Strophodus timoluebkei, Carrillo-Briceño & Stössel & Kindlimann & Klug, 2025

Strophodus timoluebkei sp. nov.

( Figs. 2 View Fig , 3 View Fig , and 4).

Etymology In honor of Mr. Timo Lübke, who found the specimen and kindly donated it to the paleontological collection of the University of Zurich.

Holotype PIMUZ A/I 5724 , three teeth and a fragment of another, in light grey limestone matrix.

Type locality and horizon South-east flank of the “ Chli Mythen ”, Sulzfluh Limestone Fm. ( Middle Oxfordian to Late Tithonian ).

Referred material The holotype and only specimen of Strophodus timoluebkei sp. nov. is represented by one anterior and two lateral crushing-type teeth likely from the same individual in semi-articulated position. Most of the tooth roots are still embedded or partially exposed in limestone matrix. Only a small fragment of the root of a fourth tooth is preserved and embedded in the same block. The assignment of these teeth to the upper or lower jaw is not possible due to the incompleteness of the material. The ZooBank LSIDs (Life Science Identifiers) for this publication is: urn:lsid:zoobank.org:pub:.

Diagnosis

Hybodontiform shark-like chondrichthyan species with a crushing-type dentition distinguished by the following features: (1) high degree of crown heterodonty between anterolateral and lateral teeth. (2) anterolateral teeth with subtriangular shape, lacking occlusal crest and characterized by a reticular ornamentation with well-defined folds that descend from the domed crown. (3) lateral teeth of the second lateral file with a subrectangular shape and wider mesio-distally than labio-lingually. The crown is high, slightly domed in the mesial part and lacking an occlusal crest, with an ornamentation that consists of a finely pitted reticulated pattern on most labial sections of the crown, which turn into numerous strong parallel folds labio-lingually aligned along the lingual section of the crown. Labial border is vertical and the lingual one inclined and shorter, and the root is high with a flat base.

Description

Anterolateral tooth. PIMUZ A/I 5724-a is a mesio-distally short tooth ( 20 mm in length, 12 mm wide and 12 mm high) with a subtriangular shape in occlusal outline and a domed crown that lacks an occlusal crest ( Fig. 2 View Fig ). The ornamentation consists of a reticular pattern with well-defined folds that descend from the dome of the crown. The enameloid of the lingual edge is ornamented with irregular vertical ridges, and the labial border and part of the root of this section are missing. The root section corresponding to the lingual surface is embedded in the matrix and thus, it cannot be examined. In general, PIMUZ A/I 5724-a appears to have a high root. The other isolated root fragment embedded in the matrix could belong to an anterior tooth, however, it does not display any diagnostic features.

Lateral teeth. Both lateral teeth PIMUZ A/I 5724-b and PIMUZ A/I 5724-c likely belong to the second lateral file. They have well-preserved crowns and are larger than the anterolateral tooth ( Fig. 3 View Fig ). The crowns are subrectangular in shape with a weakly lingually arched contour in occlusal outline. They are wider mesio-distally than labio-lingually long (PIMUZ A/I 5724-b: 51 mm length, 24 mm wide, and 20 mm high; PIMUZ A/I 5724-c: 49 mm length, 28 mm wide, and 20 mm high). The mesial part of the crown is thicker than the distal one and it becomes slightly domed, and no crest is visible. The labial border is vertical (90° to the occlusal surface, Fig. 3F View Fig ), while the lingual one is more inclined and somewhat shorter ( Fig. 3G View Fig ). The enameloid of the labial border is densely ornamented with fine irregular vertical ridges, somewhat reticulated, while on the lingual border, it is finely reticulated and pitted. The occlusal ornamentation consists of a finely pitted reticulated pattern on most labial sections of the crown, which turns into numerous parallel strong folds labio-lingually aligned along the lingual part of the crow ( Figs. 3 View Fig , 4 View Fig ). PIMUZ A/I 5724-c shows what appears to be slight signs of functional wear on the labial section of the crown ( Fig. 3C View Fig ), although we do not rule out that this could also be the result of erosion. Much of the root of both lateral teeth is still embedded in the matrix (e.g., Fig. 2 View Fig ), but the exposed parts show that it is high, with a flat base and it probably does not protrude beyond the lingual and labial edges of the crown. Foramina are randomly distributed all over the root, and small foramina are arranged in a line that follows the base of the crown on the labial side.

Comparison

Morphological features used for species identification in Strophodus focus on dental traits due to the lack of other diagnostic skeletal elements ( Stumpf et al., 2022, 2023). Consequently, we compare Strophodus timoluebkei sp. nov. from the Upper Jurassic of Switzerland to the other 13 Strophodus species from the Jurassic of Africa, Asia and Europe, and Late Cretaceous of South America ( Carrillo-Briceño & Cadena, 2022; Kumar et al., 2022; Rees & Underwood, 2008; Sharma & Singh, 2021; Stumpf et al., 2022, 2023; Szabó & Főzy, 2020); the diagnostic differences are presented below.

Strophodus timoluebkei sp. nov. differs from S. atlasensis from the Lower–Middle Jurassic of Morocco and India ( Bhosale et al., 2024; Stumpf et al., 2023), since the latter is characterized by bulbous teeth of the second lateral file with a rather flat crown with a typical subrectangular to bean-shaped occlusal outline and a finely reticulate ornamentation consisting of very small densely packed pits ( Stumpf et al., 2023, Figs. 2 View Fig , 3 View Fig ). Strophodus atlasensis was described based on an incomplete articulated well-preserved dentition, in which the anterior teeth are missing, and their morphology is thus unknown.

Strophodus dunaii from the Aalenian of Hungary can be differentiated from S. timoluebkei sp. nov., by their teeth displaying a low and wide transversal ridge that runs along the entire crown surface and by the complex ornamentation composed of branching folds and ridges at the higher crown parts turning into a minutely reticulate pattern towards the crown edges ( Szabó & Főzy, 2020, Figs. 2–3 View Fig View Fig ).

Strophodus indicus , another species from the Bathonian of India, has mesio-distally elongated, narrower lateral teeth, which are rectangular in shape, with a flat crown with an occlusal ornamentation composed of prominent enameloid folds forming a ridge-and-groovepattern ( Sharma & Singh, 2021, Fig. 4 View Fig ).

Strophodus timoluebkei sp. nov., can be differentiated from S. jaisalmerensis from the Bathonian of India by the latter having mesiodistally elongated lateral teeth with a parallelogram-shaped outline, with a remarkably thin and almost flat or gently sinuous, domed crown bearing a uniformly finely reticulated ornamentation across the entire crown ( Kumar et al., 2022, Figs. 4 View Fig , 5 View Fig ). The anterior teeth S. jaisalmerensis , although with a sub-triangular to rhomboidal occlusal outline ( Kumar et al., 2022, Fig. 4h–i View Fig ), appear to be more elongated than those from S. timoluebkei sp. nov. and lack well-defined folds that descend from the dome of the crown.

Strophodus timoluebkei sp. nov. differs from S. magnus from the Bathonian of Europe and India in the teeth of the latter species having a second lateral file with a quadrangular, mesiodistally elongated and flat or weakly domed crown with an expanded mesial extremity projected labially and with a uniformly finely reticulate ornamentation ( Bhosale et al., 2024; Rees & Underwood, 2008; Rigal & Cuny, 2016; Sharma & Singh, 2021). Anterior teeth in both S. magnus and S. timoluebkei sp. nov. have a subtriangular outline, but these teeth of the former species have an ornamentation, which is uniformly and finely reticulated ( Rees & Underwood, 2008; Rigal & Cuny, 2016). In contrast, the anterior teeth of S. timoluebkei sp. nov. appear to have a more domed crown with a reticular pattern with well-defined folds that descend from the dome.

Strophodus medius from the Bathonian of England, France, and India, was described based on an articulated dentition ( Rees & Underwood, 2008, Fig. 3 View Fig ). Its lateral teeth from the second file, defined as fourth row teeth by Rees and Underwood (2008), are characterized by a mesio-distally elongate rectangular outline with a reticulate ornamentation completely covering the occlusal part of the teeth. These teeth are more elongated than those of S. timoluebkei sp. nov. The anterior teeth of S. medius have crowns highly domed with prominent occlusal crests, characters not observed in our specimen PIMUZ A/I 5724-a.

In comparison to Strophodus rebecae from the Valanginian–Hauterivian of Colombia, this species has relatively short lateral teeth with a characteristic parallelogram outline shape with a pointed and lingually oriented mesial extremity and with a less domed crown with a finely pitted reticulated pattern ( Carrillo-Briceño & Cadena, 2022, Fig. 2 View Fig ). The shorter lateral teeth in S. rebecae differentiate this species from S. timoluebkei sp. nov. and other Jurassic Strophodus species.

Strophodus timoluebkei sp. nov. anterolateral teeth differ from those of S. reticulatus from the Middle Triassic ( S. cf. reticulatus according to Rieppel, 1981) and Middle Jurassic of Europe in possessing crowns lacking an occlusal crest with a strong ornamentation characterized by radiating ridges ( Agassiz, 1838, plate 17; Stumpf et al., 2021, Figs. 7S–7U; Brignon, 2023, Fig. 10). Anterolateral teeth of S. reticulatus are characterized by having strongly domed crowns with occlusal crests ( Brignon, 2023, Fig. 10, 11). In reference to the S. reticulatus teeth from the Callovian of the Oxford Clay at Fletton ( UK), these, according to Brignon (2023), appear to belong to a different species of Strophodus . Originally, these teeth were referred to “ Asteracanthus ornatissimus var. flettonensis ” by Woodward (1888, 1889), and later to A. ornatissimus or S. reticulatus by other authors (see Brignon, 2023, pp. 19–20). Brignon (2023) designated the teeth from the Callovian of the Oxford Clay under the new combination Strophodus flettonensis ( Woodward, 1888) , arguing that lateral teeth are characterized by a slight occlusal ridge parallel to the labial and lingual borders, while the lateral teeth of S. reticulatus lack this ridge and are relatively wider in their labiolingual direction, giving them a more robust appearance. The anterolateral and lateral teeth of the Oxford Clay differ also from the teeth of S. timoluebkei sp. nov. (see references in Brignon, 2023, pp. 19–20), and a further redescription of these Oxford Clay specimens is needed to validate them as a species distinct from S. reticulatus .

Strophodus subreticulatus from the Kimmeridgian of Switzerland differs from S. timoluebkei sp. nov. in having lateral teeth that appear to be wider mesio-distally, attaining a parallelogram-shaped occlusal outline with flat to slightly domed crowns ( Agassiz, 1838, plate 18, Figs. 5 View Fig –10).

Strophodus timoluebkei sp. nov. differs from S. smithwoodwardi from the Toarcian of Switzerland in the presence of lateral teeth in the second file with a more rectangular outline, with a straighter labial edge, a thicker and slightly domed crown in the mesial section, and an ornamentation with finely pitted reticulated pattern and numerous parallel strong folds labio-lingually aligned along the lingual part of the crow. In contrast, the equivalent teeth of the holotype of S. smithwoodwardi (see Peyer, 1946, plate 2) have less rectangular outlines with the labial and lingual edges more concave and convex, respectively, and the crown is less domed in the mesial section with a finer reticular ornamentation lacking a “pitted pattern” as in teeth PIMUZ A/I 5724b–c. The most significant difference between the lateral teeth of these two species is that in S. smithwoodwardi the lingual edge of the crown tends to be angled (acute angle) in profile view with a characteristic smooth surface ( Peyer, 1946, plate 2, Fig. 7), while in S. timoluebkei sp. nov., the lingual edge is shorter, slightly inclined, and the enameloid is densely covered with fine irregular vertical ridges ( Fig. 3G View Fig ). The smooth and angled lingual edge is a feature that we have observed in all the S. smithwoodwardi lateral teeth described by Peyer (1946). The anterior teeth in the new species described here and those of S. smithwoodwardi ( Peyer, 1946, plate 4) are similar in occlusal outline, but the crown is more domed and heavily ornamented in S. timoluebkei sp. nov.

Strophodus tenuis from Aalenian–Bathonian strata of England and Germany is differentiated from S. timoluebkei sp. nov. mainly by the presence, in the former, of mesio-distally more elongate and slenderer anterolateral and lateral teeth with a sigmoid curvature in occlusal outline and well developed and asymmetrically situated domed areas (see Agassiz, 1838, plate 18, Figs. 16–25; Rees & Underwood, 2008, plate 5, Figs. 12–16). The ornamentation of lateral teeth of S. tenuis is characterized by folds that form a reticulate pattern with smooth areas on the lateral sides ( Rees & Underwood, 2008). Strophodus longidens from the Bathonian of northern France, which is the type species of the genus, can be differentiated from S. timoluebkei sp. nov. mainly by the many mesio-distally elongate anterolateral and lateral teeth, especially the last ones having asymmetrically situated domed areas ( Agassiz, 1838, plate 16, Figs. 1 View Fig –8). No detailed information on tooth ornamentation was provided by Agassiz (1838), and apparently, the holotype was destroyed during the Second World War ( Rees & Underwood, 2008; Szabó & Főzy, 2020).

The second lateral teeth of S. udulfensis from the Kimmeridgian of Switzerland and Poland are mesio-distally elongated with a parallelogram-shaped occlusal outline, a domed crown in the mesial part with a strong reticulated ornamentation that is smaller and more densely packed along the outline of the crown ( Leuzinger et al., 2017, Fig. 7). The morphological pattern of the anterior and lateral teeth of S. udulfensis allows a differentiation from S. timoluebkei sp. nov.