View source for Dimorphodon

{{Short description|Genus of dimorphodontid pterosaur from the Early Jurassic}}
{{Automatic taxobox
| fossil_range = [[Early Jurassic]] ([[Sinemurian]]), {{fossilrange|201.3|189.6}}
| image = Dimorphodon Flight Pose.png
| image_caption = Reconstruction skeleton in flying pose at the [[Rocky Mountain Dinosaur Resource Center]]
| parent_authority = [[Harry Govier Seeley|Seeley]], 1870
| display_parents = 4
| taxon = Dimorphodon
| authority = [[Richard Owen|Owen]], 1859
| type_species = {{extinct}}'''''Dimorphodon macronyx'''''
| type_species_authority = ([[William Buckland|Buckland]], 1829)
| synonyms = 
*''Pterodactylus macronyx'' <small>Buckland, 1829</small>
*''Pterodactylus (Rhamphorhynchus) macronyx'' <small>(Buckland, 1829)</small>
}}

'''''Dimorphodon''''' ({{IPAc-en|d|aɪ|ˈ|m|ɔr|f|ə|d|ɒ|n}} {{respell|dy|MOR|fə|don}}) is a [[genus]] of medium-sized [[pterosaur]] from [[Europe]] during the early [[Jurassic]] [[Period (geology)|Period]] (about 201-191 million years ago).<ref name="Müller_et.al.2023">Müller R.T., Ezcurra M.D., Garcia M.S., Agnolín F.L., Stocker M.R., Novas F.E., Soares M.B., Kellner A.W.A. & Nesbitt S.J. (2023). ”New reptile shows dinosaurs and pterosaurs evolved among diverse precursors”. ''Nature'' '''620'''(7974): p. 589–594. [[doi:10.1038/s41586-023-06359-z]]</ref> It was named by [[Palaeontology|paleontologist]] [[Richard Owen]] in 1859. ''Dimorphodon'' means "two-form tooth", derived from the [[Ancient Greek|Greek]] {{Transliteration|grc|di-}} ({{lang|grc|δι-}}) meaning 'two', {{Transliteration|grc|morphḗ}} ({{lang|grc|μορφή}}) meaning 'shape' and {{Transliteration|grc|odṓn}} ({{lang|grc|ὀδών}}) meaning 'tooth', referring to the fact that it had two distinct types of teeth in its jaws – which is comparatively rare among reptiles. The diet of ''Dimorphodon'' has been questioned among researchers, with earlier interpretations depicting it as an insectivore or a piscivore. Recent studies have suggested that ''Dimorphodon'' likely hunted small vertebrates, though it still would have consumed soft invertebrates like insects.

==Description==
[[Image:Dimorphodon2DB.jpg|thumb|left|Restoration of a pair of ''D. macronyx''|232x232px]]
The body structure of ''Dimorphodon'' displays many "primitive" characteristics, such as, according to Owen, a very small brain-pan<ref name="cranfield-Dimorphodon" /> and proportionally short wings.<ref name="cranfield-Dimorphodon" /> The first phalanx in its flight finger is only slightly longer than its lower arm.<ref name="cranfield-Dimorphodon" /> 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 sacs could reach the hollow interior. ''Dimorphodon'' had an adult body length of {{Convert|1|m|ft}} long, with a 1.45&nbsp;metre (4.6&nbsp;ft) [[wingspan]].<ref name="cranfield-Dimorphodon" /><ref name=PW96b>{{cite book |last=Wellnhofer |first=Peter |author-link=Peter Wellnhofer |title=The Illustrated Encyclopedia of Pterosaurs |orig-year=1991 |year=1996 |publisher=Barnes and Noble Books |location=New York |isbn=0-7607-0154-7 |page=71 }}</ref> 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.<ref name="cranfield-Dimorphodon" /> The terminal end of the tail may have borne a ''[[Rhamphorhynchus]]''-like tail vane, although no <!--'soft tissues'  are unlikely to be preserved; however, they can leave an impression--> impressions have yet been found in ''Dimorphodon'' fossils to confirm this speculation.<ref name="cranfield-Dimorphodon" />

===Skull===
''Dimorphodon'' had a large, bulky skull approximately {{Convert|23|cm|in}} in length, whose weight was reduced by large openings separated from each other by thin bony partitions.<ref name="cranfield-Dimorphodon" /> Its structure, reminiscent of the supporting arches of a bridge, prompted Richard Owen to declare that, as far as achieving great strength from lightweight 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.<ref>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</ref> 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 lancets.<ref name="cranfield-Dimorphodon">"Dimorphodon." In: Cranfield, Ingrid (ed.). ''The Illustrated Directory of Dinosaurs and Other Prehistoric Creatures''. London: Salamander Books, Ltd. Pp. 288-291.</ref> Many depictions give it a speculative [[puffin]]-like 'beak' because of similarities between the two animals' skulls.

==History of discovery==
[[File:Dimorphodon macronyx holotype.jpg|thumb|left|''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.<ref name=PW96>{{cite book |last=Wellnhofer |first=Peter |author-link=Peter Wellnhofer |title=The Illustrated Encyclopedia of Pterosaurs |orig-year=1991 |year=1996 |publisher=Barnes and Noble Books |location=New York |isbn=0-7607-0154-7 |page=69 }}</ref> This region of [[Great Britain|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.<ref>Buckland, W. (1829). Proceedings of the Geological Society of London, '''1''': 127</ref> 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''.<ref name="buckland1835">{{cite journal |last1=Buckland |first1=W. |title=XI.--On the Discovery of a New Species of Pterodactyle in the Lias at Lyme Regis. |journal=Transactions of the Geological Society of London |date=1 January 1829 |volume=s2-3 |issue=1 |pages=217–222 |doi=10.1144/transgslb.3.1.217 |s2cid=129251962 |url=https://zenodo.org/record/2224681 }}</ref> The [[specific name (zoology)|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 R1034, 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.
[[Image:Macronyx.jpg|thumb|Illustration of ''D. macronyx'' specimen NHUK PV R1035|227x227px]]
In 1858, [[Richard Owen]] reported finding two new specimens, NHMUK PV OR 41212 and NHMUK PV R1035, 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''.<ref name="owen1859b">{{cite journal |last1=Owen |first1=R. |year=1859 |title=On a new genus (''Dimorphodon'') of pterodactyle, with remarks on the geological distribution of flying reptiles |journal=Report for the British Association for the Advancement of Science |volume=28 |pages=97–103 }}</ref> His first report contained no description and the name remained a ''[[nomen nudum]]''. In 1859, however, a subsequent publication by Owen provided a description.<ref>{{cite journal |title=II. On the vertebral characters of the order pterosauria (ow.) as exemplified in the genera Pterodactylus (cuv.) and Dimorphodon (ow.) |journal=Proceedings of the Royal Society of London |date=31 December 1859 |volume=9 |pages=703–704 |doi=10.1098/rspl.1857.0143 |s2cid=186208842 |doi-access= }}</ref> After several studies highlighting aspects of ''Dimorphodon''{{'}}s anatomy, Owen in 1874 made NHMUK PV R1034 the [[holotype]].<ref>{{cite journal |last1=Owen |first1=R. |year=1874 |title=Monograph of the fossil Reptilia of the Mesozoic Formations. Part I. Pterosauria |journal=Palaeontographical Society of London |volume=27 |pages=1–14 }}</ref>
[[Image:Dimorphodon macronyx - Pterosaurs Flight in the Age of Dinosaurs.jpg|thumb|left|Cast of ''D. macronyx'' specimen NHMUK PV OR 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]].<ref name="cranfield-Dimorphodon" />

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 [[sphenodontian]]s, [[dinosaur]]s and [[mammaliaform]]s have also been found.<ref name=Montellano>{{cite journal |last1=Montellano |first1=Marisol |last2=Hopson |first2=James A. |last3=Clark |first3=James M. |title=Late Early Jurassic Mammaliaforms from Huizachal Canyon, Tamaulipas, México |journal=Journal of Vertebrate Paleontology |date=2008 |volume=28 |issue=4 |pages=1130–1143 |doi=10.1671/0272-4634-28.4.1130 |jstor=20491044 |bibcode=2008JVPal..28.1130M |s2cid=128782275 }}</ref> 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.<ref name=Clark1998>{{cite journal |last1=Clark |first1=J. M. |last2=Hopson |first2=J. A. |last3=Hernández R. |first3=R. |last4=Fastovsky |first4=D. E. |last5=Montellano |first5=M. |title=Foot posture in a primitive pterosaur |journal=Nature |date=February 1998 |volume=391 |issue=6670 |pages=886–889 |doi=10.1038/36092 |bibcode=1998Natur.391..886C |s2cid=4408637 |url=http://doc.rero.ch/record/14900/files/PAL_E2042.pdf }}</ref> Later studies considered this species not closely related to ''Dimorphodon macronyx'', but an early relative of [[Anurognathidae]].<ref>{{Cite journal|last1=Wei|first1=Xuefang|last2=Pêgas|first2=Rodrigo Vargas|last3=Shen|first3=Caizhi|last4=Guo|first4=Yanfang|last5=Ma|first5=Waisum|last6=Sun|first6=Deyu|last7=Zhou|first7=Xuanyu|date=2021-03-31|title=''Sinomacrops bondei'', a new anurognathid pterosaur from the Jurassic of China and comments on the group|journal=PeerJ|language=en|volume=9|pages=e11161|doi=10.7717/peerj.11161|pmid=33850665 |pmc=8019321 |issn=2167-8359|doi-access=free}}</ref>

==Classification==
[[Image:Dimorphodon mount.jpg|thumb|Reconstructed skeleton, [[Rainbow Forest Museum]]|244x244px]]
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]]''.<ref name="cranfield-Dimorphodon" /> 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.<ref name=LoneStarPterosaurs>{{cite journal |last1=Andres |first1=Brian |last2=Myers |first2=Timothy S. |title=Lone Star Pterosaurs |journal=Earth and Environmental Science Transactions of the Royal Society of Edinburgh |date=September 2012 |volume=103 |issue=3–4 |pages=383–398 |doi=10.1017/S1755691013000303 |bibcode=2012EESTR.103..383A |s2cid=84617119 }}</ref>

{{clade| style=font-size:85%;line-height:100%
|label1=[[Pterosauria]]
|1={{clade
   |label1=
   |1={{clade
      |1={{clade
         |1=''[[Preondactylus buffarinii]]''
         |2=''[[Austriadactylus cristatus]]''}}
      |label2=
      |2={{clade
         |1=''[[Peteinosaurus zambellii]]''
         |2=[[Eudimorphodontidae]]}}}}
   |label2=[[Macronychoptera]]
   |2={{clade
      |label1=
      |1={{clade
         |1='''''Dimorphodon macronyx'''''
         |2=''[[Parapsicephalus purdoni]]''}}
      |2=[[Novialoidea]]}}}}}}

==Palaeobiology==
===Diet===
[[File:Dimorphodon.png|thumb|Restoration of ''D. macronyx'' chasing a [[sphenodontian]] on the ground|238x238px]]
The 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 biomechanical studies support Buckland's original insectivore idea better, 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.<ref name=osi2010>{{cite journal |last1=Ősi |first1=Attila |title=Feeding-related characters in basal pterosaurs: implications for jaw mechanism, dental function and diet: Feeding-related characters in pterosaurs |journal=Lethaia |date=June 2011 |volume=44 |issue=2 |pages=136–152 |doi=10.1111/j.1502-3931.2010.00230.x |url=http://real.mtak.hu/10182/1/abst_%C5%90si_A_SVP_2009b.pdf }}</ref> Mark Witton has argued that the animal was a specialised carnivore that was too large for an insectivorous diet, though he did acknowledge that it still might have eaten large insects, and thus specialised to hunt relatively small vertebrates, with its relatively weak jaw musculature indicating that it probably ate proportionally small prey.<ref name="Wilton, Mark P. 2013">{{Cite book| title = Pterosaurs: Natural History, Evolution, Anatomy|author=Wilton, Mark P. |isbn=978-0-691-15061-1|year=2013|publisher=Princeton University Press|pages=103}}</ref> [[Dental microwear]] examinations confirm its status as a vertebrate predator, as opposed to several other insectivore or piscivore early pterosaurs, though the study does acknowledge that the possibility of consuming relatively softer invertebrates cannot be excluded entirely.<ref>{{cite journal |last1=Bestwick |first1=Jordan |last2=Unwin |first2=David M. |last3=Butler |first3=Richard J. |last4=Purnell |first4=Mark A. |title=Dietary diversity and evolution of the earliest flying vertebrates revealed by dental microwear texture analysis |journal=Nature Communications |date=28 October 2020 |volume=11 |issue=1 |pages=5293 |doi=10.1038/s41467-020-19022-2|pmc=7595196  |pmid=33116130 |bibcode=2020NatCo..11.5293B |doi-access=free }}</ref>

===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.<ref name="Wilton, Mark P. 2013"/><ref>Rayner et al 2011{{full citation needed|date=November 2020}}</ref>
[[Image:Dimorphodon-macronyx jconway.jpg|thumb|Restoration of ''D. macronyx'' in flight|225x225px]]
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.
[[File:Dimorphodon reconstruction Seeley 1901.jpg|thumb|left|''D. macronyx'' in the controversial bipedal pose, Seeley, 1901|225x225px]]
[[File:Dimorphodon macronyx.jpg|thumb|left|Seeley's quadrupedal ''Dimorphodon'' pose|225x225px]]
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.<ref name="cranfield-Dimorphodon" /> 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.<ref>{{cite journal |last1=Seeley |first1=Harry G. |title=X.— Remarks on Prof. Owen's monograph on Dimorphodon |journal=Annals and Magazine of Natural History |date=August 1870 |volume=6 |issue=32 |pages=129–152 |doi=10.1080/00222937008696217 |url=https://zenodo.org/record/1826129 }}</ref> This hypothesis was revived by [[Kevin Padian]] in 1983.<ref>{{cite journal |last1=Padian |first1=Kevin |year=1983 |url=http://peabody.yale.edu/sites/default/files/documents/scientific-publications/ypmP189_1983.pdf |title=Osteology and functional morphology of ''Dimorphodon macronyx'' (Buckland) (Pterosauria: Rhamphorhynchoidea) based on new material in the Yale Peabody Museum |journal=Postilla |volume=189 |pages=1–44 |access-date=2019-02-08 |archive-date=2021-01-26 |archive-url=https://web.archive.org/web/20210126022616/http://peabody.yale.edu/sites/default/files/documents/scientific-publications/ypmP189_1983.pdf |url-status=dead }}</ref> 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''<nowiki>'s</nowiki> was elongated, clawless, and oriented to the side.<ref name="cranfield-Dimorphodon" /> [[David Unwin]] has therefore argued that even ''Dimorphodon'' was a quadruped, a view confirmed by computer modelling by [[Sarah Sangster]].<ref>{{cite journal |last1=Sangster |first1=S. |year=2001 |title=Anatomy, functional morphology and systematics of ''Dimorphodon'' |journal=Strata |volume=11 |pages=87–88 }}</ref>

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.<ref name="Wilton, Mark P. 2013"/>

==See also==
{{commons category|Dimorphodon}}
{{Portal|Paleontology}}
* [[List of pterosaur genera]]
* [[Timeline of pterosaur research]]

==References==
{{Reflist|3}}
{{Pterosauria|B.}}
{{Taxonbar|from=Q131245}}

[[Category:Pterosaurs]]
[[Category:Early Jurassic pterosaurs]]
[[Category:Jurassic reptiles of Europe]]
[[Category:Taxa named by Richard Owen]]
[[Category:Fossil taxa described in 1859]]