''Diplorrhina'' Hawle and Corda (1847) is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

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 ...

belonging to Order

Agnostida Agnostida is an order of arthropod which have classically been seen as a group of highly modified trilobites, though some recent research has doubted this placement. Regardless, they appear to be close relatives as part of the Artiopoda. They a ...

. 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 the family

Peronopsidae 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 ...

it lacks a preglabellar furrow. Both cephalon and pygidium lack spines. It is difficult to distinguish ''Diplorrhina'' from many other peronopsids.

Taxonomy

The ancestor of ''Diplorrhina'' is most likely one of the Siberian species of the genus ''

Archaeagnostus ''Archaeagnostus'' is an extinct genus from a well-known class of fossil marine arthropods, the trilobite Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest ...

''. ''D. recta'' is the most primitive species and it gave rise to ''D. cuneifera'', which was in turn ancestral to ''Diplorrhina triplicata''.

Species previously assigned to ''Diplorrhina''

* ''D. normata'' = ''Peronopsis (Proacadagnostus) normata'' * ''D. spitiensis'' = ''Peronopsis (Svenax) spitiensis''

Distribution

* ''D. triplicata'' is known from the early Middle Cambrian of the Czech Republic (''Eccaparadoxides pusillus'' and ''P. gracilis''Zones, Skryje Beds, pod hruskou, near Tyrovice and near Ginetz). * ''D. cuneifera'' has been collected from the early Middle Cambrian of the Czech Republic (''Eccaparadoxides pusillus''Zone Skryje Beds, near Tyrovice) * ''D. redita'' occurs in the early Middle Cambrian of the Czech Republic (''Paradoxides gracilis'' Zone, Jince Formation). Agnostus cambrensis Harkness & Hicks (1871, p. 390) was identified by Lake (1906, p. 18) as ''Agnostus integer'' Beyrich (now ''Peronopsis integra''), but re-examination of this specimen shows it to be referable to ''Diplorrhina redita'' (Pek & Vanĕk 1971, p.274, pl.1, figs. 4 & 5). The species was placed in ''Peronopsis'' by Rees ''et al''., (2014, p. 73). REES, A. J., THOMAS, A. T., LEWIS, M., HUGHES, H. E. & TURNER, P. 2014. The Cambrian of SW Wales: Towards a United Avalonian Stratigraphy. ''Geological Society, London, Memoirs, 42'', 1–30. From upper part of the Whitesands Bay Formation (Rees ''et al.'', 1914 p. 72), lower ''T. fissus'' Biozone. * ''D. recta'' was recovered from the early Middle Cambrian of Eastern Siberia (''Ovatoryctocara'' Zone, Molodo River, Olenek Uplift, and Kounamkite-zone, Nekekit River and Amidai River, all Western Jakutia). * ''D. lata'' is found in the Middle Cambrian of Eastern Siberia (''Kounamkites'' Zone, Nekekit River).

Description

Both border and border furrow of the cephalon are relatively narrow. The transglabellar furrow is straight or curved slightly towards posterior. The posterior glabellar lobe is parallel sided, has two pairs of lateral furrows and small basal lobes; there is no median node. The pygidial border is flattened and wide with posterolateral angles, but no spines. The pygidal lobes reach the median node but do not cross the axis. The distance between the pygidial axis and border furrow is short or sometimes touching.

Differences with ''Peronopis''

''Diplorrhina'' differs from members of the subgenus ''Peronopsis (Peronopsis)'' in the better developed transaxial furrows, better developed lateral furrows of the glabella, larger basal lobes, and in the trend towards the formation of a transverse depression of the axis.

References

{{Taxonbar, from=Q16973798 Peronopsidae Agnostida genera Cambrian trilobites Fossils of the Czech Republic Fossils of Russia