| Harpactognathus | |
|---|---|
 | |
| Life restoration | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | †Pterosauria |
| Family: | †Rhamphorhynchidae |
| Genus: | †Harpactognathus Carpenter et al., 2003 |
| Species: | †H. gentryii |
| Binomial name | |
| †Harpactognathus gentryii Carpenter et al., 2003 | |
Harpactognathus (meaning "seizing/grasping jaw") is agenus ofpterosaur, a group ofextinctflying reptiles, that lived during theKimmeridgianstage of theLate Jurassicperiod in what is nowWyoming, United States.Harpactognathus is confidently known from a single, incompleterostrum (front of theskull) found in 1996 at theBone Cabin Quarry, though an incompletemandible (lower jaw bone) andhumerus (upper arm bone) from the quarry have tentatively been referred to the genus. The rostrum was described bypaleontologistKenneth Carpenter and colleagues in 2003, who named the type and only knownspecies,H. gentryii, after Joe Gentry, a volunteer for the Western Paleontological Laboratories inLehi, Utah.
Harpactognathus is a large-sized pterosaur, with an estimated wingspan of 2.5 metres (8.2 ft) and estimated complete skull length of 280–300 millimetres (11–12 in), making it among the largest known non-pterodactyloid pterosaurs. The rostrum ofHarpactognathus is robust, broad, and wider than tall. On the midline of the skull is apremaxillary (front upper jaw bone) crest that may have been extended bysoft tissues and used forsexual display or beensexually dimorphic. Due to a lack of remains, much of its anatomy is unknown and can only be inferred from related taxa.
WhenHarpactognathus was described, it was assigned to the subfamily Scaphognathinae withinRhamphorhynchidae, a group of long-tailed, toothed non-pterodactyloid pterosaurs. However, the descriptions of the rhamphorhynchinesSericipterus andAngustinaripterus, which are similar toHarpactognathus, suggest it was a member of Rhamphorhynchinae instead. Based on its teeth, robusticity, and paleoenvironment,Harpactognathus was aterrestrialcarnivore that lived near freshwater areas in contrast to thepiscivorous lifestyles of relatives likeRhamphorhynchus.
Harpactognathus was found in thestrata of theMorrison Formation, which bears a variety of other fossils. This includes several other genera of pterosaurs, such asMesadactylus andDermodactylus, as well as many unnamed pterosaurs. In addition to pterosaurs, the Morrison Formation preserves fossils of manydinosaurs, includingsauropods,theropods, andornithischians,crocodylomorphs,mammals,lizards,turtles, and more.
In 1996 during excavations of theBone Cabin Quarry inAlbany, Wyoming, an incompleterostrum of apterosaur was unearthed in strata deriving from the upper limits of the Salt Wash Member of theMorrison Formation. These strata are composed offluvial channel deposits, coarse sand, and sand-pebbleconglomerates which date to the lateKimmeridgianstage of theLate Jurassic period.[1] In 1999, a pterosaurmandible was found within a meter of the rostrum fragment. In 2003, American paleontologistKenneth Carpenter and colleagues described the rostrum as belonging to a newgenus andspecies ofscaphognathine pterosaur,Harpactognathus gentryii. The rostrum fragment was chosen to be theholotype (specimen used as the basis for the taxon), cataloged under specimen numberNAMAL 101, whereas the status of the mandible fragment was left uncertain. The holotype resides in theStewart Museum of Paleontology atOgden's George S. Eccles Dinosaur Park innorthern Utah. The generic nameHarpactognathus, meaning "seizing/grasping jaws", comes from theGreek rootsharpact, "seize" or "grab", andgnathus, "jaws". The specific namegentryii is in honor of Joe Gentry, a volunteer for the western Paleontological Laboratories in Lehi, Utah. Prior to the naming ofHarpactognathus, the pterosaurComodactylus ostromi was named in 1981 by researcherPeter Galton on the basis of a fourthmetacarpal, a wing bone, (YPM 9150) that had been found inComo Bluff, Wyoming, another Morrison Formation site.[2]Comodactylus was later declared anomen dubium,[3] though Carpenter and colleagues noted that this fourth metacarpal may belong toHarpactognathus based on its size and rhamphorhynchid characteristics. However, a lack of overlap makes this impossible to prove.[1]
In a 2014 study, paleontologist S. Christopher Bennett argued that the mandible as well as a large pterosaurhumerus (upper arm bone; EDP-SM 2017.02.003) belong to the same individual as the holotype rostrum. This would expand the known material ofHarpactognathus from a rostrum to also include a mandible and a humerus. Bennett stated that the large size, morphology, and close proximity of the mandible and humerus to the holotype mean that they could have come from the same individual. Additionally, no other pterosaur remains were found in the Bone Cabin Quarry, making itparsimonious to assign all of these elements to the same individual.[4] However, the referral of the mandible toHarpactognathus is questionable,[1] as it is likely from a different type of rhamphorynchid or rhamphorhynchine based on its slender nature and the anatomy of itsalveoli (tooth-bearing holes in the skull).[5] In a 2025 paper, paleontologists Michael Sprague and Matthew McLain described the humerus in detail, which they assigned toHarpactognathus based on its size, location, and parsimony.[6]
Harpactognathus is definitively known from a single, incomplete rostrum that measures 130 millimetres (5.1 in) in preserved length and 42.5 millimetres (1.67 in) at its widest preserved point (estimated skull length of 280–300 mm (11–12 in)). This is extremely large for a rhamphorhynchid, indicating an estimatedwingspan of at least 2.5 m (8.2 ft).[1][7][8]: 122–124 This makesHarpactognathus among the largest known non-pterodactyloid pterosaurs, comparable in size toSericipterus,Angustinaripterus, the largestRhamphorhynchus,[9] andDearc.[10][11] EDP-SM 2017.02.003, a right humerus assigned toHarpactognathus, is among the largest known pre-Cretaceous pterosaur humeri, measuring 110.5 millimetres (4.35 in) in length.[6]
Much of the skull is missing and the preserved portion isdorsoventrally (top-bottom) compressed bytaphonomy. The rostral region itself is extremely broad and would have been wider than tall in life, a feature absent in many rhamphorhynchids. The widened portion of the rostrum contains four pairs of teeth inHarpactognathus, meanwhile inAngustinaripterus it incorporates threeand Sericipterus it only incorporates two. The tooth count differs as well between these genera, withHarpactognathus' rostrum containing at least 12 teeth whereasAngustinaripterus' bears 18 andSericipterus' has 10-14.[12] The tip of the rostrum is missing but thepremaxilla (anteriormost upper jaw bone) is preserved. The premaxilla tapers anteriorly (front) and forms a pointed tip that is made up of the two fused premaxillae. The premaxilla differs from those of other rhamphorhynchids, besidesSericipterus andAngustinaripterus, in that it bears a thin crest which extends above thenares (nose holes) from the tip of the premaxilla to likely the rest of the skull. The crest is made up of a midline process at the anterior tip of the rostrum that joins with a low premaxillary crest, together forming this thin crest. While the cross-section of this midline process is triangle-shaped inHarpactognathus, it is elliptical inSericipterus andAngustinaripterus. However, much of this premaxillary crest is missing from the holotype. Its nares are narrow, elongate, and bear openings with acute angles at their posterior (back) and anterior ends, a characteristic found inRhamphorhynchus andDorygnathus. As for the maxilla, its main body is convex and the maxilla extends across the length of the rostrum.[1][12]
Overall, the silhouette of the maxilla is similar to that ofScaphognathus andSordes,[1] though its robusticity is more similar to that ofSericipterus.[12] At its posterior end, the maxilla is divided into a jugal process and a robust nasal process. The maxilla ends posteriorly at theantorbital fenestra (a large opening in front of the eye sockets). The maxillary wall of the antorbital fenestra bears a shallow triangularfossa (a depression in bone) at its anterior edge, a characteristic absent in other rhamphorhynchid genera. At its dorsal surface,Harpatognathus' maxilla has a dorsally thickenednasalprocess (the part of the maxilla that articulates with the nasal), a characteristic distinct fromSericipterus andAngustinaripterus. Thepalate (mouth roof) is flat, deeply recessed, and contains the maxilla, premaxilla, andpalatines (palate bones). On the posterior end of the palate is a pair ofchoanae (internal nares), which are ovular, elongated, and separated by a medial bar. On the scalloped lateral surfaces of the premaxilla andmaxilla (upper jaw bone) are large gaps inbetween alveoli, a characteristicdiagnostic ofHarpactognathus. These scalloped surfaces are striking, being visible in both dorsal and lateral view.[1][12] Although unique at the time of its description, many diagnostic traits forHarpactognathus stated by Carpenteret al are now recognized as belonging toSericipterus and/orAngustinaripterus.[12] However, later studies have still recognizedHarpactognathus as diagnostic.[13][12]
Harpactognathus is a genus in the family Rhamphorhynchidae, however its position within the family is contested.Harpactognathus lacks the deep skull anatomy observed in basal non-pterodactyloids likedimorphodontids andanurognathids or the nasoantoribital fenestra (a large opening in front of the eye socket containing the nasal and antorbital fenestra) seen in pterodactyloids, allowing it to be classified as a rhamphorhynchid orcampylognathid. However,Harpactognathus cannot be classified as a campylognathid based on its tooth count and alveolar anatomy.[1] Rhamphorhyncidae contains two subfamilies; Rhamphorhynchinae and Scaphognathinae.[7][8]: 122 Rhamphorynchines are distinguished from scaphognathines by their slender skulls, flexible necks, and laterally-oriented teeth. In contrast, Scaphognathines have deep skulls with teeth that interlock vertically as well as robust necks.[8]: 128–131
When initially described,Harpactognathus was classified within the subfamily Scaphognathinae on account of its tooth count, with all of its teeth widely spaced apart from one another. Additionally, it shares a dorsally flexed anterior rostrum that creates a curve at the end of the snout with other scaphognathines. The shape and proportions of the rostrum as well as the anatomy of the alveoli are comparable to those ofScaphognathus.[1] However, aphylogenetic analysis performed by Brian Andres, James Clark and Xu Xing in 2010 recoveredHarpactognathus in Rhamphorhynchinae as a close relative of the large rhamphorhynchidsAngustinaripterus andSericipterus,[12] both of which are now classified within the tribe Angustinaripterini according to Natalia Jagielska and colleagues (2022, 2024).[11][10]Harpactognathus is similar to these genera in that it has an expanded rostrum, a premaxillary crest, a set of ventrolaterally (down and side)-oriented teeth, and an undulating rostrum margin.[12]Harpactognathus may be in the tribe Angustinaripterini, however it was not included in the phylogenetic analysis conducted by Jagielskaet al (2022) due to the fragmentary nature ofHarpactognathus.[10] Additionally, Bennett (2014) argued thatHarpactognathus cannot belong to Scaphognathinae on account of its laterally compressed, thin teeth which contrast with those ofScaphognathus. Bennett, assuming that the mandible belongs to the same individual as the holotype, noted that the shallowramus andedentulous (toothless) tip of the mandible excludeHarpactognathus from being a member of Scaphognathinae.[4]
Thecladogram (family tree) of rhamphorhynchids below is the result of a large phylogenetic analysis published by Andres & Myers in 2013.[14]
Previously, Scaphognathines were hypothesized to be specialized as aerial predators in inland freshwater habitats. However, more recent publications have suggested scaphognathines lacked specializations forpiscivory, and were likely terrestrial predators of small vertebrates orcorvid-like generalists.[8]: 51 Based on the occurrence of scaphognathines inriverine orlacustrine deposits, it was hypothesized that scaphognathines, along withHarpactognathus, preferred terrestrial freshwater environments in contrast to rhamphorhynchines who preferred coastal environments.[1][8]: 122–127 This hypothesis was supported by Andres and Xu (2010), who in their description ofSericipterus pointed out that the robust, broad skulls and highly curved teeth ofSericipterus, Angustinaripterus, andHarpactognathus are not adapted to piscivory or interaction with a water surface, supporting the idea that they were terrestrial carnivores.[12]
Cranial crests can be found across Pterosauria, however not many have been found in rhamphorhynchids. The crest ofHarpactognathus is unusual however in that it continues to the tip of the rostrum, a feature not found in the crests of other pterosaurs liketapejarids orctenochasmatoids.[15][16][1] The function of the crest ofHarpactognathus was presumed to be for displays purposes by Carpenteret al (2003) due to the fact that in other pterosaurs likePteranodon andAnhanguera, the crests aresexually dimorphic or acted as a display structure.Harpactognathus' crest likely was extended by soft tissue structures as well based on the crests ofTapejara.[1]
The Morrison Formation is a sequence of shallow marine and alluvial sediments which, according toradiometric dating, ranges between 156.77 million years old (Mya) at its base,[17] and 150 Mya at the top,[18] which places it in the lateOxfordian, Kimmeridgian, and early Tithonian stages of the Late Jurassic period. This formation is interpreted as asemi-arid environment with distinctwet anddry seasons. The Morrison Basin, where pterosaurs anddinosaurs lived, stretched from New Mexico to Alberta and Saskatchewan and was formed when the precursors to theFront Range of the Rocky Mountains started pushing up in the west. The deposits from their east-facingdrainage basins were carried by streams and rivers and deposited inswampy lowlands, lakes, river channels, andfloodplains.[19] This formation is similar in age to theLourinhã Formation inPortugal and theTendaguru Formation inTanzania.[20]
Pterosaurs known from the Morrison include the possible anurognathidMesadactylus, the pterodactyloidKepodactylus, and the possiblectenochasmatidUtahdactylus.[21] Many of the specimens referred toMesadactylus may in fact belong to other kinds of pterosaurs like pterodactyloids, illustrating a greater diversity of pterosaurs from the formation than previously assumed.[22][23][21] Dinosaurs known from the Morrison include thetheropodsCeratosaurus,Ornitholestes, andAllosaurus, thesauropodsApatosaurus,Brachiosaurus,Camarasaurus, andDiplodocus, and theornithischiansCamptosaurus,Dryosaurus, andStegosaurus.[24] Other vertebrates that shared this paleoenvironment includedray-finned fishes,frogs,salamanders,turtles,sphenodonts,lizards, andcrocodylomorphs. Shells ofbivalves and aquaticsnails are also common. The flora of the period has been revealed by fossils ofgreen algae,mosses,horsetails,cycads,ginkgoes, and several families ofconifers. Vegetation varied from river-lininggallery forests oftree ferns and ferns, to fernsavannas with occasional trees such as theAraucaria-like coniferBrachyphyllum.[25]
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