Balaenognathus Temporal range: Late Jurassic, ~ | |
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Holotype specimen | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Order: | † Pterosauria |
Suborder: | † Pterodactyloidea |
Family: | † Ctenochasmatidae |
Genus: | † Balaenognathus Martill et al., 2023 |
Species: | †B. maeuseri |
Binomial name | |
†Balaenognathus maeuseri Martill et al., 2023 | |
Balaenognathus (meaning "bowhead whale jaw") is an extinct genus of ctenochasmatid pterosaurs from the Late Jurassic Torleite Formation of Bavaria, Germany. The genus contains a single species, B. maeuseri, known from a nearly-complete, articulated skeleton. [1]
The Balaenognathus holotype specimen, NKMB P2011-633, was discovered in sediments of the Torleite Formation, dated to the upper Kimmeridgian–Tithonian ages of the late Jurassic period, near Wattendorf, Bavaria, in southern Germany. The fossil was accidentally discovered in September 2011 while crocodylomorph bones were being collected. The specimen consists of a well-preserved, nearly-complete, articulated individual. Wing membrane soft tissue is preserved in a small part of the specimen. The specimen is preserved on a slab consisting of 17 pieces, lacking only part of the left wing-finger metacarpal, the articular area of a wing-finger phalanx, including the three digits of the left wing, and a small portion of the left ilium. [1]
In 2023, Martill et al. described Balaenognathus maeuseri, a new genus and species of ctenochasmatid pterosaurs, based on these fossil remains. The generic name, "Balaenognathus", combines a reference to the bowhead whale ( Balaena mysticetus ) with the Latin word "gnathus", meaning "jaw", in reference to its inferred filter feeding strategies. The specific name, "maeuseri", honours coauthor Matthias Mäuser, who died before the paper's publication. [1]
Balaenognathus is a medium-sized ctenochasmatid, with a wingspan of 1.17 metres (3.8 ft). Its limb bones have similar proportions to Cycnorhamphus and Pterodaustro . Its snout is very distinctive among pterosaurs, with the rostrum tip forming a wide spatula shape. The upper jaw is curved more strongly than the lower jaw, indicating that Balaenognathus would have been unable to entirely close its mouth. The holotype specimen has more than 480 needle-shaped teeth, with hooked tips. The teeth are limited to the sides of the jaw, while the front remains clear. [1]
The specialized dentition and spatula-shaped rostrum strongly suggest adaptations for filter feeding. Balaenognathus may have fed in plankton-rich water, using its teeth as a form of filter trap. It likely allowed water to enter through the toothless front of the jaws, after which the water flow was split by a keel on the midline of the palate. Water could then be forced out through the interlocking teeth on both sides, allowing the food to be filtered out. [1]
Martill et al. (2023) recognized three potential methods for maintaining water flow while feeding. Firstly, there is the possibility of active ram feeding, which requires an animal to move its head forward through the water. However, they considered that it would be impossible for an individual to skim the water with the jaws while flying, due to the high water resistance and drag that would occur. The alternate form of ram feeding would be to wade, pushing the head through the water. This is also unlikely, as the neck is too short to effectively push water up the mouth. If this is how Balaenognathus fed, the most effective angle for the head would be slightly submerged at around 30° to the water's surface. [1]
The second proposed feeding method is passive suspension feeding, which is observed almost entirely only in extant invertebrates. In suspension feeding, the head is held still in the direction of a natural water current, flushing the suspended food into the mouth. To be effective, the water must be rich in food particles, and the animal would further depend on water flowing at a suitable speed and at an appropriate depth for the animal to stand in the current. [1]
The third method Martill et al. proposed, gular pumping, is similar to some extant dabbling ducks, where the mouth produces an active water current. The musculus depressor mandibulae would open the mouth using the retroarticular process as a lever, creating suction to draw water in at the front. When the mouth closed, food could be obtained. Relatively flexible tooth crowns would help ensure interlocking rows of teeth. Since the jaw curvature may have caused water loss at the front, this could be compensated by an increased swallowing capacity through a vertical downward movement of the powerful tongue. An upward movement would have enhanced the squeezing action. With this method, the animal's head could be completely submerged underwater. Balaenognathus likely implemented both passive suspension feeding and gular pumping. [1]
Martill et al. (2023) recovered Balaenognathus as a member of the Ctenochasmatidae, as the sister taxon to a clade formed by Aurorazhdarcho, Gladocephaloideus, Feilongus, Moganopterus, and Lonchodectes. Their results are shown in the cladogram below: [1]
Balaenognathus was discovered in layers of the Torleite Formation, which dates to the upper Kimmeridgian, between 152.1 ± 0.9 and 157.3 ± 1.0 million years ago. The dinosaur Sciurumimus has also been described from the formation. [2] Fossils belonging to crocodylomorphs, turtles ( Eurysternum ), rhynchocephalians ( Sphenofontis ), fish, and ammonites ( Aulacostephanus eudoxus ) have also been discovered there. [3]
Pterodactylus is a genus of extinct pterosaurs. It is thought to contain only a single species, Pterodactylus antiquus, which was the first pterosaur to be named and identified as a flying reptile and one of the first prehistoric reptiles to ever be discovered.
Rhamphorhynchus is a genus of long-tailed pterosaurs in the Jurassic period. Less specialized than contemporary, short-tailed pterodactyloid pterosaurs such as Pterodactylus, it had a long tail, stiffened with ligaments, which ended in a characteristic soft-tissue tail vane. The mouth of Rhamphorhynchus housed needle-like teeth, which were angled forward, with a curved, sharp, beak-like tip lacking teeth, indicating a diet mainly of fish; indeed, fish and cephalopod remains are frequently found in Rhamphorhynchus abdominal contents, as well as in their coprolites.
Pterodaustro is a genus of ctenochasmatid pterodactyloid pterosaur from South America. Its fossil remains dated back to the Early Cretaceous period, about 105 million years ago.
Batrachognathus is an extinct genus of anurognathid pterosaur from the Late Jurassic Karabastau Formation of the central Asian republic of Kazakhstan. The genus was named in 1948 by the Russian paleontologist Anatoly Nicolaevich Ryabinin. The type species is Batrachognathus volans. The genus name is derived from Greek batrakhos, "frog" and gnathos, "jaw", in reference to the short wide head. The specific epithet means "flying" in Latin.
Kepodactylus is an extinct genus of ctenochasmatid pterodactyloid pterosaur from the Kimmeridgian-Tithonian-age Upper Jurassic Morrison Formation of Colorado, United States.
Plataleorhynchus is a genus of ctenochasmatid pterodactyloid pterosaur from the Late Jurassic to Early Cretaceous periods of what is now the Purbeck Limestone of Dorset, England.
Ctenochasmatoidea is a group of early pterosaurs within the suborder Pterodactyloidea. Their remains are usually found in what were once coastal or lake environments. They generally had long wings, long necks, and highly specialized teeth.
Ctenochasmatidae is a group of pterosaurs within the suborder Pterodactyloidea. They are characterized by their distinctive teeth, which are thought to have been used for filter-feeding. Ctenochasmatids lived from the Late Jurassic to the Early Cretaceous periods.
The Solnhofen Limestone or Solnhofen Plattenkalk is a collective term for multiple Late Jurassic lithographic limestones in southeastern Germany, which is famous for its well preserved fossil flora and fauna dating to the late Jurassic (Kimmeridgian-Tithonian). The paleoenvironment is also often referred to as the Solnhofen Archipelago. The Solnhofen Archipelago was located at the northern edge of the Tethys Ocean as part of a shallow epicontinental sea and is firmly a part of the Mediterranean realm.
Euctenochasmatia is an extinct group of pterodactyloid pterosaurs. It was named by David Unwin in 2003 as the group that contains the most recent common ancestor of Pterodactylus and Ctenochasma, and all their descendants.
Archaeoistiodactylus is an extinct genus of wukongopterid pterosaur from the Middle Jurassic of China.
Aurorazhdarcho is an extinct genus of ctenochasmatoid pterosaur known from the Late Jurassic period of what is now Bavaria, southern Germany.
Cuspicephalus is an extinct genus of monofenestratan pterosaur known from Dorset in England. Its fossil remains date back to the Late Jurassic period.
Sciurumimus is an extinct genus of tetanuran theropod from the Late Jurassic Torleite Formation of Germany. It is known from a single juvenile specimen representing the type species, Sciurumimus albersdoerferi, which was found in a limestone quarry close to Painten in Lower Bavaria. The specimen was preserved with traces of feather-like filaments.
Bellubrunnus is an extinct genus of rhamphorhynchid pterosaur from the Late Jurassic of southern Germany. It contains a single species, Bellubrunnus rothgaengeri. Bellubrunnus is distinguished from other rhamphorhynchids by its lack of long projections on the vertebrae of the tail, fewer teeth in the jaws, and wingtips that curve forward rather than sweep backward as in other pterosaurs.
The Painten Formation is a geologic formation in Germany. It preserves fossils dating back to the Tithonian stage of the Late Jurassic period.
The Torleite Formation is a geologic formation and Lagerstätte in Germany. It preserves fossils dating to the Kimmeridgian stage of the Jurassic period. Animals recovered from the formation include the small theropod dinosaur Sciurumimus, the ctenochasmatid pterosaur Balaenognathus, and the extinct bony fish Anaethalion.
Forfexopterus is a genus of ctenochasmatid pterosaur from the Early Cretaceous Jiufotang Formation in China. It contains a single species, F. jeholensis, named from a mostly complete skeleton by Shunxing Jiang and colleagues in 2016. A second specimen, consisting of a wing, was described in 2020. While the first specimen is larger, it shows signs of being less mature than the second specimen, indicating that the developmental trajectories of Forfexopterus were variable. Like other ctenochasmatids, Forfexopterus had a long, low skull filled with many slender teeth; unlike other members of the group, however, it did not have a spatula-shaped snout tip or crests, and its teeth were more curved. A single characteristic distinguishes Forfexopterus from all other members of the wider group Archaeopterodactyloidea: of the four phalanx bones in its wing finger, the first was shorter than the second but longer than the third.
Sphenofontis is an extinct genus of sphenodontian reptile known from the Late Jurassic of Germany, with a single known species, S. velserae. It is known from a single nearly complete and articulated sub-adult specimen, found in the late Kimmeridgian aged Torleite Formation in Brunn quarry in Bavaria, Southern Germany. It is thought to be a close relative of the living tuatara, tentatively referred to Sphenodontinae.
Lusognathus is an extinct genus of gnathosaurine pterosaurs from the Late Jurassic Lourinhã Formation of Portugal. The genus contains a single species, Lusognathus almadrava, known from a parts of the upper jaw, teeth, and cervical vertebrae.