Spatiotemporal Distributions of Non-ophidian Ophidiomorphs, With Implications for Their Origin, Radiation, and Extinction

Abstract

Non-ophidian ophidiomorphs, colloquially referred to as 'dolichosaurs,' are small-bodied aquatic lizards that lived in shallow seaways, rivers, and reef environments during the Late Cretaceous. Preservational, geographic, and taphonomic biases in this group make trends in biodiversity difficult to assess. This is exemplified by the fact that the majority of the described species are monotypic and known only from single specimens, imparting very little information on morphological or spatial variation. Here we present a revision of the spatial and temporal distributions of non-ophidian ophidiomorph lizards ('dolichosaurs') from Cretaceous sediments worldwide. The fossil record of dolichosaurs begins in the Valanginian (Early Cretaceous). The late Early Cretaceous records are sparse but suggest a wide geographic distribution spanning the Tethys and Western Pacific. This is followed by a dense Cenomanian record from Tethyan and British deposits, and rarer specimens from North America. Though there is a substantial drop in the number of specimens recorded from the Turonian-Maastrichtian, these rare occurrences represent the largest geographical distribution of dolichosaurs: spanning Europe, North America, and South America before going extinct during the end-Cretaceous mass extinction. These occurrences indicate that ophidiomorphs most likely originated in the Jurassic Tethys and continued to radiate spatially and phylogenetically until the end of the Mesozoic, showing much more temporally and environmentally diverse patterns than previously indicated.

The Making of Calibration Sausage Exemplified by Recalibrating the Transcriptomic Timetree of Jawed Vertebrates

“…Most of the rich record of Cretaceous aquatic squamates has traditionally been referred to Anguimorpha, but more likely belongs to Pan-Serpentes (e.g., Garberoglio et al, 2019 ; Palci et al, 2019 ; Sobral et al, 2020 : figure S10; Simões et al, 2020 : supplementary figures 3, 4, 6, 9; and references therein). It sets in in what seems to be the Hauterivian with Kaganaias ( Evans et al, 2006 ; Campbell Mekarski et al, 2019 ); the Hauterivian ended ∼129.4 Ma ago (ICSC, uncertainty not quantified). If neither the “parviraptorids” nor Changetisaurus nor Dorsetisaurus are accepted as toxicoferans, the minimum age of Node 129 should thus be 130 Ma.…”

“…: figureS10;Simões et al, 2020: supplementary figures 3, 4, 6, 9; and references therein). It sets in in what seems to be the Hauterivian with Kaganaias(Evans et al, 2006;Campbell Mekarski et al, 2019); the Hauterivian ended ∼129.4 Ma ago (ICSC, uncertainty not quantified). If neither the "parviraptorids" nor Changetisaurus nor Dorsetisaurus are accepted as toxicoferans, the minimum age of Node 129 should thus be 130 Ma.…”

The making of calibration sausage exemplified by recalibrating the transcriptomic timetree of jawed vertebrates

“…3, 4, 6, 9; and references therein). It sets in in what seems to be the Hauterivian with Kaganaias (Evans et al, 2006; Campbell Mekarski et al, 2019); the Hauterivian ended ∼ 129.4 Ma ago (ICS, uncertainty not quantified). If neither the “parviraptorids” nor Changetisaurus nor Dorsetisaurus are accepted as toxicoferans, the minimum age of Node 129 should thus be 130 Ma.…”

The Origin and Early Evolutionary History of Snakes

“…There is general agreement as to the monophyly of Mosasauroidea, but not of Aigialosauridae ( [113] versus [115,120,121;Chapter 8]). Both groups have their earliest representatives in the Cenomanian [122]. 'Dolichosaurs' are more problematic, mainly because their skulls are poorly known.…”

“…'Dolichosaurs' are more problematic, mainly because their skulls are poorly known. Recent papers, often with overlapping groups of authors, disagree as to whether 'dolichosaurs' are monophyletic (e.g., [123; Chapter 9]) or paraphyletic (e.g., [122,124]), how they are defined and diagnosed (contrast [125] with [123,124]), and whether they are closer to snakes (forming the Ophidiomorpha of [122,125]) or to mosasauroids [123]. Most 'dolichosaur' genera were recovered from shallow marine deposits associated with either the remnant Tethys seaway (Slovenia, Croatia, Kazakhstan, Lebanon, Palestine, United Kingdom, Germany, France, Spain) or the Western Interior Seaway (North America) [122].…”