English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Two extremely-long necked elasmosaurids, AMNH 1495, holotype of  Hydralmosaurus serpentinus , and AMNH 5835, previously referred to  H. serpentinus , are here reviewed in detail. Unique features of the cervical vertebrae, which are only present on elasmosaurids from the Western Interior Seaway, are recognized based on these specimens and by comparison with penecontemporaneous taxa with biogeographic affinities. Phylogenetic analysis, bivariate graphic analysis of cervical vertebrae proportions, comparisons of different cervical vertebral types, paleobiogeographic distribution and study of the elasmosaurid axial evolution throughout the Cretaceous are here integrated. As a result, at least two separate lineages within the Elasmosauridae are identified by independently acquired extremely-long necks (over 60 cervical vertebrae). First, a still scarcely known lineage is so far represented by the lower Cenomanian  Thalassomedon haningtoni , the Turonian  Libonectes morgani  and close relatives. A second lineage is here defined as a new clade, the Styxosaurinae, which groups the Campanian genera  Terminonatator ,  Styxosaurus  (=‘ Hydralmosaurus ’),  Albertonectes  and  Elasmosaurus , the two latter forming a derived branch that includes the most extreme amniote necks known to date (more than 70 cervical vertebrae). Phylogenetic analysis supports AMNH 1495 and AMNH 5835 as being closely related to  Styxosaurus snowii . Therefore, the species  Styxosaurus browni  is re-validated, while AMNH 1495 is here referred to  Styxosaurus  sp. This research also recognizes the ‘Cimoliasauridae’ ( nomen dubium ) as a paraphyletic group but informative of a plesiomorphic cervical vertebral morphology of elasmosaurids which was persistent throughout the whole Cretaceous and from whom aristonectines, styxosaurines and  Thalassomedon  and close relatives are derived. The genus  Hydralmosaurus  is recommended for being abandoned.

Taxonomic reassessment ofHydralmosaurusasStyxosaurus: new insights on the elasmosaurid neck evolution throughout the Cretaceous