Hypsocormus posterodorsalis, 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 : 438-445

Hypsocormus posterodorsalis sp. nov.

Figs. 4B , 5A , 6–8 .

Etymology: From Latin posterodorsalis , posterior on the back; in reference to the position of the dorsal fin opposite the anal.

Holotype: GPIT /OS/00836, a complete fish skeleton in right lateral view.

Type locality: Nusplingen, Baden-Württemberg, Germany.

Type horizon: Nusplingen Lithographic Limestone, Upper Jurassic, upper Kimmeridgian, Hybonoticeras beckeri Zone , Lithacoceras ulmense Subzone ( Schweigert 1998) .

Material.— Holotype only.

Diagnosis.—As per genus, with the following unique combination of features: Elongate-fusiform body shape with the ratio of maximum body depth to standard length approximately 23% (less elongate than Simocormus macrolepidotus gen. et sp. nov. [~15%], less deep-bodied than H. insignis [~30%]),prominent temporal boss projecting onto the parietal region, maxilla with smooth to slightly granular ornamentation (prominent tubercles in Simocormus macrolepidotus , H. insignis referred material), dentary with robust, acutely pointed teeth, supraneurals absent immediately posterior to the skull (unlike all other pachycormids), pelvic fin lepidotrichia half the length of pectoral lepidotrichia, pelvic plate with expanded posterior process and narrow, elongate anterior process (as in Simocormus macrolepidotus , Orthocormus ), dorsal fin opposite anal fin (unlike Simocormus macrolepidotus , Orthocormus , Pseudoasthenocormus , H. insignis ), anterior hypural plate offset from anteroventral edge and with prominent lateral foramen and hypural process (similar to Simocormus macrolepidotus ).

Description.— General appearance: GPIT/OS/00836 ( Fig. 4B 1 ) consists of a mid-sized pachycormid fish (SL = 690 mm) preserved in right-lateral view. The skull has been slightly disrupted ( Fig. 5A 1 , A 2 ), and the scale covering on the right lateral side is absent, however the fish is largely articulated.

Cranium: The skull bones are for the most part very difficult to interpret. The rostrodermethmoid and premaxilla appear to be missing. The maxilla is a robust, mediolaterally thickened element with a broad, flat dorsal surface, bearing small teeth along its ventral margin. It becomes mediolaterally compressed posteriorly. The dentigerous margin is straight. The external surface of the maxilla is roughened in places, but lacks tubercular ornamentation ( Fig. 5A 5 ). A small anterior region of the dorsal skull roof is preserved in external view anterior to the orbit. It bears granular to tubercular ornamentation, and appears to carry a sensory canal, determined based on the presence of pores, suggesting possible identification as part of the anterior frontal and nasal. Otherwise, the dorsal dermatocranium has been rotated to the left, such that none of the bones of the skull roof are preserved in external view.

A prominent temporal boss is present ( Fig. 5A 1 , A 2 , A 7 ), and projects anteriorly over the parietal region. It consists primarily of the enlarged posttemporal posteriorly and the small, anteromedially positioned?extrascapular. Ornamentation on the external surface of both elements is strongly tuberculated. The ventrolateral surface of both bones is concave and smooth. The posttemporal bears a robust descending process for articulation with the braincase; its dorsal (external) portion transmits the sensory canal.

The braincase is preserved in lateral view ( Fig. 5A 3 , A 4 ). It is anvil-shaped in overall form. The large basi-exoccipital makes up the posteroventral portion of the braincase. Ventrally, the basi-exoccipital is underlain by the parasphenoid, while its anterodorsal edge forms a thickened ridge, articulating with the intercalary and opisthotic. The intercalar is small and rounded, with a lumpy external surface. Its suture with the opisthotic is not clear, either anteriorly or ventrally. Ventrally, a projection of the intercalar towards the basi-exoccipital forms what we interpret as the posterior edge of the vagus foramen. A discrepancy with the state described in both Orthocormus and Pachycormus exists, in which the basi-exoccipital is excluded from the vagus foramen in lateral view by a process of the intercalar ( Pachycormus ; Mainwaring 1978) or a process of the opisthotic with a small contribution from the intercalar ( Orthocormus ; Rayner 1948). Such a process may have been present, but could have been obscured during crushing. However, in either case, the dorsal edge of the vagus foramen appears to have been formed entirely by the intercalar in GPIT/OS/00836, unlike in the other taxa.

Anterior to the intercalar is a much larger element that has been interpreted as an opisthotic ( Holmgren and Stensiö 1936). The opisthotic is dorsoventrally high. Its dorsal edge is semicircular and forms the facet for the hyomandibula; the dorsolateral surface is weakly concave. Towards the anterior end of the dorsolateral surface is a small foramen not reported in other pachycormids but matching in size and position the foramen for the supratemporal branch of the glossopharyngeal nerve (IX) reported in “ Aspidorhynchus ” ( Rayner 1948; note that this specimen is not consistent Aspidorhynchus and may actually be a caturid according to Patterson 1975); a foramen for the supratemporal branch of the glossopharyngeal has not been identified in Pachycormus . Unlike in “ Aspidorhynchus ” in which the foramen is dorsally directed, in GPIT/OS/00836 it is posteriorly directed. The ventral half of the opisthotic in GPIT/OS/00836 is separated from the ventral half by a ridge, which forms part of the dorsal edge of the jugular groove. A small foramen just anterior to the intercalar and above the suture with the basi-exoccipital is interpreted as the foramen for a subsidiary branch of the vagus nerve (X), as in Pachycormus ( Mainwaring 1978) . Both the foramen for the main and subsidiary branches of the vagus nerve lie in a groove that broadens into a deep concavity on the ventrolateral opisthotic. This fossa is confluent with the jugular groove, which becomes much broader in its posterior portion. Sutures in the anterodorsal braincase are difficult to see, in part due to fragments of the overlying hyomandibula. In overall shape, a relatively poorly developed subtemporal fossa is present immediately anterior to the dorsal opisthotic, separated from the jugular groove by a ridge. The jugular groove itself runs the length of the braincase, narrowest at its anterior point and becoming broader in the region of the vestibular fontanelle. Dorsal to the jugular canal, two additional foramina of uncertain identity are present within the prootic, the larger of which may correspond to the foramen for the facial nerve (VII). A foramen in a similar location was illustrated in the braincase reconstruction of Orthocormus presented by Holmgren and Stensiö (1936), but was not labeled.

The parasphenoid underlies the braincase, and is preserved in lateral view in articulation. The ascending process of the parasphenoid is obscured by the overlying hyomandibula. The foramen for the internal carotid artery lies posterior to the ascending process, as in Pachycormus ( Rayner 1948; Mainwaring 1978), at approximately the same level as the jugular canal.

The right lower jaw is preserved in lateral view. Posterodorsally, a small surangular is present. The angular is relatively small, and weakly ornamented with ridges and tubercles posteriorly; anteriorly it is smooth. The majority of the lateral lower jaw consists of the dentary. The dentigerous margin is straight, curving dorsally only at its anteriormost end. A small groove is present ventral to the region presumably occupied by the premaxilla, suggesting a slightly larger tooth in this region. A row of small teeth is present external to the robust dentary tooth row ( Fig. 5A 6 ). The dentary teeth are large and conical, with acrodin caps and a round cross-section. The largest teeth are present in the mid-dentary region, becoming slightly smaller anteriorly. The posteriormost two tooth positions are smaller than more anterior positions, and are each made up of two small teeth, closely spaced and curving towards each other. Based on spacing and morphology, these are probably twinned (i.e., developed from a single tooth germ) ( Fig. 5A 6 ).

The palatal elements are very difficult to interpret. The right hyomandibula appears to be covering the anterior braincase as well as parts of the palate; the bones are so tightly compacted as to be difficult to differentiate ( Fig. 5A 1 , A 2 ). The left ectopterygoid and a dermopalatine are preserved internal to and covered by the hyomandibula. Posteriorly, these palatal elements are very difficult to distinguish from the overlying element, however at the anterior end they are fully exposed. The anterior end of the ectopterygoid is pointed, with the point overlapping the dermopalatine. A medial shelf is present. Anterior and ventral to the ectopterygoid and hyomandibula is a fragment interpreted as the entopterygoid. Its position overlapping the hyomandibula suggests that it originates from the right-hand side of the skull. It is relatively deformed, and nothing can be added with regard to its morphology.

The left hyomandibula is present, rotated forward and overlying the lateral braincase and palate, but is extremely poorly preserved. It is a long element with a “waisted” shape and a well-developed opercular process. The proximal articular surface in lateral view is straight, rather than semicircular. At the distal end, the hyomandibula is mediolaterally thickened, especially along the anterior edge, forming a well-developed facet for articulation with the symplectic; the latter element is not preserved.

Branchial elements are visible in the space between the anterior skull and the operculum; no associated denticles are present.

The opercle is preserved posterior to the branchial elements. It is narrow dorsally, with an anteroventral to anteriorly oriented facet for articulation with one or both suborbitals and/or preopercle. The anterior edge of the opercle forms a 150° angle, dividing the dorsal third from the ventral portion. The posterior and ventral extent of the opercle is difficult to assess. The dorsalmost subopercle is preserved in articulation with the opercle, but is ventrally incomplete and posteriorly damaged; only the anterodorsal process can be unambiguously recognized.

Postcranial axial skeleton: Approximately 105 neural arches are present anterior to the caudal fin. The dorsal fin inserts around segment 57, and the anal fin is approximately opposite. The vertebral column is aspondylous along its entire length. In the anterior abdominal region, paired neural arches and thin, elongated paired neural spines are present. Near the anterior insertion of the dorsal fin, the neural spines develop thin bony laminae anterior and posterior to the spine immediately dorsal to the arch. The antimeric neural spines are fused from this point posteriorly. At a point approximately opposite the pelvic girdle, sigmoidal supraneurals appear. The supraneurals insert between every two dorsal fin pterygiophores. Supraneurals persist until halfway along the base of the dorsal fin, at which point they cease to ossify.

In the abdominal region, well-ossified ribs are present. These are slender and elongate, with a small cup-like expansion proximally. Small, circular endochondral ossifications are irregularly present and are interpreted as basiventrals. Approximately halfway along the abdominal region, the proximal end of the ribs becomes enlarged and flattened, as if the ribs had fused with these basiventrals. At the segment corresponding to the anterior insertion of the dorsal fin, unpaired median haemal spines appear. Posterior to the midpoint of the anal fin, the haemal spines gradually become oriented increasingly parallel to the vertebral column, as do the neural spines.

Median fins ( Fig. 6 ): The dorsal fin is supported by 27 slender, elongate pterygiophores, the anteriormost of which are laterally expanded distally, forming a broad base for the lepidotrichia ( Fig. 6 ). The posteriormost element is anteroposteriorly expanded and ventrally bifurcating; based on comparisons with Pachycormus , this is most likely a compound element consisting of the posteriormost two pterygiophores, making the total number of dorsal pterygiophores 29. The dorsal fin lepidotrichia are segmented. Although the anterior rays are incomplete, the longest preserved fin rays are less than twice the length of the pterygiophores. Branching cannot be assessed due to preservation.

The anal fin base appears to have been slightly posteriorly displaced. It inserts approximately opposite- to at maximum a few segments posterior to the dorsal fin base. Twenty-nine anal pterygiophores are preserved in articulation ( Fig. 6A 2 ), and at least 13 more are scattered posterior to the fin, suggesting that the count was far higher. The anteriormost pterygiophore is more robust than the more posterior elements, and is extremely elongate, extending along most of the posterior edge of the abdominal cavity. The anal fin pterygiophores are similar in morphology to the dorsal pterygiophores. The anal fin lepidotrichia were segmented, with the robust lepidotrichia concentrated anteriorly. Posteriorly, the lepidotrichia become very delicate, and extend posteriorly beyond the articulated pterygiophores. The anal fin appears to be deepest anteriorly, and decreases in height rapidly posteriorly (falcate morphology).

The caudal fin is well preserved, but the distal tip of the dorsal lobe is missing, and the elements have been dissociated laterally ( Fig. 6A 3 ). This dissociation makes the number of lepidotrichia difficult to assess. The caudal fin is deeply forked, with an angle of approximately 110° formed between the lobes. The proximal lepidotrichia are unsegmented, but distally are divided into short segments. Fringing fulcra are of type B ( Arratia 2009), in which small fringing fulcra are intercalated between the distal lepidotrichia along the leading edge of the fin; this is true in both the dorsal and ventral lobes ( Fig. 6A 7 ). A series of long, unpaired but deeply forked basal fulcra is present in the dorsal lobe; this character could not be assessed for the ventral lobe but appears probable based on the lack of segmentation of the anterior fin elements. The basal fulcra are much shorter than the depth of the caudal fin.

The caudal fin endoskeleton as preserved consists of at least five free thickened and robust unpaired preural haemal arches ( Fig. 6A 5 , A 6 ). The dorsal surface of the preural haemal arches is saddle-shaped and anteroposteriorly short. In preurals 3–6, the proximal end is laterally expanded, and the spines taper distally. The anterior surface is concave, with two lateral ridges running the length of the spine. Preurals 5–6 have an additional extremely thin, anterolaterally directed lamina slightly distal to the proximal end. Preural 2 is proximally laterally constricted ventral to the saddle-shaped dorsal surface. A prominent lip and anterior articular facet are present, analogous to the haemal process. Dorsal to preural 2 is an element interpreted as “uroneural 4” (sensu Arratia and Lambers 1996). Posterodorsal to this element, a single elongated dorsal element, interpreted as an epural, is preserved. This identification is based on the observation that this element is a median element, and quite thin posterodistally, but with a prominent lateral expansion involving the anterior and proximal portions. The hypural plate consists of a broad, fan-shaped posterior plate and an anterior “neck”. The neck bears a large lateral foramen, indicating that the hypural plate is formed by both the parhypural and hypurals (as per Arratia and Lambers 1996) ( Fig. 6A 5 , A 6 ). The anterior dorsal hypural plate is unfortunately poorly preserved, but forms a clear anterior projection corresponding to the hypural process ( Arratia and Lambers 1996). A notch on the posteroventral surface of the hypural plate may delimit the parhypural; the total number of elements making up the plate is uncertain. The hypural plate is ornamented with radiating grooves for articulation of the lepidotrichia. An additional groove, leading to a notch on the anteroventral edge of the plate, may correspond to the path of a branch of the caudal artery ( Arratia and Lambers 1996).

Pectoral girdle and fin: The right cleithrum is largely covered by the opercle, which is deformed over it. The right supracleithrum appears to remain in articulation, also under the opercle. The left supracleithrum is displaced posteromedial to the right temporal boss. The dorsal process of the cleithrum is narrow, but a posterior expansion is present, making the element broader and more angular posteriorly than anteriorly. The glenoid is oriented posteroventrally, and is very poorly defined. Anterior to the glenoid, the cleithrum has a medial expansion, and anteriorly forms a concave bony lamina. At least two postcleithra are present.

The right endochondral pectoral girdle is exposed in lateroventral view, and appears to be broken. We consider the anterior piece to be the slender anterior process of the scapulocoracoid, and the posterior fragment to represent the main body of the element. The posterior element is large, three-dimensionally complex, and shows relatively weak endochondral ossification. The anterior edge bears a well-developed notch, potentially representing the posterior edge of the coracoid canal. Two short, broad radials are preserved posterior to the scapulocoracoid, and two elongate, distally flaring radials are present, one mixed with the pectoral lepidotrichia and the second posterodorsally displaced. A small subcircular element posterior to the scapulocoracoid is interpreted as a displaced distal radial. The pectoral lepidotrichia are robust and elongate, with a grooved ornamentation. No evidence of segmentation of pectoral lepidotrichia is observed.

Pelvic girdle and fin: The pelvic girdle, consisting of two robust pelvic plates, is exposed in dorsal view ( Fig. 7 ). Each pelvic plate is formed by a medially expanded posterior lamina and an elongate anterior process, and is grooved in dorsal view. The pelvic fin lepidotrichia are robust, curved and unsegmented, located closer to the pectoral fins than to the anal fin.

Squamation: The scales are relatively robust, and appear to have been roughly rectangular in shape. They measure ca. 3 mm along the anteroposterior axis, and appear to have a 2:1 relationship with vertebral elements. A scaly caudal apparatus (sensu Arratia and Schultze 2013) was present, but has been displaced anteroventrally. The scales of the caudal apparatus are L-shaped, narrow and rounded ventrally and becoming flattened and expanded posteriorly ( Fig. 6A 3 , A 4 ). There is also evidence for at least one mid-dorsal scute immediately anterior to the caudal fin ( Fig. 6A 3 , A 5 , A 6 ).

Paleobiology ( Fig. 8 ): Many of the ribs show irregularly distributed small swellings along their lengths ( Fig. 8A 2 ). These types of swellings could be interpreted as hyperostosis, an idiopathic condition to which many lesions in the fish axial skeleton are referred, with these lesions usually occurring predictably in certain regions of the skeleton in a given species (usually the neural and haemal spines or pterygiophores, but also occasionally ribs; reviewed by Witten and Hall 2015). Hyperostosis has not previously been described in pachycormids, and hyperostotic lesions are usually much larger than those observed in GPIT/OS/00836. The alternative is that the lesions are calluses resulting from traumatic injury to the ribs. Pathologies affecting the actinopterygian axial skeleton are rarely reported, as the probability of surviving such an injury is considered relatively low. However, callus development has been described in the neural and haemal spines of farmed cod, and in the ribs of sculpin ( Horton and Summers 2009; Fjelldal et al. 2018), and is superficially similar to the lesions observed in GPIT/OS/00836. We interpret the lesions on the ribs in GPIT/OS/00836 as calluses resulting from traumatic injury to the abdominal region.

GPIT/OS/00836 has at least two small teleosteans as gastric contents ( Fig. 8A 3 ), indicating a piscivorous diet. Remarks.— GPIT/OS/00836 has relatively large pelvic fins, positioned closer to the pectoral fins than to the anal fins, and a robust pelvic plate with an expanded posterior plate and a slender anterior process, character states only documented in Simocormus macrolepidotus gen. et sp. nov. and Orthocormus among the toothed pachycormids ( Lambers 1992). However, the scales in GPIT/OS/00836 are much larger and more heavily ossified than those of Orthocormus but smaller than those of Simocormus macrolepidotus , the dorsal fin is only slightly anterior to and largely overlapping with the anal fin base, and the posterior and ventral edges of the lower jaw form a right angle, all differing from Orthocormus and Simocormus macrolepidotus , but consistent with Hypsocormus insignis . At 69 cm SL, GPIT/ OS/00836 is similar in size to H. insignis ; the relative head length (at least 22% SL) and prominent temporal boss are equally consistent with the latter species. Distally expanded median fin pterygiophores and presence of scaly caudal apparatus have been used to diagnose Orthocormus ( Arratia and Schultze 2013) , but appear to be more widely distributed within the family, including in H. insignis (see discussion).

GPIT/OS/00836 differs from Hypsocormus insignis in several details. The supraneurals do not begin immediately posterior to the skull and the pelvic plate is robust with an expanded posterior plate and a slender anterior process in GPIT/OS/00836 but not in H. insignis ( Lambers 1992) ; however, both of these characters may be artefactual: a robust pelvic plate may be taphonomically obscured by phosphatization of soft tissues in the Bavarian material of H. insignis , and the anterior supraneurals may be lost or scattered in GPIT/OS/00836. GPIT/OS/00836 also differs from material referred to H. insignis in the lack of tubercular ornamentation on the maxilla; however, this character cannot be observed in the holotype of H. insignis . The most substantive difference exists in the morphology of the caudal endoskeleton in GPIT/OS/00836. In particular the shape of the anteroventral hypural plate and the presence of a foramen in the lateral hypural plate indicate that the parhypural is fused to the hypural plate in GPIT/OS/00836 but not in material referred to H. insignis ( Arratia and Lambers 1996) . This cannot be evaluated in the H. insignis holotype. A hypural plate consisting of both the parhypural and hypurals is also observed in Simocormus macrolepidotus gen. et sp. nov. (SNSB-JME SOS 3574b), as well as in some species of Protosphyraena ( Arratia and Lambers 1996) . GPIT/ OS/00836 differs from the H. insignis holotype (SNSB-BSPG AS VI 4 a/b) in the extensive overlap of the dorsal and anal fin bases in GPIT/OS/00836, whereas the dorsal fin is almost entirely anterior to the anal fin in SNSB-BSPG AS VI 4 a/b ( Fig. 4 ), and in the prominent apicobasal ridging of the tooth bases in SNSB-BSPG AS VI 4 a/b, but not GPIT/ OS/00836 in which the tooth bases are smooth ( Fig. 5A 6 , B 1 ). Given these differences, we refer GPIT/OS/00836 to Hypsocormus posterodorsalis sp. nov.

Stratigraphic and geographic range.— Type locality and horizon only.

Figures

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.

Fig. 6. Pachycormid fish Hypsocormus posterodorsalis sp. nov. (GPIT/OS/00836) from the Kimmeridgian (Jurassic) of Nusplingen, Germany. Unpaired fins: dorsal (A1), anal (A2), caudal (A3), arrows indicate L-shaped scales of the scaly caudal apparatus. Magnified view of scales of scaly caudal apparatus A4). Caudal fin endoskeleton (photograph A5, explanatory drawing A6). Caudal fin, dorsal lobe, fringing fulcra (A7), arrows indicate the distal tips of the procurrent rays. Abbreviations: da, neural arches; ep, “epural”; hyp, hypural plate; pu2, 3, preural haemal arches; sc, scute; un4, “uroneural” 4.

Fig. 7. Pachycormid fish Hypsocormus posterodorsalis sp. nov. (GPIT/ OS/00836) from the Kimmeridgian (Jurassic) of Nusplingen, Germany. Pelvic plates and lepidotrichia in internal view (photograph A1, explanatory drawing A2).

Fig. 8. Pachycormid fish Hypsocormus posterodorsalis sp. nov. (GPIT/ OS/00836) from the Kimmeridgian (Jurassic) of Nusplingen, Germany. Overview of abdominal region (A1). Ribs with swellings interpreted as showing callus development (indicated by arrows) (A2). Small teleosteans in gastrointestinal cavity, with certain identifiable elements outlined to increase contrast (A3). Abbreviations. lj, prey mandible; op, prey opercle; pec, Hypsocormus pectoral lepidotrichia; pel, Hypsocormus pelvic plate; pop, prey preopercle; sk1+2, prey skulls.

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. 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.