Late Jurassic ichthyosaurs from Germany

Late Jurassic ichthyosaurs from southern Germany

Erin E. Maxwell, Jule Neumann, and Giovanni Serafini

Article number: 29.2.a30
https://doi.org/10.26879/1676
Copyright Society of Vertebrate Paleontology, August 2026

Author biographies
Plain-language and multi-lingual abstracts
PDF version 
Appendices

Submission: 18 February 2026. Acceptance: 9 July 2026.

ABSTRACT

The Tithonian (Late Jurassic) represents a high point in ichthyosaurian taxonomic diversity, although ecomorphological disparity is not correspondingly high. Numerous fossil lagerstätte from a range of palaeolatitudes in both the Northern and Southern Hemispheres are thought to be responsible for the high observed generic diversity during this time interval; however, faunal provincialism has also been proposed as a driver. Here, we re-evaluate the ichthyosaur fauna of the German Plattenkalk deposits and provide a revised estimate for taxonomic diversity from these fossil lagerstätten. Unlike coeval lagerstätten, only a single accepted ichthyosaurian genus from the Late Jurassic of Germany, Aegirosaurus leptospondylus, has been described to date, suggesting considerable undersampling. Here, we describe a second genus from these deposits, Jabalisaurus tethyensis sp. nov., based on material previously included within Aegirosaurus. New observations provide additional details on the osteology, soft tissue morphology, and diet in J. tethyensis. Jabalisaurus was previously known only from the Late Jurassic of Mexico. The presence of this genus in Europe leads us to reject the faunal provincialism hypothesis, and suggests instead the existence of a unique Peri-Tethyan ichthyosaurian fauna, distinct from both the Boreal/sub-Boreal and Eastern Pacific faunas and potentially controlled by climatic variables.

Erin E. Maxwell. Staatliches Museum für Naturkunde Stuttgart, Rosenstein 1, 70191 Stuttgart, Germany; [email protected]
Jule Neumann. Fichtner GmbH & Co. KG, Stuttgart, Germany; [email protected]
Giovanni Serafini. Dipartimento di Scienze Chimiche e Geologiche, Università di Modena e Reggio Emilia, Via Campi 103, 41125 Modena, Italy; [email protected]

Keywords: Ichthyosauria; Ophthalmosauria; Plattenkalk; Altmühltal Formation; Torleite Formation; New species

Final citation: Maxwell, Erin E., Neumann, Jule, and Serafini, Giovanni. 2026. Late Jurassic ichthyosaurs from southern Germany. Palaeontologia Electronica, 29(2):a30.
https://doi.org/10.26879/1676
palaeo-electronica.org/content/2026/5919-late-jurassic-ichthyosaurs-from-germany

Copyright: August 2026 Society of Vertebrate Paleontology.
This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
creativecommons.org/licenses/by/4.0

https://zoobank.org/E557598D-F3C2-4AD2-A578-92E1A9BE98C3

INTRODUCTION

Ichthyosaurs are Mesozoic marine reptiles that first appeared in the fossil record in the Early Triassic and persisted until the early Late Cretaceous (McGowan and Motani, 2003). The high point of ichthyopterygian diversity and disparity is widely understood to have been attained during the first ~8.7 million years of the group’s evolution (Flannery Sutherland et al., 2019), attributed to high rates of morphological evolution early in the history of the clade during their initial radiation into diverse marine habitats and dietary niches (Moon and Stubbs, 2020). By the Jurassic, and especially by the end of the Aalenian (early Middle Jurassic), ichthyosaurs occupied a reduced range of ecomorphotypes (Fischer et al., 2021), and historically were viewed as being correspondingly reduced in taxonomic diversity (Sander, 2000).

In contrast to the historical view, over the past 20 years it has become evident that the Tithonian (Late Jurassic) represents a high point in raw ichthyosaurian taxonomic diversity, despite relatively low ecomorphological disparity (Fischer et al., 2014; Cleary et al., 2015; Fernández and Campos, 2015; Flannery Sutherland et al., 2019; Barrientos-Lara and Alvarado-Ortega, 2021a). The dynamics driving this pattern have yet to be been resolved: lagerstätte effects are considered to be the most likely underlying cause (Benson et al., 2010), with the Tithonian record far surpassing any other Jurassic stage in global representation of lagerstätte-quality open marine deposits, although faunal provincialism has also been proposed as a driver (Barrientos-Lara and Alvarado-Ortega, 2021a).

Ichthyosaur-bearing localities spanning high to mid-latitudes in the northern hemisphere are well-represented in the Kimmeridgian-Tithonian record and tend to show extensive taxon overlap at the generic level (Svalbard, the UK, and Volga regions: Zverkov and Efimov, 2019; Zverkov and Prilepskaya, 2019; Zverkov and Jacobs, 2020). In contrast, localities in Mexico and Argentina show a high degree of endemism (Barrientos-Lara and Alvarado-Ortega, 2021a), with few to no genera shared either with each other or with the European localities. The ichthyosaur assemblage of southern Germany is very poorly documented, but the invertebrate fauna has a more Tethyan character than that of other European localities (sub-Mediterranean Province vs. Boreal or sub-Boreal Provinces: Cecca, 1999; Westermann, 2000), and thus might provide new insights into the degree of faunal overlap or relatedness in ichthyosaurs between Europe and Mexico.

Ichthyosaurian fossils from the Late Jurassic Bavarian Plattenkalk deposits of Germany were first described during the 1850s, comprising what is now understood to be a multi-taxic assemblage (reviewed by Bardet and Fernández, 2000). None of this original material has survived into the present day, and due to the loss of this historical material, only a single monotypic genus is documented from the German Late Jurassic: Aegirosaurus Bardet and Fernández, 2000. At the time of genus naming, only six ophthalmosaurian genera were accepted as valid: Ophthalmosaurus, Brachypterygius, Caypullisaurus, Mollesaurus, Platypterygius, and Nannopterygius. Since that time, however, the number of ophthalmosaurian genera has undergone a dramatic increase, with at least 21 genera recognized depending on the author. The description of Aegirosaurus leptospondylus, while sufficient 25 years ago, is no longer detailed enough to accurately score characters in phylogenetic matrices. Moreover, it has become clear that specimens referred to this species are not congeneric with the neotype. Here, we remove SNSB-BSPG 1954 I 608 from the concept of Aegirosaurus, provide a revised diagnosis for the genus, and assign most of the referred material to a new species in the genus Jabalisaurus, to date described only from Mexico.

Institutional abbreviations. SM, Schwegler Museum, Langenaltheim, Germany; SNSB-BSPG, Bayerische Staatssammlung für Paläontologie und Geologie, Munich, Germany; JME, Jura-Museum Eichstätt, Eichstätt, Germany; MUDE, Museo del Desierto, Saltillo, Coahuila, Mexico; NHMUK, Natural History Museum, London, UK; SMNS, Staatliches Museum für Naturkunde Stuttgart, Germany.

Previous Work on Ichthyosaurs from the Bavarian Plattenkalks and the Genus Aegirosaurus

The first ichthyosaurian taxon to be named from the Late Jurassic of Bavaria was Ichthyosaurus posthumus Wagner, 1852 from the Late Jurassic of Kelheim. This species was based on an isolated tooth and is now considered to be a nomen dubium (McGowan, 1976). Ichthyosaurus leptospondylus was named the following year based on the so-called Oberndorfer specimen, also from Kelheim (Wagner, 1853a). Although not figured in the initial publication, Wagner later illustrated some of the teeth (Wagner, 1853b). The most detailed illustrations of the holotype specimen were provided by Bauer (1898), including parts of the jaws and quadrate. The holotype material was destroyed during WWII; only thin sections of the teeth survive (Scheyer and Moser, 2011). A neotype for I. leptospondylus was selected by Bardet and Fernández (2000) from the Schwegler Museum (Langenaltheim, Bavaria, Germany), and was assigned to a new genus, Aegirosaurus. The neotype remained in Langenaltheim following the death of Mr. Schwegler, but is not publicly accessible. However, a cast of the skull is available in the collections of the SNSB-BSPG. The A. leptospondylus neotype and the holotype were considered to be different species by Maisch (2015) based on supposed differences in humeral morphology; however, the humerus of the holotype was not preserved (Wagner, 1853a; Bauer, 1898).

Following his initial description, Wagner (1861) referred a second specimen (the Häberlein specimen) to ‘ Ichthyosaurus’ leptospondylus; this material was also destroyed during WWII but is not considered to be congeneric with the holotype by more recent authors (Bardet and Fernández, 2000). Bardet and Fernández (2000) referred an additional post-war specimen to A. leptospondylus, SNSB-BSPG 1954 I 608. Some authors (Maisch and Matzke, 2000; Maisch, 2015) find this specimen to be inconsistent with the neotype, and Maisch (2015) specifically considered it to be closer to Wagner’s conception of A. leptospondylus, i.e., the holotype. The enamel ornamentation has been described as differing between the holotype (ridged enamel in the holotype and neotype: Scheyer and Moser, 2011) and SNSB-BSPG 1954 I 608 (smooth enamel: Bardet and Fernández, 2000), as has the configuration of the distal facets on the humerus (Maisch, 2015). Two additional skulls, SMNS 54067 and NHMUK PV OR 42833, have also been referred to A. leptospondylus (Meyer, 1863; Bardet and Fernández, 2000; Maisch and Matzke, 2000); this material will be re-evaluated and discussed in more detail below.

In addition to the material referred to Aegirosaurus leptospondylus, Delsett et al. (2022) referred JME-SOS-08369, from the early Tithonian of Blumenberg, Germany, to Aegirosaurus sp.. They did not refer the material to A. leptospondylus due to the relatively long exposure of the maxilla (30% of snout length/40% if the suborbital portion of the maxilla is included in the measurement), somewhat longer than the values reported for material referred to A. leptospondylus (22% of snout length: SNSB-BSPG 1954 I 608; 25%: neotype (Bardet and Fernández, 2000); 27%: SMNS 54067).

From elsewhere in the world, Maisch and Matzke (2000) referred an ophthalmosaurine ichthyosaur from the Tithonian of Argentina to Aegirosaurus; however, this specimen is now considered to be distinct at the generic level (holotype of Catutosaurus gaspariniae: Fernández et al., 2021). Likewise, additional material from the Los Catutos Member of the Vaca Muerta Formation referred to Aegirosaurus by Gasparini et al. (2015) has since been determined to be generically distinct (holotype of Sumpalla argentina: Campos et al., 2021a).

Lastly, Fischer et al. (2011) referred an isolated lower jaw from the Valanginian (Early Cretaceous) of France to Aegirosaurus sp. Here we consider this specimen to be referable to Ophthalmosauria indet., following Lukeneder et al. (2022). Therefore to date, material referred to Aegirosaurus is only definitively known from the Late Jurassic of Germany.

MATERIALS AND METHODS

Geology

The Plattenkalk deposits of southern Germany have a long history of commercial exploitation and fossil collecting, and have produced spectacular vertebrate material over more than 200 years including diverse chondrichthyan and actinopterygian fishes, turtles, squamates, thalattosuchian crocodylomorphs, dinosaurs, and early birds (Arratia et al., 2015). Ichthyosaurs are a rare component of the fauna, although the number of specimens held in private collections exceeds publicly available materials. The specimens discussed here originate from the Middle Franconian Alb localities around Solnhofen (Apfelthal), Langenaltheim, Eichstätt, and Painten (Figure 1). All four localities are Late Jurassic in age, and consist of fine-grained, laminated, and planar limestones, usually lacking bioturbation (Viohl, 2015a). The Bavarian plattenkalk deposits formerly part of the “Weissjura” (Quenstedt, 1856-1858), including the localities mentioned above, are now divided into several different formations, ranging in age from the Kimmeridgian to Tithonian (Schweigert, 2007; Niebuhr and Pürner, 2014). We assigned ammonite zonation biostratigraphic ages to historical localities based on Schweigert (2007). During the Late Jurassic, this part of southern Germany was situated in a shallow tropical sea, with the laminated limestones being deposited in inter-reef basins (Viohl, 2015b).

Materials

SM. The neotype of Aegirosaurus leptospondylus is a small, three-dimensionally preserved skeleton 1.77 m in length, including some soft tissue remains from the fore- and hind limbs, and the caudal fin. The skeleton has been exposed in dorsal view (Bardet and Fernández, 2000). As the original skeleton was not available for study, all observations were made on a cast of the skull housed at the SNSB-BSPG, Munich, resulting in uncertainty regarding the position of some of the cranial sutures. Since the interpretations of Bardet and Fernández (2000, fig. 3) were found to be generally reliable where these could be confidently checked against the cast, we describe only those points where a) additional detail was both visible on the cast and important for comparison, and b) those few cases where our interpretations differed from those Bardet and Fernández (2000) (see Appendix 1 for details). SM originates from Langenaltheim, Bavaria, Germany, from the Altmühltal Formation, Rueppellianus Subzone, Hybonotum Zone, lower Tithonian.

SNSB-BSPG 1954 I 608. This specimen was described in detail by Bardet and Fernández (2000), but also corresponds to ‘Munich 5’ of McGowan (1976). SNSB-BSPG 1954 I 608 is a small individual (79.3 cm preserved length) exposed in left lateral view; a counterpart is also available. The caudal region is missing; the posterior body and extremities are somewhat disarticulated. The skeleton is surrounded by numerous Saccoccoma remains. Although not noted in previous descriptions, an outline of the soft tissue hind fin is preserved. SNSB-BSPG 1954 I 608 originates from Geisberg quarry, Apfelthal, Mörnsheim, Bavaria, in the Altmühltal Formation, Rueppellianus Subzone, Hybonotum Zone, lower Tithonian.

SMNS 54067. This specimen was acquired by the SMNS in 1985. SMNS 54067 is a laterally compressed skull and the anterior part of the torso with shattered vertebrae and rib fragments, exposed from the left-hand side. The skull is well preserved except for the narial region and the posterodorsal portion of the skull. This specimen was noted by Maisch and Matzke (2000), but figured only as a reconstruction created by combining observations with SNSB-BSPG 1954 I 608. SMNS 54067 preserves indeterminate soft tissue remains in the anterior dorsal region. The specimen originates from Painten, Bavaria, from the Torleite Formation, Ulmense Subzone, Beckeri Zone, upper Kimmeridgian.

JME-SOS-08369. JME-SOS-08369 is an articulated ichthyosaur 1.84 m in total length, and includes a complete soft tissue envelope. This ‘mummified’ type of preservation unfortunately hides many osteological details due to low contrast with the surrounding soft tissues and soft tissue remains directly covering the bones. The specimen was described and figured by Delsett et al. (2022). JME-SOS-08369 originates from Blumenberg, Eichstätt, Bavaria, from the Altmühltal Formation, Riedense Subzone, Hybonotum Zone, lower Tithonian.

NHMUK PV OR 42833. NHMUK PV OR 42833 preserves the snout of a small ichthyosaur in dorsal view. The specimen has been dorsoventrally compacted. Originally described and figured by Meyer (1863), NHMUK PV OR 42833 was also described by Bardet and Fernández (2000). It originates from Eichstätt, Bavaria, from the Altmühltal Formation, Riedense Subzone, Hybonotum Zone, lower Tithonian.

Documentation

In addition to being photographed under natural light, SMNS 54067, SNSB-BSPG 1954 I 608 and NHMUK PV OR 42833 were photographed under UV-light. Depending on the material and wavelength, the fluorescence response differs and therefore is suited to distinguish the anatomical structures from the surrounding matrix. During photography of SMNS 54067, the three UV types were tested independently from each other (photo with only UV-A; UV-B; UV-C) but also in combination (photos with UV-A/UV-C; UV-B/UV-C, UV-A/-B/-C). The UV analysis on SMNS 54067 was performed with a 95 W triple wavelength discharge lamp from WayTooCoolLLC; pictures were taken with a Canon 700D with either a 24, 50 and 100 mm lenses, of which the 24 and 50 mm were coupled with orange correction filters to counteract the blue halo from the bulbs. SNSB-BSPG 1954 I 608 and NHMUK PV OR 42833 were photographed with a hand-held LED UV torch (Alonefire SV83) emitting UV-A radiation (365 nm) with a Canon 200D. Unfortunately, SNSB-BSPG 1954 I 608 had been treated with a synthetic coating that masked soft-tissue structures under UV light.

Phylogenetic Analysis

To examine the position of Aegirosaurus and Jabalisaurus tethyensis sp. nov. in a phylogenetic context, we rescored Aegirosaurus in the matrix of Campos et al. (2025) based only on the neotype specimen, and also added J. tethyensis as an OTU. We removed Muiscasaurus catheti since in the matrix of Campos et al. this OTU is scored based on both the holotype and referred specimens (Maxwell et al., 2016; Páramo-Fonseca et al., 2021), which we do not consider to be congeneric. In addition, we updated the scoring of braincase characters for Baptanodon natans based on Massare and Connely (2022), as well as some cranial characters in J. meztli (see Appendix 2 for details). Scoring for humeral midshaft constriction was edited to ‘?’ in Catutosaurus gaspariniae and was also scored as ‘?’ for J. tethyensis because this character is known to be ontogenetically influenced (see Johnson, 1977: pl. 2), and the adult morphology is unknown in these OTUs.

In addition to these OTU-specific modifications, we reversed the character state descriptions for Ch. 9 (length of premaxillary process of the maxilla) to reflect existing scoring. We reformulated Ch. 15 (complete division of external nares) to eliminate the absence state, since in its previous formulation, it duplicated Ch. 14: state 3. Taxa in which a complete division was absent were scored as inapplicable (‘-‘). We also rescored Ch. 117 (postaxial enlargement of forefin) following Lomax et al. (2025) due to homology inconsistencies between authors focusing on ophthalmosaurian vs. non-ophthalmosaurian parvipelvians. We deleted Ch. 122 (“digital bifurcation in digit IV”). This character referred to the presence of interdigital ossicles between digits IV and V, which are known to vary both intraspecifically and asymmetrically within an individual (see Maxwell, 2012 for homology discussion). As scored, the ‘present’ state comprised interdigital ossicles between digits IV and V, true instances of digital bifurcation (e.g., some specimens of Ichthyosaurus: Motani [1999a]) and interdigital ossicles in the anterior limb (e.g., Kolb and Sander, 2009). Due to the high levels of intraspecific and intra-individual variation, this character was deleted rather than rescored or restructured.

These changes resulted in a matrix of 55 taxa and 130 characters, all of which were treated as unordered (Appendix 3). This matrix was analyzed in TnT v. 1.6 (Goloboff and Morales, 2023), using four optimization strategies: equal weights parsimony, and implied weights parsimony (k= 6, 9, 12). A new technology search was implemented using 50 iterations of the ratchet algorithm, recovering minimum length 50 times.

SYSTEMATIC PALAEONTOLOGY

ICHTHYOSAURIA de Blainville, 1835
OPHTHALMOSAURIA Motani, 1999b
PLATYPTERYGIINAE sensu Fischer et al., 2012
AEGIROSAURUS Bardet and Fernández, 2000

Type species. Aegirosaurus leptospondylus (Wagner, 1853a).

Diagnosis. As for type and only species.

Aegirosaurus leptospondylus (Wagner, 1853a)
Figure 2

Neotype. SM, a small, three-dimensional skeleton exposed in dorsal view.

Neotype locality and horizon. Langenaltheim, Bavaria; Altmühltal Formation, Rueppellianus Subzone, Hybonotum Zone, lower Tithonian.

Diagnosis (modified from Bardet and Fernández, 2000). A medium-sized ichthyosaur less than 2 m long, characterized by characterized by the following combination of character states: an extremely long and slender snout (snout ratio 0.73, similar to Brachypterygius), not markedly demarcated from the skull (unlike in e.g., Baptanodon); medium-sized orbit (orbital ratio 0.18, as in Brachypterygius); postorbital segment of the skull narrow (postorbital ratio 0.08); premaxillae comprising 63% of the skull in dorsal view; dorsoventrally deep maxilla (as in Platypterygius australis); prefrontal excluded from external nares (as in Brachypterygius, but unlike in Thalassodraco); rounded, undivided external narial opening (unlike in Parrasaurus); short, dorsoventrally compressed jugal slightly exceeding the anterior orbital margin; postorbital covering quadratojugal; presence in the cheek region of a reduced, triangular and laterally exposed squamosal (unlike in Caypullisaurus, in which the squamosal is rectangular, or Eternauta, in which it is absent); rectangular parietals with long interparietal suture (unlike in Palvennia, Janusaurus, Jabalisaurus); frontals mediolaterally broad with small temporal process (unlike in Palvennia, in which the temporal process is absent); external exposure of postfrontal greatly reduced, almost or entirely excluded from participation in the supratemporal fenestra (as in Leninia); angular largely exposed laterally reaching as far anteriorly as the surangular; surangular fossa greatly reduced in depth and anteroposterior length (as in Brachypterygius); acutely pointed teeth with enamel crown ornamented with pronounced apicobasal ridges (density = 8-10/5 mm, unlike in Thalassodraco and Catutosaurus in which the enamel is smooth, and unlike in Jabalisaurus in which the enamel ridges are much finer and more densely spaced); forelimb with massive humerus bearing three distal articulations for radius, intermedium (the smallest) and ulna (as in Brachypterygius but unlike in all other Jurassic ophthalmosaurians); an extrazeugopodial element and associated digit distal to the radius (unlike in Brachypterygius, in which the extrazeugopodial element is anterior to the radius); six digits of which the fourth is the longest and comprises 23 elements; short hind limb with massive femur half the length of the humerus, articulating distally with two elements, and four digits (unlike in Sumpalla, in which the femur has three distal facets); both paddles composed of proximally packed polygonal elements becoming more widely spaced and rounded distally (unlike in Baptanodon, Arthropterygius, Palvennia, Janusaurus in which the limb elements are rounded).

Remarks. See Appendix 1 for a brief cranial description based on the SNSB-BSPG cast (Figure 2). We do not consider any of the previously referred specimens to be consistent with the neotype of Aegirosaurus leptospondylus.

ICHTHYOSAURIA de Blainville, 1835
OPHTHALMOSAURIA Motani, 1999b
OPHTHALMOSAURINAE sensu Fischer et al., 2012
JABALISAURUS Barrientos-Lara and Alvarado-Ortega, 2021a

Type species. Jabalisaurus meztli Barrientos-Lara and Alvarado-Ortega, 2021a.

Diagnosis (modified from Barrientos-Lara and Alvarado-Ortega, 2021a). A mid-sized ophthalmosaurian ichthyosaur ~2.0-3.2 m in length characterized by the following combination of character states: large orbit (orbital ratio ≥0.23, similar to Ophthalmosaurus); frontals medially elongate; parietals with short interparietal suture (as in Palvennia, Janusaurus, but differing from Aegirosaurus); postorbital crescentic, large, deeper than long, covering more than two-thirds of the cheek region (as in Aegirosaurus); snout slender (snout depth ratio < 0.045, as in Acamptonectes); external nares bilobate (as in Baptanodon, Ophthalmosaurus but differing from Aegirosaurus); distal end of humerus with three articular facets for the radius, ulna, and a preaxial element (as in Baptanodon, Ophthalmosaurus but differing from Aegirosaurus); manual phalanges polygonal (unlike in Baptanodon, Ophthalmosaurus).

Remarks. Many aspects of the cranial morphology of the holotype of Jabalisaurus meztli appear to be taphonomically influenced by head-first seafloor arrival and subsequent telescoping and differential compaction (see Wahl, 2009; Johnson et al., 2025), or are likely to have been misinterpreted due to said damage (especially in the narial region and skull roof); these characters have been excluded from our modified diagnosis. In general, Jabalisaurus meztli shows strong morphological similarities in skull proportions and anatomy to Ophthalmosaurus and Baptanodon (Gilmore, 1905; Moon and Kirton, 2016), differing most notably in the presence of tightly packed polygonal phalanges, and also in the extensive contribution of the splenial to the mandibular symphysis (Barrientos-Lara and Alvarado-Ortega, 2021a). The maximum body size estimate for the genus is based on the proportions of JME-SOS-08369 (see below) applied to the J. meztli holotype.

Jabalisaurus tethyensis sp. nov.
Figure 3, Figure 4, Figure 5, Figure 6, Figure 7, Figure 8, Figure 9, Figure 10
zoobank.org/A31C8BAC-80F4-4261-B042-5D2901E89DD0

v. 1976 Ichthyosaurus ? leptospondylus ? Wagner; McGowan (as Munich 5), p. 669.

v. 1978 Ichthyosaurus (Macropterygius) posthumus Wagner; Barthel, colour pl. 8 fig. 1.

v. 1990 Macropterygius posthumus (Wagner); Barthel et al., fig. 7.74.

vp. 2000 Aegirosaurus leptospondylus (Wagner); Bardet and Fernández, figs 2, 4, 7.

vp. 2000 Aegirosaurus leptospondylus (Wagner); Maisch and Matzke, fig. 8.

v. 2022 Aegirosaurus sp.; Delsett et al., figs 2, 5-7.

vp. 2022 Aegirosaurus ? sp.; Serafini et al., p. 10, table 1.

Holotype. SNSB-BSPG 1954 I 608, a small juvenile (osteologically immature) individual preserved as part and counterpart (Figure 3, Figure 4, Figure 5, Figure 6).

Etymology. The specific epithet refers to the palaeogeographical distribution of this species along the northern Tethyan shelf.

Type locality and horizon. Geisberg quarry, Apfelthal, Mörnsheim, Bavaria. Altmühltal Formation, Rueppellianus Subzone, Hybonotum Zone, lower Tithonian.

Diagnosis. A mid-sized ophthalmosaurian estimated at 2.0-2.9 m total length (upper limit calculated based on a neonatal/maternal skull length ratio of 45% for Stenopterygius, with total length extrapolated from skull length using proportions of JME-SOS-08369) and differing from the type species based on a reduced contribution of the splenial to the mandibular symphysis (<50%; assessed based on JME-SOS-08369, vs. 60% in J. meztli). The following character states differentiate Jabalisaurus tethyensis from all other ophthalmosaurians: High-crowned skull with slender snout and short postorbital region; participation of prefrontal in posterodorsal external narial opening (as in Ophthalmosaurus and Thalassodraco but unlike in Aegirosaurus); bilobate external nares; triangular squamosal (unlike in Caypullisaurus); surangular fossa bordered dorsally by sharp crest (unlike in Aegirosaurus, Brachypterygius); delicate teeth, enamel ornamented with fine apicobasal ridges (density ~17-18/5 mm, unlike in Thalassodraco and Catutosaurus in which the enamel is smooth); humerus with three distal facets for the radius, ulna, and preaxial element (unlike in Aegirosaurus, Brachypterygius in which the middle facet articulates with the intermedium); tightly packed polygonal phalanges (unlike in Baptanodon, Ophthalmosaurus); bipartite pelvic girdle with completely fused, plate-like ischiopubis retaining the obturator foramen (unlike in Undorosaurus and Thalassodraco in which the ischium and pubis are medially separate, and also differing from Caypullisaurus and Janusaurus in which the obturator foramen has been lost). In overall morphology, Jabalisaurus tethyensis resembles Ophthalmosaurus icenicus, but differs in forefin anatomy distal to the humerus.

Referred specimens. SMNS 54067, JME-SOS-08369.

Locality and horizon (referred specimens). SMNS 54067, Torleite Formation, Painten, Bavaria, Ulmense Subzone, Beckeri Zone, upper Kimmeridgian; JME-SOS-08369, Altmühltal Formation, Blumenberg, Eichstätt, Riedense Subzone, Hybonotum Zone, lower Tithonian.

Remarks. The holotype and both referred specimens are consistent with a single taxon based on similar cranial shape and proportions, dentition, visible cranial anatomy consistent with Ophthalmosaurus, in combination with polygonal phalanges in the forelimbs (in SNSB-BSPG 1954 I 608 and JME-SOS-08369). Thus, while the three specimens are not characterized by any unambiguous features conclusively uniting them as a single taxon, overall anatomical similarities as well as similar geographic and temporal provenance suggest that they are conspecific. The features uniting these three specimens are inconsistent with Aegirosaurus leptospondylus, the only other named ichthyosaur taxon from the Bavarian Plattenkalk deposits. While at least two additional taxa were likely present in the Late Jurassic of Germany, these are differentiated from Jabalisaurus tethyensis by relative tooth size and cranial proportions, with both the undescribed taxa being much more robust and with larger teeth. Thus, the most parsimonious hypothesis is that SNSB-BSPG 1954 I 608, SMNS 54067, and JME-SOS-08369 represent a single taxon. However, in case this conclusion becomes unjustified in the future, we base the description and diagnosis on the holotype specimen SNSB-BSPG 1954 I 608 unless otherwise noted.

Despite its immature ontogenetic stage, SNSB-BSPG 1954 I 608 was selected as the holotype of Jabalisaurus tethyensis since it is by far the most complete specimen of the three in terms of the amount of anatomical detail visible.

Description

Based on holotype specimen SNSB-BSPG 1954 I 608 unless otherwise noted.

General observations. The holotype specimen is a very young juvenile, preserved in lateral view (Figure 3). The snout ratio = 0.62 (referred specimens both = 0.65; Table 1), and the skull is high-crowned, although appears lower due to damage to the dorsal orbit. The orbit is completely filled by the scleral ring, and is rather large (orbital ratio = 0.26; referred specimens = 0.23-0.26). Despite the much smaller size of SNSB-BSPG 1954 I 608, both the external diameter and aperture of the scleral ring are larger than in the Aegirosaurus leptospondylus neotype. The narial opening is clearly bilobate, separated by a robust descending process of the nasal and a small ascending process of the maxilla (Figure 4A, B).

Premaxilla. The premaxilla has greatly reduced dorsal exposure relative to the Aegirosaurus neotype, composing just over 1/2 (52%) of the snout (vs. 48% nasal), and 45-48% of the lateral surface relative to the maxilla (vs. 55% premaxillary ratio in the Aegirosaurus neotype). As with the neotype, the premaxillary fossa is present but discontinuous. The dorsal premaxilla is broken immediately anterior to the narial opening; UV photography indicates that the bone fragment identified as the supranarial process by Bardet and Fernández (2000) is part of the underlying nasal. The subnarial process of the premaxilla contacts the anterior jugal posteriorly (Figure 4A, B). The lacrimal appears to be excluded from contact with the premaxilla. The snout is very slender in all three skulls, but appears most slender in JME-SOS-08369 (Figure 9B). However, the dorsal surface of the latter skull appears to still be partially embedded in matrix, exaggerating the slenderness of the rostrum.

In SMNS 54067, the anteriormost premaxillae do not contact each other medially and are rather pointed anteriorly.

Maxilla. The maxilla has limited exposure laterally, being very short anteriorly (barely exceeding the external nares in length) and laterally covered by the jugal posteriorly and premaxilla anteriorly (Figure 4A, B). There is a small lateral exposure of the maxilla ventral to the anterior external nares and anterior to the lacrimal, the posterior edge of which forms a small dorsal process that does not contact the descending process of the nasal. Approximately 16 maxillary tooth positions are present (vs. 12: McGowan, 1976), with the difference in count likely due to the suborbital tooth positions that were difficult to differentiate under natural light.

Delsett et al. (2022) noted differences in maxillary morphology between JME-SOS-08369 and SNSB-BSPG 1954 I 608. These include a proportionately longer maxilla in JME-SOS-08369 relative to the external narial opening (but not relative to the premaxilla; see premaxillary ratios in Table 1). This difference is attributed to dorsoventral compaction of the snout, resulting in the concealment of the anterior lobe of the external narial opening in JME-SOS-08369. JME-SOS-08369 has ca. 21 maxillary tooth positions/18 teeth preserved (vs. 16: SNSB-BSPG 1954 I 608).

SMNS 54067 has ~23 maxillary tooth positions, a much higher count than SNSB-BSPG 1954 I 608. This skull also has the lowest premaxillary ratio (=0.45), indicating that a proportionately longer maxilla could be responsible for the higher maxillary tooth count; however an increase in the number of tooth positions with increasing jaw length is also possible, and may also explain the discrepancy between JME-SOS-08369 and SNSB-BSPG 1954 I 608. In both JME-SOS-08369 and SMNS 54067, the maxillary tooth row extends well under the orbit (Figure 7A-B, Figure 9B), almost to the orbital mid-point; as noted above damage to the suborbital bar may be influencing this trait in SNSB-BSPG 1954 I 608.

Lacrimal. In SNSB-BSPG 1954 I 608, the lacrimal forms the posterior and ventral edges of the posterior external narial opening (Figure 4A-B). A poorly developed ridge is visible on the lateral surface of the orbital process of the element, likely representing the edge of the circumorbital area. The distance between the orbit and external nares is very short. The dorsal surface of the anterior process has a scalloped edge and is thickened. Dorsally, the lacrimal is excluded from contact with the nasal by the narial process of the prefrontal. Ventrally, the lacrimal contacts the jugal and maxilla in lateral view. The lacrimal does not contact the subnarial process of the premaxilla.

Vomer. The vomer is visible in the narial opening, pushed outward during compression of the skull (Figure 4A-B). The vomer is dorsoventrally expanded ventral to the descending process of the nasal. This expanded surface forms a concave choanal wall separated from the more anterior wall of the vestibulum nasi by a ridge. The morphology appears to be identical to that of Ophthalmosaurus, and differs notably from e.g., Platypterygius australis, in which the crest of the vomer forms two diverging processes (Kear, 2005; Moon and Kirton, 2016).

Nasal. The nasal forms the dorsal surface of 48% of the snout. The surface dorsal to the external nares forms three arches in lateral view: a low anterior one, a large, more steeply angled middle arch that forms a laterally projecting flange that descends into the narial opening, and a small, dorsally positioned posterior arch that also bulges slightly laterally and might represent a foramen. The nasal does not contact the lacrimal (Figure 4A-B).

SMNS 54067 preserves a portion of the skull roof, including the posterior nasals. A well-developed internarial depression is present; the internasal suture in this region appears to show extensive asymmetry. The nasals overlap the frontals posteriorly and posterolaterally and articulate with the prefrontal laterally (Figure 7A-E).

Prefrontal. The prefrontal makes up the anterior dorsal edge of the orbit, and sends a broad, poorly mineralized narial process ventrally to form the posterodorsal edge of the external narial opening (Figure 4A-B).

SMNS 54067 preserves the posterior portion of the prefrontal (Figure 7C-D). The prefrontal has a very small medial contact with the frontal and articulates with the postfrontal posteriorly. Evidence of damage to the superficial layer of bone in the region of the frontal-prefrontal articulation means that this contact may have been covered by the overlapping nasal in external view, as is the case in Ophthalmosaurus icenicus (Moon and Kirton, 2016).

Postfrontal. Only the posteriormost postfrontal is preserved in SNSB-BSPG 1954 I 608, overlapping the anterior ramus of the supratemporal on the lateral surface of the skull. A contact with the squamosal is small, if present at all in external view.

The postfrontal is also preserved in SMNS 54067, but has been extensively damaged. It makes up the anterior edge of the upper temporal fenestra, as well as the anterior portion of the lateral edge, and appears to have a small contact with the frontal anteromedially (Figure 7C-E). Posteriorly, the postfrontal articulates with the supratemporal, and posteroventrally with the postorbital. However, the superficial layer of bone has been removed in the lateral temporal region, making the relationships between the postfrontal and other elements difficult to distinguish in lateral view.

Frontal. The frontals are preserved only in SMNS 54067 (Figure 7C-E). The frontals are externally convex. Anteriorly, the internasal depression extends posteriorly onto the anterior frontals. The anterior right frontal is exposed in medial view; in this view it is evident that the frontals extend much further anteriorly under the nasals than is externally exposed. The left and right frontals enclose the anterior parietal foramen. The suture between the posterior frontals and the parietal is somewhat crenulated. The nasals overlap the frontals anteriorly.

Parietal. The parietals are preserved only in SMNS 54067 (Figure 7C-E). The right and left parietals remain in articulation along the interparietal suture, but only the left one is usefully exposed. The parietals form the posterior edge of the parietal foramen and anteriorly are overlapped laterally by the frontals. Posteriorly, the parietal shows a concave posterior edge well anterior to its articulation with the supratemporal. Based on this morphology, the length of the interparietal suture appears to have been very short, and the posterolateral process relatively long.

Postorbital. The postorbital is relatively broad, crescentic in shape (Figure 4C-D, Figure 7A, B). The anterodorsal portion forms a transverse flange, as in Ophthalmosaurus, whereas the posterior and ventral components are laterally oriented.

Supratemporal. Only the posterolateral supratemporal is visible in SNSB-BSPG 1954 I 608; it has a broad exposure on the lateral surface of the cheek, articulating with the squamosal ventrally (Figure 4C-D).

In SMNS 54067, the supratemporal is also preserved (Figure 7A-D). Although somewhat damaged, some general observations can be made. The anterior ramus makes up most of the lateral edge of the upper temporal fenestra, with an elongate anteromedial process excluding the postfrontal from the posterolateral UTF, and a shorter lateral ramus. The medial ramus of the supratemporal forms an interdigitating suture with the posterolateral process of the parietal.

Squamosal. The squamosal is small, triangular, and laterally oriented (Figure 4C-D). It does not appear to reach the postfrontal anteriorly, but this region is not well preserved. Ventrally, the squamosal contacts the quadratojugal.

Quadratojugal. The dorsal portion of the quadratojugal is tall and narrow (Figure 4C-D; Figure 7A-B). The ventral edge is elongate, extending almost as far anteriorly as the anteriormost postorbital, as in Ophthalmosaurus icenicus (Moon and Kirton, 2016). A small quadrate process is present.

Jugal. The dorsal ramus of the jugal is deeply bowed ventral to the postorbital (Figure 3); this is known to be ontogenetically influenced in other ichthyosaurs, related to larger eye size in small juveniles (Miedema and Maxwell, 2022), and this is also likely the case here. The dorsal ramus articulates with the postorbital anteriorly, and the quadratojugal posteriorly (Figure 4C-D, Figure 7A-B). Anteriorly, the jugal extends well past the orbital margin and broadly covers the posterolateral maxilla to contact the subnarial process of the premaxilla (Figure 4A-B). The portion of the jugal ventral to the orbit is not preserved.

In SMNS 54067, the jugal is still deeply bowed ventral to the orbit but bears a small posterior heel (Figure 7A-B). The jugal is grooved along its lateral surface, both posteriorly (SMNS 54067) and anteriorly (JME-SOS-08369; Figure 9B).

Lower jaw. The angular has extensive exposure on the retroarticular process, but rapidly narrows anteriorly (Figure 3, Figure 7A-B). The surangular fossa is well-developed. The dentary fossa begins as intermittent foramina anteriorly and becomes continuous more posteriorly.

The skull of JME-SOS-08369 is exposed in lateroventral view, thus exposing more of the ventral surface of the lower jaw (Figure 9B). This angle of preservation is the reason for the perceived larger angular exposure in this specimen than in the other two skulls. The angular and surangular extend approximately the same distance anteriorly, to a point just posterior to the mandibular symphysis. The splenial is exposed along the medial surface of the lower jaw, and makes up slightly less than half of the mandibular symphysis.

Dentition. Contrary to previous reports, enamel is likely not preserved in SNSB-BSPG 1954 I 608. This was assessed both in natural light and under UV, where differential fluorescence was only faintly developed in some of the maxillary teeth. However, the enamel was clearly ridged, based on faint scalloping of the external surface of the teeth when light was reflected off the dentine (Figure 4E). Enamel ridges appear to have extended from the tooth apex to the base of the enamel layer. Basal to the crown, the surface of the root is smooth and ungrooved. Tooth roots are round in cross-section.

SMNS 54067 has an exceptionally well-preserved dentition, with at least 57 teeth preserved in the upper and 39 teeth preserved in the lower jaw (Figure 7A-B, F). Enamel ridges occur at a density of 17-18/5 mm (Serafini et al., 2022), and are well developed at the crown base but become reduced or absent towards the apex. Heterodonty is pronounced, with posterior maxillary teeth being much shorter and blunter than the anterior dentition. The width at the crown base of the mid-premaxillary teeth is ca. 3.4 mm, becoming broader in the anterior maxillary teeth and narrower in the anteriormost teeth; crown height = 7.0 mm in the mid-premaxillary teeth, becoming reduced posteriorly. Tooth roots are oval in cross-section.

JME-SOS-08369 also shows densely ridged enamel, ca. 18 ridges/5 mm (Figure 9B-C). As in SMNS 54067, the posterior maxillary tooth crowns are much shorter and blunter than the anterior teeth. Tooth crowns in the mid-snout dentition are approximately 2.5 mm wide at the crown base, and crown height is ca. 5 mm.

Scleral ring. The scleral ring of SNSB-BSPG 1954 I 608 is composed of ~14 plates, and measures 79 x 68 mm externally and the aperture diameter is 34 x 32 mm.

The scleral ring in SMNS 54067 consists of 13 plates and measures 106 x 91 mm externally and the aperture diameter is 43 x 42 mm.

Postcranium

Axial skeleton. The anteriormost vertebral column is disarticulated, but beginning in the anterior dorsal region to the posterior dorsal region, the column is in articulation (Figure 3). The wide neural canal observed in SNSB-BSPG 1954 I 608 is likely ontogenetically influenced, caused by negative allometry of the central nervous system relative to the postcranium. The poorly defined di- and parapophyses on the lateral surfaces of the anterior dorsal centra, which are not separated by cortical bone from either each other, the articular face of the centrum or the neural arch facets are also indicative of a young ontogenetic stage.

The atlas-axis neural spines in SNSB-BSPG 1954 I 608 are preserved posterior to the skull. That of the atlas has notably more slender ventral pedicles than that of the axis, and a much shorter neural spine. A weak anterior bulge marks an incipient proatlas process. The atlas neural spine overlaps that of the axis posteriorly.

The anterior dorsal neural spines in SNSB-BSPG 1954 I 608 are capped by a layer of tissue separate from the spines themselves; this is interpreted as mineralizing cartilage at the growing end of the spine and differs in both position and texture from the structures described dorsal to the neural spines in Stenopterygius (McGowan, 1992).

The ribs in SNSB-BSPG 1954 I 608 bear prominent grooves along their anterior and posterior surfaces. As noted by Bardet and Fernández (2000), the tuberculum and capitulum of the ribs are confluent; i.e., the rib has two articular facets but is effectively unicipital (= sheathed bicapitate morphology). This is interpreted as resulting from the extreme osteological immaturity of the specimen, but this character has not been previously described as ontogenetically variable. Gastralia were present, preserved as slender, curved rods.

The anteriormost neural spine preserved in SMNS 54067 is greatly thickened distally. This is very different in morphology from that of the atlantal neural spine of SNSB-BSPG 1954 I 608, and the significance of this thickening is unclear. SMNS 54067 preserves ribs that are clearly bicipital, with broad separation between the capitulum and tuberculum in the anterior dorsal region.

The ribs of JME-SOS-08369 have also been described as bicipital (Delsett et al., 2022). The gastral basket in JME-SOS-08369 is complete and extensive, with the gastralia extending from the pectoral girdle to within ca. 5 centra of the pelvic girdle. A median gastral element is absent. JME-SOS-08369 preserves the complete vertebral column, although preservation makes detailed observations impossible (Figure 9A). Seventy postflexural centra are ossified (Delsett et al., 2022).

Pectoral girdle and forelimb. Of the girdle elements, the interclavicle is preserved in external view, displaced from the rest of the girdle (Figure 3, Figure 5A). It is approximately T-shaped, although the transverse bar is anteriorly convex, and posteriorly is connected to the median stem via broad laminae. The thickened convex portion of the transverse bar projects ventrally relative to the rest of the interclavicle. The transverse bar is slightly longer than the median stem, and bears a ridge parallel to its anterior margin. The median stem is straight and not posteriorly expanded. A partial scapula (right) is preserved in external view; however, the anterior and posterior portions are separated by a broad crack making assessment of details difficult (Figure 3, Figure 5B). The dorsal anterior portion is concave. Assuming the scapula remains in articulation with the coracoid, the coracoid is also from the right side and preserved in external view, and is mediolaterally/ anteroposteriorly equidimensional. The coracoid is partially overlain by the right clavicle; the left clavicle is preserved above. Medially, the clavicles are broad and sheet-like with interdigitating surfaces; laterally they narrow to thin spines. The internal surface at the point where the clavicles narrow is deeply grooved.

Both forelimbs are partially preserved and articulated. A humerus, interpreted as the left one based on the position of the process closer to the midline than to the anterior margin and therefore identified as the dorsal process, is exposed (Figure 3, Figure 5B, C). The distal end of the humerus is damaged anteriorly on the main slab, but two concave facets are present: a larger one for the ulna and a smaller anterior facet for the radius. The facets are clearly offset. A large preaxial facet is visible on the counterpart (Figure 5C). The distal end of the humerus is wider than the proximal end on the main slab, but on the counterslab, it appears that the proximal end is also quite wide, giving the humerus a short, squat shape as is typical for very young individuals. The humerus does not appear to be strongly waisted at the midpoint, but this might also be an ontogenetically dependent character (Johnson, 1977). Proximally, a protruding triangular dorsal process is present, angled anteriorly and situated nearer to the midline of the humerus than to the anterior edge. The crest does not reach the proximodistal midpoint of the humerus.

Both ulnae are preserved, although that on the right is damaged posteriorly (Figure 3, Figure 5B). The ulna has six sides, the smallest being the anterior surface for articulation with the radius. It is unclear if the posterior surface of the ulna was covered in cortical bone; however this trait is expected to be ontogenetically influenced so absence in this individual is not conclusive of the state in the taxon (Maxwell et al., 2014). The radius is pentagonal. The intermedium, while not preserved, would have articulated between the radius and ulna. The left forelimb is disrupted, with a block of six elements oriented distal-to-proximal directly below the radius and ulna. These are assumed to have been displaced from the right limb. Phalanges are generally tightly packed and rectangular in shape, becoming more rounded at the periphery of the fin.

The phalanges in JME-SOS-08369 were previously described as rounded (Delsett et al., 2022); however, numerous polygonal phalanges are visible on this specimen (Figure 10A-B).

Pelvic girdle. Both ischiopubes and both ilia are preserved in SNSB-BSPG 1954 I 608 (Figure 3, Figure 6A-C). The right ischiopubis has been somewhat displaced and is exposed in lateral view (Figure 6A-B); based on this interpretation the left ischiopubis (Figure 6C) is also exposed in lateral view. Bardet and Fernández (2000) interpreted an obturator foramen as absent; Maisch and Matzke (2000, fig. 32) assumed this foramen was present but could not observe it directly. Under UV light, a foramen appears to be present (Figure 6A). The ischiopubis is fully fused and plate-like, measuring 28 mm in length. The ilia are robust and comma-shaped, 23 mm in length.

An ischiopubis is also present in JME-SOS-08369, interpreted as the right and measuring 48 mm in length (Figure 10C). We interpret the ischiopubis as having flipped such that its internal surface is directed externally, and the anterior surface is facing posteriorly. This interpretation may seem implausible given the high degree of articulation of this specimen; however, the contralateral ischiopubis and hind limbs do not appear to be in articulation, indicating some disruption to the region. Moreover, the posteriorly facing edge of the ischiopubis is more consistent with the anterior edge of an ischiopubis based on morphology. No obturator foramen is visible; however, the posteriorly facing side of the element is damaged in a way suggestive of the pubis having been broken near the foramen. The medial (distal) edge is plate-like. Delsett et al. (2022) interpreted two straight, rod-like elements in the posterior abdominal region as ilia. These are morphologically distinct from the ilia of SNSB-BSPG 1954 I 608, which are strongly curved rather than straight. It seems likely that these elements have been misidentified, especially since the figured example (left) does not fluoresce in the same way as the other ossified elements under UV light (Delsett et al., 2022, fig. 6c).

Hind limb. The femur in SNSB-BSPG 1954 I 608 is much shorter than the ischiopubis (Figure 6B-C). Given its close association with the proximal ischiopubis, it is most likely to be the left femur, and the position of the trochanter indicates that it is exposed in dorsal view. Two distal articular facets are visible; the fibular facet appears slightly larger, although incomplete ossification of the distal femur makes this difficult to assess with confidence. Assorted limb elements are preserved near the femur and pelvic girdle, with another cluster further distally. The latter cluster is an articulated hind fin surrounded by preserved soft tissues (Figure 6D). As with Stenopterygius and Hauffiopteryx, the skeletal elements are situated asymmetrically within the soft tissue envelope, nearer to the leading edge of the fin than to the trailing edge (Maisch, 2008; Maxwell and Cortés, 2020). The tibia is large, with a convex proximal facet for articulation with the femur. The fibula appears to be missing or may be situated in the cluster of elements near the femur (Figure 6C). A large postaxial element is preserved, but is not associated with either proximal or distal elements. Functionally, the hind limb has three digits, the middle of which is the longest and the anterior of which is the shortest. Distally, the tibia articulates with a small distal tarsal (see Moon and Kirton, 2016), a large astragalus, and posteriorly with the fibula. The astragalus articulates entirely with the tibia, rather than being positioned between the tibia and fibula. The anterior digit has about three elements anterodistal to the tibia, the central digit has seven elements distal to the tibia, and the posterior digit has seven elements distal to the fibula. The distal posterior digit curves anteriorly, as in Hauffiopteryx. Although more rounded and less tightly articulated than the forelimb elements, the hind limb elements are less rounded and more tightly packed than those of Ophthalmosaurus.

Ontogeny. Numerous postcranial markers, including the orbit completely filled by the scleral ring (Fernández et al., 2005), open sutures between the forelimb elements (Johnson, 1977), lack of definition of the di- and parapophyses in the anterodorsal centra (Maxwell et al., 2016), and a broad neural canal are all indicative of the immature ontogenetic status of SNSB-BSPG 1954 I 608. Based on the number and unambiguous nature of these markers, in combination with the small size of the individual, a relatively early postnatal stage can be inferred. Poor development of the capitulum and tuberculum is here tentatively suggested to represent a useful ontogenetic marker in ophthalmosaurians.

At 473 mm jaw length, SMNS 54067 is the largest specimen in the sample. Using the proportions of JME-SOS-08369, SMNS 54067 would correspond to an individual 1.98 m in total length (vs. 1.84 m for JME-SOS-08369). This is only 68% of the hypothetical maximum inferred length for this species (2.91 m); however, this maximum estimate assumes that SNSB-BSPG 1954 I 608 is a neonate and thus is likely an overestimate. Neither JME-SOS-08369 nor SMNS 54067 are well-enough preserved to confidently assess skeletal maturity. In any case, Jabalisaurus tethyensis was likely not a very large ichthyosaur species.

Soft tissue preservation. Despite originating from different formations and horizons and having undergone highly variable degrees of decay, all three specimens discussed here show extensive soft tissue preservation. In SNSB-BSPG 1954 I 608, this includes the outline of the hind fin (damaged post-collection, but still visible distally), as well as poorly preserved phosphatic remains concentrated mostly in the posterior abdominal region.

In JME-SOS-08369, the body outline is complete and has been described in detail elsewhere (Delsett et al., 2022). In the anterior dorsal region, a small accumulation of indeterminate ganoid scales are preserved, interpreted here as gut contents.

Lastly, in SMNS 54067, there are two types of soft tissue preservation, one of which is only clearly visible under UV-light. The soft tissue easily visible under natural light is located in the anterior abdominal region and dorsal to the vertebral column. Under natural light, the tissue has a cream-white colour and irregular folds, with fine regular ridges faintly visible beneath (Figure 8A). This soft tissue appears dark reddish-brown under UV-light (Figure 8B, D). The soft tissue that is only clearly visible under UV light appears yellow-orange (depending on the UV-light combination that is used) and is located anterodorsal to the other tissue type (Figure 8B-C). Using macro photography, very fine regular ridges are visible, running approximately parallel to the long axis of the body. The soft tissues preserved in this specimen are interpreted as the epidermis and dermis. The whitish, smooth tissue visible under natural light resembles the outermost layer of skin, with the smooth texture and irregular pattern resulting from decomposition forming folds (Lindgren et al., 2018). The second type is interpreted as the dermis, with the ridges corresponding either to dermal ridges formed at the epidermal-dermal interface (Lindgren et al., 2018) or dermal fibres (Lingham-Soliar, 2001). Regardless of interpretation, these morphologies correspond almost exactly with the skin of the early-diverging baracromian ichthyosaur Stenopterygius (Keller, 1992; Lindgren et al., 2018).

OPHTHALMOSAURIA indet.

Referred materials. NHMUK PV OR 42833 (Figure 11). A brief updated description is presented in Appendix 1.

Remarks. Meyer (1863) estimated that 45 mm was missing from the anterior rostrum of NHMUK PV OR 42833; here we consider this a substantial overestimate. Although the anteriormost premaxilla is damaged in this specimen, no more than a few millimeters is missing. The premaxilla contributes 51% to the dorsal snout, more consistent with Jabalisaurus tethyensis than Aegirosaurus leptospondylus, and the premaxillary and prenarial ratios are likewise more consistent with J. tethyensis. However, NHMUK PV OR 42833 cannot be referred to Jabalisaurus tethyensis: the rostrum does not appear to have been demarcated from the skull, as noted by Bardet and Fernández (2000), the prefrontal does not participate in the external narial opening, and the best-preserved tooth indicates that that the enamel was more coarsely ridged (Figure 11B), at ~8 ridges/5 mm. Given the lack of any named ichthyosaurian material from the German plattenkalk deposits exhibiting a similar character state combination, we do not consider this specimen to be referable to any genus at the present time; however, it unquestionably represents a third taxon, distinct from both Aegirosaurus and Jabalisaurus.

Results: Phylogenetic Analysis

Analysis under equal weights parsimony resulted in 80 MPTs of length 604, with most taxa within Ophthalmosauria resolved in a large polytomy. IterPCR pruned 10 taxa, including Jabalisaurus meztli, and resulted in the recovery of a sister-group relationship between Ophthalmosaurus icenicus and J. tethyensis at the base of Ophthalmosauria, whereas Aegirosaurus was resolved near the base of the platypterygiine subclade comprising Caypullisaurus and Platypterygius. Implied weights parsimony (k=12) resulted in a single MPT of length 26.72; Jabalisarus meztli and J. tethyensis formed a sister-group relationship within Ophthalmosaurinae, whereas Aegirosaurus was sister to Parrasaurus in a resolved clade at the base of the platypterygiine subclade recovered under equal weights (Figure 12). Implied weights (k=9) resulted in five MPTs of length 32.60. Jabalisaurus spp. are optimized as the earliest-diverging ophthalmosaurians, whereas the ophthalmosaurines are distributed in a pectinate arrangement along the platypterygiine stem, rootward of Aegirosaurus. Implied weights (k=6) resulted in an incomplete search. Based on congruence with morphology, broad consistency with previously published topologies (Barrientos-Lara and Alvarado-Ortega, 2021b; Campos et al., 2025), and improved resolution relative to the equal weights tree, the IW k=12 topology is preferred.

DISCUSSION

Comparison to the Neotype of Aegirosaurus leptospondylus

Despite its early ontogenetic status, SNSB-BSPG 1954 I 608 is clearly distinct from the neotype of Aegirosaurus leptospondylus, including but not limited to having a less elongated snout (snout ratio of 0.62 vs. 0.73), of which the nasals form a proportionately greater contribution, a shorter, shallower maxilla (premaxillary ratio of 0.48 vs. 0.55), a larger eye, both in absolute as well as relative terms (orbital ratio of 0.26 vs. 0.18), a higher-crowned skull, a narial process of the prefrontal, bilobate external nares, absence of a humerus-intermedium contact and presence of a large facet for the preaxial element, and a much shorter and more rounded hind fin in which the tibia supports the astragalus to the exclusion of the fibula. While not all characters are visible on SMNS 54067 and JME-SOS-08369, the cranial ratio characters in these specimens (Table 1), as well as dental characters, differ from the Aegirosaurus leptospondylus neotype.

Comparison to Jabalisaurus Meztli

Jabalisaurus meztli is described as differing in a suite of characters from J. tethyensis, including the morphology of the posterodorsal narial region and the skull roof. Although we have not had the opportunity to personally examine the holotype material, photographs generously provided by MUDE can clarify a few of these characteristics. The posterolateral process of the frontal, contributing to its unique ‘L’-shape, can confidently be identified as the anteromedial postfrontal, giving the skull roof a much more typical ophthalmosaurian configuration. The relationships between elements in the narial region are difficult to understand, but it seems likely that the lacrimal-prefrontal suture is very similar in morphology to SMNS 54067, and that the anterior prefrontal is quite broad. However, as noted in the diagnosis of Jabalisaurus tethyensis, there is no indication that the splenial in this species plays as large a role in the lower jaw as in J. meztli. Moreover, J. meztli is of larger body size. Thus, we consider the two taxa to be distinct at the species level. The sister-group relationship between J. meztli and J. tethyensis to the exclusion of Ophthlamosaurus icenicus is supported by the presence of a descending process on the posterior dorsal border of the nares, a descending process of the nasal on the dorsal border of the nares, a gracile postorbital ramus of the jugal, a short medial contact between the parietals, and the presence of tightly packed polygonal phalanges.

Comparison to Other Late Jurassic Ophthalmosaurian Ichthyosaurs

Jabalisaurus tethyensis differs substantially from the large-bodied platypterygiines Brachypterygius, Undorosaurus, and Caypullisaurus, which are characterized by robust jaws, a proportionally long postorbital segment, and a rostrum not clearly offset from the skull, in addition to differences involving more subtle osteological features. Caypullisaurus and Brachypterygius are also characterized by substantial differences in forelimb construction: in Caypullisaurus, the intermedium is situated distal to the radius, rather than between the radius and ulna (Fernández, 2001), whereas in Brachypterygius, the intermedium articulates directly with the humerus (Moon and Kirton, 2018).

The platypterygiines Sumpalla argentina and Eternauta patagonica, from the Eastern Pacific of Argentina, while having a slenderer rostrum and less robust dentition than the above taxa, differ from Jabalisaurus tethyensis in several characters. Sumpalla, previously referred to Aegirosaurus (Gasparini et al., 2015), is characterized by a long interparietal suture, a strongly anteriorly deflected preaxial facet on the distal humerus, and the absence of medial fusion between the pubis and ischium in the pelvic girdle (Campos et al., 2021a). In contrast, Eternauta patagonica is more incomplete, but differs from J. tethyensis in the much more anteriorly extensive postorbital, slightly broader quadratojugal, absence of the squamosal, and the dentition, which has an enamel ridge density of only 5-6/5 mm (Campos et al., 2026; measured from fig. 8).

Jabalisaurus is quite similar to Catutosaurus gaspariniae from Argentina(Fernández et al., 2021); this genus also includes material formerly referred to Aegirosaurus (Maisch and Matzke, 2000). C. gaspariniae is characterized by four articular facets on the distal humerus (vs. 3: Jabalisaurus), and the anterior facet is proportionately small. Moreover, the nasal dorsal to the external nares bears a long descending spur in Catutosaurus, rather than a broad constriction, and the tooth enamel is subtly ridged to smooth (Fernández et al., 2021). The participation of the splenial in the mandibular symphysis in Catutosaurus is extensive, more similar to J. meztli than to J. tethyensis.

In addition to rounded, loosely packed phalanges, Arthropterygius spp. differ from J. tethyensis in a broad posterolateral process of the parietal, and the absence of an obturator foramen in the ischiopubis (Delsett et al., 2017; Zverkov and Prilepskaya, 2019).

Gengasaurus, from coeval strata in Italy, is quite fragmentary, but differs from J. tethyensis in the relatively long, narrow humerus, with a small preaxial facet. The pentagonal radius of J. tethyensis also differs from the more rectangular radius (sensu Zverkov and Efimov, 2019) of Gengasaurus.

Jabalisaurus tethyensis bears a great resemblance to Ophthalmosaurus icenicus in overall cranial morphology, and also in postcranial morphology. Jabalisaurus spp. share a sister group relationship with Ophthalmosaurus based on a small, spur-like descending process of the nasal on the dorsal border of the nares and an interclavicle with a median stem equal or exceeding the length of the transverse bar. However, some notable differences are present between the taxa. The posterolateral process of the parietal is more elongate and slender in J. tethyensis, the anterior jugal contacts the premaxilla, the anterior process of the lacrimal does not extend as far anteriorly relative to the narial opening, and the narial process of the prefrontal is more prominent relative to Ophthalmosaurus (Moon and Kirton, 2016). These differences are more similar to the morphologies observed in Nannopterygius; however, Jabalisaurus differs from the latter genus in having a broad, plate-like ischiopubis, relatively prominent preaxial humeral facet, lack of indication of posteriorly pointed coracoids, and details of the dentition (Zverkov and Jacobs, 2020). Moreover, the polygonal phalanges in Jabalisaurus do not closely match the state in either Ophthalmosaurus, Baptanodon, Thalassodraco, or Nannopterygius, with the exception of N. saveljeviensis (Zverkov and Jacobs, 2020).

Palaeobiogeography

The palaeobiogeography of Late Jurassic ichthyosaurian genera has been comprehensively discussed in the literature, with a focus on inferring potential dispersal corridors (Barrientos-Lara and Alvarado-Ortega, 2021a; Campos et al., 2021b) or, in studies undertaken prior to the extensive taxonomic revisions of the past decade, assuming a global distribution of genera (McGowan, 1978; Gasparini and Fernández, 1997; Bardet et al., 2014; Zverkov and Efimov, 2019). Both approaches addressed the problem in a similar way, i.e., asking what ichthyosaur distribution can tell us about palaeogeography and marine habitat connectivity in the Late Jurassic. From these approaches, and from a general understanding of ophthalmosaurian anatomy and palaeogeography, habitat connectivity is expected to have been high.

Despite the apparent high Late Jurassic marine habitat connectivity, the Late Jurassic ichthyosaurian fauna from the proto-Gulf of Mexico has been interpreted as being highly endemic (Barrientos-Lara and Alvarado-Ortega, 2021a). With the description of Jabalisaurus tethyensis, two closely related species-pairs have now been recovered from the German Plattenkalk deposits and the Gulf of Mexico region, namely Jabalisaurus meztli and J. tethyensis, and Parrassaurus yacahuitztli and Aegirosaurus leptospondylus (Figure 12; see also Barrientos-Lara and Alvarado-Ortega, 2021b). These findings challenge the hypothesis of strong endemicity in the Proto-Caribbean, and suggest instead a similar warm-temperate to tropical ichthyosaurian fauna across the northwestern Tethys and proto-Caribbean, possibly showing regional species-level divergence.

Differing from the Tethyan fauna noted above, high latitude European Late Jurassic localities are dominated by Arthropterygius spp. sensu Zverkov and Prilepskaya, 2019 (Svalbard: Arthropterygius [Palvennia] hoybergeti, Ar. [Janusaurus] lundi, Ar. [Kelhauia] sp., Undorosaurus kristiansenae [Delsett et al., 2019; Druckenmiller et al., 2012; Roberts et al., 2014]). Arthropterygius is also present in the sub-Boreal Province, although much less abundant. Undorosaurus, Nannopterygius, and Brachypterygius are widespread in the sub-Boreal Province (UK: Brachypterygius extremus, Nannopterygius enthekiodon, and Thalassodraco etchesi [Jacobs and Martill, 2020; Moon and Kirton, 2018; Zverkov and Jacobs, 2020]; Volga District: Arthropterygius sp., Undorosaurus gorodischensis, U. nessovi, Brachypterygius pseudoscythicus, B. alekseevi, Nannopterygius saveljeviensis, N. yasykovi [Zverkov et al., 2015; Zverkov and Efimov, 2019; Zverkov and Prilepskaya, 2019; Zverkov and Jacobs, 2020]; Poland: Undorosaurus kielanae [Tyborowski, 2016]). Although like Arthropterygius, Undorosaurus is found in both Boreal and sub-Boreal localities, it is in contrast more prevalent in sub-Boreal localities than Boreal ones. The Argentinian (temperate Eastern Pacific) fauna overlaps with the European faunas only in the presence of Arthropterygius (Campos et al., 2020); all other reported genera are endemic (Catutosaurus gaspariniae, Sumpalla argentina, Caypullisaurus bonapartei, and Eternauta patagonica [Fernández, 2007; Fernández et al., 2021; Campos et al., 2021, 2026]).

To explain these distributions patterns, we hypothesize that climate may have exerted a profound influence on ichthyosaurian palaeobiogeography, either indirectly due to its effects on prey species distribution and abundance, or due to inherent genus-level physiological temperature tolerances or adaptations to specific habitats, as in extant toothed whales (Whitehead et al., 2008).

Palaeobiological Significance

Despite a rich fossil record, the palaeobiology of Late Jurassic ichthyosaurs is poorly documented and is generally extrapolated from stratigraphically older taxa. Details of body and caudal fin shape are only known from the Aegirosaurus leptospondylus neotype (Bardet and Fernández, 2000), two indeterminate isolated caudal fins from the Tithonian of Germany (Bauer, 1898; Delsett et al., 2022), and Jabalisaurus tethyensis (JME-SOS-08369; Delsett et al., 2022). Soft-tissue fore- and hind limb outlines are known only for the Aegirosaurus leptospondylus neotype, and now the hind limb outline of the J. tethyensis holotype (Figure 6D). Unlike overall body outlines, which do not seem to show marked disparity between taxa, considerable variation in hind fin shape appears to have persisted into the Late Jurassic in ophthalmosaurians, including short, blunt, rounded fins in J. tethyensis (Figure 13), and more elongate, pointed fins in Aegirosaurus. SMNS 54067 cannot provide details regarding overall body shape; however, the smooth skin preserved in the anterior dorsal region is consistent with what has been reported in other baracromian ichthyosaurs (e.g., Stenopterygius, ? Muiscasaurus sp.) (Lindgren et al., 2018; Martinez-Motta et al., 2026) and adds to the growing body of literature on ichthyosaur skin morphology.

Likewise, direct evidence of diet has previously only been documented in two Late Jurassic ichthyosaurian taxa: an individual from the Oxfordian likely referable to Baptanodon natans (cephalopod hooklets: Massare and Young, 2005; Massare et al., 2014), and a small immature specimen from the Kimmeridge Clay likely referable to Brachypterygius sp. (actinopterygian fish remains and cephalopod hooklets: Naish and Moon, 2020). Gastric contents preserved in JME-SOS-08369 indicate that the diet of J. tethyensis included small ganoid-scaled actinopterygian fishes (Figure 13), contributing to this rather sparse record.

CONCLUSIONS

We report a second named genus of ophthalmosaurian ichthyosaur from the late Kimmeridgian-early Tithonian of Bavaria, Germany, Jabalisaurus, previously only known from the Kimmeridgian of Mexico. This increases the documented generic diversity of Late Jurassic ichthyosaurs from southern Germany, a finding that is consistent with the high ichthyosaurian genus-level diversity in sympatry documented from coeval Lagerstätte in both the northern and southern hemispheres.

We refer the German material to a new species, J. tethyensis, based on the reduced splenial contribution to the mandibular symphysis relative to the type species J. meztli, as well as and uncertainties regarding the influence of taphonomy on described cranial morphology in J. meztli. J. tethyensis is distinct from the co-occurring genus Aegirosaurus based on a suite of discrete and ratio-based cranial and postcranial characters.

Preserved gut contents suggest Jabalisaurus tethyensis consumed small bony fishes as part of its diet; soft-tissue preservation indicates that the skin on the torso was smooth, as in all baracromians documented thus far.

The occurrence of the genus Jabalisaurus in the northwestern Tethys weakens the interpretation of the proto-Caribbean region as a hotspot of ichthyosaur endemism during the Late Jurassic, suggesting instead that a tropical Tethyan ichthyosaurian fauna was broadly distributed globally, distinct from the more temperate to polar faunas described from the UK, Svalbard, and Russia, and Argentina.

ACKNOWLEDGMENTS

Thanks to S. Cooper (SMNS) for assisting with photographic documentation of JME-SOS-08369; C. Ifrim (JME), O. Rauhut (SNSB-BSPG), and M. Jones (NHMUK) for collections access, and to J. Madrazo Fanti (MUDE) for providing photos of Jabalisaurus meztli. The Lauer Foundation for Paleontology, Science and Education is profoundly thanked for providing to GS the necessary equipment for the triple wavelength UV analysis. GS was founded by an Erasmus + traineeship 2022/2023 program during the study and analysis of SMNS 54067.

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