The Peronopsidae (which may also be called peronopsids) comprise the earliest family of the Agnostina suborder. Species of this family occurred on all paleocontinents. The earliest representatives of this family first occur just before the start of the

Middle Cambrian Middle or The Middle may refer to: * Centre (geometry), the point equally distant from the outer limits. Places * Middle (sheading), a subdivision of the Isle of Man * Middle Bay (disambiguation) * Middle Brook (disambiguation) * Middle Creek (di ...

, and the last disappeared just after the start of the Upper Cambrian.

Distribution

Peronopsidae are

cosmopolitan Cosmopolitan may refer to: Internationalism * World citizen, one who eschews traditional geopolitical divisions derived from national citizenship * Cosmopolitanism, the idea that all of humanity belongs to a single moral community * Cosmopolitan ...

Temporal distribution

Temporal distribution: * ''

Archaeagnostus ''Archaeagnostus'' is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived from the terminal Toyonian Cambrian Stage 4 is the still unnamed fourth stage of the Cambrian and the upper stage of Cambrian S ...

'',

Toyonian Cambrian Stage 4 is the still unnamed fourth stage of the Cambrian and the upper stage of Cambrian Series 2. It follows Cambrian Stage 3 and lies below the Wuliuan. The lower boundary has not been formally defined by the International Commission ...

( ''Nephrolenellus multinodus''-zone) and Amgaian ('' Ovatoryctocara''-zone). * ''

Eoagnostus ''Eoagnostus'' is an extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity ...

'', Toyonian (''Nephrolenellus multinodus''-zone) and Amgaian (''Ovatoryctocara''-zone). * '' Peronopsis (Proacadagnostus)'', Amgaian (''Ovatoryctocara''- and lower ''Kounamkites''-zones). * ''

Diplorrhina ''Diplorrhina'' Hawle and Corda (1847) is a genus of trilobite belonging to Order Agnostida. It lived during the early Middle Cambrian ( Amgan and Mayan stages) in what are now the Czech Republic and the North Siberian plateau. as in members of ...

'', Amgaian (''Ovatoryctocara''- and ''Kounamkites''-zones) * '' Peronopsis (Peronopsis)'', Amgaian (''Ovatoryctocara''-, ''Kounamkites''- and ''Triplagnostus gibbus''-zones). * '' Pentagnostus (Pentagnostus)'', Amgaian (''Ovatoryctocara''-, ''Kounamkites''- and ''Triplagnostus gibbus''-zones). * '' Pentagnostus (Meragnostus)'', Amgaian (''Kounamkites''- and ''Triplagnostus gibbus''-zones). * '' Peronopsis (Vulgagnostus)'', Amgaian (''Kounamkites''-, ''Triplagnostus gibbus''- and ''T. fissus''/'' Ptychagnostus atavus''-zones). * ''

Itagnostus ''Itagnostus'' is a genus of trilobite restricted to the Middle Cambrian. Its remains have been found in Asia, Australia, Europe, and North America. Distribution * ''Itagnostus elkedrensis'' occurs in the Middle Cambrian of Australia (''Ptych ...

'', Amgaian (''Kounamkites''-, ''Triplagnostus gibbus''- and ''T. fissus''/''Ptychagnostus atavus''-zones) to Mayanian (''Ptychagnostus punctuosus''-zone). * '' Quadragnostus'', Amgaian (''Kounamkites''-, ''Triplagnostus gibbus''- and ''T. fissus''/''Ptychagnostus atavus''-zones) to Mayanian (''Ptychagnostus punctuosus''- and ''Goniagnostus nathorsti''-zones). * '' Peronopsis (Svenax)'', Amgaian (''T. fissus''/''Ptychagnostus atavus''-zones) to Mayanian (''Ptychagnostus punctuosus''- and ''Goniagnostus nathorsti''-zones). * '' Micagnostus'', Amgaian (''Triplagnostus gibbus''-zone). * '' Redeagnostus'', Amgaian (''T. fissus''/''Ptychagnostus atavus''-zones) to Mayanian (''Ptychagnostus punctuosus''-, ''Goniagnostus nathorsti''- and '' Lejopyge laevigata''-zones). * '' Gratagnostus'', Amgaian (''T. fissus''/''Ptychagnostus atavus''-zones) to Mayanian (lowest ''Ptychagnostus punctuosus''-zone). * ''

Acadagnostus ''Acadagnostus'' is a genus of trilobite from the Middle Cambrian, with 7 species currently recognized. The type species ''A. acadicus'' has the widest distribution known from any peronopsid (with ''Peronopsis, Peronopsis integer'' and ''P. scut ...

'', Amgaian (''Triplagnostus gibbus''- and ''T. fissus''/''Ptychagnostus atavus''-zones) to Mayanian (''Ptychagnostus punctuosus''-zone). * '' Baltagnostus'', Amgaian (''Triplagnostus gibbus''- and ''T. fissus''/''Ptychagnostus atavus''-zones) to lowest Ayusok-Kanskian.

Taxonomy

The Peronopsidae are considered to be the earliest family of the Agnostina. This implicates that the earliest Peronopsid genus (''Archaeagnostus'') probably descended directly from the Eodiscoid genus '' Tannudiscus'' (

Weymouthiidae The Weymouthiidae are an extinct family of eodiscinid agnostid trilobites. They lived during the late Lower Cambrian and earliest Middle Cambrian (Botomian to Delamaran) in the so-called ''Olenellus''- and ''Eokochaspis''-zones in the former ...

).Whittington, H. B. et al. Part O, Treatise on Invertebrate Paleontology. Revised, Volume 1 – Trilobita – Introduction, Order Agnostida, Order Redlichiida. 1997 Some scholars do not consider the Agnostina true trilobites, and consequently rejected the idea that they were related to the Eodiscina.

Relations within the Peronopsidae

Many lineages are thought to have evolved within the Peronopsidae, six of which gave rise to later Agnostina families. * ''Archaeagnostus'' developed into ''Pentagnostus'', which sprouted the

Ptychagnostidae Ptychagnostidae is a family of agnostid trilobites from the 5th Stage to the Paibian Age of the Cambrian ( to million years ago). The family includes several important index fossils. Description Like all agnostids, ptychagnostids have cepha ...

family early on, and also developed into the advanced subgenus ''Pentagnostus (Meragnostus)''. ''Archaeagnostus'' also developed into the effaced genus ''Eoagnostus''. ''Archaeagnostus'' is finally the ancestor of the subgenus ''Peronopsis (Peronopsis)''. * The early nominate subgenus of ''Peronopsis'' gave rise to the genera ''Quadragnostus'' and ''Diplorrhina'', either of which developed into ''Gratagnostus''. * ''Peronopsis (Peronopsis)'' contains the ancestor of ''Iniospheniscus''. * ''Peronopsis (Peronopsis)'' fathered the subgenus ''Peronopsis (Svenax)'', which early on sprouted the genus ''Redeagnostus'', itself the ancestor of the

Agnostidae Agnostidae is a family (biology), family of Agnostida trilobites. Like all Agnostina, they were eyeless and had only two thorax, thoracic segments. These trilobites inhabited benthic waters worldwide from 508 to 461 million years ago. The family i ...

family. Later ''Peronopsis (Svenax)'' probably developed into ''Itagnostus'', which is transitional to the Doryagnostidae family. * ''Peronopsis (Peronopsis)'' brought forth the subgenus ''Peronopsis (Vulgagnostus)'', itself the ancestor of ''Baltagnostus'' from which the Ammagnostidae descended. The effaced genus ''Eoagnostus'' also descends from ''Peronopsis (Vulgagnostus)''. * A further lineage from ''Peronopsis (Peronopsis)'' includes ''Peronopsis (Proacadagnostus)'', ''Acadagnostus'', and ''Pseudoperonopsis'', the earliest genus of the Diplagnostidae family. * ''Peronopsis palmadon'' is transitional to the

Condylopygoidea The Condylopygidae RAYMOND, P. E., 1913: Some changes in the names of genera of trilobites. ''The Ottawa Naturalist'', 26: 137−142. are a family of small trilobites that lived during the Middle Cambrian, and found in Canada (Newfoundland and No ...

superfamily.

Genera previously assigned to the Peronopsidae

* ''Connagnostus'' is reassigned to the

* ''Euagnostus'' is reassigned to the Doryagnostidae * ''Pseudoperonopsis'' is reassigned to the Diplagnostidae

Description

Like all Agnostida, members of the Peronopsidae are diminutive, with the headshield (or

cephalon Cephalon, Inc. was an American biopharmaceutical company co-founded in 1987 by pharmacologist Frank Baldino Jr., Frank Baldino, Jr., neuroscientist Michael Lewis, and organic chemist James C. Kauer—all three former scientists with the DuPont ...

) and tailshield (or

pygidium The pygidium (: pygidia) is the posterior body part or shield of crustaceans and some other arthropods, such as insects and the extinct trilobites. In groups other than insects, it contains the anus and, in females, the ovipositor. It is compos ...

) of approximately the same size (or isopygous) and outline. Like all Agnostina, Peronopsidae have only two thorax segments. The cephalon and pygidium usually have a complete set of furrows. The preglabellar furrow - between the front and the central raised area of the cephalon (or

glabella The glabella, in humans, is the area of skin between the eyebrows and above the nose. The term also refers to the underlying bone that is slightly depressed, and joins the two brow ridges. It is a cephalometric landmark that is just superior ...

) - is lacking or incomplete. The cephalon carries no spines. The border around the pygidium is not forked.

References

{{Taxonbar, from=Q1232968 Agnostoidea Trilobite families Cambrian trilobites Cambrian first appearances Furongian extinctions