View source for Biology:Keilhauia

{{Short description|Extinct genus of reptiles}}
{{Italic title}}
{{Speciesbox
| name = ''Keilhauia''
| fossil_range = [[Earth:Berriasian|Berriasian]]<br>~{{fossilrange|145|140}}
| image = Keilhauia-3.png
| image_upright = 1.15
| image_caption = Diagram of holotype specimen as preserved
| genus = Keilhauia
| parent_authority = Delsett ''et al.'', 2017
| species = nui
| authority = Delsett ''et al.'', 2017
| synonyms = 
}}

'''''Keilhauia''''' is a genus of [[Biology:Ophthalmosauridae|ophthalmosaurid]] [[Biology:Ichthyosaur|ichthyosaur]], a type of dolphin-like, large-eyed marine reptile, from the [[Earth:Early Cretaceous|Early Cretaceous]] shallow marine Slottsmøya Member of the [[Earth:Agardhfjellet Formation|Agardhfjellet Formation]] in [[Place:Svalbard|Svalbard]], {{wipe|Norway}}. The genus contains a single species, '''''K. nui''''', known from a single specimen discovered in 2010 and described by Delsett ''et al.'' in 2017. In life, ''Keilhauia'' probably measured approximately {{convert|4|m}} in length; it can be distinguished by other ophthalmosaurids by the wide top end of its ilium and the relatively short ischiopubis (the fusion of the ischium and the pubis) compared to the [[Biology:Femur|femur]]. Although it was placed in a basal position within the Ophthalmosauridae by [[Biology:Phylogenetics|phylogenetic analysis]], this placement is probably incorrect.

==Description==
[[File:Keilhauia Scale.svg|thumb|left|Size comparison]]
Judging by the partially preserved holotype specimen, ''Keilhauia'' has been estimated at {{convert|3.8|-|4.3|m}} based on comparisons to the related [[Biology:Ophthalmosauridae|ophthalmosaurid]] ''[[Biology:Cryopterygius|Cryopterygius]]''.<ref name="keilhauia"/><ref name="cryo">{{cite journal | last1 = Druckenmiller | first1 = P.S. | last2 = Hurum | first2 = J.H. | last3 = Knutsen | first3 = E.M. | last4 = Nakrem | first4 = H.A. | title = Two new ophthalmosaurids (Reptilia: Ichthyosauria) from the Agardhfjellet Formation (Upper Jurassic: Volgian/Tithonian), Svalbard, Norway | journal = Norwegian Journal of Geology | volume = 92 | date = 2012 | pages = 311–339 | issn = 0029-196X}}</ref> This specimen was probably mature or close to maturity at time of death, judging by the convex head of the [[Biology:Humerus|humerus]] and the smooth texture of the humeral shaft.<ref name="keilhauia">{{cite journal | last1 = Delsett | first1 = L.L. | first2 = A.J. | last2 = Roberts | first3 = P.S. | last3 = Druckenmiller | first4 = J.H. | last4 = Hurum | title = A New Ophthalmosaurid (Ichthyosauria) from Svalbard, Norway, and Evolution of the Ichthyopterygian Pelvic Girdle | journal = PLOS ONE | volume = 12 | issue = 1 | date = 2017 | page = e0169971 | doi = 10.1371/journal.pone.0169971 | pmid = 28121995 | pmc = 5266267 | bibcode = 2017PLoSO..1269971D | doi-access = free }}</ref><ref name="onto">{{cite journal | last1 = Johnson | first1 = R. | title = Size independent criteria for estimating relative age and the relationships among growth parameters in a group of fossil reptiles (Reptilia: Ichthyosauria) | journal = Canadian Journal of Earth Sciences | date = 1977 | volume = 14 | issue = 8 | pages = 1916–1924 | doi = 10.1139/e77-162 | bibcode = 1977CaJES..14.1916J }}</ref>

===Skull and axial skeleton===
Although only a small portion of the snout is known, it seems to be taller than that of ''[[Biology:Aegirosaurus|Aegirosaurus]]'',<ref name="aegiro">{{cite journal | last1 = Bardet | first1 = N. | last2 = Fernandez | first2 = M. | title = A new ichthyosaur from the Upper Jurassic lithographic limestones of Bavaria | volume = 74 | issue = 3 | journal = Journal of Paleontology | pages = 503–511 | date = 2000 | doi = 10.1666/0022-3360(2000)074<0503:ANIFTU>2.0.CO;2 | s2cid = 131190803 | url = http://doc.rero.ch/record/14941/files/PAL_E2088.pdf }}</ref> instead being more similar to those of ''Cryopterygius''<ref name="cryo"/> and ''[[Biology:Caypullisaurus|Caypullisaurus]]''.<ref name="caypulli">{{cite journal | last1 = Fernandez | first1 = M. | title = Redescription and phylogenetic position of ''Caypullisaurus'' (Ichthyosauria: Ophthalmosauridae) | pages = 368–375 | doi = 10.1666/0022-3360(2007)81[368:RAPPOC]2.0.CO;2 | date = 2007 | volume = 81 | issue = 2 | url = http://jpaleontol.geoscienceworld.org/content/81/2/368 | journal = Journal of Paleontology| s2cid = 130457040 }}</ref> A shallow groove that housed blood vessels, known as the [[Biology:Nutrient canal|nutrient foramen]], is visible on the side of the jaw. About ten teeth are preserved; they are conical, narrow at the tip, and slightly curved.<ref name="keilhauia"/>
[[File:Keilhauia-4.png|thumb|right|Snout fragment (A-B) and vertebrae (C-L) of ''Keilhauia'']]
It is difficult to estimate the exact number of vertebral segments that were present in front of the [[Biology:Sacrum|sacrum]]; the preserved [[Biology:Vertebra#structure|centra]] suggest that there are at least 43. This is more than the 42 in ''[[Biology:Athabascasaurus|Athabascasaurus]]'',<ref name="athabasca">{{cite journal | last1 = Druckenmiller | first1 = P.S. | last2 = Maxwell | first2 = E.E. | title = A new Lower Cretaceous (lower Albian) ichthyosaur genus from the Clearwater Formation, Alberta, Canada | journal = Canadian Journal of Earth Sciences | volume = 47 | issue = 8 | date = 2010 | pages = 1037–1053 | doi = 10.1139/E10-028 | bibcode = 2010CaJES..47.1037D }}</ref> the 41 in ''[[Biology:Nannopterygius|Nannopterygius]]'', and the 37 in ''[[Biology:Platypterygius|Platypterygius americanus]]'',<ref name="americanus">{{cite journal | last1 = Maxwell | first1 = E.E. | last2 = Kear | first2 = B.P. | title = Postcranial anatomy of ''Platypterygius americanus'' (Reptilia: Ichthyosauria) from the Cretaceous of Wyoming | journal = Journal of Vertebrate Paleontology | volume = 30 | issue = 4 | date = 2010 | pages = 1059–1068 | doi = 10.1080/02724634.2010.483546 | s2cid = 85817541 }}</ref> but less than the 46 in ''Platypterygius australis''<ref name="australis">{{cite journal | last1 = Zammit | first1 = M. | last2 = Norris | first2 = R.M. | last3 = Kear | first3 = B.P. | title = The Australian Cretaceous ichthyosaur ''Platypterygius australis'': a description and review of postcranial remains | journal = Journal of Vertebrate Paleontology | volume = 30 | date = 2010 | issue = 6 | doi = 10.1080/02724634.2010.521930 | pages = 1726–1735 | s2cid = 85089080 }}</ref> and the 50 or more in ''Cryopterygius'',<ref name="cryo"/> ''Aegirosaurus'',<ref name="aegiro"/> and ''Platypterygius platydactylus''. The posterior dorsal vertebrae are wider and taller than those near the front, and their front and rear faces are rounded. The first few caudal vertebrae are the proportionally tallest and widest of all the vertebrae,<ref name="swim">{{cite journal | last1 = Buchholtz | first1 = E.A. | title = Swimming styles in Jurassic ichthyosaurs | journal = Journal of Vertebrate Paleontology | volume = 21 | issue = 1 | pages = 61–73 | date = 2001 | doi = 10.1671/0272-4634(2001)021[0061:SSIJI]2.0.CO;2 | s2cid = 85925883 }}</ref> but the vertebrae quickly become shorter vertically prior to the bend in the tail that supported the tail fluke.<ref name="keilhauia"/>

Each [[Biology:Vertebra#structure|neural spine]] is about the same length as the underlying centrum, which is similar to ''Cryopterygius''<ref name="cryo"/> but not ''[[Biology:Ophthalmosaurus|Ophthalmosaurus]]'' (in which they are proportionally longer in the posterior cervical vertebrae). Similar to ''[[Biology:Gengasaurus|Gengasaurus]]'',<ref name="genga">{{cite journal | last1 = Paparella | first1 = I. | last2 = Maxwell | first2 = E.E. | last3 = Cipriani | first3 = A. | last4 = Roncace | first4 = S. | last5 = Caldwell | first5 = M.W. | title = The first ophthalmosaurid ichthyosaur from the Upper Jurassic of the Umbrian–Marchean Apennines (Marche, Central Italy) | date = 2016 | journal = Geological Magazine | volume = 154 | issue = 4 | pages = 837–858 | doi = 10.1017/S0016756816000455
 | s2cid = 132955874 }}</ref> the first few neural spines are taller than the corresponding centra, but then decrease in height gradually. The tops of the neural spines, which are the thinnest parts of the bones, are straight, instead of being notched like ''Cryopterygius''<ref name="cryo"/>  or ''Platypterygius australis''.<ref name="australis"/>  The ribs are shaped like a [[Lemniscate|figure eight]] in cross section near their top ends, but this is less obvious closer to the bottom; such a morphology is typical among ophthalmosaurids, except for ''[[Biology:Acamptonectes|Acamptonectes]]''<ref name="acampto">{{cite journal | last1 = Fischer | first1 = V. | last2 = Maisch | first2 = M.W. | last3 = Naish | first3 = D. | last4 = Kosma | first4 = R. | last5 = Liston | first5 = J. | last6 = Joger | first6 = U. | last7 = Kruger | first7 = F.J. | last8 = Pardo-Perez | first8 = J. | last9 = Tainsh | first9 = J. | last10 = Appleby | first10 = R.M. | title = New Ophthalmosaurid Ichthyosaurs from the European Lower Cretaceous Demonstrate Extensive Ichthyosaur Survival across the Jurassic–Cretaceous Boundary | journal = PLOS ONE | volume = 7 | issue = 1 | doi = 10.1371/journal.pone.0029234 | pmid = 22235274 | pmc = 3250416 | date = 2012 | page = e29234| bibcode = 2012PLoSO...729234F | doi-access = free }}</ref> and ''[[Biology:Mollesaurus|Mollesaurus]]''.<ref name="molle">{{cite journal | last1 = Fernandez | first1 = M.S | last2 = Talevi | first2 = M. | title = Ophthalmosaurian (Ichthyosauria) records from the Aalenian–Bajocian of Patagonia (Argentina): an overview
 | journal = Geological Magazine | volume = 151 | issue = 1 | date = 2014 | pages = 49–59 | doi = 10.1017/S0016756813000058 | bibcode = 2014GeoM..151...49F | s2cid = 129936214 | url = https://www.cambridge.org/core/journals/geological-magazine/article/div-classtitleophthalmosaurian-ichthyosauria-records-from-the-aalenianbajocian-of-patagonia-argentina-an-overviewdiv/E85609F12F82AE00D5340BCF99806F2A| hdl = 11336/37342 | hdl-access = free }}</ref> The dorsal ribs are around {{convert|75|-|81|cm|abbr=on}} long, while the first few caudal ribs are only {{convert|2|-|5|cm|abbr=on}} long.<ref name="keilhauia"/>

===Forelimb and pectoral girdle===
In ''Keilhauia'', the [[Biology:Scapula|scapula]] has a relatively straight blade that was broadened at its front end into a fan-like acromion process. This process is less prominent than that of ''Acamptonectes''<ref name="acampto"/> and ''[[Biology:Sveltonectes|Sveltonectes]]'',<ref name="svelto">{{cite journal | last1 = Fischer | first1 = V. | last2 = Masure | first2 = E. | last3 = Arkhangelsky | first3 = M.S. | last4 = Godefroit | first4 = P. | title = A new Barremian (Early Cretaceous) ichthyosaur from western Russia | pages = 1010–1025 | journal = Journal of Vertebrate Paleontology | volume = 31 | issue = 5 | date = 2011 | doi = 10.1080/02724634.2011.595464 | hdl = 2268/92828 | s2cid = 86036325 | url = https://orbi.uliege.be/handle/2268/92828 }}</ref> instead being more similar to that of ''Cryopterygius'',<ref name="cryo"/> ''Platypterygius hercynicus'', and ''[[Biology:Sisteronia|Sisteronia]]''.<ref name="sister">{{cite journal | last1 = Fischer | first1 = V. | last2 = Bardet | first2 = N. | last3 = Guiomar | first3 = M. | last4 = Godefroit | first4 = P. | title = High Diversity in Cretaceous Ichthyosaurs from Europe Prior to Their Extinction | date = 2014 | journal = PLOS ONE | volume = 9 | issue = 1 | page = e84709 | doi = 10.1371/journal.pone.0084709 | pmid = 24465427 | pmc = 3897400 | bibcode = 2014PLoSO...984709F | doi-access = free }}</ref> The scapula formed more of the glenoid than the coracoid; like ''Sveltonectes''<ref name="svelto"/> but unlike ''Cryopterygius'',<ref name="cryo"/> the glenoid does not extend onto the bottom face of the scapula. The ''de facto'' blade of the scapula was widest near the middle, and angled slightly downwards; like ''Acamptonectes''<ref name="acampto"/> but unlike all other ophthalmosaurids, the blade has a relatively uniform thickness along its entire length.<ref name="keilhauia"/>
[[File:Keilhauia-8.png|thumb|left|Scapula (A-B), clavicle (C-D), coracoid (E), and humerus (F-H) of ''Keilhauia'']]
The [[Biology:Clavicle|clavicle]], which is not fused to other elements in the [[Biology:Shoulder girdle|pectoral girdle]], bears a thickened process on its frontal bottom edge which points towards the midline of the torso. This process is relatively short, square-shaped from the front, and bordered by a rim on its back edge. In most other ophthalmosaurids, this same process is more finger-like, although some specimens of ''Ophthalmosaurus'' have similar processes. The back part of the clavicle gradually narrows into a curved point, as in ''Ophthalmosaurus'', ''[[Biology:Ophthalmosaurus|Baptanodon]]'', and ''[[Biology:Janusaurus|Janusaurus]]''.<ref name="janu">{{cite journal | last1 = Roberts | first1 = A.J. | last2 = Druckenmiller | first2 = P.S. | last3 = Saetre | first3 = G.-P. | last4 = Hurum | first4 = J.H. | title = A New Upper Jurassic Ophthalmosaurid Ichthyosaur from the Slottsmøya Member, Agardhfjellet Formation of Central Spitsbergen | date = 2014 | doi = 10.1371/journal.pone.0103152 | pmid = 25084533 | pmc = 4118863 | volume = 9 | issue = 8 | journal = PLOS ONE | page = e103152| bibcode = 2014PLoSO...9j3152R | url = https://www.duo.uio.no/bitstream/10852/43544/1/journal-pone-0103152-roberts.pdf | doi-access = free }}</ref><ref name="keilhauia"/>

The coracoid is a kidney-shaped bone that is about as long as it is wide, compared to ''Cryopterygius'',<ref name="cryo"/> ''Nannopterygius'', and ''Sveltonectes'',<ref name="svelto"/> where it is not as wide proportionally. Like ''Ophthalmosaurus'' and ''[[Biology:Arthropterygius|Arthropterygius]]'',<ref name="arthro"/> the coracoid bears a prominent notch on its front edge; it also bears a ridge on the frontal part of its midline, like ''Ophthalmosaurus'' and ''Acamptonectes'',<ref name="acampto"/> but unlike ''Caypullisaurus''<ref name="caypulli"/> and ''Platypterygius australis''.<ref name="australis"/> Its articular facets with the scapula and glenoid are clearly separate, as in ''Sveltonectes''<ref name="svelto"/> but not ''Acamptonectes''.<ref name="acampto"/> The former is only about 45% of the latter in length; this figure is 50% in ''Cryopterygius'',<ref name="cryo"/> and the two facets are effectively the same length in ''Janusaurus''.<ref name="janu"/><ref name="keilhauia"/>

There are two prominent processes on the [[Biology:Humerus|humerus]]. The longer, less prominent, and more ridge-like of these is the dorsal process. This process is remarkably short compared to other ophthalmosaurids, being less than half of the length of the humeral shaft, a condition also seen in ''[[Biology:Undorosaurus|Undorosaurus]]'' and ''Aegirosaurus'';<ref name="aegiro"/> in ''Ophthalmosaurus'', ''[[Biology:Brachypterygius|Brachypterygius]]'', ''Paraophthalmosaurus'', and ''Cryopterygius'',<ref name="cryo"/> the process reaches the midpoint of the humerus, while it is even longer in ''Arthropterygius'',<ref name="arthro"/> ''Platypterygius americanus'',<ref name="americanus"/> ''Platypterygius australis'',<ref name="australis"/> and ''Platypterygius hercynicus''.<ref name="hercynicus">{{cite journal | last1 = Kolb | first1 = C. | last2 = Sander | first2 = P.M. | title = Redescription of the ichthyosaur ''Platypterygius hercynicus'' (Kuhn 1946) from the Lower Cretaceous of Salzgitter (Lower Saxony, Germany) | journal = Palaeontographica Abteilung A | volume = 288 | issue = 4 | pages = 151–192 | doi = 10.1127/pala/288/2009/151 | date = 2009}}</ref> The other process is the deltopectoral crest, which is similarly small among ophthalmosaurids (i.e. less than half of the shaft length) in the same manner as ''Arthropterygius'',<ref name="arthro"/> ''Platypterygius hercynicus'',<ref name="hercynicus"/>  and ''Janusaurus'';<ref name="janu"/> it is about half of the shaft length in ''Ophthalmosaurus'', and is almost as long as the entire shaft in ''Sisteronia'',<ref name="sister"/> ''Acamptonectes'',<ref name="acampto"/> and ''Platypterygius americanus''.<ref name="americanus"/><ref name="keilhauia"/>

At the midpoint of the humeral shaft, the bone is mildly constricted, being approximately 20% narrower than the maximum width. The bottom end of the humerus is larger than the top end; it bears three articular facets, with one for the preaxial accessory element (the smallest of the three), one for the [[Biology:Radius (bone)|radius]] (the tallest of the three), and one for the [[Biology:Ulna|ulna]] (which forms an angle of 120° with the radial facet). ''Sveltonectes'',<ref name="svelto"/> ''Nannopterygius'', ''Platypterygius hauthali'',<ref name="hauthali">{{cite journal | last1 = Fernandez | first1 = M. | last2 = Aguierre-Urreta | first2 = M.B. | journal = Journal of Vertebrate Paleontology | volume = 25 | issue = 3 | pages = 583–587 | doi = 10.1671/0272-4634(2005)025[0583:ROPHVH]2.0.CO;2 | date = 2005 | title = Revision of ''Platypterygius hauthali'' von Huene, 1927 (Ichthyosauria, Ophthalmosauridae) from the Early Cretaceous of Patagonia, Argentina | s2cid = 130393321 | hdl = 11336/93640 | hdl-access = free }}</ref> and ''Platypterygius platydactylus'' all only have two; ''[[Biology:Maiaspondylus|Maiaspondylus]]'',<ref name="maia">{{cite journal | last1 = Maxwell | first1 = E.E. | last2 = Caldwell | first2 = M.W. | title = A new genus of ichthyosaur from the Lower Cretaceous of Western Canada | journal = Palaeontology | doi = 10.1111/j.1475-4983.2006.00589.x | volume = 49 | issue = 5 | date = 2006 | pages = 1043–1052 | doi-access = free }}</ref> ''Aegirosaurus'',<ref name="aegiro"/> ''Brachypterygius'', and ''Platypterygius americanus''<ref name="americanus"/> also have three, but the second facet articulates with a different bone; ''Cryopterygius'' has two on the left humerus and three on the right;<ref name="cryo"/> and ''Platypterygius australis''<ref name="australis"/> and ''Platypterygius hercynicus''<ref name="hercynicus"/> have up to four facets.<ref name="keilhauia"/>

===Hindlimb and pelvic girdle===
[[File:Keilhauia-9.png|thumb|Ilium (A-D), ischiopubis (E), and femur (F-H) of ''Keilhauia'']]
The ilium of ''Keilhauia'' is rather short compared to that of other ophthalmosaurids; ''Aegirosaurus'' is the only other ophthalmosaurid that possibly approaches ''Keilhauia'' in this respect.<ref name="aegiro"/> The side of the ilium directed towards the back of the body is concave, like ''Ophthalmosaurus'', ''Athabascasaurus'',<ref name="athabasca"/> and ''Janusaurus'',<ref name="janu"/> with the curve being more pronounced in the latter two. The acetabulum, on the lower end of the ilium, is thickened relative to the rest of the bone, and does not bear any distinct articular facets. [[Biology:Autapomorphy|Autapomorphically]], the top end of the ilium is 1.5 times the width of the acetabular end.<ref name="keilhauia"/>

The ischium and the pubis are fused together into a single, continuous, solid trapezoid-shaped element known as the ischiopubis, with the wider edge (1.4 times the width of the other end, which is shorter proportionally than that of ''Aegirosaurus'',<ref name="aegiro"/> ''Janusaurus'',<ref name="janu"/> ''Ophthalmosaurus'', and ''Athabascasaurus''<ref name="athabasca"/>) being at the midline of the body. This complete fusion is also seen in ''Janusaurus'',<ref name="janu"/> ''Sveltonectes'',<ref name="svelto"/> ''Athabascasaurus'',<ref name="athabasca"/> ''Aegirosaurus'',<ref name="aegiro"/> ''Caypullisaurus'',<ref name="caypulli"/> and possibly ''Platypterygius australis'';<ref name="australis"/> meanwhile, ''Ophthalmosaurus'', ''Cryopterygius'',<ref name="cryo"/> ''Undorosaurus'', and ''Paraophthalmosaurus'' retain a small hole in the ischiopubis.  The probable portion of the ischiopubis that represents the pubis is thicker than the rest of the bone. Also uniquely among ophthalmosaurids, this fused element is shorter than the [[Biology:Femur|femur]].<ref name="keilhauia"/>

Both ends of the femur of ''Keilhauia'' are approximately the same width, with the middle of the femoral shaft being slightly narrower. The top end was slightly thicker than the rest of the bone along its front rim. Like ''Arthropterygius''<ref name="arthro">{{cite journal | last1 = Maxwell | first1 = E.E. | title = Generic reassignment of an ichthyosaur from the Queen Elizabeth Islands, Northwest Territories, Canada | volume = 30 | issue = 2 | journal = Journal of Vertebrate Paleontology | pages = 403–415 | date = 2010 | doi = 10.1080/02724631003617944 | s2cid = 85143039 }}</ref> but unlike ''Ophthalmosaurus'', the femoral dorsal and ventral processes were rather reduced. At the bottom end, there are two facets, one for the [[Biology:Tibia|tibia]] and one for the [[Biology:Fibula|fibula]]; this is typical of ophthalmosaurids, but ''Platypterygius hercynicus'',<ref name="hercynicus"/> ''Platypterygius americanus'',<ref name="americanus"/> ''Platypterygius australis'',<ref name="australis"/> and ''Paraophthalmosaurus'' all have three. Both facets in ''Keilhauia'' were roughly the same length, and the fibular facet was directed slightly to the back, forming an angle of 120° with the tibial facet.<ref name="keilhauia"/>

==Discovery and naming==
[[File:Keilhauia-1.png|thumb|Map showing location of ''Keilhauia'''s discovery on the island of Spitsbergen]]
Excavations led by the Spitsbergen Mesozoic Research Group from 2004 to 2012 recovered 29 [[Biology:Ichthyosaur|ichthyosaur]] specimens from outcrops of the Slottsmøya Member lagerstätte, which belongs to the greater [[Earth:Agardhfjellet Formation|Agardhfjellet Formation]], on the island of Spitsbergen, [[Place:Svalbard|Svalbard]], {{wipe|Norway}}. These outcrops likely date to the Tithonian-[[Earth:Berriasian|Berriasian]] based on [[Biology:Ammonite|ammonite]] [[Earth:Biostratigraphy|biostratigraphy]]. From these, the new genera and species ''[[Biology:Cryopterygius|Cryopterygius kristiansenae]]'', ''[[Biology:Palvennia|Palvennia hoybergeti]]'',<ref name="cryo"/> and ''[[Biology:Janusaurus|Janusaurus lundi]]''<ref name="janu"/> have previously been described.<ref name="keilhauia"/>

Four ichthyosaur specimens were prepared at the University of Oslo and subsequently described in 2016; they include PMO 222.655, the holotype of ''Keilhauia'', discovered from the Berriasian portions of the Slottsmøya Member in 2010. This articulated partial skeleton, which was preserved lying on its left side, consists of part of the snout, the dorsal and anterior caudal vertebrae, the right forelimb and [[Biology:Shoulder girdle|pectoral girdle]], the majority of the [[Biology:Pelvis|pubic girdle]], and both of the [[Biology:Femur|femora]]. Since all of the cervical vertebrae and parts of the dorsal vertebrae are missing, it is difficult to assign precise numberings to the existing dorsal vertebrae. The other three described specimens were PMO 222.670 and PMO 227.932, both discovered in 2011; and PMO 222.662, discovered in 2007.<ref name="keilhauia"/>

The genus name ''Keilhauia'' honours the Norwegian geologist Baltazar Mathias Keilhau, who conducted an expedition to Spitsbergen in 1827. Meanwhile, the species name ''nui'' is derived from the acronym of the environmental organization Natur og Ungdom, the fiftieth anniversary of which occurred in 2017.<ref name="keilhauia"/>

==Classification==
In 2017, ''Keilhauia'' was referred to the clade [[Biology:Ophthalmosauridae|Ophthalmosauridae]]. This was on account of it bearing an articular facet on the [[Biology:Humerus|humerus]] for the attachment of an anterior accessory element (a specialized limb bone that ichthyosaurs gained), as well as its forelimb elements lacking notches on their front edges.<ref name="acampto"/> A [[Biology:Phylogenetics|phylogenetic analysis]] likewise recovered ''Keilhauia'' as an ophthalmosaurid. Its specific relationships within the ophthalmosaurids, however, were difficult to elucidate due to the lack of cranial material. Thus, the authors considered the [[Biology:Basal (phylogenetics)|basal]] placement of ''Keilhauia'' in the below phylogenetic tree somewhat suspect (a similar problem occurs for ''[[Biology:Undorosaurus|Undorosaurus]]'', which was also placed basally despite having a forelimb similar to ''[[Biology:Cryopterygius|Cryopterygius]]'').<ref name="keilhauia"/>

{{clade| style=font-size:85%; line-height:85%
|label1=[[Biology:Ophthalmosauridae|Ophthalmosauridae]]
|1={{clade
      |1='''''Keilhauia hui'''''
      |2={{clade
         |1=''[[Biology:Arthropterygius|Arthropterygius chrisorum]]''
         |2={{clade
            |1=''[[Biology:Undorosaurus|Undorosaurus gorodischensis]]''
            |2={{clade
               |label1=[[Biology:Platypterygiinae|Platypterygiinae]]
               |label2=[[Biology:Ophthalmosaurinae|Ophthalmosaurinae]]
               |1={{clade
                  |1={{clade
                     |1=''[[Biology:Platypterygius|Platypterygius hercynicus]]''
                     |2={{clade
                        |1=''[[Biology:Platypterygius|Platypterygius australis]]''
                        |2=''[[Biology:Caypullisaurus|Caypullisaurus bonapartei]]''}}}}
                  |2={{clade
                     |1=''[[Biology:Brachypterygius|Brachypterygius extremus]]''
                     |2={{clade
                        |1=''[[Biology:Maiaspondylus|Maiaspondylus lindoei]]''
                        |2={{clade
                           |1=''[[Biology:Sveltonectes|Sveltonectes insolitus]]''
                           |2=''[[Biology:Aegirosaurus|Aegirosaurus leptospondylus]]''}}}}}}}}
               |2={{clade
                  |1={{clade
                     |1=''[[Biology:Acamptonectes|Acamptonectes densus]]''
                     |2={{clade
                        |1=''[[Biology:Leninia|Leninia stellans]]''
                        |2=''[[Biology:Ophthalmosaurus|Ophthalmosaurus icenicus]]''}}}}
                  |2={{clade
                       |1=''[[Biology:Mollesaurus|Mollesaurus periallus]]''
                       |2={{clade
                           |1=''[[Biology:Athabascasaurus|Athabascasaurus bitumineus]]''
                           |2=''[[Biology:Cryopterygius|Cryopterygius kristiansenae]]''
                           |3=''[[Biology:Palvennia|Palvennia hoybergeti]]''}}}}}}}}}}}}}}}}

''Keilhauia'' can be distinguished from its contemporaries by various characters. Unlike ''Cryopterygius'', the [[Biology:Ulna|ulna]]r facet of the [[Biology:Humerus|humerus]] is angled backwards, and there is no opening in the fused ischiopubis.<ref name="cryo"/> ''Janusaurus'' has comparatively more robust humeri and more strongly-developed dorsal and ventral processes on the [[Biology:Femur|femur]].<ref name="janu"/> Additionally, the [[Biology:Autapomorphy|autapomorphies]], or traits unique to this genus, provide further evidence for its distinctness.<ref name="keilhauia"/>

==Paleobiology==
A statistical analysis of [[Biology:Ichthyosaur|ichthyosaur]]ian proportions conducted in the description of ''Keilhauia'' showed that, throughout their evolutionary history, ichthyosaurs did not significantly reduce the relative size of their ilium, but their [[Biology:Femur|femora]] did become proportionally longer relative to their [[Biology:Humerus|humeri]]. ''Keilhauia'' has a small [[Biology:Pelvis|pelvic girdle]] as well as a small humerus and femur, but it falls within the normal range of variation between [[Biology:Parvipelvia|parvipelvia]]n ichthyosaurs.<ref name="keilhauia"/>

==Paleoecology== 
The Slottsmøya Member of the [[Earth:Agardhfjellet Formation|Agardhfjellet Formation]], from which ''Keilhauia'' is known, consists of a mix of [[Chemistry:Shale|shale]]s and [[Earth:Siltstone|siltstone]]s. It was deposited in a shallow marine environment, near a patch of deeper [[Earth:Marine sediment|marine sediment]].<ref name="arcticlager">{{cite journal | last1 = Hurum | first1 = J.H. | last2 = Nakrem | first2 = H.A. | last3 = Hammer | first3 = O. | last4 = Knutsen | first4 = E.M. | last5 = Druckenmiller | first5 = P.S. | last6 = Hryniewicz | first6 = K. | last7 = Novis | first7 = L.K. | title = An Arctic Lagerstätte – the Slottsmøya Member of the Agardhfjellet Formation (Upper Jurassic-Lower Cretaceous) of Spitsbergen | journal = Norwegian Journal of Geology | volume = 92 | pages = 55–64 | date = 2012 | issn = 0029-196X | url = http://www.geologi.no/images/NJG_articles/NJG_2_3_2012_1_Hurum_Pr.pdf}}</ref> The seafloor, which was located about {{convert|150|m}} below the surface, seems to have been relatively dysoxic, or oxygen-poor, although it was periodically oxygenated by [[Earth:Clastic rock|clastic sediments]].<ref name="lagerstatte">{{cite book | last1 = Delsett | first1 = L.L. | last2 = Novis | first2 = L.K. | last3 = Roberts | first3 = A.J. | last4 = Koevoets | first4 = M.J. | last5 = Hammer | first5 = O. | last6 = Druckenmiller | first6 = P.S. | last7 = Hurum | first7 = J.H. | chapter = The Slottsmøya marine reptile ''Lagerstätte'': depositional environments, taphonomy and diagenesis | series = Geological Society of London, Special Publications | volume = 434 | pages = 165–188 | title = Mesozoic Biotas of Scandinavia and its Arctic Territories | journal = Geological Society, London, Special Publications | editor-last1 = Kear | editor-first1 = B.P. | editor-last2 = Lindgren | editor-first2 = J. | editor-last3 = Hurum | editor-first3 = J.H. | editor-last4 = Milan | editor-first4 = J. | editor-last5 = Vajda | editor-first5 = V. | doi = 10.1144/SP434.2 | date = 2015 | s2cid = 130478320 | url = http://sp.lyellcollection.org/online-first/434 | chapter-url = http://sp.lyellcollection.org/content/early/2015/12/17/SP434.2.full.pdf }}{{Dead link|date=February 2020 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> Despite this, near the top of the member, various diverse assemblages of invertebrates associated with [[Earth:Cold seep|cold seep]]s have been discovered; these include [[Biology:Ammonite|ammonite]]s, [[Biology:Lingulata|lingulate brachiopods]], [[Biology:Bivalvia|bivalves]], [[Biology:Rhynchonellata|rhynchonellate brachiopods]], [[Biology:Serpulidae|tubeworms]], [[Biology:Belemnoidea|belemnoids]], [[Biology:Tusk shell|tusk shell]]s, [[Biology:Sponge|sponge]]s, [[Biology:Crinoid|crinoid]]s, [[Biology:Sea urchin|sea urchin]]s, [[Biology:Brittle star|brittle star]]s, [[Biology:Starfish|starfish]], [[Biology:Crustacean|crustacean]]s, and [[Biology:Gastropoda|gastropods]], numbering 54 taxa in total.<ref name="invert">{{cite journal | last1 = Hryniewicz | first1 = K. | last2 = Nakrem | first2 = H.A. | last3 = Hammer | first3 = O. | last4 = Little | first4 = C.T.S. | last5 = Kaim | first5 = A. | last6 = S. | first6 = M.R. | last7 = Hurum | first7 = J.H. | title = The palaeoecology of the latest Jurassic–earliest Cretaceous hydrocarbon seep carbonates from Spitsbergen, Svalbard | journal = Lethaia | volume = 48 | issue = 3 | pages = 353–374 | date = 2015 | doi = 10.1111/let.12112| url = http://eprints.whiterose.ac.uk/85127/1/Hryniewicz_et_al_J-K_seep_palaeoecology_Svalbard_Preformat.docx }}</ref> Outside of the cold seeps, many of these invertebrates were also present in abundance.<ref name="lagerstatte"/>

Besides ''Keilhauia'', 16 other [[Biology:Ichthyosaur|ichthyosaur]] specimens are also known from the Slottsmøya Member. These include the three that were described alongside it, as well as the type and only specimens of ''[[Biology:Cryopterygius|Cryopterygius kristiansenae]]'', ''[[Biology:Palvennia|Palvennia hoybergeti]]'',<ref name="cryo"/> and ''[[Biology:Janusaurus|Janusaurus lundi]]''.<ref name="janu"/> Additionally, 21 [[Biology:Plesiosaur|plesiosaur]]ian specimens are also known from the site, including two belonging to the large ''[[Biology:Pliosaurus|Pliosaurus funkei]]'', three to ''[[Biology:Colymbosaurus|Colymbosaurus svalbardensis]]'', and one each to ''[[Biology:Spitrasaurus|Spitrasaurus wensaasi]]'' and ''[[Biology:Spitrasaurus|S. larseni]]''. Many of these specimens are preserved in three dimensions and partially in articulation; this is correlated with high abundance of organic elements in the sediments they were buried in, as well as a lack of invertebrates locally.<ref name="lagerstatte"/>

==References==
{{Reflist|2}}

{{Taxonbar|from=Q28744991}}

[[Category:Berriasian life]]
[[Category:Agardhfjellet Formation]]

{{Sourceattribution|Keilhauia}}