Terminology.—The terminology used herein follows the osteological terminology outlined by Schultze (2008) and Wiley (2008). Postcranial morphology follows the terminology outlined in Arratia (2008). In instances where terminology has varied in the literature over the years, the traditional terminology is presented here in parentheses: parietals (frontals), postparietals (parietals), infraorbitals posterior to orbit (postinfraorbitals), infraorbitals below orbit (subinfraorbitals), posttemporal (suprascapulars), anterior infraorbitals (lachrymals or lacrimals), temporal canal (postorbital or otic canal). The infraorbitals are described by position relative to the orbit, rather than numbered, to avoid potential homology problems (see Jollie, 1986).

Anatomical abbreviations.—a.io, anterior infraorbital (lacrimal); ang, angular; ar, articular; bchst, branchiostegal; bf, basal fulcra; b.pr, branched principal ray; ch, ceratohyal; cl, cleithrum; d.scu, dorsal scute; d, dentary; dpt, dermopterotic; dsph, dermosphenotic; ecp, ectopterygoid; enp, endopterygoid; ex, extrascapular; ff, fringing fulcra; HL, head length, measured from tip of snout to posterior end of operculum; io, infraorbital; iop, interoperculum; n, nasal; mx, maxilla; MBD, maximum body depth, measured from dorsal to ventral margins at the deepest portion of the body; op, operculum; p.bf, paired basal fulcra; p.ff, paired fringing fulcra; p, parietal (frontal); pcl, postcleithrum; pmx, premaxilla; pop, preoperculum; pp, postparietal (parietal); part, prearticular; pr, principal ray; psph, parasphenoid; pspi, postspiracular; ptt, posttemporal; q, quadrate; qj, quadratojugal; rar, retroarticular; SL, standard length, measured from tip of snout to the posterior end of the vertebral column; scl, supracleithrum; so, supraorbital; sop, suboperculum; suo, suborbital.

Taxonomic and morphological character sampling for phylogenetic analysis.—For this study, all three species of †Lophionotus were coded for the 90 characters included in López-Arbarello (2012) analysis of extinct and extant ginglymodian evolutionary relationships. Taxonomic sampling for this study included the 37 representatives of extinct and extant actinopterygian fishes included in the study by López-Arbarello (2012), as well as †L. sanjuanensis, †L. chinleana, new species, and †L. kanabensis.

The following is an abbreviated list of morphological characters from López-Arbarello (2012). In instances where the character was taken or modified from another study by López-Arbarello (2012), the initial source of the character is indicated. For a more detailed description and discussion of these characters, please refer to López-Arbarello (2012).

No character definitions from López-Arbarello (2012) were modified in this study; however, additional specimens of †Semionotus capensis examined yielded new information, and the following characters have been modified from López-Arbarello (2012) for †S. capensis: character 19, ‘?’ changed to ‘1’; character 28, ‘?’ changed to ‘1’; character 36, ‘?’ changed to ‘1’; character 50, ‘?’ changed to ‘0’; character 51, ‘?’ changed to ‘0’; character 52, ‘?’ changed to ‘1’. Further examination of specimens of †Semionotus elegans indicates the assignment of character 30 from ‘?’ to ‘1’; additionally, specimens of †S. elegans examined in this study were observed to possess a triangular lateral expansion on the anterior of the parietals (frontals), resulting in a change of coding from ‘0’ to ‘1’. The morphological character state matrix is presented in Table 1.

Table 1. 

Morphological Data Matrix of 90 Characters Modified from the Investigation of López-Arbarello (2012). Polymorphisms are indicated by a cell with more than one state.

Table 1. 

Continued.

Table 1. 

Continued.

Table 1. 

Continued.

Phylogenetic analyses of morphological data.—The dataset used for this study was assembled in Mesquite version 2.75 (Maddison and Maddison, 2010). A parsimony analysis was performed with TNT version 1.1 (Goloboff et al., 2008) with 20 independent heuristic searches and tree-bisection-reconnection (TBR) branch swapping. Characters were treated as unordered and of equal weight. Polymorphisms are treated as multistate. Symmetric resampling bootstraps (Goloboff et al., 2003) were performed with 100 replicates in TNT, with group frequencies presented. The subholostean genus †Perleidus was designated the outgroup, with the following genera acting as functional outgroups for the analysis: halecomorphs †Watsonulus eugnathoides and Amia calva; stem teleosts †Leptolepis coryphaenoides, †Pholidophorus bechei, and †Siemensichthys macrocephalus; and †Dapedium.

Type species.—†Lophionotus sanjuanensis, Gibson, 2013.

Revised generic diagnosis.—Small- to medium-sized semionotiform fish; single, narrow anamestic suborbital (multiple suborbitals in genera such as †Tlayuamichin, †Macrosemimimus, †Callipurbeckia, and †Sangiorgioichthys); deep ventral infraorbitals that expand below suborbital and contact the anterior ramus of the preoperculum (narrow infraorbitals in †Semionotus); closed circumorbital ring (open circumorbital ring in †Callipurbeckiidae, †Macrosemiidae); parietals less than three times longer than their maximum width (long parietals in †Semionotus); two supraorbitals (three or more present in genera such as †Semionotus, †Macrosemimimus, †Callipurbeckia, and †Tlayuamichin); anterior supraorbital narrow and of equal to greater length than posterior supraorbital (supraorbitals of approximately equal length in genera such as †Macrosemimimus); gape of mouth small (as compared to Lepisosteidae); maxilla short and dentelous (as compared to genera such as †Sangiorgioichthys, †Paralepidotus, †Tlayuamichin, and †Macrosemimimus) styliform teeth on maxilla, premaxilla, and dentary (as opposed to tritoral dentition seen in †Semiolepis, †Paralepidotus, †Macrosemimimus, †Tlayuamichin, and †Callipurbeckia); lacks dermal component of sphenotic (dermal component of sphenotic present in †Semionotus).

Holotype.—UMNH VP 19417 (field number LV05-51): specimen in left lateral view (Figs. 2AB, 3, 4).

Paratypes.—UMNH VP 19418 (field number LV05-100): nearly complete specimen in left lateral view, missing fins and caudal peduncle (Fig. 2CD); AMNH 5682: specimen in left lateral view, missing anterior portion of skull (Schaeffer, 1967:pl. 21 number 5; Fig. 5). AMNH 5683A,B; UMNH VP 19415A, B (field number LV05-12); UMNH VP 19428 (field number LV05-17).

Specific diagnosis.—The diagnosis for this species is based upon the unique combination of the following characters: infraorbitals below the orbit deep, becoming narrower anteriad (infraorbitals below orbit in †Lophionotus sanjuanensis remain deep); presence of narrow infraorbital posterior to orbit (no posterior infraorbital in †L. kanabensis); narrow preoperculum with vertical dorsal arm (more anteriorly inclined in †L. kanabensis); ventral arm of preoperculum long and as equal to slightly wider than dorsal arm (short, broad ventral arm in †L. sanjuanensis); suborbital rectangular and wedge-shaped (suborbital large and rectangular in †L. kanabensis); one pair of lateral extrascapulars and one median extrascapular (one pair of extrascapulars in †L. sanjuanensis and †L. kanabensis); presence of postspiracular (absent in †L. sanjuanensis and †L. kanabensis); gently curved dorsal body border (lacking postcranial hump seen in †L. sanjuanensis); small body size (average SL is 68 mm as compared to average SL of 87.7 mm in †L. sanjuanensis and 50–60 mm SL in †L. kanabensis); lacking dense tuberculation (dense tuberculation seen in †L. sanjuanensis).

Description.—†Lophionotus chinleana, new species, is a small fusiform fish with gently curved dorsal and ventral body borders. Average standard length (SL) of †L. chinleana is 69 mm, with an average maximum body depth (MBD) of about 26 mm. Skull is triangular in shape and slightly longer than deep. Average head length (HL) of †L. chinleana is about 18.3 mm, about 26% of the SL. Ratio of MBD to SL in †L. chinleana is about 37%.

Skull roof contains a pair of parietals and postparietals. Parietals are wide, shorter than species of †Semionotus, and comprise majority of skull roof (Figs. 2–Fig. 3. Fig. 4. 5). Anterior margin is digitate and articulates with ascending process of premaxilla (Figs. 2BD, 4). Parietals are widest at posterior margin, constrict over the orbits, and taper slightly anterior to the antorbital process. Suture between parietals is weakly digitate. Parietals articulate with supraorbitals laterally, postparietals posteriorly, and dermopterotic dorsolaterally (Figs. 2–Fig. 3. Fig. 4. 5).

Postparietals are rectangular, slightly longer than wide. Postparietals articulate with parietals anteriorly, dermopterotics laterally, and extrascapulars posteriorly (Figs. 2–Fig. 3. Fig. 4. 5).

Dermopterotic is rectangular and longer than deep. Anterior margin slightly narrower than posterior margin. Small notch on posterodorsal margin at articulation of dermopterotic and postparietal; notch is convex on dermopterotic and concave on postparietal (Figs. 2–Fig. 3. Fig. 4. 5). Dorsal border curves slightly anteroventrad and articulates with posteroventral corner of the parietal (Fig. 4). Dermopterotic articulates anteriorly with dermosphenotic, ventrally with preoperculum and suborbital, and posteriorly with extrascapular (Figs. 2–Fig. 3. Fig. 4. 5).

Single pair of lateral extrascapulars posterior to postparietals. A median extrascapular is visible on UMNH VP 19417 (Figs. 2B, 3, 4) and AMNH 5682 (Fig. 5). Anterior margin of extrascapulars articulates with postparietals and dermopterotics in a smooth suture. Lateral extrascapulars are trapezoidal in shape, wider at lateral margin and tapering mediad (Figs. 3, 4). Surface of extrascapulars smooth (lacking ornamentation or tuberculation).

Posttemporals are best preserved in UMNH VP 19417 (Figs. 2AB, 3, 4) and AMNH 5682 (Fig. 5). They lie posterior to extrascapulars and triangular in shape, tapering mediad. A small anteroventral process articulates with dorsal margin of operculum. This process is slightly concave posteriorly and articulates with postspiracular between posttemporal and supracleithrum (Figs. 2–Fig. 3. Fig. 4. 5).

Specimens UMNH VP 19417 and UMNH VP 19418 contain poorly preserved snout; however, both specimens preserve paired nasals (Figs. 2–Fig. 3. 4). Median rostral bone cannot be interpreted in any specimen. Nasal is small without a distinctive shape, and sits above the ascending process of the premaxilla (Fig. 4).

Antorbital bone is thin, long, and sits above the premaxilla. It articulates posteriorly with anterior infraorbitals (lacrimals) and curves at approximately a 90-degree angle to a thin process that wraps around anterior of snout (Figs. 2BD, 3, 4).

†Lophionotus chinleana has a closed circumorbital ring, which is well preserved in UMNH VP 19417 (Figs. 2AB, 3, 4), UMNH VP 19418 (Fig. 2CD), and AMNH 5682 (Fig. 5). At least two anamestic supraorbitals are dorsal to orbit and adjacent to lateral edge of parietal (Fig. 4). Supraorbital bones are narrow and smooth. They articulate posteriorly with dermosphenotic and anteriorly with anterior infraorbitals (Fig. 4).

Dermosphenotic forms posterodorsal corner of the orbital ring and bears juncture of infraorbital canal and temporal canal (Figs. 2–Fig. 3. Fig. 4. 5). Dermosphenotic articulates dorsally with lateral edge of parietal, posteriorly with dermopterotic, and its smaller ventral process articulates with infraorbital posterior to orbit (disarticulated in UMNH VP 19417, Fig. 4).

Five infraorbitals comprise posterior and ventral portions of circumorbital ring, and best preserved in UMNH VP 19417 (Figs. 2AB, 3, 4). A single, narrow infraorbital lies posterior to orbit and articulates with dermosphenotic dorsally, suborbital posteriorly, and larger posteroventral corner infraorbital (disarticulated in Figs. 4, 5). Infraorbital in posteroventral corner of circumorbital ring has narrow anterodorsal process and expands posteroventrally to fill open area below suborbital and anterior ramus of preoperculum (Figs. 2–Fig. 3. Fig. 4. 5). Infraorbitals below orbit are deep; series narrows anteriad. Anteriormost infraorbital is narrow and articulates with anterior infraorbital series (lachrymals or lacrimals of traditional terminology). Exact number of anterior infraorbitals is not known because all elements may not have been preserved. Specimen UMNH VP 19417 has three to four anterior infraorbitals preserved (Fig. 4).

†Lophionotus chinleana's suborbital is wedge-shaped, narrow, and deep; lateral surface is smooth and unornamented (Figs. 2–Fig. 3. Fig. 4. 5). It lies flush with other cheek bones, rather than overlying other dermal bones. Dorsal margin is square-shaped and articulates with anteroventral edge of dermopterotic. Anterior margin is straight and articulates with posterior edges of infraorbital posterior to orbit (Figs. 2–Fig. 3. Fig. 4. 5). Anteroventral margin curves convexly posteroventrad and articulates with concave posterodorsal margin of large infraorbital in posteroventral corner of circumorbital series (Figs. 4, 5), closing “gap” between anterior ramus of the preoperculum and circumorbital series.

Preoperculum is crescent-shaped and best preserved in UMNH VP 19417 (Figs. 2AB, 3, 4) and AMNH 5682 (Fig. 5). Dorsal portion of preoperculum is vertical and rod-like. Ventral and dorsal processes are of about equal length (Figs. 2AB, 3–Fig. 4. 5). Dorsal process articulates with operculum posteriorly. Anterodorsally, it articulates with wedge-shaped suborbital and infraorbitals. Dorsal margin contacts posteroventral edge of dermopterotic (Figs. 4, 5). As it curves anteroventrad, its posterior margin contacts ascending process of suboperculum and interoperculum (Figs. 4, 5).

Operculum large and ovoid in shape. Anterior and ventral margins are essentially straight with curving posterior border (Figs. 2–Fig. 3. Fig. 4. 5). Operculum is smooth and lacks ornamentation or ridging. Dorsal border articulates with extrascapular, postspiracular, supracleithrum. Posterior border articulates with supracleithrum and dorsal postcleithrum (Figs. 4, 5).

Suboperculum is overlapped dorsally by ventral margin of operculum. Suboperculum is triangular with curving ventral border that tapers posterodorsad (Figs. 4, 5). Anterior margin contacts interoperculum in a straight suture. A narrow ascending process extends from anterodorsal corner of suboperculum. Exposed depth of suboperculum is about one-third or less than depth of operculum (Fig. 4).

Interoperculum is small and triangular, articulating posteriorly with suboperculum and dorsally overlain by the preoperculum. It has a relatively straight ventral margin (Figs. 2AB, 3–Fig. 4. 5).

Premaxilla robust with ascending process. Ascending process curves inward from anterior process and is covered by nasal and antorbital bones (Figs. 2–Fig. 3. 4). Ascending process articulates posterodorsally with anterior margin of parietals (Figs. 2–Fig. 3. 4). Anterior portion of premaxilla expands horizontally and bears a series of large, conical, blunt teeth (Figs. 2–Fig. 3. 4).

Maxilla short, narrows anteriad to a small process that articulates with premaxilla beneath antorbitals (Figs. 2AB, 3, 4). Maxilla widens posteriorly and ends with a gently curved margin. Maxilla bears a single row of at least seven teeth along ventral margin. Supramaxilla not preserved in any specimen.

Dentary is narrow and bears at least seven to ten styliform teeth. In labial view, trapezoidal angular articulates anteriorly with posterior margin of dentary with a wavy suture (Fig. 4). In lingual view, dentary has thick ventral “lip” (Figs. 2, 4). Dentary cups mediad and prearticular articulates with dorsal margin of ventral lip of dentary. Prearticular is long and tapers anteriad with shape of labial portion of dentary (Figs. 2BD, 4). Retroarticular is poorly preserved on posterior margin of mandible (Fig. 4).

Quadrate and quadratojugal are preserved in UMNH VP 19417 (Fig. 4). Only ventral portion of quadrate is visible; dorsal portion is overlain by infraorbital series. Posteroventral edge of quadrate forms a strong lip that is strongly appressed to quadratojugal. Quadratojugal is long and splint-like, and rests along the dorsal margin of ventral arm of preoperculum (Fig. 4).

Neurocranial elements are not visible in any specimen of †L. chinleana. Ceratohyal is visible on ventral margin, and is robust with expansions at anterior and posterior ends of the bone. Branchiostegals are preserved as a series of long horizontal bones with tapered ends below interoperculum and suboperculum. Five to seven branchiostegals are preserved in UMNH VP 19417 (Figs. 2B, 4).

Supraorbital canal is observed as a row of pores that runs on the lateral edge of the parietals, above articulation with supraorbital bones (Figs. 2B, 3, 4). Canal continues posteriad into postparietals. Supraorbital bones themselves are anamestic (Fig. 4).

Preopercular sensory canal is prominent as a deep groove that runs along anterior side of preoperculum (Figs. 2B, 3–Fig. 4. 5). Ventral arm of preopercular is perforated with a series of ventrally directed grooves, which house exits for branches of preopercular sensory canal (Figs. 3–Fig. 4. 5). Preopercular sensory canal exits anteriorly and continues as mandibular sensory canal (Fig. 4).

Mandibular sensory canal runs along ventral ramus of dentary. It is visible in UMNH VP 19417 (Figs. 2AB, 3, 4) and UMNH VP 19418 (Fig. 2CD) as series of elongated pores.

Infraorbital sensory canal begins in dermosphenotic and travels ventrad through infraorbital series, continuing into anterior infraorbitals and antorbitals (Fig. 4). Posterodorsally, infraorbital sensory canal connects to temporal sensory canal in dermosphenotic (Fig. 4). Connection to supraorbital canal in dermosphenotic cannot be directly observed but may be suggested by presence of pores.

Temporal canal begins in dermosphenotic at junction with infraorbital canal. It continues through lateral portion of the dermopterotic and extrascapular. Canal branches into occipital commissure on extrascapular series. Main canal continues on posttemporal and supracleithrum, where it connects with the main lateral line canal on body (Fig. 4).

Cleithrum, postcleithra, and supracleithrum are preserved in lateral aspect. Two postcleithra sit posterior to operculum and cleithrum. Ventral postcleithrum is trapezoidal to triangular in shape (Figs. 2–Fig. 3. Fig. 4. 5). Dorsal edge of ventral postcleithrum articulates in wavy suture with dorsal postcleithrum (Figs. 2–Fig. 3. Fig. 4. 5). Posterior edge of ventral postcleithrum is slightly. Dorsal postcleithrum is deeper than ventral postcleithrum. It tapers dorsad, and it articulates on anterior margin with operculum anterodorsally, cleithrum anteriorly, and supracleithrum dorsally. Supracleithrum lies dorsal to postcleithrum and posterodorsal to operculum. It is elongate, and ventral process articulates with operculum anteriorly and slightly overlies dorsal postcleithrum (Fig. 4). It is also deep and narrow, and tapers ventrad.

Cleithrum is a robust, long, gently curving, anteriorly inclined bone. It lies ventral to suboperculum and interoperculum and extends dorsad between suboperculum anteriorly and postcleithra posteriorly. Dorsal tip of cleithrum may reach below operculum (Fig. 4).

Well-developed basal fulcra precede all fins of †Lophionotus chinleana. Fringing fulcra originate on first lepidotrichium. Due to incomplete preservation, exact number of lepidotrichia is not known. Number provided here is an estimate of number of lepidotrichia for each fin.

Pectoral fin is preserved in UMNH VP 19417 (Figs. 2A, 3, 4) and is comprised of at least three basal fulcra and approximately seven fringing fulcra on first lepidotrichium. Number of rays is indeterminable in available specimens but is estimated at five lepidotrichia.

Pelvic fins are preserved in AMNH 5682 (though poorly preserved, Fig. 5), UMNH VP 19417 (Figs. 2A, 3) and UMNH VP 19418 (Fig. 2C). They indicate a ventral origin approximately midway between pectoral fins and anal fin. Pelvic fin has approximately two to three basal fulcra and approximately four to five rays, first ray bearing anywhere from three to six fringing fulcra.

Triangular dorsal fin originates just posterior to origination of pelvic fins. It is comprised of one uniserial fulcral scale and three basal fulcra, each longer than preceding one. Fringing fulcra in dorsal fin of UMNH VP 19417 are well preserved and number approximately ten (Figs. 2A, 3). Dorsal fin has eight to 11 branched, segmented rays.

Anal fin is triangular and is slightly smaller to equal in size to dorsal fin (Figs. 2AC, 3, 5). It originates slightly behind posterior edge of dorsal fin, and has three basal fulcra, five fringing fulcra, and seven to nine lepidotrichia, becoming segmented distally.

Caudal fin is not completely preserved in any specimen. Specimen AMNH 5682 (Fig. 5) preserves caudal peduncle and dorsal lobe in impression, but distal ends of rays of fin are faintly preserved or not preserved at all. Caudal fin is abbreviated heterocercal (hemiheterocercal). Dorsal lobe of caudal fin has at least four basal fulcra, long and attenuated (Fig. 5). Ventral lobe is poorly preserved but shows at least three to four basal fulcra (Fig. 3). There are approximately seven rays in dorsal lobe, and nine to 11 rays in ventral lobe (Fig. 5).

Endoskeleton is not observed in any specimen. Body is covered with smooth, rhombic scales. Scales on flank are quandrangular and possess typical peg-and-socket articulation, as is observed in occasional disarticulated scales. Scales vary little in size across flank, only becoming smaller and more rhomboidal in area of caudal peduncle (Figs. 2AC, 5). †Lophionotus chinleana shows relatively little serration on posterior edge of any flank scales, though this could be due to weathering and preservation of the specimens.

There are approximately 30 scales in lateral line. Lateral line scales are notched on posterior margin; these notches allow for an opening of lateral line canal to surface (Figs. 3, 5).

Dorsal ridge scales are similar to those seen in other semionotiforms, with a prominent, acuminate process that points posteriad. Anterior dorsal ridge scales are shorter with a small process. Scales become more elongated posteriad. Dorsal ridge scales are well preserved in UMNH VP 19417 (Figs. 2A, 3) and AMNH 5682 (Fig. 5). Ventral ridge scales are ovate and large. Dorsal scutes on caudal peduncle between dorsal and caudal fins are ovate and have a small acuminate process on posterior end (Figs. 3, 5).

Type locality.—Walt's Quarry, Lisbon Valley, San Juan County, Utah (Fig. 1).

Age, habitat, and distribution.—†Lophionotus chinleana, new species, is found in the Upper Triassic (Norian) Church Rock Member, Chinle Formation. As was discussed previously, the Church Rock Member of the Chinle is interpreted as a freshwater fluvial-lacustrine system. The complete geographic distribution of †L. chinleana is unknown.

Etymology.—The specific name chinleana refers to the Upper Triassic Chinle Formation, from which specimens of this new species have been recovered.

Holotype.—AMNH 8870: complete fish with uncrushed skull (Fig. 6).

Paratypes.—AMNH 8871: dorsoventrally crushed and partly dissociated skull and anterior portion of body (Fig. 7); USNM 18399: laterally compressed skull with well-preserved cheek area and mandible, also section of body including dorsal and anal fins (Schaeffer and Dunkle, 1950:figs. 4, 6); USNM 18400: patches of scales and broken skull elements.

Specific diagnosis.—Revised from Schaeffer and Dunkle (1950) to include only differential diagnostic features. The diagnosis for this species is based upon the unique combination of the following characters: parietals long and narrow (shorter, broad parietals in †Lophionotus sanjuanensis and †L. chinleana); infraorbitals below the orbit narrower than posteroventral infraorbital (compared to deep infraorbitals of †L. sanjuanensis); posteroventral infraorbital articulates directly with dermosphenotic (at least one infraorbital present between dermosphenotic and posteroventral infraorbital in †L. sanjuanensis and †L. chinleana); no infraorbital posterior to orbit (one infraorbital present in †L. chinleana, two infraorbitals present in †L. sanjuanensis); preoperculum anteriorly inclined and “boomerang”-shaped (vertically inclined and L-shaped in †L. sanjuanensis, vertically inclined and crescent-shaped in †L. chinleana); ventral arm of preoperculum wider than dorsal arm (equal width in †L. chinleana); suborbital large and rectangular (narrow and wedge-shaped in †L. chinleana, narrow in †L. sanjuanensis); maxilla edentulous (toothed maxilla in †L. sanjuanensis and †L. chinleana); single pair extrascapulars, lacking median extrascapular (median extrascapular present in †L. chinleana); lacking postspiracular (present in †L. chinleana); gently curved dorsal border (lacking postcranial hump seen in †L. sanjuanensis); small body size (approximately 50–60 mm in available specimens, compared to average 87.7 mm SL in †L. sanjuanensis and average 68 mm SL in †L. chinleana); lacking dense tuberculation (tuberculation present in †L. sanjuanensis).

Description.—†Lophionotus kanabensis is a small fusiform fish with gently curved dorsal border, similar to †L. chinleana. Body is either not completely preserved or distorted in available specimens, so estimated SL is between 50–60 mm. Skull is triangular, longer than deep, and HL is 18 mm, about 30% SL.

Skull roof contains a pair of parietals and postparietals. Parietals are long and narrow (approximately two and a half times longer than wide) and comprise majority of skull roof (Figs. 6A–D, 7). Anterior margin is strongly digitate, and articulates with ascending process of premaxilla (Fig. 6A–D). Parietals are widest at posterior margin, constrict over the orbits, and widen anterior to orbital constriction (antorbital process), and taper anterior to antorbital process. Suture between parietals is linear, with some minor sinuous articulation and asymmetry. Parietals articulate with supraorbitals and anterior infraorbitals laterally, postparietals posteriorly, and dermopterotic dorsolaterally (Fig. 6).

Postparietals are rectangular and slightly longer than deep. Suture between postparietals is undulous. They articulate with parietals anteriorly, dermopterotic laterally, and extrascapulars posteriorly (Figs. 6A–E, 7).

Dermopterotic is rectangular, longer than deep. Dorsal border articulates with lateral edge of postparietals (Fig. 6D). At anterodorsal corner, dorsal margin curves anteroventrad and articulates with dorsoventral corner of parietal (Fig. 6D).

Extrascapulars are poorly preserved in AMNH 8870 (Fig. 6) and USNM 18399. They are triangular (wider at the lateral margin and tapering medially) and articulate anteriorly with postparietals (Fig. 6C). Posterior to extrascapulars, posttemporals are very poorly preserved or obscured. They may be present in AMNH 8871 (Fig. 7B), but poor preservation makes this difficult to interpret.

Nasal and rostral bones are not preserved in any specimen of †Lophionotus kanabensis. Antorbital bone is preserved as a small fragment in USNM 18399 (Schaeffer and Dunkle, 1950:fig. 6B).

†Lophionotus kanabensis has a closed circumorbital ring, but entire series is not preserved in any one specimen. Specimen USNM 18399 retains three poorly preserved elements that are possibly broken elements of a supraorbital (Schaeffer and Dunkle, 1950:figs. 4A, 6B). AMNH 8870 contains one slender supraorbital that articulates with lateral edge of parietal (Fig. 6D).

Dermosphenotic forms posterodorsal corner of orbital ring and bears the junction of the infraorbital and temporal canals. Dermosphenotic articulates dorsally with lateral edge of the parietal, posteriorly with dermopterotic, and ventrally with expanded infraorbital posteroventral to orbit (Fig. 6CD).

A series of infraorbitals comprise posteroventral and ventral portions of circumorbital ring, best preserved in USNM 18399 (Schaeffer and Dunkle, 1950:fig. 6B) and AMNH 8870 (Fig. 6D). Posteroventral corner infraorbital articulates dorsally with dermosphenotic, is large, and expands ventrally to contact anterior ramus of preoperculum (Fig. 6CD). Infraorbital series continues anterior to posteroventral infraorbital and ventral to orbit (Fig. 6D; Schaeffer and Dunkle, 1950:fig. 6B). These infraorbitals are narrow and articulate with anterior infraorbital series. At least two anterior infraorbitals are present, as seen in USNM 18399 (Schaeffer and Dunkle, 1950:fig. 6B). Schaeffer and Dunkle (1950) interpreted one as a circumorbital, and did not label other anterior infraorbital. An anterior infraorbital is also visible in AMNH 8870 (Fig. 6CD).

†Lophionotus kanabensis has a single anamestic suborbital (Fig. 6). Suborbital is large, rectangular, longer than wide (approximately one and a half to two times longer than wide). Surface of suborbital is smooth and overlies anterior portion of dorsal process of preoperculum. Dorsal edge of suborbital articulates with anteroventral edge of the dermopterotic. Anteriorly, suborbital articulates with dermosphenotic and articulates anteroventrally with posterodorsal corner of expanded infraorbital (Fig. 6BCD). Posteriorly, suborbital articulates with anterior edge of preoperculum.

Preoperculum is anteroventrally inclined and boomerang-shaped. Ventral and dorsal processes are of about equal length (Fig. 6CD). Dorsal process articulates with operculum posteriorly (Fig. 6CD), is overlain by suborbital anteriorly, and contacts posteroventral edge of the dermopterotic on dorsal margin (Fig. 6D). Ventrally, preoperculum contacts ascending process of suboperculum and interoperculum. Anterodorsally, it articulates with suborbital and infraorbital in posteroventral corner of orbit (Fig. 6CD).

Operculum large and oval. Anterior and ventral margins are straight, with curving posterior border (Figs. 6, 7). Dermal surface of operculum is smooth and lacks ornamentation or ridging. Dorsal border articulates with extrascapular; posterior border articulates with supracleithrum and cleithrum (Fig. 6BE); ventral border articulates with suboperculum (Figs. 6BCD, 7).

Suboperculum is overlapped dorsally by ventral margin of operculum (Fig. 7B). Suboperculum is triangular with a curving ventral border that tapers posterodorsad toward posterior of the operculum. Anterior margin articulates with interoperculum. A narrow ascending process extends dorsad from anterodorsal corner of suboperculum. Exposed depth of suboperculum is about one-third or less than depth of operculum (Schaeffer and Dunkle, 1950; Figs. 6BCD, 7).

Interoperculum is a small, rectangular bone, articulating posteriorly with suboperculum and dorsally overlain by preoperculum. It is wider at posterior margin and tapers anteriad. It has a relatively straight ventral margin (Fig. 6BCD).

Premaxilla is well preserved and has a large ascending process that contains a large foramen (Fig. 7). Ascending process curves inward from anterior margin of premaxilla and articulates with strongly digitate anterior margin of parietals (Fig. 6ABCD). Anterior portion of premaxilla expands laterally and bears a series of large, conical, blunt teeth (Figs. 6BCD, 7), numbering around five to seven.

Maxilla is short and edentulous. It narrows anteriad to a small medial process that articulates with premaxilla in a hinge-like manner (Figs. 6, 7). Maxilla widens posteriorly and ends with a gently curved margin (Figs. 6, 7). Supramaxilla is poorly preserved in USNM 18399 and articulates with posterodorsal margin of the maxilla (Schaeffer and Dunkle, 1950:fig. 6B).

Lower jaw is best preserved in USNM 18399 and AMNH 8860 (Fig. 6BCD). Dentary is narrow with a high coronoid process and bears at least seven to ten styliform teeth (Schaeffer and Dunkle, 1950:fig. 6B). Schaeffer and Dunkle (1950) noted “somewhat procumbent marginal teeth on either side of the symphysis…An inner row of stouter teeth is also present, but their form cannot be determined.” In labial view, the trapezoidal angular articulates anteriorly with the posterior margin of the dentary with a strongly digitate suture (Fig. 6D). This suture ends dorsally with the articulation of the surangular, a small triangular bone forming the high coronoid process of the lower jaw (seen in USNM 18399, Schaeffer and Dunkle, 1950:fig. 6B).

Quadrate is seen in AMNH 8870 (Fig. 6C) and AMNH 8871 (Fig. 7B), and is a small, thick triangular element, rounded at mandibular articulation (Fig. 6C). It articulates with a splint-like quadratojugal that rests parallel to anterior edge of preoperculum (Fig. 7B). Schaeffer and Dunkle (1950) identified this quadratojugal as a symplectic (Schaeffer and Dunkle, 1950:fig. 6A). Symplectic is visible in USNM 18399 (Schaeffer and Dunkle, 1950:fig. 6B) beneath infraorbital posteroventral to orbit and anterior to preoperculum.

A few palatal elements are visible in all specimens. Ectopterygoid is narrow and curved convexly (Fig. 6BC). Posterior end is flat with short dorsal process and ventral processes (Fig. 6C). Endopterygoid is seen in AMNH 8871 (Fig. 7B) and USNM 18399 (Schaeffer and Dunkle, 1950:fig. 6B), and is broad and rectangular. Parasphenoid is poorly preserved in USNM 18399 but not labeled in any figure.

Complete hyoid arch is not visible in any specimen. Some elements of hyoid arch are visible in a few of the specimens. Specimen USNM 18399 preserves impression of hyomandibula that was described in Schaeffer and Dunkle (1950) as having an “essentially vertical position and about three times longer than the width at the neurocranial articulation.”

Ceratohyal is visible on ventral margin of USNM 18399, and is a robust bone expanded proximally and distally. Schaeffer and Dunkle (1950) identified two poorly preserved ossifications anterior to ceratohyal as hypohyal and “glossohyal,” but due to poor preservation they really cannot be identified with such confidence.

Branchiostegals are preserved as a series of long horizontal bones with tapered ends below the interoperculum and suboperculum. Five to seven branchiostegals are preserved in USNM 18399 (Schaeffer and Dunkle, 1950:fig. 6B). A single branchiostegals is preserved in AMNH 8870 (Fig. 6C).

Supraorbital canal is observed as a row of pores that runs on lateral edge of parietals and continues on the lateral edge of the postparietals (Figs. 6ABC, 7).

Preopercular sensory canal is observed as a series of prominent pores (Figs. 6BCD, 7). Ventral arm of preoperculum is perforated with ventrally directed grooves, which house exits for branches of preopercular sensory canal (Figs. 6C, 7B). Preopercular sensory canal exits ventral arm of preoperculum anteriad.

Mandibular canal runs along ventral ramus of mandible. It is visible in USNM 18399 as a series of large, weathered pores (Schaeffer and Dunkle, 1950:fig. 6B).

Infraorbital canal begins in dermosphenotic and travels ventrally through infraorbital series (Fig. 6CD). It is not seen in anterior infraorbitals.

Temporal canal begins in dermosphenotic and continues posteriad through dermopterotic (Figs. 6D, 7B). Remainder of sensory canal not preserved, but continues as main lateral line system of body.

Pectoral girdle is very poorly preserved in all specimens of †Lophionotus kanabensis. Supracleithrum is preserved in AMNH 8870 and AMNH 8871. It lies dorsal to postcleithrum and posterodorsal to operculum. Supracleithrum has a long ventral process that articulates with operculum. It preserves two pores on AMNH 8871 that represent the main lateral canal (Fig. 7B). Cleithrum is long, gently curving, and anteriorly inclined. It lies posterior to suboperculum and operculum (Fig. 6B).

Basal fulcra precede all fins of †Lophionotus kanabensis. Fringing fulcra originate on the first lepidotrichium. Due to incomplete preservation and/or missing portions of some specimens, exact number of lepidotrichia is not known. Number provided here is an estimate of number of lepidotrichia for each fin.

The pectoral fin is comprised of at least three basal fulcra and approximately seven to nine rays (Fig. 6E). Pelvic fins are not preserved in any specimen.

Dorsal fin is triangular and originates anterior to origination of anal fin. It is comprised of one uniserial fulcral scale and three basal fulcra, each longer than preceding one, and approximately 11 branched, segmented rays (Fig. 6E; Schaeffer and Dunkle, 1950:fig. 4B).

Anal fin is preserved in USNM 18399, is triangular and slightly smaller than dorsal fin (Schaeffer and Dunkle, 1950:fig. 4B). It has three to four basal fulcra, at least three of which are biserial (Schaeffer and Dunkle, 1950). Anal fin has two to five fringing fulcra, and seven lepidotrichia, becoming segmented distally (Schaeffer and Dunkle, 1950).

Caudal fin is preserved in AMNH 8870, but is twisted as to obscure important details (Fig. 6F). It is reconstructed in Schaeffer and Dunkle (1950:fig. 1). Caudal fin is abbreviated heterocercal (hemiheterocercal).

Endoskeleton is not observed in any specimen. Body is covered with smooth, rhombic scales. Scales on flank are quandrangular and possess peg-and-socket articulation, as is observed in occasional disarticulated scales. Scales vary little in size across the flank (Fig. 6E). Schaeffer and Dunkle (1950) recognized a number of flank scales that show about four fine serrations on posterior edge. Scales along lateral line are not well preserved in any specimen. Dorsal ridge scales are not well preserved in any specimen, but do show a prominent, acuminate process that points posteriad.

Schaeffer and Dunkle (1950) did a histological study of scales of specimens of †Lophionotus kanabensis. Scales are composed of a relatively thick, bony layer containing sparse, simple canals (Williamson's Canals) covered by thinner enamel (ganoin). This is a quintessential example of lepidosteoid ganoid scales (Goodrich, 1907).

Type locality.—Near Kanab, Kane County, Utah (approximately Sec.27,T.43S.,R.6W), United States. The original field site was estimated as being one mile east and 400 feet above the old Kanab schoolhouse (Camp, 1930).

Age, habitat, and distribution.—The original specimens of †Lophionotus kanabensis (Schaeffer and Dunkle, 1950) were collected in the Lower Jurassic Whitmore Point Member of the Moenave Formation (the Type Horizon). The Whitmore Point is interpreted as a large lacustrine deposit (Wilson, 1967; Milner et al., 2006b). The complete distribution of †L. kanabensis is in need of further investigation.

Etymology.—Named for the city of Kanab, Utah, United States, near where the Moenave Formation specimens described by Schaeffer and Dunkle (1950) were found.

Remarks and comparisons.—A distinctive morphology that diagnoses †Lophionotus from †Semionotus is the ventrally expanded infraorbital series. All other currently described and valid species of †Semionotus (e.g., †Semionotus elegans, †Semionotus bergeri) have a narrow infraorbital series, where the ventral edge does not articulate with any other bones in the skull (Olsen and McCune, 1991:fig. 6). This arrangement leaves an “open” cheek region, exposing the metapterygoid and endopterygoid. †Lophionotus, however, differs in that the infraorbitals are enlarged and expanded ventrad and anterior to the suborbital bone. This expansion allows the ventral edge of the infraorbitals to contact the anterior ramus of the preopercular. While this character state is also observed in the Chinese taxa †Kyphosichthys grandei (Xu and Wu, 2012) and †Sangiorgioichthys sui (López-Arbarello et al., 2011), European taxa †‘Lepidotes’ microrhis (Wenz, 2003), †Paralepidotus ornatus (Tintori, 1996), †Sangiorgioichtys aldae (Tintori and Lombardo, 2007), †Semiolepis brembanus (Lombardo and Tintori, 2008), and the South American taxa †Araripelepidotes temnurus (Santos, 1990) and †Neosemionotus puntanus (López-Arbarello and Codorniú, 2007), this character, as well as the combination of other shared characters between the taxa (see revised generic diagnosis), confidently defines the species described in this study as belonging to the western United States genus †Lophionotus.

Several characters clearly distinguish †Lophionotus chinleana, †Lophionotus kanabensis, and the previously described species †Lophionotus sanjuanensis. †Lophionotus sanjuanensis is larger and deeper bodied, with a large, tuberculated, postcranial hump (Gibson, 2013). Both †L. chinleana and †L. kanabensis are smaller and slender bodied with a gently curving dorsal border and lacking tuberculation. †L. sanjuanensis has a distinct preoperculum with a short, broad, paddle-like ventral process (Gibson, 2013), whereas †L. chinleana has a vertical crescent-shaped preoperculum and †L. kanabensis has a boomerang-shaped, anteriorly inclined preoperculum. †Lophionotus sanjuanensis and †L. chinleana possess short, broad parietals and more pronounced expanded infraorbitals, whereas in †L. kanabensis, the parietals are longer and slender, and only the posteroventral corner infraorbital is expanded, and the infraorbital ventral to the orbit are narrow. There are other differences: †L. chinleana has a median extrascapular, whereas only one lateral pair of extrascapulars is preserved in †L. sanjuanensis and †L. kanabensis.

Adult specimens of †Lophionotus chinleana are smaller overall when compared to adult specimens of †L. sanjuanensis, in addition to being slender and lacking a postcranial hump and tuberculation. Gibson (2013) identified a juvenile specimen of †L. sanjuanensis that, although similar in size to †L. chinleana, clearly possess a postcranial hump (though lacking tuberculation), and similar skull morphology as the adult forms of †L. sanjuanensis (Gibson, 2013:fig. 7).

Phylogenetic relationships of †Semionotidae.—The parsimony analysis in TNT found the same 16 most parsimonious trees (tree length of 286, consistency index of 0.399, retention index of 0.727) for each of the 20 independent search replicates. The strict consensus and 50-percent majority rule consensus tree from the 16 most parsimonious trees are shown in Figure 8, and are largely consistent with the results of López-Arbarello (2012), indicating a monophyletic Ginglymodi and †Semionotiformes, and with †Lepidotes removed from †Semionotiformes and placed within Lepisosteiformes. Unambiguous synapomorphies to all 16 equally parsimonious trees are plotted on the strict consensus tree (Fig. 8), with symmetric bootstrap group frequencies for each node plotted on the 50-percent majority rule tree (Fig. 8).

Fig. 8. 

Phylogenetic relationships of ginglymodian fishes based on a strict (left) and 50-percent majority rule (right) consensus tree from 16 equally parsimonious trees. Unambiguous synapomorphies occurring in each of the 16 trees are indicated on the strict consensus, with symmetric bootstrap frequencies for clades indicated on the 50-percent majority rule consensus tree. (A) †Semionotidae; (B) †Semionotiformes; (C) Lepisosteiformes; (D) Ginglymodi.

Gibson (2013) placed †Lophionotus within the order †Semionotiformes, and the results of this study indicate that the genus †Lophionotus is monophyletic and sister to the genus †Semionotus. The genus †Lophionotus is herein recognized as belonging to the family †Semionotidae (†Lophionotus and †Semionotus) based on the following synapomorphic characters: presence of a triangular lateral expansion of antorbital portion of parietal (frontal), presence of large basal fulcra in the dorsal and anal fins, and presence of dorsal ridge scales with a conspicuous high spine (Fig. 8). The genus †Lophionotus is supported by the two unambiguous synapomorphies 23 and 36, with a clade comprised of the Late Triassic species †L. sanjuanensis and †L. chinleana sister to the Early Jurassic species †L. kanabensis (Fig. 8). Within the genus †Semionotus, the eastern United States species †S. elegans is the sister group to a clade that includes the African species †S. capensis and the European species †S. bergeri (Fig. 8).

The work in this study furthers our knowledge of extinct biodiversity. It also clearly shows the need for continued collecting and taxonomic work, which in turn provide new insights into the evolutionary relationships of extinct and modern fishes.