Oneirosaurus, new mosasaur from Cretaceous of Colombia + basal elasmosaurid from Cretaceous of England (free pdfs)
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Ben Creisler
Oct 30, 2025, 10:01:18 PM (7 days ago) Oct 30
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Ben Creisler
Jose P. O’Gorman and Roger B.J. Benson (2025)
A basal elasmosaurid plesiosaur from the upper Albian– lower Cenomanian? Cambridge Greensand
Acta Palaeontologica Polonica 70(4): 613-628
doi:10.4202/app.01219.2024
https://www.app.pan.pl/article/item/app012192024.html
Free pdf:
https://www.app.pan.pl/archive/published/app70/app020192024.pdf
An historical indeterminate elasmosaurid specimen CAMSM X50356 (CAMSM = Sedgwick Museum) collected during the 19th century is described. The specimen comes from the Cenomanian Cambridge Greensand although the possibility of an Albian–lower Cenomanian age is discussed. CAMSM X50356 is recovered within the Elasmosauridae. Our phylogenetic analysis indicates that elongated cervical centra with absence of the lateral ridge are the basal condition of elasmosaurids. The lateral ridge is present in almost all other elasmosaurids with the exception of some taxa that have secondarily shortened the cervical centra such as the aristonectines and Nakonanectes bradti. The lack of correlation between cervical elongation and the lateral ridge is thus recorded here for the first time as CAMSM X50356 is the only elasmosaurid with cervical centra longer than high but without the lateral ridge.
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New papers:
Oneirosaurus caballeroi gen. et sp. nov.
María Eurídice Páramo Fonseca, José Alejandro Narváez Rincón, Cristian David Benavides-Cabra
Oneirosaurus caballeroi gen. et sp. nov., a new mosasaur from Colombia
Oneirosaurus caballeroi gen. et sp. nov., un nuevo mosasaurio de Colombia
Earth Sciences Research Journal 29(3): 231-247
doi: https://doi.org/10.15446/esrj.v29n3.117157
https://revistas.unal.edu.co/index.php/esrj/article/view/117157/95968
A new mosasaur specimen found in the Coniacian beds of Lebrija, Santander, Central Colombia, is here described. The new specimen represents a new genus and species of plioplatecarpine mosasaurid that we name Oneirosaurus caballeroi gen. et sp. nov. Oneirosaurus is a plioplatecarpine characterized by one character unknown in any other plioplatecarpine: the presence of two external foramina for the exit of nerves X, XI, and XII. It is also distinguished by a combination of characters that includes among others: prefrontal and postorbitofrontal separated at the roof of the orbit; broad frontal, with short triangular surface anterior to the orbits; triangular and broad anterodorsal surface of the parietal contacting the postorbital for a short distance; infrastapedial process of the quadrate robust without being fused to the suprastapedial process; small otosphenoidal crest of prootic not covering the exit of nerve VII; basioccipital canal opening into the floor of the braincase through two large foramina separated by a medial septum; lingual alveolar parapet of dentary lower than labial; marginal teeth crown with subcircular cross-section at base and with two carinae arranged at 180º; and presence of a notch in anterior border of the atlas neural arch. The morphological comparisons and the cladistic analysis show the new taxon as an intermedium plioplatecarpine with phylogenetic proximity to the Colombian species Yaguarasaurus columbianus from the lower Turonian and to the species Ectenosaurus clidastoides from the Santonian-Campanian of the USA. Our phylogenetic results shows tethysaurines and halisaurines as plesio-pelvic and plesiopedal groups separated from the hydropelvic and hydropedal derived groups Tylosaurinae, Plioplate-carpinae, and Mosasaurinae.
Free pdf:
Oneirosaurus caballeroi gen. et sp. nov.
María Eurídice Páramo Fonseca, José Alejandro Narváez Rincón, Cristian David Benavides-Cabra
Oneirosaurus caballeroi gen. et sp. nov., a new mosasaur from Colombia
Oneirosaurus caballeroi gen. et sp. nov., un nuevo mosasaurio de Colombia
Earth Sciences Research Journal 29(3): 231-247
doi: https://doi.org/10.15446/esrj.v29n3.117157
https://revistas.unal.edu.co/index.php/esrj/article/view/117157/95968
A new mosasaur specimen found in the Coniacian beds of Lebrija, Santander, Central Colombia, is here described. The new specimen represents a new genus and species of plioplatecarpine mosasaurid that we name Oneirosaurus caballeroi gen. et sp. nov. Oneirosaurus is a plioplatecarpine characterized by one character unknown in any other plioplatecarpine: the presence of two external foramina for the exit of nerves X, XI, and XII. It is also distinguished by a combination of characters that includes among others: prefrontal and postorbitofrontal separated at the roof of the orbit; broad frontal, with short triangular surface anterior to the orbits; triangular and broad anterodorsal surface of the parietal contacting the postorbital for a short distance; infrastapedial process of the quadrate robust without being fused to the suprastapedial process; small otosphenoidal crest of prootic not covering the exit of nerve VII; basioccipital canal opening into the floor of the braincase through two large foramina separated by a medial septum; lingual alveolar parapet of dentary lower than labial; marginal teeth crown with subcircular cross-section at base and with two carinae arranged at 180º; and presence of a notch in anterior border of the atlas neural arch. The morphological comparisons and the cladistic analysis show the new taxon as an intermedium plioplatecarpine with phylogenetic proximity to the Colombian species Yaguarasaurus columbianus from the lower Turonian and to the species Ectenosaurus clidastoides from the Santonian-Campanian of the USA. Our phylogenetic results shows tethysaurines and halisaurines as plesio-pelvic and plesiopedal groups separated from the hydropelvic and hydropedal derived groups Tylosaurinae, Plioplate-carpinae, and Mosasaurinae.
====
Free pdf:
Jose P. O’Gorman and Roger B.J. Benson (2025)
A basal elasmosaurid plesiosaur from the upper Albian– lower Cenomanian? Cambridge Greensand
Acta Palaeontologica Polonica 70(4): 613-628
doi:10.4202/app.01219.2024
https://www.app.pan.pl/article/item/app012192024.html
Free pdf:
https://www.app.pan.pl/archive/published/app70/app020192024.pdf
An historical indeterminate elasmosaurid specimen CAMSM X50356 (CAMSM = Sedgwick Museum) collected during the 19th century is described. The specimen comes from the Cenomanian Cambridge Greensand although the possibility of an Albian–lower Cenomanian age is discussed. CAMSM X50356 is recovered within the Elasmosauridae. Our phylogenetic analysis indicates that elongated cervical centra with absence of the lateral ridge are the basal condition of elasmosaurids. The lateral ridge is present in almost all other elasmosaurids with the exception of some taxa that have secondarily shortened the cervical centra such as the aristonectines and Nakonanectes bradti. The lack of correlation between cervical elongation and the lateral ridge is thus recorded here for the first time as CAMSM X50356 is the only elasmosaurid with cervical centra longer than high but without the lateral ridge.
===
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