Ostariophysi

Arratia, Gloria, 2018, Otomorphs (= otocephalans or ostarioclupeomorphs) revisited, Neotropical Ichthyology 16 (3), pp. 1-24 : 6

Ostariophysi.

Ostariophysans are characterized by numerous features, with only a few listed here: basisphenoid absent; sacculi and lagena with a posterior position and nearer midline; dermal portion of the palatine (= dermopalatine) absent and represented only by the autopalatine; gas bladder divided into smaller anterior and larger posterior chambers; presence of a unique alarm substance in epidermis (absent in gymnotiforms, with electrical signaling); and presence of nuptial tubercles with well-developed keratinous caps. For other characters and comments see Fink, Fink (1981, 1996), Fink et al. (1984), Lecointre, Nelson (1996), and Wiley, Johnson (2010).

Ostariophysans ( Fig. 4 c-g) comprise ca. 10,400 species contained in about 1,350 genera, 80 families and five orders ( Nelson et al., 2016) included in two sections, Anatophysa (sensu Betancur-R et al., 2017 or Anatophysi of Fink, Fink, 1981), which contains Gonorynchiformes and Otophysa (sensu Betancur-R et al., 2017 or Otophysi of Fink, Fink, 1981), which in turn, includes Cypriniformes , Characiformes , Siluriformes , and Gymnotiformes . Although there are differences between morphological and most molecular phylogenetic hypotheses of the orders, there is now consensus concerning the monophyly of the group ( Fink, Fink, 1981, 1996; Betancur-R et al., 2017; Arcila et al., 2017) and also of the otophysans. Major differences include: (1) a few molecular studies have questioned the monophyly and relationships of the Characiformes ( Nakatani et al., 2011; Chen et al., 2013; Chakrabarty et al., 2017), but monophyly of the group and its position as the sister to Gymnotiformes + Siluriformes was recently supported by other molecular studies ( Arcila et al., 2017; Betancur-R et al., 2017); (2) the family Diplomystidae appears as the most primitive catfish group in morphological studies of Siluriformes (e.g., Arratia, 1987; Grande, 1987), whereas Nematogenyidae plus other loricarioids is the sister to Diplomystidae plus all other catfishes in molecular studies (e.g., Sullivan et al., 2006; Arcila et al., 2017; Betancur-R et al., 2017). For other references on the subject see Arratia, Quezada-Romegialli (2017). Most extant ostariophysans are primarily freshwater fishes with a global distribution (except Antarctica, Greenland, and New Zealand), but there are about 120 marine species restricted to the Siluriformes ( Nelson et al., 2016) . Numerous fossils interpreted as possible stem taxa have been recovered in marine or estuarine strata, a fact that opens interesting questions concerning the evolution of the environment of Ostariophysi or of its particular orders.

Contrary to the current state of clupeiform research, ostariophysans -fossil and extant species- receive an enormous amount of attention, especially those living in the Neotropical Region; this is reflected in hundreds of publications produced by special projects, such as the “All Catfish Species Inventory” and “ Cypriniformes Tree of Life” and other special publications ( Malabarba et al., 1998; Reis et al., 2003; Arratia et al., 2003; Grande et al., 2010; Albert, Reis, 2011).

The oldest known ostariophysan is the Late Jurassic † Tischlingerichthys viohli from Germany, which is interpreted as incertae sedis ( Fig. 5a ). Numerous Early Cretaceous ostariophysans belonging to the Gonorynchiformes are known from Spain and Brazil [e.g., † Rubiesichthy s, † Gordichthys ( Fig. 5d ), and † Dastilbe ; see Dietze, 2007; Brito, Amaral, 2008; Poyato-Ariza et al., 2010] and Mexico († Sapperichthys; Amaral et al., 2013). Additionally, † Chanoides macropoma from the Middle Eocene of Monte Bolca, Italy and † Nardonoides chardoni from the Upper Cretaceous of Nardò have recently been confirmed as stem otophysans ( Mayrinck et al., 2015a). Restudy of † Santanichthys diasii from the Early Cretaceous (Albian) of Brazil, which was previously described as the oldest characiform ( Filleul, Maisey, 2004), has been re-interpreted as a stem otophysan ( Malabarba, Malabarba, 2010). † Salminops ibericus from the Cenomanian of Portugal previously described as one of the oldest characiforms ( Gayet, 1985) is not an ostariophysan, but possibly a crossognathiform ( Mayrinck et al., 2015b), and † Sorbinicharax verraesi from the Upper Cretaceous of Nardò, Italy, previously interpreted as another characiform, has been re-interpreted as Teleostei incertae sedis by Mayrinck et al. (2017).

Figures

Fig. 4. Diagrammatic representation of different otomorph groups such as: a. clupeiformes; b. alepocephaliforms; c. gonorynchiforms; d. cypriniforms; e. characiforms; f. siluriforms; g. gymnotiforms.

Fig. 5. Fossil otomorphs in lateral view. a. ostariophysan incertae sedis †Tischlingerichthys viohli Arratia, 1997; Upper Jurassic, Germany; holotype JM-E Moe 8; photograph courtesy of H. Tischlinger; b. clupeomorph †Santanaclupea silvasantosi Maisey, 1993; Lower Cretaceous, Brazil; paratype DNPM DGM1338-P; photograph courtesy of D. Mayrinck; c. clupeomorph †Ranulfoichthys dorsonudum Alvarado-Ortega, 2014; Lower Cretaceous, Mexico; paratype IGM 9034; photograph courtesy of J. Alvarado-Ortega; d. gonorynchiform †Gordichthys conquensis Poyato-Ariza, 1994; holotype MCCM-LH-1228; Lower Cretaceous, Spain; photograph by J.A. Gracia; courtesy by F.J. Poyato-Ariza. Scale bars = 1 cm.