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| Apolithabatis seioma Türtscher, Jambura, Spindler & Kriwet, 2025 |
Abstract
The Late Jurassic fossil deposits of southern Germany, collectively known as the ’Solnhofen Archipelago’, are one of the world’s most important sources of Mesozoic vertebrates. Complete skeletons of cartilaginous fishes (Chondrichthyes), whose skeletal remains are rare in the fossil record and therefore all the more valuable, are represented, among others, by exceptionally well-preserved rays (superorder Batomorphii). Despite their potential for research in several areas, including taxonomy, morphology, ecology, and phylogeny, the number of studies on these chondrichthyans is still very limited. Here, we identify a previously unknown ray, †Apolithabatis seioma gen. et sp. nov., which represents the first record of a ray species from the upper Kimmeridgian of Painten, Germany, and thus the oldest Late Jurassic ray taxon from Germany based on skeletal remains. This new batomorph is characterised by a unique body shape and a combination of skeletal features that distinguish it readily from all other known Late Jurassic rays. Two different morphometric approaches confirm differences in body shape and proportions to all known Late Jurassic conspecifics. We thus extend the recent taxonomic revision of these rays and include all described holomorphic specimens in a phylogenetic framework using strict cladistic principles. The phylogenetic analysis reveals all Late Jurassic batomorphs to represent a monophyletic group, for which we introduce the new order Apolithabatiformes, which is sister to all other batomorphs representing a stem group. While the phylogenetic relationships within Apolithabatiformes ord. nov. remain largely unresolved, †Apolithabatis gen. nov. is placed as the sister to †Aellopobatis. This highlights that, despite considerable progress in our understanding of the diversity and phylogeny of early rays, difficulties remain in establishing robust relationships within batomorphs. We therefore emphasise the importance of comprehensive studies of completely preserved fossil cartilaginous fishes to obtain a better understanding of chondrichthyan evolution and their systematics in deep time.
Systematic palaeontology
Class CHONDRICHTHYES Huxley, 1880
Subclass ELASMOBRANCHII Bonaparte, 1838
Cohort EUSELACHII Hay, 1902
Subcohort NEOSELACHII Compagno, 1977
Superorder BATOMORPHII Cappetta, 1980
†APOLITHABATIFORMES ord. nov.
We consequently propose a new order, †Apolithabatiformes ord. nov., which includes the single family, †Spathobatidae with the genera †Aellopobatis, †Apolithabatis gen. nov., †Asterodermus, †Belemnobatis, †Kimmerobatis, and †Spathobatis. This order represents the most plesiomorphic clade within Batomorphii being placed on the stem of the total group Batomorphii. It is possible that the hitherto undescribed Late Jurassic batomorph from Argentina, previously considered merely as Batomorphii indet. by Cione (1999) [14], also belongs to this order, which, however, can only be clarified by a detailed examination of the specimen.
Type species. †Apolithabatis seioma gen. et sp. nov.
Included taxa: †Aellopobatis bavarica, †Apolithabatis seioma gen. et sp. nov., †Asterodermus platypterus, †Belemnobatis spp., †Kimmerobatis etchesi, †Spathobatis spp.
Etymology: The name ’Apolithabatiformes’ is composed of two Greek words, i.e., ’aπολίθωμα’ (apolíthoma) meaning ’fossil’ and ’βατίς’ (batís) meaning ’ray’ or ’skate’.
Diagnostic characters. Elongated mesopterygium contiguous with propterygium and similar in shape; lateral articulation of antorbital cartilages (if present) to nasal capsules; two true fin spines anterior to dorsal fins (absent in some taxa);
Family †SPATHOBATIDAE Dames, 1888
†APOLITHABATIS gen. nov.
Type species. †Apolithabatis seioma gen. et sp. nov.
Etymology: Identical to that of the order †Apolithabatiformes (see above): the genus name ’Apolithabatis’ is composed of two Greek words, i.e., ’Απολίθωμα’ (apolíthoma) meaning ’fossil’, and ’βατίς’ (batís) meaning ’ray’ or ’skate’.
Stratigraphic and geographic distribution: Only known from the upper Kimmeridgian (Upper Jurassic) of the ’Solnhofen Archipelago’ (Painten), Bavaria, Germany.
Diagnosis: A guitarfish-like batomorph unique in having the following combination of characters: heart-shaped disc that is wider than long; pointed snout; antorbital cartilages present but reaching less than halfway between the nasal capsules and the propterygium; vertebral centra extending less than half of the synarcual length; large mesopterygium tangent to the propterygium; 40 pectoral radials (9 propterygial, 11 mesopterygial, 20 metapterygial); no pectoral radials articulate directly with the scapulocoracoid between the meso- and metapterygium; pectoral radials segmented in up to five segments; at least 16 pairs of ribs; 19 basipterygial radials (including one compound radial); puboischiadic bar curved anteriorly; no postpelvic processes present; broad and triangular lateral prepelvic processes; well-developed and plate-like haemal and supraneural spines; conspicuous bulge-like structure formed by the supraneural spines in front of each dorsal fin; no fin spines present.
†APOLITHABATIS SEIOMA gen. et sp. nov.
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| Environmental reconstruction showing †Apolithabatis seioma gen. et sp. nov. in association with a juvenile pleurosaurid. |
Julia Türtscher, Patrick L. Jambura, Frederik Spindler and Jürgen Kriwet. 2025. Insights into Stem Batomorphii: A New holomorphic Ray (Chondrichthyes, Elasmobranchii) from the upper Jurassic of Germany. PLoS ONE. 20(1): e0310174. DOI: doi.org/10.1371/journal.pone.0310174
