In the Ordovician many new genera of the Testicardines make their appearance, such as Strophomena, Leptaena, Atrypa, Rhynchonella, Clitambonites, etc., but the extraordinary abundance and variety of Orthis is most remarkable. The Ecardines are reinforced by such forms as Trematis and Siphonotreta. It is, however, in the Silurian that the Testicardinate Brachiopoda attain their maximum, for in addition to a great development of species amongst the older forms, a host of new genera for the first time occur here (Spirifera, Athyris, Conchidium, Stricklandia, Chonetes, Cyrtia, etc.); and the Trimerellidae are especially characteristic of the Wenlock.
With the commencement of Devonian times many species and genera become extinct, but new forms come in (Terebratula, Orthothetes, Productus, etc.), and some genera are wholly confined to this formation (Uncites, Stringocephalus). The Carboniferous is marked by the maximum development of Productus and Spirifera; Orthothetes, Stenochisma, and Athyris are also abundant, but there is a considerable extinction of the older genera and species, and a great diminution in the number of individuals and species of those that persist.
A further reduction occurs in the Permian, where the most important genera are Productus, Strophalosia, and Stenochisma; but Aulosteges is a new form peculiar to this period. In the Trias a new era commences; the principal families and genera of the older rocks disappear entirely; a few spire-bearing genera persist (Spiriferina, Athyris), and the genus Koninckina is restricted to this formation.
The enormous development of species of the Terebratulidae and Rhynchonellidae is the most noticeable feature in Jurassic times; and a few ancient types linger on into the Lias (Spiriferina, Suessia, a sub-genus of Spirifera); Koninckella here occurs.
The Cretaceous Brachiopoda are closely allied to the Jurassic; Magas and Lyra are peculiar to the period, and the Terebratulidae and Rhynchonellidae are very abundant, together with the Ecardinate genus Crania.
With the commencement of Tertiary times the Brachiopoda have lost their geological importance, and have dwindled down into an insignificant proportion of the whole Invertebrate fauna.
The distribution of the Brachiopoda in past time is shown in the following table:—
| Palaeozoic | Mesozoic | |||||||||||
| C | ||||||||||||
| a | ||||||||||||
| r | ||||||||||||
| O | b | C | ||||||||||
| r | o | r | ||||||||||
| C | d | S | D | n | J | e | T | |||||
| a | o | i | e | i | P | u | t | e | ||||
| m | v | l | v | f | e | r | a | r | R | |||
| b | i | u | o | e | r | T | a | c | t | e | ||
| r | c | r | n | r | m | r | s | e | i | c | ||
| i | i | i | i | o | i | i | s | o | a | e | ||
| a | a | a | a | u | a | a | i | u | r | n | ||
| ECARDINES | n | n | n | n | s | n | s | c | s | y | t | |
| Lingulidae | Lingula | ___ | ___ | ___ | ___ | ___ | ___ | ___ | ___ | ___ | ___ | ___ |
| Lingulella | ___ | |||||||||||
| Obolidae | Obolus | ___ | ___ | |||||||||
| Obolella | ___ | ___ | ||||||||||
| Kutorgina | ___ | ___ | ||||||||||
| Linnarssonia | ___ | |||||||||||
| Trematis | ___ | ___ | ||||||||||
| Siphonotreta | ___ | ___ | ||||||||||
| Acrotreta | ___ | |||||||||||
| Discinidae | Discina | ___ | ___ | ___ | ___ | ___ | ___ | ___ | ___ | ___ | ___ | |
| Craniidae | Crania | ___ | ___ | ___ | ___ | ___ | ___ | ___ | ___ | ___ | ___ | |
| Trimerellidae | Trimerella | ___ | ||||||||||
| Dinobolus | ___ | |||||||||||
| TESTICARDINES | ||||||||||||
| Productidae | Productus | ___ | ___ | ___ | ||||||||
| Chonetes | ___ | ___ | ___ | |||||||||
| Strophalosia | ___ | ___ | ___ | |||||||||
| Strophomenidae | Orthis | ___ | ___ | ___ | ___ | ___ | ||||||
| Skenidium | ___ | ___ | ||||||||||
| Clitambonites | ___ | |||||||||||
| Strophomena | ___ | ___ | ||||||||||
| Stropheodonta | ___ | ___ | ___ | |||||||||
| Leptaena | ___ | ___ | ___ | ___ | ||||||||
| Orthothetes | ___ | ___ | ___ | |||||||||
| Davidsonia | ___ | |||||||||||
| Koninckinidae | Koninckina | ___ | ||||||||||
| Koninckella | ___ | |||||||||||
| Spiriferidae | Spirifera | ___ | ___ | ___ | ___ | |||||||
| Spiriferina | ___ | ___ | ___ | ___ | ___ | |||||||
| Cyrtia | ___ | ___ | ___ | |||||||||
| Syringothyris | ___ | |||||||||||
| Uncites | ___ | |||||||||||
| Athyris | ___ | ___ | ___ | ___ | ___ | |||||||
| Merista | ___ | ___ | ||||||||||
| Retzia | ___ | ___ | ___ | ___ | ___ | |||||||
| Atrypidae | Atrypa | ___ | ___ | ___ | ___ | ___ | ___ | |||||
| Dayia | ___ | |||||||||||
| Coelospira | ___ | |||||||||||
| Rhynchonellidae | Rhynchonella | ___ | ___ | ___ | ___ | ___ | ___ | ___ | ___ | ___ | ___ | |
| Stenochisma | ___ | ___ | ___ | |||||||||
| Stricklandia | ___ | |||||||||||
| Conchidium | ___ | ___ | ||||||||||
| Terebratulidae | Terebratula | ___ | ___ | ___ | ___ | ___ | ___ | ___ | ___ | |||
| Terebratulina | ___ | ___ | ___ | ___ | ||||||||
| Waldheimia | ___ | ___ | ___ | ___ | ||||||||
| Terebratella | ___ | ___ | ___ | ___ | ||||||||
| Kingena | ___ | ___ | ||||||||||
| Magas | ___ | |||||||||||
| Centronella | ___ | ___ | ___ | |||||||||
| Argiopidae | Argiope | ___ | ___ | ___ | ___ | |||||||
| Cistella | ___ | ___ | ___ | ___ | ||||||||
| Stringocephalidae | Stringocephalus | ___ | ||||||||||
| Thecidiidae | Thecidium | ___ | ___ | ___ | ___ | ___ | ||||||
| Oldhamina | ___ | |||||||||||