Romano et al.—Early Triassic Fishes of Elko County (Nevada)
Cb, ceratobranchial; Cf, caudal fin (lepidotrichia); Cl, cleithrum; De, dentary (external plate); Df, dorsal fin (lepidotrichia); Dh, dermohyal; Dmp, ‘dermometapterygoid’; Dp, dermopterotic; Dpl, dermopalatine; Ds, dermosphenotic; Eb,epibranchial; Ect, ectopterygoid; Ent, entopterygoid;
eth.ca., ethmoidal canal; ex. na., external narial openings; F, frontal; Ff, fringing fulcrum;Hm, hyomandibula;
int.lam.an., internal lamina of the angular; int.
lam.de., internal lamina of the dentary;
int.lam.mx.,internal lamina of the maxilla;
io.ca., infraorbital sensory canal; L, lachrymal; lc.dh., longitudinal crest on the dermohyal; Mx, maxilla (external plate);
md.ca., mandibular sensory canal; Nao, nasaloantorbital; Op, operculum; P, parietal; pBf,paired basal fulcrum;
p.ca., postotic section of the lateral line sensory canal; Par, prearticular; Pop, preoperculum;
pop.ca., preopercular sensory canal;Q, quadratumportion of the palatoqudratum;Rpm, rostro-premaxilla; Sa,surangular; Sc, scale; Scu, scute;
so.ca., supraorbital sensory canal; Sob, suborbital; Sop, suboperculum; uBf, unpaired basal fulcrum.
Class Osteichthyes Huxley, 1880
Subclass Actinopterygii Cope, 1887, emend. Rosen et al., 1981 Family Birgeriidae Aldinger, 1937, emend. Nielsen, 1949
Remarks.—The family includes only Birgeria Stensiö, 1919. Two other genera formerly referred to Birgeriidae, the Early Jurassic Ohmdenia Hauff, 1953 and the Early Cretaceous Psilichthys Hall, 1900, have been shown to be unrelated (Waldman, 1971; Friedman, 2012).
Genus Birgeria Stensiö, 1919, emend. Romano and Brinkmann, 2009
Type species.—Birgeria mougeoti (Agassiz, 1843) from the Middle Triassic of Bayreuth, Germany.
Remarks.—Stensiö (1919) erected the genus based on a maxilla from the Middle Triassic of Germany that contains teeth resembling those of the type material of ‘Saurichthys’ mougeoti Agassiz, 1843, which henceforth became the type species of Birgeria. The type material from the Muschelkalk of France and Germany is composed of several isolated teeth and dentigerous maxilla fragments, which clearly cannot be attributed to Saurichthys Agassiz, 1834, because in this taxon the maxilla lacks such large teeth (e.g., Stensiö, 1925; Rieppel, 1985; Mutter et al., 2008; Maxwell et al., 2015; Kogan and Romano, 2016a). The material of Agassiz (1833–1843) and Stensiö (1919) is too fragmentary for identification at the species level, but bears close resemblance to material of other, much better known species referred to Birgeria. Additional, more complete material from the Early Triassic of Spitsbergen (Svalbard, Arctic Norway), supposedly belonging to B. mougeoti (Agassiz, 1843), was figured and described by Stensiö (1919, 1921, 1932). One specimen of Stensiö’s (1932) material, however, was later considered as a separate species, B. aldingeri Schwarz, 1970. Although Schwarz (1970) did not explicitly comment on the taxonomic status of other material from Spitsbergen (Stensiö, 1919, 1921, 1932), we agree that it is likely not con- specific with that from the Middle Triassic Germanic Basin, due to notable differences in the angle of the anterior margin of the
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postorbital maxillary blade (see Discussion). Pending a proper revision of the type species and the species from Spitsbergen, we follow previous authors and treat B. mougeoti from the Muschelkalk Sea as a valid species, whereas Stensiö’s (1919, 1921, 1932) material from Spitsbergen is herein provisionally referred to as B. cf. aldingeri (except for the holotype of B. aldingeri).
Occurrence.—Marine Triassic, global: from the Griesbachian (earliest Triassic) of Greenland to the Rhaetian (latest Triassic) of Europe.
Birgeria americana new species Figures 3, 4
Holotype.—NMMNH P-66225 (Figs. 3, 4), from upper lower Smithian to lower upper Smithian beds (Thaynes Group), ~2.75km south-southeast of the Winecup Ranch, east-central Elko County, Nevada, USA (Fig. 1). P-66225 is a partial skull preserved within a large limestone nodule, with its right side exposed. A digital 3D surface scan of P-66225 is available at MorphoMuseuM (Romano et al., 2017).
Differential diagnosis.—Very large (>150 cm) birgeriid (larger than B. groenlandica Stensiö, 1932, B. nielseni Lehman, 1948, B. liui Jin, 2001, B. guizhouensis Liu, Yin, and Luo in Liu et al., 2006, and B. acuminata [Agassiz, 1843]); postorbital blade of maxilla elongate, anteriorly low, posteriorly high, with inclined anterior border (relatively shorter, anteriorly about as high as posteriorly, with steep anterior margin in B. mougeoti [Agassiz, 1843], B. stensioei Aldinger, 1931, and B. acuminata); antoperculum present; suboperculum dorsoventrally elongate (absent or weakly ossified in B. stensioei; dorsoventrally shorter in B. groenlandica and B. nielseni); five to six postmandibular branchiostegal rays (four to five in B. nielseni, three to five in B. groenlandica, maximum one in B. stensioei); teeth of the intermediate row on the maxilla and dentary mostly widely spaced, varying in size, butmostly high (small, equal-sized, close- set intermediate teeth in B. stensioei and B. acuminata); labial teeth distinct (smaller in B. stensioei, absent in B. acuminata).
Description.—NMMNHP-66225 (Figs. 3, 4) shows the portion between the cleithrum posteriorly, and the level of the hind margin of the orbital opening anteriorly. The preserved part has a length of 26 cm. Most bones are still in situ. Parts of the maxilla, the preoperculum, the suborbitals, and the lower jaw were damaged due to weathering. Upper jaw.—The maxilla is the dominant bone of the upper
jaw (Fig. 3). It consists of a cleaver-shaped external plate (composed of a low suborbital portion and a high, elongate postorbital blade) and an internal lamina. The postorbital blade of the maxillary bone is confined by a slanted, concave anterior margin, a nearly straight dorsal border, a posterior margin that is straight in its upper segment and distinctly sigmoid in its lower part, and a dentigerous ventral margin, which is largely straight except for its posteriormost portion, which is concave. The postorbital plate is mostly flat except for the posteroventral part, which is laterally convex. The ornamentation of the maxilla is only preserved in proximity to the tooth-bearing margin, where
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