Euhelopodidae is a

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

sauropod Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their b ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...

s of disputed membership and affinities, which contains '' Euhelopus'' and its close relatives. Most proposed euhelopodids are from East Asia. Euhelopodidae was first recognized by Carl Wiman in 1929, under the name Helopodidae, as ''Euhelopus'' was originally named ''Helopus''. However, the name had already been proposed for a bird, so in 1956 Alfred Sherwood Romer proposed the name ''Euhelopus'' and Euhelopodinae as replacements; Romer classified Euhelopodinae as a subfamily of Brachiosauridae, in which he also included Camarasaurinae and Cetiosaurinae, rather than as a family of its own. In addition to ''Euhelopus'' itself, Romer included ''Chiayusaurus'', ''Omeisaurus'', and ''Tienshanosaurus'' in Euhelopodinae. The taxonomic content of Euhelopodidae is uncertain, as a result of the unstable position of ''Euhelopus'' itself. Some studies have concluded that ''Euhelopus'' is a non-neosauropod closely related to ''Mamenchisaurus'', which would make Euhelopodidae equivalent to

Mamenchisauridae Mamenchisauridae is a family of sauropod dinosaurs belonging to the Eusauropoda known from the Jurassic and Early Cretaceous of Asia and Africa. Mamenchisaurids are characterized by their proportionately extremely long necks. Some members of the ...

. Other studies have interpreted ''Euhelopus'' as neosauropod united with titanosaurs in Somphospondyli. A joint study by Jeffrey Wilson and Paul Upchurch, who had previously taken opposite sides in the debate, concluded that ''Euhelopus'' was closely related to titanosaurs. However, the lack of research on ''Mamenchisaurus''-like taxa has hindered proper testing of this hypothesis, and there are several similarities between ''Euhelopus'' and ''Mamenchisaurus''-like taxa that have not been taken into account in most analyses. Michael D'Emic (2012) formulated the first phylogenetic definition of Euhelopodidae, defining it as the clade containing " neosauropods more closely related to ''Euhelopus zdanskyi'' than to '' Neuquensaurus australis''". Below is a cladogram presenting the cladistic hypothesis of Euhelopodidae proposed by D'Emic. In their 2021

description Description is any type of communication that aims to make vivid a place, object, person, group, or other physical entity. It is one of four rhetorical modes (also known as ''modes of discourse''), along with exposition, argumentation, and narr ...

of '' Silutitan'', Wang ''et al.'' recovered it as a derived euhelopodid, as the sister taxon to '' Euhelopus''. The results of their

phylogenetic analysis In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical data ...

, which included several other euhelopodid taxa, are shown in the

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

below:

References

{{Taxonbar, from=Q2633155 Macronaria Dinosaur families