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| Balaenognathus maeuseri Martill, Frey, Tischlinger, Mäuser, Rivera-Sylva & Vidovic, 2023 |
Abstract
A new long-legged, spatula-beaked, filter-feeding pterodactyloid pterosaur from Upper Jurassic plattenkalk limestones at Wattendorf, Bavaria, Southern Germany, is remarkable for its completeness, unusual dentition and hints of the preservation of soft tissues, including wing membranes. The fully articulated specimen displays both jaws each side with over one hundred sub-parallel-sided teeth with a small, slightly hooked expansion at the crown tip. There are at least 480 teeth in total. The tip of the rostrum widens to a spatula-like, laterally concave structure with teeth only along its lateral margins. The straight anterior margin is devoid of teeth allowing plankton-rich water to stream in, while the teeth interdigitate forming a fine mesh trap. A slightly up swept rostrum assisted filtering by probable pulsating movements of the long neck, while wading or swimming through shallow water.
Keywords: Pterosauria, Ctenochasmatidae, Jurassic, Lagerstätte, Filter-feeding, Germany
Systematic palaeontology
Pterosauria Kaup, 1834
Monofenestrata Lü et al., 2010
Pterodactyloidea Plieninger, 1901
Family Ctenochasmatidae Nopcsa, 1928.
Genus Balaenognathus n. gen.
Derivation of generic name. Balaena is the generic name of the bowhead whale (Balaena mysticetus) a ram filter feeding cetacean. Thus balaena (Latin) for the bowhead whale and gnathus (Latin) for jaw. The genus name refers to the filter mechanism of bowhead whales that have superficially similar feeding strategies.
Balaenognathus maeuseri n. g., n. sp.
Derivation of specific name. “maeuseri” after our coauthor and good friend Matthias Mäuser who so sadly passed away during the writing of this paper.
Holotype. A single articulated specimen housed at the Naturkunde-Museum Bamberg (Natural History Museum Bamberg) under collection number NKMB P2011-633 (Fig. 2).
Type locality. Quarry of Andreas Schorr GmbH & Co. KG near Wattendorf, Bavaria, Southern Germany (Fig. 1B), at coordinates 50° 02′ 17″ N 11° 06′ 57″ E.
Type horizon and age. Bed 12 of the Wattendorf Plattenkalk, Torleite Formation, Eudoxus ammonite Biozone, Upper Jurassic, Upper Kimmeridgian to Tithonian (~ 157–145 mya).
Diagnosis: Autapomorphies: The new specimen is distinguished as a new taxon on account of two conspicuous apomorphies: 1. terminal end of the jaws forming a triangular spatulate platform lacking teeth on its anterior border, 2. teeth long, slender and with a hook on the crown tip, 3. a unique combination of wing and hindlimb bone ratios typical of the Ctenochasmatidae.
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| Balaenognathus maeuseri gen. et sp. nov. (NKMB P2011-633): holotype and only reported specimen, Torleite Formation of Wattendorf (Late Jurassic). Some small gaps in the slab have been infilled with minor restoration of some bones. A portion of the distal extremity of the left metacarpal IV and part of the left anterior ilium process are known to be missing. Some other missing elements (e.g., the pteroids) may be concealed under larger bones |
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| Balaenognathus maeuseri gen. et sp. nov.: possible methods of suspension feeding. A Surface thrust feeding; notice that the filter zone should be above the water surface; B B′, gular pump feeding, B, intake phase, B′, filter phase with lingual assistance. C, D Range of water depth for passive ram feeding. C minimum water level; D maximum water level |
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| Balaenognathus maeuseri gen. et sp. nov.: tentative line reconstruction of the skull |
Conclusions:
A Late Jurassic pterosaur from the Wattendorf Plattenkalk of the Torleite Formation of Wattendorf, southern Germany, represents a new genus and species of ctenochasmatid pterosaur, Balaenognathus maeuseri. It is diagnosed on three apomorphies: 1, long and slender teeth terminating in a small hook or knob; 2, a truncated edentulous anterior jaw termination, and 3, a tooth count greater than 480. The immense number of fine, slender teeth that interdigitate in occlusion mechanically precludes any mode of feeding other than filter feeding. In a cladistic analysis, Balaenognathus nests within the Ctenochasmatidae together with other well-known forms such as Pterodaustro, Ctenochasma and Gnathosaurus; however, the group remains rather unresolved. Within the Ctenochasmatoidea, Balaenognathus appears to be a sister taxon to the clade Moganopterinae sensu Longrich et al. (2018) comprising Aurorazhdarcho, Gladocephaloides, Feilongus, Moganopterus and Lonchodectes. The unique jaw morphology, especially of the anterior terminus of the rostrum reveals a wide, edentulous rostral spatula narrowing posteriorly in the manner of a funnel for the ingress of plankton that was filtered out over its array of interlocking needle-shaped teeth. The function of the hooked tooth crowns remains an enigma, but they appear to have limited the gape of the jaws.
David M. Martill, Eberhard Frey, Helmut Tischlinger, Matthias Mäuser, Héctor E. Rivera-Sylva and Steven U. Vidovic. 2023. A New pterodactyloid Pterosaur with A unique Filter-feeding Apparatus from the Late Jurassic of Germany. PalZ. DOI: 10.1007/s12542-022-00644-4
