Dimorphodon

Dimorphodon /daɪˈmɔːrfədɒn/ was a genus of medium-sized pterosaur from the early Jurassic Period. It was named by paleontologist Richard Owen in 1859. Dimorphodon means "two-form tooth", derived from the Greek δι (di) meaning "two", μορφη (morphe) meaning "shape" and οδων (odon) meaning "tooth", referring to the fact that it had two distinct types of teeth in its jaws – which is comparatively rare among reptiles.

Dimorphodon
Temporal range: Early Jurassic, 195–190 Ma
Dimorphodon Flight Pose
Reconstruction skeleton in flying pose at the Rocky Mountain Dinosaur Resource Center
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Order: Pterosauria
Family: Dimorphodontidae
Subfamily: Dimorphodontinae
Seeley, 1870
Genus: Dimorphodon
Owen, 1859
Type species
Dimorphodon macronyx
(Buckland, 1829)
Species

D. macronyx (Buckland, 1829)
D. weintraubi Clark et al., 1998

Synonyms

Pterodactylus macronyx Buckland, 1829

Description

Dimorphodon2DB
Restoration of a pair of D. macronyx

The body structure of Dimorphodon displays many "primitive" characteristics, such as, according to Owen, a very small brain-pan[1] and proportionally short wings.[1] The first phalanx in its flight finger is only slightly longer than its lower arm.[1] The neck was short but strong and flexible and may have had a membranous pouch on the underside. The vertebrae had pneumatic foramina, openings through which the air sacks could reach the hollow interior. Dimorphodon had an adult body length of 1 metre (3.3 ft) long, with a 1.45 metre (4.6 ft) wingspan.[1][2] The tail of Dimorphodon was long and consisted of thirty vertebrae. The first five or six were short and flexible, but the remainder gradually increased in length and were stiffened by elongated vertebral processes.[1] The terminal end of the tail may have borne a Rhamphorhynchus-like tail vane, although no impressions have yet been found in Dimorphodon fossils to confirm this speculation.[1]

Skull

Dimorphodon had a large, bulky skull approximately 23 centimetres in length, whose weight was reduced by large openings separated from each other by thin bony partitions.[1] Its structure, reminiscent of the supporting arches of a bridge, prompted Richard Owen to declare that, as far as achieving great strength from light-weight materials was concerned, no vertebra was more economically constructed; Owen saw the vertebrate skull as a combination of four vertebrae modified from the ideal type of the vertebra.[3] The front of the upper jaw had four or five fang-like teeth followed by an indeterminate number of smaller teeth; the maxilla of all exemplars is damaged at the back. The lower jaw had five longer teeth and thirty to forty tiny, flattened pointed teeth, shaped like a lancet.[1] Many depictions give it a speculative puffin-like 'beak' because of similarities between the two animals' skulls.

History of discovery

Dimorphodon macronyx holotype
D. macronyx holotype specimen, NHMUK PV R 1034

The first fossil remains now attributed to Dimorphodon were found in England by fossil collector Mary Anning, at Lyme Regis in Dorset, UK in December 1828.[4] This region of Britain is now a World Heritage Site, dubbed the Jurassic Coast; in it layers of the Blue Lias are exposed, dating from the Hettangian-Sinemurian. The specimen was acquired by William Buckland and reported in a meeting of the Geological Society on 5 February 1829.[5] In 1835, after a thorough study by William Clift and William John Broderip, this report, strongly expanded, was published in the Transactions of the Geological Society, describing and naming the fossil as a new species. As was the case with most early pterosaur finds, Buckland classified the remains in the genus Pterodactylus, coining the new species Pterodactylus macronyx.[6] The specific name is derived from Greek makros, "large" and onyx, "claw", in reference to the large claws of the hand. The specimen, presently NHMUK PV R 1034, consisted of a partial and disarticulated skeleton on a slab, lacking the skull. Buckland in 1835 also assigned a piece of jaw from the collection of Elizabeth Philpot to P.macronyx. Later, the many putative species assigned to Pterodactylus had become so anatomically diverse that they began to be broken into separate genera.

Macronyx
Illustration of D. macronyx specimen NHUK PV R 1035

In 1858, Richard Owen reported finding two new specimens, NHMUK PV R 41212 and NHMUK PV R 1035, again partial skeletons but this time including the skulls. Having found the skull to be very different from that of Pterodactylus, Owen assigned Pterodactylus macronyx its own genus, which he named Dimorphodon.[7] His first report contained no description and the name remained a nomen nudum. In 1859, however, a subsequent publication by Owen provided a description.[8] After several studies highlighting aspects of Dimorphodon 's anatomy, Owen in 1874 made NHMUK PV R 1034 the holotype.[9]

Dimorphodon macronyx - Pterosaurs Flight in the Age of Dinosaurs
Cast of D. macronyx specimen NHMUK PV R 41212

Meanwhile, though Dimorphodon is not a very common fossil, other fragmentary specimens were found. Some of these were acquired by Othniel Charles Marsh between 1873 and 1881 from the London fossil dealer Bryce McMurdo Wright. One of these had been recovered from early Jurassic strata at the south bank of the Severn river, at the Aust Cliff.[1]

An additional species of Dimorphodon, D. weintraubi, was named by James Clark et al in 1998 from a partial skeleton recovered in siltstones from the site Huizachal Canyon in La Boca Formation in Tamaulipas, Mexico, from the Early Jurassic (Pliensbachian), where remains of sphenodontians, dinosaurs and mammaliaforms have also been found .[10] It is known from the type specimen, IGM 3494 (Instituto Geológico de México, of the Universidad Nacional Autónoma de México), that comprises articulated pieces of the skeleton including the posterior part of skull, four cervical vertebrae, the scapulocoracoids, left humerus, partial right wing and right leg distal to mid tibiotarsus. This specimen is larger than D. macronyx and the well preserved foot of it shows that pterosaurs do not have a digitigrade posture in their hindlimbs, but that it have a plantigrade gait, as has been inferred from footprints. The name of the species is a homage to Dr. Robert L. Weintraub.[11]

Classification

Dimorphodon mount
Reconstructed skeleton, Rainbow Forest Museum

In 1870, Seeley assigned Dimorphodon to its own family, Dimorphodontidae, with Dimorphodon as the only member. It was suggested in 1991 by the German paleontologist Peter Wellnhofer that Dimorphodon might be descended from the earlier European pterosaur Peteinosaurus.[1] Later exact cladistic analyses are not in agreement. According to Unwin, Dimorphodon was related to, though probably not a descendant of, Peteinosaurus, both forming the clade Dimorphodontidae, the most basal group of the Macronychoptera and within it the sister group of the Caelidracones. This would mean that both dimorphodontid species would be the most basal pterosaurs known with the exception of Preondactylus. According to Alexander Kellner, however, Dimorphodon is far less basal and not a close relative of Peteinosaurus.

The cladogram recovered by Andres and Myers in 2013 is reproduced below.[12]

Pterosauria

Preondactylus buffarinii

Austriadactylus cristatus

Peteinosaurus zambellii

Eudimorphodontidae

Macronychoptera

Dimorphodon macronyx

Parapsicephalus purdoni

Novialoidea

Palaeobiology

Diet

Dimorphodon
Restoration of D. macronyx chasing a sphenodontian on the ground

Our knowledge of how Dimorphodon lived is limited. It perhaps mainly inhabited coastal regions and might have had a very varied diet. Buckland suggested it ate insects. Later, it became common to depict it as a piscivore (fish eater), though Buckland's original idea is more well supported by biomechanical studies, and inconsistent with the animal's habits (see flight below). Dimorphodon had an advanced jaw musculature specialized for a "snap and hold" method of feeding. The jaw could close extremely quickly, but with relatively little force or tooth penetration. This, along with the short and high skull and longer, pointed front teeth suggest that Dimorphodon was an insectivore, though it may have occasionally eaten small vertebrates and carrion as well.[13] Mark Witton has argued that the animal was a specialised carnivore, being too large for an insectivorous diet and therefore specialised to hunt small lizards, sphenodonts and mammals, though its relatively weak jaw musculature probably meant that it ate proportionally small prey.[14]

Locomotion

Like many pterosaurs, Dimorphodon has been perceived as a soarer in the past, correlating to historical perceptions of pterosaurs as seabird analogues. However, more recent studies show that the animal was actually a rather poor flyer: its wings are proportionally short in relation to the body and its skeleton rather robust, offering very little gliding potential. In life, Dimorphodon probably relied on frantic short flights in the same manner as modern fowl, tinamous and woodpeckers, being unable to fly for long distances and probably only taking to the air as a last resort.[14][15]

Dimorphodon-macronyx jconway
Restoration of D. macronyx in flight

Its derived position amidst primitive pterosaurs implies that this ineptitude is a developed trait, not an ancestral characteristic, as earlier pterosaurs like Preondactylus were capable aeronauts.

Dimorphodon reconstruction Seeley 1901
D. macronyx in the controversial bipedal pose, Seeley, 1901

Owen saw Dimorphodon as a quadruped. He speculated that the fifth toe supported a membrane between the tail and the legs and that the animal was therefore very ungainly on the ground.[1] However, his rival Harry Govier Seeley, propagating the view that pterosaurs were warm-blooded and active, argued that Dimorphodon was either an agile quadruped or even a running biped due to its relatively well developed hindlimbs and characteristics of its pelvis.[16] This hypothesis was revived by Kevin Padian in 1983.[17] However, fossilised track remains of other pterosaurs (ichnites) show a quadrupedal gait while on the ground and these traces are all attributed to derived pterosaurs with a short fifth toe. Dimorphodon's was elongated, clawless, and oriented to the side.[1] David Unwin has therefore argued that even Dimorphodon was a quadruped, a view confirmed by computer modelling by Sarah Sangster.[18]

Like most non-pterodactyloid pterosaurs, Dimorphodon was a competent climber, possessing proportionally large and curved ungals and a low center of gravity. Like modern squirrels, it probably moved in a saltatorial manner as it climbed.[14]

See also

References

  1. ^ a b c d e f g h i j k l "Dimorphodon." In: Cranfield, Ingrid (ed.). The Illustrated Directory of Dinosaurs and Other Prehistoric Creatures. London: Salamander Books, Ltd. Pp. 288-291.
  2. ^ Wellnhofer, Peter (1996) [1991]. The Illustrated Encyclopedia of Pterosaurs. New York: Barnes and Noble Books. p. 71. ISBN 0-7607-0154-7.
  3. ^ Padian. K. (1995). "Pterosaurs and Typology: Archetypal Physiology in the Owen-Seeley Dispute of 1870", In: Sarjeant, W.A.S. & Halstead, L.N. (ed.) Vertebrate fossils and the evolution of scientific concepts: writings in tribute to Beverly Halstead, by some of his many friends, Gordon & Breach 1995
  4. ^ Wellnhofer, Peter (1996) [1991]. The Illustrated Encyclopedia of Pterosaurs. New York: Barnes and Noble Books. p. 69. ISBN 0-7607-0154-7.
  5. ^ Buckland, W. (1829). Proceedings of the Geological Society of London, 1: 127
  6. ^ Buckland, W. (1835). "On the discovery of a new species of Pterodactyle in the Lias at Lyme Regis." Transactions of the Geological Society of London, series 23: 217-222.
  7. ^ Owen, R. (1859). "On a new genus (Dimorphodon) of pterodactyle, with remarks on the geological distribution of flying reptiles." Rep. Br. Ass. Advmnt Sci., 28 (1858): 97–103.
  8. ^ Owen, R. (1857/1859). "On the vertebral characters of the order Pterosauria (Ow.), as exemplified in the genera Pterodactylus (Cuv.) and Dimorphodon (Ow.)", Proceedings of the Royal Society of London, 9: 703-704
  9. ^ Owen, R. (1874). "Monograph of the fossil Reptilia of the Mesozoic Formations. Part I. Pterosauria", Palaeontographical Society of London, 27: 1-14
  10. ^ Marisol Montellano, James A. Hopson and James M. Clark (2008). Late Early Jurassic Mammaliaforms from Huizachal Canyon, Tamaulipas, México. Journal of Vertebrate Paleontology, Vol. 28, No. 4 (Dec. 12, 2008), pp. 1130-1143.
  11. ^ J. M. Clark, J. A. Hopson, R. Hernández R., D. E. Fastovsky & M. Montellano (1998). Foot posture in a primitive pterosaur. Nature 391, 886-889 (26 February 1998). doi:10.1038/36092.
  12. ^ Andres, B.; Myers, T. S. (2013). "Lone Star Pterosaurs". Earth and Environmental Science Transactions of the Royal Society of Edinburgh. 103 (3): 383–398. doi:10.1017/S1755691013000303.
  13. ^ Osi, A. (2010). "Feeding-related characters in basal pterosaurs: implications for jaw mechanism, dental function and diet." Lethaia, doi:10.1111/j.1502-3931.2010.00230.x
  14. ^ a b c Wilton, Mark P. (2013). Pterosaurs: Natural History, Evolution, Anatomy. Princeton University Press. ISBN 0691150613.
  15. ^ Rayner et all 2011
  16. ^ Seeley, H. G. (1870). "Remarks on Prof. Owen's Monograph on Dimorphodon", Annals and Magazine of Natural History, Series 4, 6:129
  17. ^ Padian, K. (1983). "Osteology and functional morphology of Dimorphodon macronyx (Buckland) (Pterosauria: Rhamphorhynchoidea) based on new material in the Yale Peabody Museum", Postilla, 189: 1-44
  18. ^ Sangster, S. (2001). "Anatomy, functional morphology and systematics of Dimorphodon", Strata 11: 87-88
1859 in paleontology

Paleontology or palaeontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 1859.

Astrosaurs

Astrosaurs is a series of children's science fiction novels written by Steve Cole, which have been released since 2005. The main characters are space-going dinosaurs named Teggs Stegosaur (a Stegosaurus), Gipsy Saurine (a Corythosaurus), Arx Orano (a Triceratops) and Iggy Tooth (an Iguanodon). The series are published by Random House. The first two Astrosaurs books were released on 1 February 2005, with over twenty books following. The Teeth of the T. Rex was a special edition book written especially for World Book Day. Free trading cards come with each Astrosaur book, featuring foes, weapons, crew members, ships, aliens and many other characters and things found in the relevant book, with a set of 'bonus cards' available to order from the Steve Cole website, which are now believed to have gone out of print, and featured characters from the first eight books. The World Book Day title The Teeth of the T. Rex does not include cards, and is much shorter than the other books. The first five Astrosaurs books have now been released in Audiobook format on CD in the UK. The series is a huge hit with children nationwide. Beginning in late 2010, the books have been re-released with new cover artwork. Currently, books 12–15 are the only ones not to have been given the new covers. Woody Fox is the illustrator on every Astrosaurs book, who also draws the illustrations for the trading cards, with Charlie Fawkes having designed the Astrosaurs logo, consisting of the word 'ASTROSAURS' with the four main characters above it.

Aust Cliff

Aust Cliff (grid reference ST565894) is a 5.3 hectare geological Site of Special Scientific Interest adjacent to the Severn Estuary, near the village of Aust, South Gloucestershire, notified in 1954. The Severn Bridge crosses the cliff.

Its SSSI designation is due to the presence of fossil beds. The site is famous for its Rhaetic bone bed, and is also the most productive locality in Britain for Triassic insects.

The lower part of the cliff is a red mudstone, with bands of nodules of pinkish-white alabaster. Above the red mudstone is green mudstone, followed by the Rhaetic bone bed at the base of a band of black shale. Above the shale are cream-coloured limestone beds.

Averostra

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.

Caelestiventus

Caelestiventus ( sə-LES-tih-VEN-təs, meaning "heavenly wind") is a pterosaur genus from the Late Triassic (Norian or Rhaetian) found in western North America. The type species, Caelestiventus hanseni, honors Robin Hansen, the Bureau of Land Management geologist (BLM), who facilitated access to the excavation site.

Caelestiventus is important because it is the sole example of a desert-dwelling non-pterodactyloid pterosaur and is 65 million years older than other known desert-dwelling pterosaurs. Additionally, it shows that even the earliest pterosaurs were morphologically and ecologically diverse and that the Dimorphodontidae originated in the Triassic Period.

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.

Dorygnathus

Dorygnathus ("spear jaw") was a genus of pterosaur that lived in Europe during the Early Jurassic period, 180 million years ago when shallow seas flooded much of the continent. It had a short 1.5 meters (4.9 feet) wingspan, and a relatively small triangular sternum, which is where its flight muscles attached. Its skull was long and its eye sockets were the largest opening therein. Large curved fangs that "intermeshed" when the jaws closed featured prominently at the front of the snout while smaller, straighter teeth lined the back. Having variable teeth, a condition called heterodonty, is rare in modern reptiles but more common in primitive pterosaurs. The heterodont dentition in Dorygnathus is consistent with a piscivorous (fish-eating) diet. The fifth digit on the hindlimbs of Dorygnathus was unusually long and oriented to the side. Its function is not certain, but the toe may have supported a membrane like those supported by its wing-fingers and pteroids. Dorygnathus was according to David Unwin related to the Late Jurassic pterosaur, Rhamphorhynchus and was a contemporary of Campylognathoides in Holzmaden and Ohmden.

Flying Monsters 3D

Flying Monsters 3D is a natural history documentary about the pterosaurs. It was written and presented by David Attenborough and was produced by National Geographic and Atlantic Productions for Sky 3D. Originally broadcast on Christmas Day 2010, it was the first 3D documentary to be screened on British television and was released in theatres and IMAX cinemas the following year. Flying Monsters 3D went on to become the first 3D programme to win a BAFTA award.Featured animalsDimorphodonDarwinopterusPteranodonTapejaraQuetzalcoatlus

Jingshanosaurus

Jingshanosaurus (meaning "Jingshan lizard") is a genus of sauropodomorph dinosaurs from the early Jurassic period.

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.

Parapsicephalus

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.

Peteinosaurus

Peteinosaurus ( peh-TY-nə-SOR-əs; meaning "winged lizard") was a prehistoric genus of Pterosaur. It lived in the late Triassic period in the late Norian age (about 221 to 210 million years ago), and at a wingspan of around 60 cm (24 in), was one of the smallest and earliest Pterosaurs.

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.

Zapatadon

Zapatadon is an extinct genus of sphenodontid reptile from the end of the Early Jurassic in the lower part of La Boca Formation of Tamaulipas, Mexico. Is known from a nearly complete skull with mandible of a post-hatchling individual (the specimen IGM 3497, in the Instituto de Geologia, of the Universidad Nacional Autónoma de Mexico), and is one of the smallest skulls between the sphenodontians, with an estimated total length of 11.3 millimetres, a bit smaller than the hatchling individuals observed in the modern tuatara (Sphenodon); features like the oblique mandibular symphysis suggests that the holotype is from an individual in a relatively mature stage of ontogenic development. Zapatadon is diagnosed by their hatchling tooth series located in a depression in the anterior part of the dentary bone, the prefrontal bone surrounding the dorsal process of the maxilla and the broad jugal that extends over the maxillary suborbital process, been almost excluded of the orbit.Zapatadon was first described and named by Víctor-Hugo Reynoso and James M. Clark in 1998, and the name of the genus is a homage to the Mexican revolutionary leader Emiliano Zapata, added to the Greek sufix -odon, "tooth", common in other sphenodontian taxa; the name of the type species, ejidoensis is in gratitude to the people of the ejido (communal land area) of El Huizachal, that allow the investigation of the fossils.In the La Boca Formation, where the fossils of Zapatadon were collected, also have been found fossils of another sphenodontian taxa like Cynosphenodon huizachalensis and the possibly venomous Sphenovipera jimmysjoyi, the primitive diapsid Tamaulipasaurus morenoi, the primitive pterosaur Dimorphodon weintraubi, the tritylodont Bocatherium mexicanum and the mammaliaforms Bocanodon tamaulipensis, Victoriaconocodon inaequalis and Huestaconocodon wiblei, along with fragmentary cranial and postcranial remains of crocodyliforms, and teeth of theropod and ornithischian dinosaurs.

Languages

This page is based on a Wikipedia article written by authors (here).
Text is available under the CC BY-SA 3.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.