Mawsoniidae is an extinct

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

of prehistoric

coelacanth The coelacanths ( ) are fish belonging to the order Actinistia that includes two extant species in the genus ''Latimeria'': the West Indian Ocean coelacanth (''Latimeria chalumnae''), primarily found near the Comoro Islands off the east coast ...

fishes which lived during the

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

periods. Members of the family are distinguished from their sister group, the

Latimeriidae Latimeriidae is the only extant family of coelacanths, an ancient lineage of lobe-finned fish. It contains two extant species in the genus ''Latimeria'', found in deep waters off the coasts of southern Africa and east-central Indonesia. In additio ...

(which contains the living coelacanths of the genus ''

Latimeria ''Latimeria'' is a rare genus of fish which contains the only living species of coelacanth. It includes two Extant taxon, extant species: the West Indian Ocean coelacanth (''Latimeria chalumnae'') and the Indonesian coelacanth (''Latimeria menado ...

'') by the presence of ossified ribs, a coarse rugose texture on the

dermatocranium The dermatocranium is the portion of the cranium that is composed of dermal bone, as opposed to the endocranium and splanchnocranium, which are composed of endochondral bone. The dermatocranium comprises the skull roof, the facial skeleton (usuall ...

and cheek bones, the absence of the suboperculum and the spiracular, and reduction or loss of the descending process of the

supratemporal The supratemporal bone is a paired cranial bone present in many tetrapods and tetrapodomorph fish. It is part of the temporal region (the portion of the skull roof behind the eyes), usually lying medial (inwards) relative to the squamosal and latera ...

. Mawsoniids are known from North America, Europe, South America, Africa, Madagascar and Asia. Unlike Latimeriidae, which are exclusively marine, Mawsoniidae were also native to freshwater and brackish environments. Mawsoniids represent among the youngest known coelacanths, with the youngest known remains of the freshwater genus ''

Axelrodichthys ''Axelrodichthys'' is an extinct genus of mawsoniid coelacanth from the Cretaceous of Africa, North and South America, and Europe. Several species are known, the remains of which were discovered in the Lower Cretaceous (Aptian-Albian) of Brazil ...

'' from France and an indeterminate marine species from Morocco being from the final stage of the Cretaceous, the

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval from ...

, roughly equivalent in age to the youngest known fossils of latimeriids. Species of '' Mawsonia'' and ''

Trachymetopon ''Trachymetopon'' is an extinct genus of prehistoric coelacanth from the Jurassic of Europe. Fossils have been found in the Early Jurassic Posidonia Shale of Germany the Middle Jurassic Marnes de Dives of France, and probably the Late Jurassic Ki ...

'' are known to have exceeded 5 metres in length, making them among the largest known bony fish to have ever existed.

Phylogeny

The following cladogram is after Torino, Soto and Perea, 2021.

References

Triassic bony fish Jurassic bony fish Cretaceous bony fish Triassic first appearances Cretaceous extinctions Prehistoric lobe-finned fish families {{Jurassic-fish-stub