Parapsicephalus (meaning "beside arch head") is a genus of long-tailed rhamphorhynchid pterosaurs from the Lower Jurassic Whitby, Yorkshire, England. It contains a single species, P. purdoni, named initially as a species of the related rhamphorhynchid Scaphognathus in 1888 but moved to its own genus in 1919 on account of a unique combination of characteristics. In particular, the top surface of the skull of Parapsicephalus is convex, which is otherwise only seen in dimorphodontians. This has been the basis of its referral to the Dimorphodontia by some researchers, but it is generally agreed upon that Parapsicephalus probably represents a rhamphorhynchid. Within the Rhamphorhynchidae, Parapsicephalus has been synonymized with the roughly contemporary Dorygnathus; this, however, is not likely given a large number of differences between the two taxa, including the aforementioned convex top surface of the skull. Parapsicephalus has been tentatively referred to the Rhamphorhynchinae subgrouping of rhamphorhynchids, but it may represent a basal member of the group instead.
|Fossil skull showing brain endocast (AMNH 1694)|
The type skull of Parapsicephalus, which is 14 centimetres (5.5 in) long as preserved, suggests that it was of medium size. Comparisons with the related pterosaurs Scaphognathus, Dorygnathus, and Jianchangnathus indicates that the full skull would have been 18–19.6 centimetres (7.1–7.7 in) long. Wellnhofer estimated its wingspan at 1 metre (3 ft 3 in); more recently, a referred humerus, which is 10 centimetres (3.9 in) long, has produced wingspan estimates of 1.68–3.26 metres (5 ft 6 in–10 ft 8 in).
When viewed from the side, the convex top of the skull formed a gentle slope. The elongate frontal process of the premaxilla, which extends backwards towards the eyes, may have supported a low crest along its midline. Below the nostril, the premaxilla meets with the maxilla; their junction is marked by a discontinuity in the surface texture of the bone. Overall, the oval-shaped antorbital fenestra, situated behind and separate from the nostril, measures 45 millimetres (1.8 in) long and 24 millimetres (0.94 in) tall. The maxilla extends backwards in a half-moon shape to encircle the front end of the fenestra, with the top prong of the maxilla forming a 45° angle with the horizontal. The top end of the fenestra is enclosed by the thin, rectangular, and slightly concave nasal, and the lacrimal, which is not well-preserved but may have been long, slender, and triangular. On the underside of the skull, the maxilla forms the majority of the palate (not the premaxilla, as previously assumed), extending back from below the external nostrils. Along the midline of the maxilla is situated a thin strip of bone, the vomer, which connects back to join the pterygoid.
At the back of the antorbital fenestra is the jugal, which has often been illustrated as a small V-shaped, two-pronged structure, but it is actually large and has four prongs. The lacrimal process extends 20 millimetres (0.79 in) forward and upward from the main body of the jugal, while the more robust postorbital process extends 18 millimetres (0.71 in) backward and upward. Collectively, they enclose the bottom of the eye socket, with angles of 45° on each side. The pear-shaped eye socket measures 34 millimetres (1.3 in) tall and 32 millimetres (1.3 in) wide at the widest point. Behind the jugal is the quadratojugal, which has traditionally been depicted as hypertrophied and occupying the location of the back portion of the jugal; it is actually a small, half moon-shaped bone wedged between the jugal and the quadrate and situated below the elongate infratemporal fenestra. Overall, the infratemporal fenestra is shaped similarly to the eye socket. The quadrates are strap-like, and wrap around from the back to the bottom of the skull. Although mostly obscured, the removal of the parietal during preparation has exposed part of the endocast of the brain, which has a large flocculus and cerebrum.
The frontal, which is located on the top of the skull between the premaxilla and the eye socket, takes the shape of a sub-rectangle with a large, rhombic process extending forward to meet the nasal. The frontal process of the premaxilla cuts into the frontal along the midline of this rhombus. Contacting the rear ends of both the frontal and jugal is the thin and triangular postorbital, about 15 millimetres (0.59 in) long along the bottom, extends backwards to separate the infratemporal and supratemporal fenestrae. The supratemporal fenestra itself is a somewhat four-sided oval. Behind the postorbital and closing off the supratemporal fenestra is the three-pronged squamosal, which is partially overlapped by the robust, spatula-like paroccipital processes of the occipital. Between the processes is the foramen magnum, which is a 7 millimetres (0.28 in) oval. Further below is the basoccipital, which forms a rounded plate that encloses the back of the skull.
The humerus referred to Parapsicephalus probably had a slightly deflected deltopectoral crest. It bears a sub-triangular medial process, 7 millimetres (0.28 in) wide and 25 millimetres (0.98 in) long, that originates close to the humeral head. In cross-section, the shaft of the humerus is sub-rectangular, and about 7 millimetres (0.28 in) wide at the midpoint; the bottom third of the shaft is bowed forward. The scapula and coracoid appear to be completely fused; they are respectively 67 millimetres (2.6 in) and 59 millimetres (2.3 in) long, and form an angle of 70° to each other, creating overall a V-shaped structure as in Sericipterus. The outer end of the scapula is noticeably wider than the inner end, and the glenoid is positioned entirely on the scapula, with the shaft curving about 15° towards the glenoid. Meanwhile, the portion of the coracoid closest to the glenoid is very expanded.
Parapsicephalus is only definitely known from a single partial skull lacking the snout, but including a detailed endocast of the brain. It is catalogued under the specimen number GSM 3166, and is stored at the British Geological Survey in Keyworth, Nottinghamshire. It was collected in the 1880s by Reverend D.W. Purdon from the Loftus Alum Shale Quarry, in Loftus, North Yorkshire, from which fossils had been discovered as early as the early nineteenth century. The quarry has since become disused since operations ceased in 1860. The exposed rocks, which consist of pyrite-rich shales with calcareous concretions, are part of the upper Alum Shale Member of the Whitby Mudstone Formation, which has been dated to about 182 million years ago, or the Toarcian stage of the Jurassic period.
GSM 3166 was described by Edwin Tulley Newton, who loaned it from Rev. Purdon, in 1888. He described it as a species of Scaphognathus, S. purdoni, named after Purdon; he did not include it in the type species S. crassirostris due to differences in the curvature of the top of the skull, as well as the midline channel on the top of the skull. In his description of the braincase, he noted its intermediate morphology between that of lizards and birds, which he considered evidence of a close relationship between birds, pterosaurs, and "reptiles". F. Plieninger subsequently compared GSM 3166 to Campylognathoides, and expressed that it was not as close to Scaphognathus as Newton had presumed. Later, in 1919, Gustav von Arthaber, based on the shape of the top of the skull, the elongated nostrils and prefrontal bones, the large antorbital fenestra and eye socket, the deep jugal, and the presence of seven teeth in the maxilla, referred GSM 3166 to the new genus Parapsicephalus.
In 2003, David Unwin, Kenneth Carpenter, and others suggested that Parapsicephalus was actually closer to the roughly contemporaneous Dorygnathus from German deposits. Unwin formally renamed it to the new combination Dorygnathus purdoni. This renaming was adopted by some researchers but not others. However, a 2017 redescription of GSM 3166 noted a number of ways in which Dorygnathus differed from Parapsicephalus: the greater angle of the lacrimal process of the maxilla, the more reduced maxillary process of the premaxilla, the broader angle of the jugal beneath the eye socket, the overall thinner jugal relative to skull height, the more rounded the eye socket, the more oval-shaped supratemporal fenestra, and the convex top of the skull (which is unique among pterosaurs except for dimorphodontians). On the basis of these characteristics, the study recognized Parapsicephalus as a distinct genus.
The specimen NHMUK PV R36634 was found in 2011 within a concretion in Saltwick Bay, which also belongs to the Alum Shale Member. It consists of a scapula, coracoid, and humerus; the head of the humerus was broken off during excavation as a result of the concretion being hammered open (which is the usual method for exposing ammonites preserved in concretions). Although it is impossible to refer this specimen to Parapsicephalus with confidence, its provenance and similarity to Dorygnathus were the basis of the tentative identification of the specimen as belonging to this genus. An additional possible specimen is a skull collected in 1994 from Altdorf, Bavaria, Germany, which bears great similarity to GSM 3166 and also preserves some additional elements. It is currently held by a private collector, but will soon be donated to an institution in the UK.
Although Newton originally considered Parapsicephalus as being a species of Scaphognathus, Arthaber remarked that it was actually more similar to Dimorphodon instead. The prevailing view since Arthaber's renaming of Parapsicephalus as a distinct genus has been that Parapsicephalus represents some kind of rhamphorhynchid, although several phylogenies by Brian Andres and colleagues supported Arthaber's hypothesis of it being closely affiliated with Dimorphodon. Characters which support this placement include the convex top of the skull, the pear-shaped eye socket, the angle of the quadrate, and the thick jugal. The topology recovered by Andres and Myers in 2013, showing Parapsicephalus as a dimorphodontian, is reproduced below.
A 2017 analysis of Parapsicephalus found little support for it being placed in the Dimorphodontia: its skull was comparatively longer; the snout is slightly upturned with outward-projecting teeth, as in rhamphorhynchids; the quadrate is not as vertical; the antorbital fenestra is offset below the nostril instead of being at the same level; and, although the top of the skull is convex in both, the condition in Parapsicephalus is not quite as extreme. Thus, affinities with the Rhamphorhynchidae were considered more probable. Within the Rhamphorhynchidae, unlike the scaphognathines, the antorbital fenestra is more than twice as long as it is tall, and has a concave back margin; the angle of the quadrate is also more than 120°. This implies that Parapsicephalus is a member of the Rhamphorhynchinae.
However, there are some factors that complicate a rhamphorhynchine position. In particular, the pear-shaped infratemporal fenestra and the overall size of the antorbital fenestra are more similar to scaphognathines than rhamphorhynchines. Additionally, like more basal non-rhamphorhynchid pterosaurs, there is a half moon-shaped process of the premaxilla extending beneath the nostril. It is thus possible that Parapsicephalus represents a basal rhamphorhynchid that is not in either group, which is not unexpected given its temporal context. The contemporary Allkaruen is also a potentially viable subject of comparison, although its material and that of Parapsicephalus do not readily overlap.
The Alum Shale Member of the Whitby Mudstone Formation was probably deposited in an oxygen-poor, shallow-water environment. A number of marine reptiles are known from this locality: the ichthyosaurs Stenopterygius, Temnodontosaurus, and Eurhinosaurus; the plesiosaurs Eretmosaurus, Sthenarosaurus, and Microcleidus; and the thalattosuchians Steneosaurus and Pelagosaurus. Indeterminate theropod remains have also been found.
Averostra, or "bird snouts", is a clade that includes most theropod dinosaurs that have a promaxillary fenestra (fenestra promaxillaris), an extra opening in the front outer side of the maxilla, the bone that makes up the upper jaw. Two groups of averostrans, the Ceratosauria and the Orionides, survived into the Cretaceous period. When the Cretaceous–Paleogene extinction event occurred, ceratosaurians and two groups of orionideans within the clade Coelurosauria, the Tyrannosauroidea and Maniraptoriformes, were still extant. Only one subgroup of maniraptoriformes, Aves, survived the extinction event and persisted to the present day.Avetheropoda
Avetheropoda, or "bird theropods", is a clade that includes carnosaurians and coelurosaurs to the exclusion of other dinosaurs.Boulby Quarries
Boulby Quarries (grid reference NZ745200) is a 40.3 hectare geological Site of Special Scientific Interest in Redcar and Cleveland, North Yorkshire, England notified in 1989. It is located close to the coast and the village of Boulby.In England SSSIs are designated by Natural England and Boulby Quarries is one 18 SSSIs in the Cleveland area of search. The site is identified as being of national importance in the Geological Conservation Review.
The quarries are wholly within the North Yorkshire and Cleveland Heritage Coast and partly within the North York Moors National Park and the historic North Riding of Yorkshire.
The fossil content of Boulby Quarry is particularly important with two plesiosaur species (Eretmosaurus macroptera and Thaumatosaurus zetlandicus), an ichthyosaur Ichthyosaurus crassimonus and the only Upper Lias pterosaur known in Britain, Parapsicephalus being found at the site. The fossil are found in the bifrons zone, and although not abundant, it is very different from surrounding fossil sites.Cerapoda
Cerapoda ("ceratopsians and ornithopods") is a clade of the dinosaur order Ornithischia.Dimorphodontia
Dimorphodontia is a group of early "rhamphorhynchoid" pterosaurs named after Dimorphodon, that lived in the Late Triassic to Early Jurassic.
A family, Dimorphodontidae, was named in 1870 by Harry Govier Seeley (as "Dimorphodontae") with Dimorphodon as the only known member. In 2003 David Unwin defined a clade Dimorphodontidae, as the group consisting of the last common ancestor of Dimorphodon macronyx and Peteinosaurus zambellii, and all its descendants. However, later studies found that Dimorphodon may not be closely related to Peteinosaurus, so this definition of Dimorphodontidae would therefore be superfluous. In 2014, Brian Andres and colleagues defined another clade, Dimorphodontia, as a replacement. Dimorphodontia would include all pterosaurs more closely related to Dimorphodon than to Pterodactylus. According to the analysis published by Andres et al., Dimorphodontia is also a small group, including only Dimorphodon and Parapsicephalus.In 2018, a close relative of Dimorphodon was described from the Late Triassic of North America by Britt and colleagues, and was named Caelestiventus. This discovery expanded the geographic, temporal and also the ecological range of dimorphodontians, as it was discovered in the Late Triassic Nugget Sandstone in Utah, which was a desert at the time. Britt and colleagues also redefined Dimorphodontidae as the least inclusive clade containing Dimorphodon macronyx and Caelestiventus hanseni.Dinosauriformes
Dinosauriformes is a clade of archosaurian reptiles that include the dinosaurs and their most immediate relatives. All dinosauriformes are distinguished by several features, such as shortened forelimbs and a partially to fully perforated acetabulum, the hole in the hip socket traditionally used to define dinosaurs. The oldest known member is Asilisaurus, dating to about 245 million years ago in the Anisian age of the middle Triassic period.Haya griva
Haya is an extinct genus of basal neornithischian dinosaur known from Mongolia.Jeholosauridae
Jeholosaurids were herbivorous neornithischian dinosaurs from the Cretaceous Period (Aptian - Santonian, with a possible Campanian record) of Asia. The family was first proposed by Han et al. in 2012. The jeholosaurids were defined as those ornithischians more closely related to Jeholosaurus shangyuanensis than to Hypsilophodon foxii, Iguanodon bernissartensis, Protoceratops andrewsi, Pachycephalosaurus wyomingensis, or Thescelosaurus neglectus. The Jeholosauridae includes the type genus Jeholosaurus and Yueosaurus.Jingshanosaurus
Jingshanosaurus (meaning "Jingshan lizard") is a genus of sauropodomorph dinosaurs from the early Jurassic period.Melanorosauridae
The Melanorosauridae were a family of sauropodomorph dinosaurs which lived during the Late Triassic and Early Jurassic. The name Melanorosauridae was first coined by Friedrich von Huene in 1929. Huene assigned several families of dinosaurs to the infraorder "Prosauropoda": the Anchisauridae, the Plateosauridae, the Thecodontosauridae, and the Melanorosauridae. Since then, these families have undergone numerous revisions. Galton and Upchurch (2004) considered Camelotia, Lessemsaurus, and Melanorosaurus members of the family Melanorosauridae. A more recent study by Yates (2007) indicates that the melanorosaurids were instead early sauropods.Neotheropoda
Neotheropoda (meaning "new theropods") is a clade that includes coelophysoids and more advanced theropod dinosaurs, and the only group of theropods who survived the Triassic–Jurassic extinction event. Yet all of the neotheropods became extinct during the early Jurassic period except for Averostra.Orionides
Orionides is a clade of tetanuran theropod dinosaurs from the Middle Jurassic to the Present. The clade includes most theropod dinosaurs, including birds.Orodrominae
Orodrominae is a subfamily of parksosaurid dinosaurs from the Cretaceous of North America and Asia.Rhamphorhynchidae
Rhamphorhynchidae is a group of early "rhamphorhynchoid" pterosaurs named after Rhamphorhynchus, that lived in the Late Jurassic. The family Rhamphorhynchidae was named in 1870 by Harry Govier Seeley.Riojasauridae
Riojasauridae is a family of sauropod-like dinosaurs from the Upper Triassic. It is known primarily from the genera Riojasaurus and Eucnemesaurus. Sites containing Riojasauridae include the Lower Elliot Formation of Orange Free State, South Africa (where fossils of Eucnemesaurus have been found), and Ischigualasto, in La Rioja Province, Argentina ( where fossils of Riojasaurus have been recovered).Unaysauridae
Unaysauridae is a family of basal sauropodomorphs from the Late Triassic of India and Brazil.Whitby Mudstone Formation
The Whitby Mudstone Formation is a Toarcian (Lower Jurassic) geological formation in England. Dinosaur remains are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus.One of the more notable discoveries is the skull of Parapsicephalus.Xixiposaurus
Xixiposaurus is a genus of prosauropod dinosaur which existed in what is now Lower Lufeng Formation, China during the lower Jurassic period. It was first named by Sekiya Toru in 2010 and the type species is Xixiposaurus suni.Yueosaurus
Yueosaurus is an extinct genus of basal ornithopod dinosaur known from Zhejiang Province, China.