Simocormus, Maxwell & Lambers & López-Arbarello & Schweigert, 2020

Maxwell, Erin E., Lambers, Paul H., López-Arbarello, Adriana & Schweigert, Günter, 2020, Re-evaluation of pachycormid fishes from the Late Jurassic of Southwestern Germany, Acta Palaeontologica Polonica 65 (3), pp. 429-453 : 432-438

Genus Simocormus nov.

ZooBank LSID: urn:lsid:zoobank.org:act:3A5ADFC0-37A2-4A8A-9981-D59499A8D8F5

Type species: Simocormus macrolepidotus sp. nov.; see below.

Etymology: From Greek simo, snub-nosed, in reference to the profile of the rostrodermethmoid in lateral view and cormus, tree-trunk, here used to indicate affinities to Pachycormidae .

Diagnosis.— As for the type and only known species. Simocormus macrolepidotus sp. nov. Description ( SMNS 96988 /4 from Nusplingen, Fig. 3A 1 ) .

Figs. 2 , 3 . — General appearance: SMNS 96988/4 ( Fig. 3A 1 ) consists of a skull preserved in right ventrolateral view,

1894 Hypsocormus Wagner, 1863 ; Woodward 1894: 511.

1895 Hypsocormus macrodon ( Wagner, 1863) ; Woodward 1895: 305. pectoral girdles and left pectoral fin. The specimen as

1992 Hypsocormus macrodon ( Wagner, 1863) ; Lambers 1992: 262: preserved measures 28 cm long and 33 cm deep. The skull fig. 17. length (anteriormost point of rostrodermethmoid to

2012 “ Hypsocormus ” macrodon ( Wagner, 1863) ; Friedman 2012: posteriormost point of the opercle) is 21 cm,

947–948, fig. 2. corresponding to a fish of ~ 105 cm SL.

2019 Hypsocormus Wagner, 1893 ; Liston et al. 2019: 6. Skull roof and snout: The rostrodermethmoid forms the

ZooBank LSID: urn:lsid:zoobank.org:act: 3D8F19DE-D08E-4B30- anterodorsal border of the mouth. It does not project anterior

AF7B-BB7CBE2E5EE1 to the mandibular symphysis ( Fig. 3A 1 –A 3 ). As preserved

Etymology: From Greek macrolepidotus , large scales; present in a 1: 1 in lateral view, the rostrodermethmoid bears a single large,

ratio with the axial elements. procumbent tooth (“tusk” or “fang”), with an apicobasal

Holotype: NHMUK PV P 6011, an articulated fish preserving the skull height of 12.2 mm. Posterior to the fang, the rostrodermeth-

in ventrolateral view ( Fig. 2 ). moid bears some small teeth (ca. 1.5 mm apicobasal

Type locality: Germany, Bavaria. height). The anterior rostrodermethmoid is ornamented

Type horizon: Late Jurassic. with tuber-cles. While sensory pits are present, poor

Material.—Abundant referred material is present in col- preservation and complex ornamentation prevent tracing

lections around the world (see Table 2 for some examples), the course of the sensory canal.

including SMNS 96988/4 (described below). Simocormus The premaxilla is approximately oval in shape and taper-

macrolepidotus gen. et sp. nov. comprises material previ- ing anteriorly to form a process parallel to the oral margin.

ously referred to Hypsocormus macrodon . It is a short, narrow, dentigerous bone articulating with the

Diagnosis (modified from Woodward 1895 and Wagner rostrodermethmoid anteriorly and the maxilla posteriorly

1863).— Large fish with an elongate body shape, up to ( Fig. 3A 1 –A 3 ). Its lateral surface is ornamented with

1.5 m in length, with skull approximately 20% SL; snout tuber-cles, which gradually grade into larger denticles and short and obtuse, with large rostrodermethmoidal teeth di- small teeth ventrally. The premaxilla supported at rected almost vertically; second suborbital (so2) element minimum two moderately large teeth. The more posterior much larger than the first suborbital (so1), and ornamented of these has an apicobasal height of 4.4 mm, the with prominent radiating ridges; external bones, scales, and anteriormost appears to have been larger.

fin rays ornamented with tubercles; scales present in a 1:1 The maxilla is elongate and narrow (dentigerous edge =

ratio with the axial skeleton; small dorsal fin originating 82 mm, max. depth = 9 mm), gently bowed with a slightly posterior to the anal fin; caudal fin with strong development concave dentigerous margin. The external surface of the of lepidotrichial segmentation. maxilla is ornamented with tubercles, which gradually grade

Table 2. Comparative Late Jurassic pachycormid material examined. All localities into larger are in denticles Bavaria, and Germany small. Age teeth correlations ventrally for (Fig localities. 3A3). from The

Schweigert (2007). “–” age or exact locality unknown.

larger maxillary teeth are located lingual to these denticles. The maxillary teeth are largest at approximately the midpoint of the element, but are in general 2–3 mm in apicobasal height. The marginal dentition extends the entire length of the maxilla. Some larger teeth (up to 9 mm in apicobasal height) are scattered between the maxilla and dentary, but it is unclear whether these originate from the dentary or a more medially positioned element. The posterodorsal maxilla is overlapped by the supramaxilla.

The supramaxilla is relatively large (38 mm long and 14 mm deep at its posterior end), overlapping the posterior maxilla and ventral edge of so2 ( Fig. 3A 1 , A 2 ). The supramaxilla is roughly triangular in shape, and ornamented with tubercles, which are best developed on its anteroventral edge.

The antorbital is situated posterior to the rostrodermethmoid, dorsal to the premaxilla, and overlies a bone of uncertain identity. The antorbital is not well preserved, but its clearest characteristic is a posterodorsally directed process with a series of dorsally oriented grooves extending along its anterior edge ( Fig. 3A 1 –A 3 ).

It is likely that some fragments posterodorsal to the rostrodermethmoid and anterior to the dermosphenotic correspond to the nasal; however, these are poorly preserved. The dermosphenotic forms at minimum the posterodorsal edge of the orbit. Its lateral edge is dorsally convex, curving ventrally. Sensory pits are present in the dermosphenotic at the posterodorsal corner of the orbit.

The right side of the skull roof is preserved, consisting of the frontal, parietal, and dermopterotic ( Fig. 3A 1 , A 2 , A 4 ). It is crushed anteriorly, medial to the dermosphenotic, but was at least 107.1 mm in length (anterior rostrodermethmoid to posterior end of ornamented surface of the parietal, measured along the midline) and 25.6 mm in posterior width excluding the lateral articular facet for so1). The skull roof is covered with tubercular ornamentation ( Fig. 3A 4 ). The supraorbital sensory canal extends from the medial dermosphenotic posteriorly through the lateral dermopterotic, parallel to the edge of the skull roof. The lateral dermopterotic forms an unornamented facet, this one edged laterally with a feathered bone structure ( Fig. 3A 4 ). The facet is interpreted as the articular facet for so1, and is oriented anteroposteriorly and is roughly straight. The frontal and parietal appear to have contacted their antimeres via a straight suture. A mediolaterally oriented linear feature in the ornamentation bordered by ridges, parallel to the posterior edge of the parietal, presumably corresponds to a sensory canal. Posteriorly, the dermopterotic, with a small medial contribution from the parietal, forms a large, unornamented concave flange interpreted as the articular facet for the posttemporal.

A small sagittal eminence was present, extending as far forward as the dermosphenotics. The frontals and parietals appear to be primarily involved, although comparative development of this eminence is difficult to evaluate because the specimen is quite flat. Based on the morphology of the posterior parietals (not thickened or divergent), the temporal boss is unlikely to have projected over the parietal region ( Gouiric-Cavalli and Cione 2015).

Posteroventral to the dermopterotic is an oval fragment of very thin bone traversed by a prominent sensory canal ( Fig. 3A 1 , A 2 , A 4 ), interpreted as a fragment of the presupracleithrum.

An element preserved anterior to the mandible is possibly a vomer based on position and approximate shape. The visible part of the tooth preserved overlying this bone is not ankylosed to it, and it is unclear if the tooth and bone were originally associated.

The sclerotic ring has been displaced dorsally, and is partially overlying the skull roof ( Fig. 3A 1 , A 2 ). It is well ossified. The external surface of the ring is convex. Around the edge of the aperture, the bone of the sclerotic ring is weakly ornamented with a similar roughened- to tubercular texture as the other cranial elements. Away from the aperture, the external surface of the ring is smooth.

Cheek and opercular series: The posterolateral surface of the skull is dominated by a greatly enlarged so2 ( Fig. 3A 1 , A 2 ). so1 is not preserved; however, it was certainly much smaller than so2. Both the right and the left suborbitals are preserved in external view; that on the right has been displaced ventral to the skull. so2 is roughly triangular in shape, with a concave ventral edge and a convex posterior edge. The posterior third of the ventral edge is more strongly deflected ventrally, and a small facet on the ventral edge immediately anterior to this deflection point would have been overlapped by the supramaxilla. The anteriormost corner of the suborbital has been invaded by sensory canals, suggesting that the ventralmost infraorbital may be fused to the suborbital. The suborbital has a roughened ornamentation, becoming more noticeably tubercular towards the ventral edge. However, the most obvious aspect of the ornamentation are five ridges, beginning at approximately 1/3 of the length of the suborbital and extending to the posterior edge. A single long, narrow infraorbital is preserved between the braincase and skull roof ( Fig. 3A 1 , A 2 ).

The preopercle ( Fig. 3A 1 , A 2 ) is preserved at the posteroventral edge of the subopercle. The dorsal ramus has been displaced internal to the suborbital, and is visible only in the deformation of the latter. The preopercle broadens ventrally, and is exposed externally near the opercle-subopercle contact, curving anteriorly to the angular. It is ornamented with tubercles, and carries the preopercular sensory canal. No interopercle is preserved. The opercle ( Fig. 3A 1 , A 2 ) is a large bone (68 mm deep, ventral edge 45 mm long), much larger than the subopercle. Its posterior dorsal edge is broken; however, based on preserved growth lines it is clear that the dorsal edge was narrower than the ventral edge. The opercle-subopercle suture is oriented anteroposteriorly, and slightly dorsally. The opercle is ornamented with tubercles. The subopercle ( Fig. 3A 1 , A 2 ) is small and quadrangular in external view (externally exposed portion 23 mm deep, 48 mm long). The externally exposed portion is ornamented with tubercles. The dorsal edge underlies the opercle, and is anteriorly drawn up into a dorsal process. The subopercle contacts the preopercle anteriorly.

The gular is situated between the lower jaw rami. Preservation of this element is quite poor and little can be said regarding its morphology, however ornamentation at the anterior end is coarsely tubercular.

Numerous branchiostegal rays are present between the gular and the subopercle. This region is poorly preserved and is covered by a hash of bone fragments, scales, teeth, and pharyngeal denticles. The outward-facing surface of each branchiostegal ray is divided into a smooth posterior surface that is overlapped by the succeeding ray, and an ornamented anterior surface covered by a roughened- to tubercular ornamentation. The ornamented portion of each branchiostegal ray is a wide as the smooth portion, indicating that an individual ray had relatively limited external exposure.

Endocranium: The endocranium is preserved as disarticulated elements anterodorsal to the suborbital. The lateral ethmoid is robust, with a thinner dorsal process and an anteroposteriorly expanded base ( Fig. 3A 3 ). A ventral depression separates the anterior and posterior edges. A posterior element may represent a fragment of the anterior basisphenoid.

The basisphenoid is situated posterior to the ethmoid region. It has a complex morphology, with an anterior dorsal projection making up part of the interorbital septum Fig. 3A 3 ), a posterior dorsal lamina, and a posterolateral projection. The dorsal edge of the interorbital projection is thickened and curves laterally. The posterior edge of this interorbital process forms a semi-circular notch, part of the foramen for the optic nerve (II). At the midpoint of the interorbital projection anterior to the foramen is a prominent tubercle. Ventral to the foramen for cranial nerve II, the basisphenoid forms a lateral projection. The posterior dorsal lamina of the basisphenoid extends further dorsally than the interorbital projection, and contacts the pterosphenoid. The posterolateral projection lies on top of the dorsal lamina, and may represent the anterior edge of the myodome that has been displaced due to crushing.

The pterosphenoid articulates anteriorly with the posterior lamina of the basisphenoid. Its posterior surface is concave, and the posterior edge is thickened. Ventrally, the pterosphenoid forms the dorsal edge the foramen for the oculomotor nerve (III). A roughened ridge extends dorsal to the foramen. Posterodorsal to the pterosphenoid, a small fragment of the sphenotic projects ventral to the dermosphenotic. The dermal and endochondral portions are unfused, and are clearly separated by matrix. The prootic is preserved anteromedial to the hyomandibula ( Fig. 3A 4 ). The lateral surface is concave, traversed by two ridges. Anteriorly, the element is pierced by several foramina, however, the influence of lateral compression on the shape precludes more detailed interpretations.

The basi-exoccipital is preserved in condylar view Fig. 3A 4 ), partially overlain by the presupracleithrum. There are two condyles, consisting of oval facets lacking perichondral lining and separated by a groove, proportionately much larger than those described in Pachycormus ( Mainwaring 1978) .

Branchial arch: Only a portion of the dorsal end of the right hyomandibula is exposed. The articular end is convex. The right quadrate is preserved in medial view, slightly displaced from the glenoid ( Fig. 3A 1 , A 2 ). Its articular end is well-developed and anteroposteriorly elongate, directed anteroventrally and forming two articular facets delineated by a groove on the medial surface. There is a constriction separating the articular end of the quadrate from the fan-shaped dorsal portion, characterized by a well-developed posterior notch. A prominent tubercle is positioned at this point on the anterior half of the quadrate. Anterior to the scapulocoracoid, a semicircular bony plate-like element and an additional endochondral element are preserved; their identity is unclear but they may belong to the visceral arch.

Mandible: The lower jaw consists of three elements in external view: the angular, surangular, and dentary ( Fig. 3A 1 , A 2 ). In overall shape, the mandible is robust and relatively deep, deflected slightly dorsally at its anterior end. It measures 146 mm in anteroposterior length. The dentary makes the largest contribution to the external surface of the mandible. The dentary is thickened along its dorsal edge, and is ornamented with striations postero-dorsally and tubercles over most of its surface ( Fig. 3A 3 ). These become more pronounced towards the dentigerous margin and at the symphyseal end. The tubercles at the dentigerous margin lingually grade gradually into an external field of small teeth. Whether the larger lingually placed teeth are borne on the dentary itself is unclear. A posterodorsally-anteroventrally angled suture separates the posterior dentary from the angular and surangular ( Fig. 3A 1 , A 2 ). However, the suture between the latter two elements is largely obscured. The mandibular canal does not extend parallel to the ventral edge of the lower jaw but is roughly oriented from the posterior ventral corner of the lower jaw towards the symphysis. The posterior and ventral edges of the mandible form a ~60° angle, such that the glenoid is directed posterodorsally.

Some details of the left mandible are visible in medial view. The articular is exposed on the posterior end, and the glenoid surface is preserved. Two facets are visible, separated by a slight change in angle: an anteromedial facet, and a posterolateral facet. These correspond to the two facets of the quadrate. At the posterior end of the glenoid, the articular forms a small process. The dorsal portion of the prearticular is also exposed, but has been slightly posteriorly displaced. A posterior process of the prearticular forms the anteromedial edge of the glenoid.

Dentition: The teeth are conical, with relatively blunt acrodin caps ( Fig. 3A 3 ). The cap enameloid is smooth, but the collar enameloid bears well-developed apicobasal ridges. Most of the marginal teeth are slightly curved lingually. At least four size classes of teeth are present on the marginal jaw elements.

Numerous pharyngeal denticles are preserved. These are tiny, slender structures, much more acutely pointed than the teeth. As far as can be determined, an acrodin cap is also present.

Pectoral girdle: The right supracleithrum has been ventrally displaced ( Fig. 3A 1 , A 2 ). It is a large, flat bone, with a striated texture along its anterior edge and with granular ornamentation posteriorly. The anterior end is broken.

Both cleithra are exposed, the right in external view and the left in internal view. The cleithra are robust, with a well-developed slender ascending posterior process that broadens ventrally. In external view, a short, slender medially directed ventral ridge is visible anterior to the scapulocoracoid facet. The anterior edge of this ridge forms a concave lamina of bone. The external ventral portion of the cleithrum is covered by reticular ornamentation. In internal view, the ascending posterior process forms a ridge on the internal surface of the cleithrum, extending to a facet for articulation with the scapulocoracoid ( Fig. 3A 5 ). This facet is strongly ossified, forming a well-defined cup. The dorsal edge of the ventral cleithrum is convex in internal view, but recessed relative to the dorsal process. Anterior to the scapulocoracoid facet is a second anterior ridge, bordered ventrally by a concavity. Several postcleithra remain in articulation with the left cleithrum, and are exposed in medial view ( Fig. 3A 1 , A 2 ). These include two small dorsal postcleithra, as well as a much larger ventral postcleithrum.

The left scapulocoracoid is preserved in anterior view, slightly displaced from articulation with the cleithrum ( Fig. 3A 1 , A 2 , A 5 ). Although most of the surfaces are weakly ossified, the internal surface of the upper muscular canal is well-ossified, as is a posterior facet in articulation with the second radial. A convex facet is present for articulation with the propterygium, separated by a groove from the second radial facet. The right scapulocoracoid is exposed in external view.

The propterygium and anteriormost fin ray are fused. The propterygium is proximodistally short, and has a concave surface anteriorly for articulation with the endochondral girdle ( Fig. 3A 5 ). The posterior end consists of a convex bulbous extension spanning lepidotrichia 2–4. Lateral to the concave surface, the opening of the propterygial canal is visible. Both the right and left second pectoral radials are preserved; these are somewhat oval in shape, and are proximally thickened. An extremely elongated, spindle-shaped posterior radial is visible on the left side, overlapped by scales and lepidotrichia.

The left pectoral fin is slightly disrupted around its edges, but consists of a minimum of 28 lepidotrichia. The fin is gladiform in overall morphology (sensu Liston et al. 2019), with a broad base and a narrow tip, and is long in proportion to the skull (preserved length = 16 cm, proximal base = minimum 5 cm). Each fin ray is ornamented with grooves and tubercles ( Fig. 3A 5 ), and becomes flattened and broadened distally. The distal half of the anteriormost ray is ornamented with a series of small ridges, similar to some specimens of Pachycormus ( Wenz 1967) . However, unlike in Pachycormus no separate fringing fulcra are observed. The posterior fin rays are segmented distally. The fin is composed of two distinct regions: an anterior region, with relatively narrow rays, and a small posterior region, in which the lepidotrichia branch asymmetrically with a narrow anterior ramus and a wide posterior ramus, causing the posterior edge of the fin to be deflected ( Fig. 3A 5 ). The longest rays are found along the anterior fin.

Squamation: Fragmentary scales are preserved in the area around the pectoral fin and between the mandibular rami. These show a roughened, tuberculated surface.

Remarks.— SMNS 96988/4 is referable to Pachycormidae based on the presence of a toothed rostrodermethmoid separating the premaxillae, a supramaxilla posterodorsal to the maxilla, a large, plate-like posteriorly expanded suborbital, and a pectoral fin with reduced lepidotrichial segmentation and asymmetrical branching of fin rays ( Mainwaring 1978; Lambers 1992; Liston 2008). Based on the robust mandible and dentition, in particular the presence of large paramedial teeth on the rostrodermethmoid, SMNS 96988/4 is most consistent with the clade of pachycormids containing Hypsocormus and macrocarnivorous forms, and likely also Sauropsis and Pseudoasthenocormus ( Liston 2008; Friedman et al. 2010).

SMNS 96988/4 differs from Orthocormus spp. , Orthocormus? tenuirostris , and Protosphyraena in the absence of both an edentulous projection of the rostrodermethmoid anterior to the mandibular symphysis and laterally compressed teeth, and from Pseudoasthenocormus in the absence of an overbite. In addition, the rostrodermethmoid is not dorsally flattened in SMNS 96988/4, and the skull roof forms a steep angle with the horizontal, unlike in the aforementioned genera ( Mainwaring 1978). Thus, SMNS 96988/4 is most consistent with the genera Sauropsis , Simocormus , and Hypsocormus .

Hypsocormus historically comprises two species from the Late Jurassic of Germany, H. insignis and “ H. macrodon ” (= Simocormus macrolepidotus ) ( Table 1). Hypsocormus leedsi , from the Middle Jurassic of the UK, is very fragmentary, making meaningful comparisons with SMNS 96988/4 difficult ( Mainwaring 1978, Lambers 1992). Neither Hypsocormus insignis nor Simocormus macrolepidotus gen. et sp. nov. are well described. H. insignis is a fusiform fish, with cranial elements ornamented with sparse and fine granulations, which are better developed on the dentary and maxilla, and pectoral fin rays lacking segmentation ( Woodward 1895). Although it has been described as having smooth scales, personal observation (SNSB-JME SOS 3557) suggests that the scales near the dorsal midline are small and have a finely granulated ornamentation. Simocormus macrolepidotus , in contrast, is an elongate fish with a posteriorly placed dorsal fin, larger than but otherwise similar in morphology to Sauropsis depressus (see below). The well-developed longitudinal ridges ornamenting so2 appear to be unique to Simocormus macrolepidotus ( Woodward 1895) .

Sauropsis comprises three species from the Late Jurassic of Germany, Sauropsis longimanus , Sauropsis depressus , and Sauropsis curtus ( Eastman 1914) , of which Sauropsis depressus is relatively abundant. Fragmentary material referred to Sauropsis has also been identified from the Late Jurassic of Cuba ( Sauropsis woodwardi ; Gregory 1923), and in addition, two Early Jurassic species have been described Sauropsis veruinalis and Sauropsis latus ; White 1925). As with Hypsocormus , all species of Sauropsis are poorly known and the genus is in need of revision. The three Late Jurassic Bavarian species are all relatively small (<50 cm SL). Sauropsis longimanus and Sauropsis curtus can be differentiated from SMNS 96988/4 by the extensive external exposure of the preopercle in lateral view, as well as the very high, narrow opercle (see e.g., Lambers 1992: fig. 14). Sauropsis depressus is more problematic, as it shares many characteristics with Simocormus macrolepidotus gen. et sp. nov. (e.g., elongate body shape, posteriorly placed dorsal fin, large scales, large supramaxilla, relative size, shape, and ornamentation of the opercle and subopercle, segmentation of distal pectoral lepidotrichia). However, it appears to lack the pattern of radiating ridges on the suborbital characteristic of Simocormus macrolepidotus .

When compared to all other Late Jurassic pachycormids from Germany, SMNS 96988/4 is most consistent with Simocormus macrolepidotus gen. et sp. nov., with no observations contradicting referral to this taxon. In addition to the characteristics discussed above, the two share large body size and flattened, expanded posterior lepidotrichia.

Stratigraphic and geographic range.— Kimmeridgian–Tithonian, Bavaria and Baden-Württemberg, Germany .

Figures

Fig. 3. Pachycormid fish Simocormus macrolepidotus gen. et sp. nov. (SMNS 96988/4) from the Kimmeridgian (Jurassic) of Nusplingen, Germany. Specimen in ventrolateral view (A1). Explanatory drawing of skull (A2). Close-up of jaws, showing ornamentation, dentition, and distribution of denticles external to the main tooth row on both the maxilla and dentary (A3). Skull roof and posterior braincase, asterisk indicates foramina of uncertain identity in the prootic (A4). Pectoral fin and girdle, scapulocoracoid outlined to better distinguish the poorly ossified endochondral component from the matrix (A5). Arrows indicate the expanded posterior hemilepidotrchia. Abbreviations: ao, antorbital; an, angular; ar, articular; bo, basi-exoccipital; bsp, basisphenoid; bsr, branchiostegal rays; cl, cleithrum; cl(f), facet on the internal cleithrum for articulation with the endochondral pectoral girdle; de, dentary; dpt, dermopterotic; dpcl, dorsal postcleithrum; dspo, dermosphenotic; f, frontal; gu, gular; hyo, hyomandibula; io, infraorbital; le, lateral ethmoid; mc, mandibular canal; mx, maxilla; hlt1, dorsal and ventral first hemilepidotrichia; op, opercle; pa, parietal; par, prearticular; pcl, postcleithra; pm, premaxilla; pop, preopercle; pr, posterior pectoral radial; pro, prootic; prpt, propterygium; psc, presupracleithrum; pts, pterosphenoid; qu, quadrate; r2, second pectoral radial; rdme, rostrodermethmoid; sa, surangular; sc, sensory canal; scl, supracleithrum; sco, scapulocoracoid; scr, sclerotic ring; smx, supramaxilla; so2, second suborbital + fused infraorbital; sop, subopercle; spo, sphenotic.

Fig. 1. Nusplingen and other localities of fossiliferous Late Jurassic Plattenkalks in SW Germany (modified from Fürsich et al. 2007 based on Schweigert 2007).

Fig. 2. Pachycormid fish Simocormus macrolepidotus gen. et sp. nov. (holotype NHMUK PV P 6011) from the Late Jurassic of Solnhofen, Bavaria, Germany. Overview (A1), detail of skull and pectoral fins illustrating the prominent ridged ornamentation on suborbital 2 (A2). © The Trustees of the Natural History Museum, London, photographer A. McArdle, used with permission.

Fig. 4. Pachycormid fish Hypsocormus Wagner, 1863 from the Late Jurassic of Germany. A. Hypsocormus insignis (Wagner, 1860) (holotype SNSB-BSPG AS VI 4a, mirrored), Bavaria, Germany. B. Hypsocormus posterodorsalis sp. nov. (holotype GPIT/OS/00836), Nusplingen, Germany. Arrows indicate anterior insertion of median fins.

Fig. 5. Pachycormid fish Hypsocormus Wagner, 1863 from the Late Jurassic of Germany. A. Hypsocormus posterodorsalis sp. nov. (GPIT/OS/00836) from the Kimmeridgian of Nusplingen. Skull preserved in right lateral view, photograph (A1), explanatory drawing (A2). Braincase in lateral view, photograph (A3), explanatory drawing (A4). Anterior skull in ventrolateral view showing the maxillary dentition and the absence of strong tubercular ornamentation on the lateral surface of the maxilla (A5). Posterior dentary teeth, white arrows indicate posterior two tooth positions showing twinning of tooth germ, black arrows indicate small teeth external to main dentary tooth row (A6). Temporal boss in lateral view (A7). B. Hypsocormus insignis Wagner, 1860) (holotype SNSB-BSPG AS VI 4a), dentition in lingual view showing apicobasal ridges (anterior to the left). Abbreviations: an, angular; bo, basi-exoccipital; cl, cleithrum; de, dentary; dpcl, dorsal postcleithrum; dpl, dermopalatine; ecp, ectopterygoid; enp, entopterygoid; fica, foramen for the internal carotid artery; ex,?extrascapular; f.VII?, foramina potentially transmitting the facial nerve; fstIX, foramen for the supratemporal branch of the glossopharyngeal nerve; fsX, foramen for a subsidiary branch of the vagus nerve; hyo, hyomandibula; ic, intercalar; jg, jugular groove; mx, maxilla; oca, occipital arch; oo, opisthotic; op, opercle; op.hyo, opercular process of the hyomandibula; ps, parasphenoid; pt, posttemporal; sc, sensory canal; scl, supracleithrum; sco, scapulocoracoid; vf, vestibular fontanelle; vpcl, ventral postcleithrum; X, formen for the vagus nerve.