Equatorial pliosaurid from Venezuela marks the youngest South American occurrence of the clade

Abstract

Pliosaurids were the dominant macropredators in aquatic environments at least since the Middle Jurassic until their extinction in the early Late Cretaceous. Until very recently, the Cretaceous record of Pliosauridae has been poor and difficult to interpret from the taxonomic and phylogenetic perspective. Despite that the knowledge of Cretaceous pliosaurids improved in recent years, numerous aspects of their evolutionary history still remain only poorly known. Here, we report the first pliosaurid material from Venezuela. The taxon is most likely earliest Cenomanian in age, thus representing the youngest occurrence of Pliosauridae from South America. The Venezuelan taxon is based on a well-preserved tooth crown whose morphology and outer enamel structural elements appear to resemble especially those observable in the giant pliosaurid Sachicasaurus vitae from the Lower Cretaceous of Colombia. The new discovery extends the pliosaurid record on the continent by more than 10 million years and likely marks the southernmost Upper Cretaceous occurrence of Pliosauridae, worldwide. We also briefly discuss the affinities of the enigmatic Venezuelan elasmosaurid Alzadasaurus tropicus and highlight similarities to elasmosaurids from the Western Interior Seaway.

Historical significance and taxonomic status ofIschyrodon meriani(Pliosauridae) from the Middle Jurassic of Switzerland

“…The basal cross-section is sub-circular, similar to the condition observed in Acostasaurus pavachoquensis ( Gómez-Pérez & Noè, 2017 ), Brachauchenius lucasi ( Liggett et al, 2005 ; Albright, Gillette & Titus, 2007 ), Monquirasaurus boyacensis ( Hampe, 1992 ; Noè & Gómez-Pérez, 2021 ), Kronosaurus queenslandicus ( McHenry, 2009 ), Liopleurodon ferox ( Noè, 2001 ), Marmornectes candrewi ( Ketchum & Benson, 2011a ), Megacephalosaurus eulerti ( Madzia, Sachs & Lindgren, 2019 ), Pachycostasaurus dawni ( Cruickshank, Martill & Noè, 1996 ; Noè, 2001 ), Peloneustes philarchus ( Ketchum & Benson, 2011b ), ‘ Pliosaurus ’ andrewsi ( Tarlo, 1960 ; Noè, 2001 ; Zverkov et al, 2018 ), ‘ Polyptychodon ’ hudsoni (D. Madzia, personal observation, 2018), Sachicasaurus vitae ( Páramo-Fonseca, Benavides-Cabra & Gutiérrez, 2018 ), Simolestes vorax ( Tarlo, 1960 ; Noè, 2001 ; Zverkov et al, 2018 ), the assemblage historically assigned to ‘ Polyptychodon interruptus ’ ( Madzia, 2016 ), and other isolated pliosaurid teeth with indeterminate taxonomic status and phylogenetic placement ( e.g. , Kear et al, 2014 ; Zverkov, 2015 ; Madzia & Machalski, 2017 ; Zverkov et al, 2018 ; Lukeneder & Zverkov, 2020 ; Solonin, Vodorezov & Kear, 2021 ; Bastiaans et al, 2021 ). It differs from Gallardosaurus itturraldei ( Gasparini, 2009 ), Luskhan itilensis ( Fischer et al, 2017 ), Makhaira rossica ( Fischer et al, 2015 ), Pliosaurus ( e.g.…”

“…Enamel surface shows clear ridglets, similar to those in L. ferox , some species of Pliosaurus , some isolated pliosaurid tooth crowns from the Jurassic/Cretaceous boundary interval of Russia ( Zverkov et al, 2018 ), some tooth crowns from the assemblage historically assigned to ‘ Polyptychodon ’ ( Madzia, 2016 ; Zverkov et al, 2018 ), and Sa. vitae and the ‘Venezuelan pliosaurid’ ( Bastiaans et al, 2021 ).…”

“…In order to explore the morphospace occupation of NMB L.D.37 among thalassophonean pliosaurids, and assess previously mentioned similarities of the type of Ischyrodon to Pliosaurus ( Lydekker, 1889 ) and Liopleurodon ( Tarlo, 1960 ), we performed cluster and principal coordinates analyses. We used the dataset of Bastiaans et al (2021) , which is a recent version of the one first published by Zverkov et al (2018) , and added NMB L.D.37. No further modifications have been provided.…”

“…We used the same protocol as Zverkov et al (2018) and Bastiaans et al (2021) . The analyses were carried out in the R statistical environment (RStudio Version 1.2.5033 R Studio Team, 2019 ).…”

“…The description of the characters of the outer enamel surface is provided using the nomenclature advocated by Zverkov et al (2018) and followed in Páramo-Fonseca, Benavides-Cabra & Gutiérrez (2018) , Madzia, Sachs & Lindgren (2019) , Lukeneder & Zverkov (2020) , Bastiaans et al (2021) , Madzia, Szczygielski & Wolniewicz (2021) : apicobasal ridges, longitudinally running enamel ridges of variable apicobasal extent that can be developed around the entire crown circumference and are usually semicircular or triangular in cross-section; ridglets, subtle apicobasally-oriented enamel structures often developed between adjacent apicobasal ridges or on an unridged enamel surface; the appearance of ridglets varies from being very smooth to producing a distinct vermicular pattern (see Madzia, 2016 : Fig. 7).…”