Diaphanometopidae is a

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 ...

trilobite Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the At ...

s. Its representatives lived during the

Arenig In geology, the Arenig (or Arenigian) is a time interval during the Ordovician period and also the suite of rocks which were deposited during this interval. History The term was first used by Adam Sedgwick in 1847 with reference to the "Areni ...

and Llanvirn stages of the

Ordovician Period The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. The ...

, approximately 479 to 463 million years ago.Moore, R. C. (ed.). Treatise on Invertebrate Paleontology. Part O – Arthropoda (Trilobitomorpha). 1959 The Diaphanometopidae are thought to have been an early transitional group between the

Ptychopariida Ptychopariida is a large, heterogeneous order of trilobite containing some of the most primitive species known. The earliest species occurred in the second half of the Lower Cambrian, and the last species did not survive the Ordovician–Silurian ...

ancestors and all other

Phacopina The Phacopina comprise a suborder of the trilobite order Phacopida. Species belonging to the Phacopina lived from the Lower Ordovician (Tremadocian) through the end of the Upper Devonian (Famennian).Moore, R.C. (ed.). Treatise on Invertebrate Pale ...

. Diaphanometopidae, are found in the Lower and Middle Ordovician of Sweden and Russia. Three species are assigned to this family: ''Diaphanometopus volborthi'' that has been found in the

Dapingian The Dapingian is the third stage of the Ordovician period and the first stage of the Middle Ordovician series. It is preceded by the Floian and succeeded by the Darriwilian. The top of the Floian is defined as the first appearance of the conodont s ...

Baltica Baltica is a paleocontinent that formed in the Paleoproterozoic and now constitutes northwestern Eurasia, or Europe north of the Trans-European Suture Zone and west of the Ural Mountains. The thick core of Baltica, the East European Craton, is mo ...

, ''Gyrometopus lineatus'' occurring in the

Floian The Floian is the second stage of the Ordovician Period. It succeeds the Tremadocian with which it forms the Lower Ordovician epoch. It precedes the Dapingian Stage of the Middle Ordovician. The Floian extended from to million years ago. The lowe ...

of Baltica and ''Prodalmanitina nikolaevi'' that is known from the

Kolyma Kolyma (russian: Колыма́, ) is a region located in the Russian Far East. It is bounded to the north by the East Siberian Sea and the Arctic Ocean, and by the Sea of Okhotsk to the south. The region gets its name from the Kolyma River an ...

. These species have many ancestral characters compared to other Phacopina, but they do not seem to be each other's nearest relatives, which makes it unlikely this family will be maintained when the

phylogeny A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spec ...

has been studied in more detail.

References

External links

* Dalmanitoidea Trilobite families Ordovician trilobites Early Ordovician first appearances Middle Ordovician extinctions {{phacopida-stub