{{Short description|Extinct clade of dinosaurs}} {{Automatic taxobox | name = Eusauropods | fossil_range = Early Jurassic—Late Cretaceous, {{fossilrange|184.5|66}} | image = Jobaria head.jpg | image_caption = Skull of ''Jobaria'' | taxon = Eusauropoda | authority = Upchurch, 1995 | subdivision_ranks = Subgroups | subdivision = * {{extinct}}Cetiosauridae * {{extinct}}Mamenchisauridae * {{extinct}}Turiasauria * {{extinct}}Neosauropoda {{Collapse top|title=Uncertain affinity and basal genera|left=yes|padding=0|border=0|border2=0|bg=clear|bg2=clear}} * {{extinct}}''Algoasaurus''? * {{extinct}}''Asiatosaurus''? * {{extinct}}''Atlasaurus''? * {{extinct}}''Bagualia'' * {{extinct}}''Barapasaurus''? * {{extinct}}''Bellusaurus'' * {{extinct}}''Cetiosauriscus'' * {{extinct}}''Chebsaurus'' * {{extinct}}''Chondrosteosaurus''? * {{extinct}}''Ferganasaurus''? * {{extinct}}''Huashanosaurus'' * {{extinct}}''Jinchuanloong'' * {{extinct}}''Jobaria'' * {{extinct}}''Klamelisaurus''? * {{extinct}}''Kotasaurus''? * {{extinct}}''Lapparentosaurus'' * {{extinct}}''Liubangosaurus''? * {{extinct}}''Nebulasaurus'' * {{extinct}}''Ohmdenosaurus''? * {{extinct}}''Qinlingosaurus''? * {{extinct}}''Rhoetosaurus''? * {{extinct}}'''Amygdalodontidae''' ** {{extinct}}''Amygdalodon'' ** {{extinct}}''Isanosaurus'' ** {{extinct}}''Gongxianosaurus'' ** {{extinct}}''Tuebingosaurus''? ** {{extinct}}''Tienshanosaurus''? * {{extinct}}''Shunosaurus'' * {{extinct}}''Spinophorosaurus''? * {{extinct}}''Tharosaurus'' * {{extinct}}''Volkheimeria''? * {{extinct}}''Yantaloong'' {{collapse bottom}} }}

'''Eusauropoda''' (meaning "true lizard foot") is a derived clade of sauropod dinosaurs. Eusauropods represent the node-based group that includes all descendant sauropods starting with the basal eusauropods of ''Shunosaurus'', and possibly ''Barapasaurus'', and ''Amygdalodon'', but excluding ''Vulcanodon'' and ''Rhoetosaurus''.<ref name="WCR05"/> The Eusauropoda was coined in 1995 by Paul Upchurch to create a monophyletic new taxonomic group that would include all sauropods, except for the vulcanodontids.<ref name="U95">{{cite journal | last1 = Upchurch | first1 = P | year = 1995 | title = The evolutionary history of sauropod dinosaurs | journal = Philosophical Transactions of the Royal Society of London B | volume = 349 | issue = 1330| pages = 365–390 | doi=10.1098/rstb.1995.0125| bibcode = 1995RSPTB.349..365U | url = http://doc.rero.ch/record/16651/files/PAL_E2783.pdf }}</ref>

Eusauropods are herbivorous, quadrupedal, and have long necks. They have been found in South America, Europe, North America, Asia, Australia, and Africa.<ref name="Xing12"/> The temporal range of Eusauropoda ranges from the early Jurassic to the Latest Cretaceous periods.<ref name="WCR05"/> The most primitive forms of eusauropods are not well-known because the ''Vulcanodon'' cranial material is not available, and the distribution of some of these shared derived traits that distinguish Eusauropoda is still completely unclear.<ref name="WCR05"/><ref name="WS98"/> However the discovery of ''Tazoudasaurus'', which does preserve cranial material, did help refine some of the characteristics.<ref>{{Cite journal |last1=Allain |first1=Ronan |last2=Aquesbi |first2=Najat |last3=Dejax |first3=Jean |last4=Meyer |first4=Christian |last5=Monbaron |first5=Michel |last6=Montenat |first6=Christian |last7=Richir |first7=Philippe |last8=Rochdy |first8=Mohammed |last9=Russell |first9=Dale |last10=Taquet |first10=Philippe |date=May 2004 |title=A basal sauropod dinosaur from the Early Jurassic of Morocco |url=http://cr-palevol.fr/3/25 |journal=Comptes Rendus Palevol |language=en |volume=3 |issue=3 |pages=199–208 |doi=10.1016/j.crpv.2004.03.001|bibcode=2004CRPal...3..199A |url-access=subscription }}</ref>

==Description== Eusauropods are long-necked, strictly herbivorous, obligate quadrupeds.<ref name="TWPJ">{{cite journal|last1=Taylor|first1=M.P.|last2=Wedel|first2=M.J.|title=Why sauropods had long necks; and why giraffes have short necks|journal=PeerJ|year=2013|volume=1|pages=e36|doi=10.7717/peerj.36|pmid=23638372|pmc=3628838 |doi-access=free }}</ref> They have a highly specialized set of skeletal adaptions due to their large size, and are graviportal.<ref name="YBNCB09">{{cite journal|last1=Yates|first1=A.M.|last2=Bonnan|first2=M.F.|last3=Neveling|first3=J.|last4=Chinsamy|first4=A.|last5=Blackbeard|first5=M.G.|title=A new transitional sauropodomorph dinosaur from the Early Jurassic of South Africa and the evolution of sauropod feeding and quadrupedalism|journal=Proceedings of the Royal Society B: Biological Sciences|year=2009|volume=277|issue=1682|pages=787–794|doi=10.1098/rspb.2009.1440|pmid=19906674|pmc=2842739}}</ref>

===Teeth and mouth=== Yates and Upchurch described eusauropod evolution as moving towards a "bulk-browsing mode of feeding". They describe the development of lateral plates on the alveolar margins of tooth-bearing bones. These plates can be used to strip foliage, the eusauropod's "U-shaped" jaws create a wide bite, and their loss of "fleshy cheeks" increased the gape.<ref name="YBNCB09"/> The crowns of eusauropod teeth also have "wrinkled enamel textures", but it is unclear what this meant for their feeding habits.<ref name="WCR05">{{cite book|last1=Wilson|first1=J.A.|last2=Curry-Rogers|first2=K.A.|year=2005|title=The Sauropods: evolution and paleobiology|publisher=University of California Press|location=Berkeley|isbn=978-0-520-24623-2}}</ref>

===Head and neck=== {{main|Sauropod neck posture}} thumb|left|Reconstruction of selected sauropod necks, showing posture and length The skull length of the basal eusauropod, ''Patagosaurus'', is about {{convert|60|cm}}.<ref name="Novas09">{{cite book|last1=Novas|first1=F.E.|title=The age of dinosaurs in South America|year=2009|publisher=Indiana University Press|location=Bloomington|isbn=978-0-253-35289-7}}</ref> One of the most basal eusauropods, ''Shunosaurus'', has two characteristic features of the eusauropod elongated neck: the incorporation of the equivalent of the first dorsal vertebra into the cervical region of the spine, and the addition of two cervical vertebra in the middle of the cervical vertebrae.<ref name="WS98">{{cite journal|last1=Wilson|first1=J.A.|last2=Sereno|first2=P.C.|title=Early Evolution and Higher-Level Phylogeny of Sauropod Dinosaurs|journal=Journal of Vertebrate Paleontology|year=1998|volume=18|issue=2|pages=1–79|doi=10.1080/02724634.1998.10011115|bibcode=1998JVPal..18S...1W |url=http://doc.rero.ch/record/13900/files/PAL_E840.pdf }}</ref>

Other synapomorphies of Eusauropoda includes a retracted position of the external nares. Unlike prosauropods and theropods, which have a snout with smooth, unprotruding alveolar and subnarial regions, eusauropods have snouts with "stepped anterior margins". Further distinguishing features of eusauropods include the absence of the contact between the squamosal and the quadratojugal, the absence of the anterior (front) process of the prefrontal, and a distally elongated anterior ramus of the quadratojugal. Separating the anteroventral process of the nasal from the posterolateral process of the premaxilla, eusauropods also have a long maxilla that forms the posteroventral margin of the external naris.<ref name="WCR05"/>

===Feet and limbs=== Eusauruopods are hypothesized to have had a semi-digitigrade foot posture, demonstrated by footprint evidence.<ref name="WS98"/> This differs from theropods and prosauropods, which had a digitigrade pes (foot) where the heel and metatarsals were lifted off the ground. Eusauropods show asymmetry in their metatarsal shaft diameters where metatarsal I was broader than the others, suggesting that their weight was mostly assumed by their inner feet.<ref name="WCR05"/> According to Steven Salisbury and Jay Nair, basal eusauropods retained four pedal unguals (the toe bones which supported claws) but reduced their phalangeal count in their fourth digit to three.<ref name="NS12">{{cite journal|last1=Nair|first1=J.P.|last2=Salisbury|first2=S.W.|title=New anatomical information on ''Rhoetosaurus'' Longman, 1926, a gravisaurian sauropodomorph dinosaur from the Middle Jurassic of Queensland, Australia|journal=Journal of Vertebrate Paleontology|year=2012|volume=32|issue=2|pages=369–394|doi=10.1080/02724634.2012.622324|s2cid=85317450 }}</ref> The metatarsus in eusauropods is less than a quarter of their tibial length, unlike sauropod outgroups that have long hindlimbs and metatarsus that are almost half of their tibial length.<ref name="WS98"/>

==Distribution== Eusauropods are found on all major continents, with diplocodoids being widespread in the Northern Hemisphere, and titanosaurs being found in Southern Hemisphere. However, basal eusauropods that do not fall into either group are fairly well represented.<ref name="Upchurch04"/>

Early eusauropods such as ''Volkeimeria'' and ''Amygdalodon'', and more derived eusauropods such as ''Patagosaurus'' have been found in South America.<ref name="Novas09"/> ''Volkeimeria'' is classified as a basal eusauropod, though in 2004 Paul Upchurch was suspicious of its placement, because of its "opisthoceolous cervical centra, the absence of a femoral anterior trochanter, and laterally projecting cnemial crest of the tibia", and instead thought it may be a generic sauropod.<ref name="Upchurch04">{{cite book|last=Upchurch|first=P.|year=2004|chapter=Sauropoda|editor-last=Weishampel|editor-first=D.B.|editor2-last=Osmolska|editor2-first=H.|editor3-last=Dodson|editor3-first=P.|title=The Dinosauria|url=https://archive.org/details/dinosauriandedit00weis|url-access=limited|publisher=University of California Press|pages=[https://archive.org/details/dinosauriandedit00weis/page/n279 261]–299|isbn=0-520-24209-2|edition=2nd}}</ref>

African eusauropods may include ''Spinophorosaurus'', from Niger, although that taxon may instead be closer to ''Vulcanodon'' and outside Eusauropoda.<ref name="Xing12">{{cite journal|last1=Xing|first1=Lida|title=A new basal eusauropod from the Middle Jurassic of Yunnan, China, and faunal compositions and transitions of Asian sauropodomorph dinosaurs|journal=Acta Palaeontologica Polonica|date=2013|doi=10.4202/app.2012.0151|doi-access=free}}</ref><ref name="NS12"/> Also, ''Atlasaurus'' was found in Morocco, and ''Jobaria'' was found in Niger. However, both genera have been found as possible Macronarians, but ''Atlasaurus'' was found to be a turiasaurian, and ''Jobaria'' a eusauropod, by a phylogenetic analysis of Xing in 2012.<ref name="Xing12"/><ref name="Upchurch04"/>

In Europe, the clade Turiasauria has been found in France, Spain, and possibly England, with multiple genera from the same locality in Spain.<ref name="Upchurch04"/><ref name="RT09">{{cite journal|last1=Royo-Torres|first1=R.|last2=Cobos|first2=A.|last3=Luque|first3=L.|last4=Aberasturi|first4=A.|last5=Espilez|first5=E.|last6=Fierro|first6=I.|last7=Gonzalez|first7=A.|last8=Mampel|first8=L.|last9=Alcala|first9=L.|title=High European sauropod dinosaur diversity during Jurassic-Cretaceous transition in Riodeva (Teruel, Spain)|journal=Palaeontology|date=September 2009|volume=52|issue=5|pages=1009–1027|doi=10.1111/j.1475-4983.2009.00898.x|doi-access=free|bibcode=2009Palgy..52.1009R }}</ref> ''Cetiosaurus'' skeletons have also been found in England, along with the possibly eusauropod genera ''Cardiodon'' and ''Oplosaurus'', known only from teeth.<ref name="Upchurch04"/>

The family Mamenchisauridae is found widespread throughout Asia. A majority of the genera are found in China, although a possible specimen of ''Mamenchisaurus'' has been found in Thailand.<ref name="Xing12"/><ref name="Upchurch04"/> Also in China, the basal eusauropod ''Nebulasaurus taito'' was found to be a sister taxon to ''Spinophorosaurus'', and more derived than Mamenchisauridae, but less derived than ''Patagosaurus'', and the genus ''Shunosaurus'' is likely one of the most basal eusauropods.<ref name="Xing12"/><ref name="Upchurch04"/> The genus ''Barapasaurus'' has been found in India, and may represent a cetiosaurid, a basal eusauropod, or a genus outside Eusauropoda.<ref name="Xing12"/><ref name="NS12"/><ref name="Upchurch04"/>

==Paleobiology== The data around sauropod evolution, as Novas points out, is largely based on a few formations mostly in the Northern Hemisphere. However, other beds in places such as Tanzania, specifically the Canadon Asfalto and Canadon Calcereo formations, reveal a more diverse and widespread paleobiology of eusauropods in the Late Jurassic period.<ref name="Novas09"/>

==Classification== Cladogram of Eusauropoda after Gomez et al. (2024):<ref name=":1">{{Cite journal |last1=Gomez |first1=Kevin L. |last2=Carballido |first2=José L. |last3=Pol |first3=Diego |date=2024-10-14 |title=Cranial anatomy of ''Bagualia alba'' (Dinosauria, Eusauropoda) from the Early Jurassic of Patagonia and the implications for sauropod cranial evolution |journal=Journal of Systematic Palaeontology |volume=22 |issue=1 |doi=10.1080/14772019.2024.2400471 |bibcode=2024JSPal..2200471G |issn=1477-2019}}</ref>{{clade|{{clade |1=''Antetonitrus'' |2={{clade |1=''Ingentia'' |2=''Lessemsaurus'' }} |3={{clade |1=''Ledumahadi'' |2=''Pulanesaura'' |3={{clade |1={{clade |1=''Gongxianosaurus'' |2=''Amygdalodon'' |3=NHMUK PVR 36834 }} |4={{clade |1=''Archaeodontosaurus'' |2=''Volkheimeria'' |3=''Sanpasaurus'' |4=''Vulcanodon'' |5=''Tazoudasaurus'' |label6=Eusauropoda |6={{clade |1=''Shunosaurus'' |2={{clade |1=''Barapasaurus'' |2={{clade |1={{clade |1=''Patagosaurus'' |2={{clade |1=''Bagualia'' |2={{clade |1=''Nebulasaurus'' |2=''Spinophorosaurus'' }} }} }} |5={{clade |1=''Tonganosaurus'' |2={{clade |1=Mamenchisauridae |2={{clade |1=''Cetiosaurus'' |2={{clade |1=Turiasauria |2={{clade |1=''Jobaria'' |2=Neosauropoda }} }} }} }} }} }} }} }} }} }} }} }}|label1=Sauropoda}}Cladogram of Sauropoda after Holwerda et al. (2021):<ref>{{Cite journal |last1=Holwerda |first1=Femke M. |last2=Rauhut |first2=Oliver W. M. |last3=Pol |first3=Diego |date=2021-07-22 |title=Osteological revision of the holotype of the Middle Jurassic sauropod dinosaur Patagosaurus fariasi Bonaparte, 1979 (Sauropoda: Cetiosauridae) |url=https://bioone.org/journals/geodiversitas/volume-43/issue-16/geodiversitas2021v43a16/Osteological-revision-of-the-holotype-of-the-Middle-Jurassic-sauropod/10.5252/geodiversitas2021v43a16.full |journal=Geodiversitas |volume=43 |issue=16 |doi=10.5252/geodiversitas2021v43a16 |issn=1280-9659|url-access=subscription |hdl=11336/166442 |hdl-access=free }}</ref>{{clade|{{clade |1={{clade |1=''Vulcanodon'' |2=''Tazoudasaurus'' }} |2={{clade |1={{clade |1=''Barapasaurus'' |2={{clade |1=''Spinophorosaurus'' |2=''Volkheimeria'' }}}} |label2=Eusauropoda |2={{clade |1=''Shunosaurus'' |2={{clade |label1=Cetiosauridae |1={{clade |1=''Cetiosaurus oxoniensis'' |2={{clade |1=''Patagosaurus'' |2=''Cetiosaurus'' Rutland specimen }}}} |2={{clade |label1=Mamenchisauridae |1={{clade |1=''Omeisaurus'' |2=''Mamenchisaurus'' }} |2={{clade |1=Turiasauria |2={{clade |1=''Jobaria'' |2=Neosauropoda }}}}}}}}}}}}}}|label1=Sauropoda}}Cladogram after Li et al. (2025):<ref>{{Cite journal |last1=Li |first1=Ning |last2=Zhang |first2=Xiaoqin |last3=Ren |first3=Xinxin |last4=Li |first4=Daqing |last5=You |first5=Hailu |date=2025-05-23 |title=A new eusauropod (Dinosauria, Sauropodomorpha) from the Middle Jurassic of Gansu, China |url=https://www.nature.com/articles/s41598-025-03210-5 |journal=Scientific Reports |language=en |volume=15 |issue=1 |page=17936 |doi=10.1038/s41598-025-03210-5 |pmid=40410409 |bibcode=2025NatSR..1517936L |issn=2045-2322|pmc=12102329 }}</ref>{{clade|{{clade |1=''Shunosaurus'' |2={{clade |1=''Omeisaurus'' |2={{clade |1=Mamenchisauridae |2={{clade |1={{clade |1=''Jobaria'' |2=''Lapparentosaurus'' }} |3={{clade |1=''Jinchuanloong'' |2={{clade |1=Turiasauria |2=Neosauropoda }} }} }} }} }} }}|label1='''Eusauropoda'''}}

==References== {{Reflist}}

{{Sauropodomorpha|B.}} {{Portal bar|Dinosaurs}} {{Taxonbar|from=Q1936183}}

Category:Sauropoda Category:Dinosaur clades