Deiphoninae Raymond, 1913

Subfamily Deiphoninae Raymond, 1913

= Cyrtometopinae Öpik, 1937

Included genera: Actinopeltis Hawle & Corda, 1847 ; Cyrtometopus Angelin, 1854 (= Ancyginaspis Přibyl and Vaněk in Přibyl et al., 1985); Ellipsocoryphe Lu, 1975 ; Deiphon, Barrande, 1850 ; Hemisphaerocoryphe Reed, 1896 (= Cyrtometopella Nikolaisen, 1961 );? Hinggania Zhao, Zhang, Cheng and Shu, 1997; Junggarella Xiang and Zhang in Zhang T., 1981; Krattaspis Öpik, 1937 ; Mainbrookia Adrain & Pérez-Peris, 2021 ; Onycopyge Woodward, 1880 ; Reraspis Öpik, 1937 ; Sphaerocoryphe Angelin, 1854 ;? Zazvorkaspis Přibyl & Vaněk, 1964 .

Diagnosis: Glabella moderately inflated with anterior margin anteriorly bowed; anterior border of cranidium dorsally overlapped by glabella and downturned from horizontal; S2 and S3 narrow (tr.) and transversally directed; thoracic pleural furrow slightly oblique at most proximal par, trasnverse distally; second pygidial axial ring not differentiated from pleural field by axial furrow.

Discussion: Te results obtained suggest that “cyrtometopines” sensu Pärnaste (2003) are a paraphyletic grade at the base of a clade representing Deiphoninae . Consequently, “Cyrtometopinae” must be considered an invalid group and all the members previously assigned to it are included in Deiphoninae . Tese results contradict the hypothesis of Lane (1971, 2002), who included the “cyrtometopines” with an anteroposterior pleural constriction within Cheirurinae. Lane (1971, 2002) suggested that the thoracic pleural furrow of “cyrtometopines” and cheirurines are almost identical, though it is distinctively more transversely oriented in “cyrtometopines”. Lane (1971, 2002) also pointed out that the proximal part of the thoracic furrow in the genus Cyrtometopus runs obliquely from the anterior corner of the pleura as it does in cheirurines. However, in cheirurines the pleural furrow runs obliquely from the anterior corner of the pleura to the most distal region, where it then curves anteriorly. Tis configuration is completely different from the condition seen in deiphonines, which have a pleural furrow running transversely from the most proximal to the most distal part, or with only the most proximal part running obliquely as in Cyrtometopus and Krattaspis . Moreover, besides the pleural furrow there are other morphological characters that support the inclusion of “cyrtometopines” within Deiphoninae : the inflation of the glabella, the greatly bowed anteriorly anterior margin of the glabella, the downturned anterior border of the cranidium and the relatively short (sag.) hypostome. Krattaspis popovi Pärnaste, 2003 from the Mäeküla and Vassilkovo beds, Billingen Stage (Floian), St. Petesburg Region ( Russia), is a perfect example of a “cyrtometopine” with strong similarities to more derived deiphonines. Te glabella of Krattaspis popovi displays a transglabellar S1 ( Pärnaste, 2003, Fig. 6 View Fig . L-O, p. 248), which is a morphological characteristic of deiphonines such as Sphaerocoryphe . In addition, the anterior part of the glabella of Krattaspis popovi is more inflated than the rest of “cyrtometopines”, resembling the glabellar inflation found in Hemisphaerocoryphe or Mainbrookia . In summary, all of these morphological features combined with the phylogenetic results, favour the inclusion of “cyrtometopines” within Deiphoninae .

Te idea of deiphonines as derived “cyrtometopines” has been suggested since Schmidt (1881), who in his pioneering early work proposed a link between Cyrtometopus and Sphaerocoryphe via the species Hemisphaerocoryphe pseudohemicranium ( Nieszkowski, 1859) . Subsequently, Öpik (1937) proposed Cyrtometopinae, recognizing the close link between the two subfamilies and the validity of both of the subfamilies as coherent groupings. Tis view, of deiphonines as derived “cyrtometopines” but recognizing the latter as a valid named group was followed by several subsequent authors (e.g., Pärnaste, 2003; Prantl & Přibyl, 1948; Přibyl et al., 1985). Pärnaste (2003, p. 245) pointed out the necessity of testing the validity of “Cyrtometopinae” within an analysis comparing them with the rest of cheirurid subfamilies. Finally, Adrain and Pérez-Peris (2021) suggested the paraphyly of “cyrtometopines” and their basal position to the deiphonines. Te phylogenetic framework herein supports previous hypotheses of close relationship between Deiphoninae and “Cyrtometopinae”. However it rejects “cyrtometopines” as a monophyletic group, considering them as a paraphyletic grade.