approximately 59.2 Ma to around 56.0 Ma (million years ago). It is preceded by the Selandian age of the Paleocene and is followed by the Ypresian age of the Eocene. The oldest perissodactyls ane known from this stage.
Definition[]
The GSSP of the Thanetian stage was ratified in 2008. The lower boundary is fixed in Zumaia section, northern Spain, and related to the base of the magnetic chronozone C26n, about 78 m above the Cretaceous-Paleogene boundary. The GSSP of the lower Selandian stage has been established in the same section.[2]
Thanetian life[]
Life continued to evolve both in the seas and on land. Coastal shallow waters were inhabited by a variety of mollusks, including gastropods (Colposigma, Euspira, Botelloides, Puncturella), bivalves (Bornia, Cuspidaria, Electroma, Limea) and scaphopods (Fissidentalium, Dentalium, Gadila, Compressidens). Nautilid cephalopods (Aturoidea, Eutrephoceras) hunted in the water column, as in the Mesozoic, although the number and diversity of this group of mollusks decreased markedly. Brachiopods like Oleneothyris, Platidia and Argyrotheca lived near the coasts. Among marine vertebrates, fishes dominated. Numerous cartilaginous fish lived in deep and shallow waters, near the bottom in the water column, and some of them still exist today. In the Thanetian strata of Nee Jersey, USA, various carcharhiniforms (Scyliorhinus), lamniforms (Odontaspis, Isurus, Lamna, Striatolamna), myliobatiforms (Myliobatis, Rhombodus), rajiforms (Ischyrhiza) and chimaeriforms (Edaphodon) have been found. Along with them lived bony fish, such as long-toothed Enchodus, the ancient perch Sphyraenodus, and Istiophorus homalorhamphus, an extinct species of sailfish.
Titanoboa and other huge Colombian reptiles of the time.
The coastal waters were inhabited by a variety of reptiles, including sea turtles (Peritresius, Euclastes), snakes (Cheilophis, Palaeophis) and crocodiles (Thoracosaurus). Despite the fact that the Cenozoic is considered the age of mammals, reptiles remained the dominant animals in some areas. During Selandian-Thanetian, several huge reptiles lived in rivers of Colombia. Puentemys, the largest known bothremydid turtle, reached 1.51 m in carapace length. Carbonemys, a podocnemidid, was even larger, around 1.8 m in carapace length. Another enormous reptile from the same locality was Titanoboa. With a length of more than 12 m, this snake could attack crocodiles, including small Cerrejonisuchus and large (about 5 m) Acherontisuchus.
Mammals at that time lived mainly on land. Primitive groups like non-placental multituberculates (Ptilodus, Neoplagiaulax, Hainina) still existed. Among cimolestans, another archaic group, several large herbivorous and omnivorous forms (Pantolambda, Titanoides, Archaeolambda) have appeared. Smaller shrew-like Bisonalveus fed on plants and insects. Some of the mammals of the Thanetian have survived from the Mesozoic. These were Peradectes, a small tribosphenid that lived in trees, and the group of Pantolestoidea, which includes small (rat-sized) animals like Leptonysson and Bessoecetor.
The warm climate contributed to the spread of numerous small placental mammals. Various nyctitheriids (Remiculus, Leptacodon), elephant shrews (Berrulestes, Litocherus, Gigarton) and jumping leptictids (Myrmecoboides, Phakodon) hunted insects in the forests of Europe and North America. Cedrocherus, a relative of hedgehogs, was found in Wyoming, USA. Among the more advanced placental mammals, there also existed several primitive forms, whose related relationships are questionable. Arctostylopids (Arctostylops) are likely relatives of rodents and lagomorphs. Pseudictops, a true gliriform, is known from the Thanetian of Mongolia and China. Eomylus and Eurymylus were even closer relatives of rodents and lagomorphs. More distant relatives of rodents are primatomorphs, a group including modern colugos (dermapterans) and primates. Elpidophorus is probably the oldest known colugo, while Plesiadapis, Carpodaptes and Ignacius are close relatives of primates. All of them lived in trees, where they fed on leaves, small invertebrates and plundered bird nests.
The diversity of ungulates can be traced from this age. Reaching a length of more than 2 m, Prodinoceras had small tusks, which it probably used to dig out nutritious roots from the ground. Later its descendants reached the size of rhinoceroses. Phenacodontids like Ectocion and Phenacodus were likely omnivorous. Tricuspiodon, a hyopsodontid, was probably fossorial. Phenacodontids and hyopsodontids are relatives of perissodactyls, the oldest of which (Paschatherium, Teilhardimys) appeared in this age. Among the ungulates of that time there were predatory mesonychids like Dissacus and Pachyaena. Other predatory mammals of the time include primitive, arboreal arctocyonids (Arctocyon, Mimotricentes, Chriacus), and more specialized oxyaenids (Oxyaena, Tytthaena) and viverravids (Protictis, Raphictis).
In general, by the end of the Paleocene, mammals were already showing great diversity, which predated their even larger radiation in the Eocene.
References[]
- ↑ "Latest version of international chronostratigraphic chart". International Commission on Stratigraphy. https://stratigraphy.org/chart#latest-version.
- ↑ "GSSP Table - Cenozoic Era". https://timescalefoundation.org/gssp/index.php?parentid=2.