Dimorphodon
Encyclopedia
Dimorphodon 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 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.
, at Lyme Regis
in Dorset, UK in December 1828. 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. 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. 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.
In 1858, Richard Owen
reported the find of 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. His first report contained no description and the name remained a nomen nudum
. In 1859 however, a subsequent publication by Owen provided a description. After several studies highlighting aspects of Dimorphodon 's anatomy, Owen in 1874 made NHMUK PV R 1035 the holotype
.
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
.
Dimorphodon had a large, bulky skull approximately 22 centimetre in length, whose weight was reduced by large openings separated from each other by thin bony partitions. Its structure, reminiscent of the supporting arches of a bridge, prompted Richard Owen to declare that, in 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. 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. Many depictions give it a speculative puffin
-like 'beak' because of similarities between the two animals' skulls.
The body structure of Dimorphodon displays many "primitive" characters, such as, according to Owen, a very small brain-pan and proportionally short wings. The first phalanx in its flight finger is only slightly longer than its lower arm. The neck was short but strong and flexible and may have had a membraneous 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 meter (4.6 ft) wingspan
.
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. The terminal end of the tail may have borne a Rhamphorhynchus
-like tail vane, although no soft tissues have yet been found of Dimorphodon to confirm this speculation.
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. His rival Harry Govier Seeley however, 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. This hypothesis was revived by Kevin Padian
in the nineteen eighties. However, fossilised track remains of other pterosaurs (ichnite
s) show a quadruped
al 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. David Unwin has therefore argued that even Dimorphodon was a quadruped, a view confirmed by computer modelling by Sarah Sangster.
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. 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 Dimorphodon was an insectivore
, though it may have occasionally eaten small vertebrates and carrion as well.
, with Dimorphodon as the only member. It was suggested in 1991 by German paleontologist Peter Wellnhofer
that Dimorphodon might be descended from the earlier European pterosaur Peteinosaurus
. 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.
Pterosaur
Pterosaurs were flying reptiles of the clade or order Pterosauria. They existed from the late Triassic to the end of the Cretaceous Period . Pterosaurs are the earliest vertebrates known to have evolved powered flight...
from the early Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
Period. It was named by paleontologist Richard Owen
Richard Owen
Sir Richard Owen, FRS KCB was an English biologist, comparative anatomist and palaeontologist.Owen is probably best remembered today for coining the word Dinosauria and for his outspoken opposition to Charles Darwin's theory of evolution by natural selection...
in 1859. Dimorphodon means "two-form tooth", derived from Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean 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.
Discovery
The first fossil remains now attributed to Dimorphodon were found in England by fossil collector Mary AnningMary Anning
Mary Anning was a British fossil collector, dealer and palaeontologist who became known around the world for a number of important finds she made in the Jurassic age marine fossil beds at Lyme Regis where she lived...
, at Lyme Regis
Lyme Regis
Lyme Regis is a coastal town in West Dorset, England, situated 25 miles west of Dorchester and east of Exeter. The town lies in Lyme Bay, on the English Channel coast at the Dorset-Devon border...
in Dorset, UK in December 1828. This region of Britain
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...
is now a World Heritage Site
World Heritage Site
A UNESCO World Heritage Site is a place that is listed by the UNESCO as of special cultural or physical significance...
, dubbed the Jurassic Coast
Jurassic Coast
The Jurassic Coast is a World Heritage Site on the English Channel coast of southern England. The site stretches from Orcombe Point near Exmouth in East Devon to Old Harry Rocks near Swanage in East Dorset, a distance of ....
; in it layers of the Blue Lias
Blue Lias
The Blue Lias is a geologic formation in southern, eastern and western England and parts of South Wales, part of the Lias Group. The Blue Lias consists of a sequence of limestone and shale layers, laid down in latest Triassic and early Jurassic times, between 195 and 200 million years ago...
are exposed, dating from the Hettangian
Hettangian
The Hettangian is the earliest age or lowest stage of the Jurassic period of the geologic timescale. It spans the time between 199.6 ± 0.6 Ma and 196.5 ± 1 Ma . The Hettangian follows the Rhaetian and is followed by the Sinemurian.In Europe stratigraphy the Hettangian is a part of the time span in...
-Sinemurian
Sinemurian
In the geologic timescale, the Sinemurian is an age or stage in the Early or Lower Jurassic epoch or series. It spans the time between 196.5 ± 2 Ma and 189.6 ± 1.5 Ma...
. The specimen was acquired by William Buckland
William Buckland
The Very Rev. Dr William Buckland DD FRS was an English geologist, palaeontologist and Dean of Westminster, who wrote the first full account of a fossil dinosaur, which he named Megalosaurus...
and reported in a meeting of the Geological Society on 5 February 1829. In 1835, after a thorough study by William Clift
William Clift
William Clift, , British naturalist, born at Burcombe, about half a mile from the town of Bodmin in Cornwall, on 14 Feb. 1775, was the youngest of the seven children of Robert Clift, who died a few years later, leaving his wife and family in the depths of poverty.-Education:The boy was sent to...
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
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Pterodactylus
Pterodactylus
Pterodactylus is a genus of pterosaurs, whose members are popularly known as pterodactyls. It was the first to be named and identified as a flying reptile...
, coining the new species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
Pterodactylus macronyx. 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
Elizabeth Philpot
Elizabeth Philpot was an early 19th century British fossil collector, amateur palaeontologist and artist who collected fossils from the cliffs around Lyme Regis in Dorset on the southern coast of England. She is best known today for her collaboration and friendship with the well known fossil...
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.
In 1858, Richard Owen
Richard Owen
Sir Richard Owen, FRS KCB was an English biologist, comparative anatomist and palaeontologist.Owen is probably best remembered today for coining the word Dinosauria and for his outspoken opposition to Charles Darwin's theory of evolution by natural selection...
reported the find of 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. His first report contained no description and the name remained a nomen nudum
Nomen nudum
The phrase nomen nudum is a Latin term, meaning "naked name", used in taxonomy...
. In 1859 however, a subsequent publication by Owen provided a description. After several studies highlighting aspects of Dimorphodon 's anatomy, Owen in 1874 made NHMUK PV R 1035 the holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
.
Meanwhile, though Dimorphodon is not a very common fossil, other fragmentary specimens were found. Some of these were acquired by Othniel Charles Marsh
Othniel Charles Marsh
Othniel Charles Marsh was an American paleontologist. Marsh was one of the preeminent scientists in the field; the discovery or description of dozens of news species and theories on the origins of birds are among his legacies.Born into a modest family, Marsh was able to afford higher education...
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
Aust Cliff
Aust Cliff 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....
.
Anatomy
Ideal type
Ideal type , also known as pure type, is a typological term most closely associated with antipositivist sociologist Max Weber . For Weber, the conduct of social science depends upon the construction of hypothetical concepts in the abstract...
of the vertebra. The front of the upper jaw had four or five fang-like teeth followed by an indeterminate number of smaller teeth; the maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
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. Many depictions give it a speculative puffin
Puffin
Puffins are any of three small species of auk in the bird genus Fratercula with a brightly coloured beak during the breeding season. These are pelagic seabirds that feed primarily by diving in the water. They breed in large colonies on coastal cliffs or offshore islands, nesting in crevices among...
-like 'beak' because of similarities between the two animals' skulls.
Wingspan
The wingspan of an airplane or a bird, is the distance from one wingtip to the other wingtip. For example, the Boeing 777 has a wingspan of about ; and a Wandering Albatross caught in 1965 had a wingspan of , the official record for a living bird.The term wingspan, more technically extent, is...
.
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. The terminal end of the tail may have borne a Rhamphorhynchus
Rhamphorhynchus (animal)
Rhamphorhynchus , "beak snout", 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 diamond-shaped vane...
-like tail vane, although no soft tissues have yet been found of Dimorphodon to confirm this speculation.
Gait
Biped
Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs, or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning "two feet"...
due to its relatively well developed hindlimbs and characteristics of its pelvis. This hypothesis was revived by Kevin Padian
Kevin Padian
Kevin Padian is a Professor of Integrative Biology at the University of California, Berkeley, Curator of Paleontology, University of California Museum of Paleontology and President of the National Center for Science Education. Padian's area of interest is in vertebrate evolution, especially the...
in the nineteen eighties. However, fossilised track remains of other pterosaurs (ichnite
Ichnite
An ichnite is a fossilised footprint. This is a type of trace fossil. Over the years, many ichnites have been found, around the world, giving important clues about the behaviour of the animals that made them...
s) show a quadruped
Quadruped
Quadrupedalism is a form of land animal locomotion using four limbs or legs. An animal or machine that usually moves in a quadrupedal manner is known as a quadruped, meaning "four feet"...
al gait while on the ground and these traces are all attributed to derived pterosaurs with a short fifth toe. Dimorphodon
Ecology
Piscivore
A piscivore is a carnivorous animal which eats primarily fish. Piscivory was the diet of early tetrapods , insectivory came next, then in time reptiles added herbivory....
(fish eater), though Buckland's original idea is more well supported by biomechanical studies. 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 Dimorphodon was an insectivore
Insectivore
An insectivore is a type of carnivore with a diet that consists chiefly of insects and similar small creatures. An alternate term is entomophage, which also refers to the human practice of eating insects....
, though it may have occasionally eaten small vertebrates and carrion as well.
Phylogeny
In 1870 Seeley assigned Dimorphodon its own family, the DimorphodontidaeDimorphodontidae
Dimorphodontidae is a family of early "rhamphorhynchoid" pterosaurs named after Dimorphodon, that lived in the Late Triassic to Early Jurassic....
, with Dimorphodon as the only member. It was suggested in 1991 by German paleontologist Peter Wellnhofer
Peter Wellnhofer
Peter Wellnhofer is a German paleontologist at the "Bayerische Staatssammlung fur Paläontologie" in Munich. He is best known for his work on the various fossil specimens of Archaeopteryx or "Urvogel", the first known bird...
that Dimorphodon might be descended from the earlier European pterosaur Peteinosaurus
Peteinosaurus
Peteinosaurus was a prehistoric reptile genus belonging to the Pterosauria. It lived in the late Triassic period in the middle Norian .-Name:...
. 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
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
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
Preondactylus
Preondactylus is a genus of long-tailed pterosaur from the Late Triassic that inhabited what is now Italy. It was discovered by Nando Buffarini in 1982 near Udine in the Preone valley of the Italian Alps.-Anatomy:...
. According to Alexander Kellner
Alexander Kellner
Alexander Wilhelm Armin Kellner is a Liechtensteinian/Brazilian paleontologist, a leading expert in the field of the study of pterosaurs....
however, Dimorphodon is far less basal and not a close relative of Peteinosaurus.