A new basal snake from the mid-Cretaceous of Morocco

Abstract

12 Fossil snakes are relatively well represented in the Upper Cretaceous of northern Africa, with 13 material known from Morocco, Sudan, Egypt, Libya, Algeria, and Niger. The Moroccan Kem 14 Kem beds yield a particularly diverse snake assemblage, with Simoliophiidae, Madtsoiidae, 15 ?Nigerophiidae and several unnamed taxa co-occurring. These fossils are important for our 16 understanding of the early evolutionary history of snakes, and may shed light on the ecology 17 and initial diversification of basal snakes. We describe a new taxon, Norisophis begaa gen. et 18 sp. nov., from the Kem Kem beds of Begaa, in southeast Morocco. It is characterised by a 19 marked interzygapophyseal constriction, parazygantral foramina, an incipient 20 prezygapophyseal process, and an anterio-posteriorly short centrum. Several characteristics 21 shared with Najash, Seismophis, Madtsoiidae, and Coniophis suggest that Norisophis is a stem 22 ophidian. N. begaa further increases the diversity and disparity of snakes within the Kem Kem 23 beds, supporting the hypothesis that Africa was a mid-Cretaceous hotspot for snakes. 24 25

Evolution and dispersal of snakes across the Cretaceous-Paleogene mass extinction

“…Cretaceous snake fossils are predominantly, but not exclusively, found in Gondwanan deposits, in line with previous analyses, which suggest a Gondwanan origin for crown snakes 34 . Diverse assemblages have been noted from as early as the Cenomanian, such as the Moroccan Kem Kem beds, which include both aquatic and terrestrial taxa [49][50][51] . This is also reflected in morphological disparity, with early Late Cretaceous disparity rivalling that achieved later in the Cretaceous (Fig.…”

“…Problematically, the snake fossil record is beset by a number of issues that complicate the development of unambiguous calibration schemes, relating primarily to the patchy and fragmentary nature of the snake fossil record. This has led to a number of disagreements regarding, e.g., the phylogenetic placement of fossils across the snake tree of life 33 , 34 , 37 , 38 ; the rarity of distinctive, unambiguous synapomorphies in vertebral specimens 49 ; and the absence of a comprehensive morphological phylogenetic framework with which to evaluate the affinities of problematic fossils 66 , 67 . These effects underlie differences in calibration choices between the scheme developed in this study and previously published calibration schemes 37 , 38 , such as the decision to remove Simoliophiidae and Australophis as calibrations due to their controversial phylogenetic placement (see Supplementary Information 2.1 for full discussion and Supplementary Figs.…”

Geology and paleontology of the Upper Cretaceous Kem Kem Group of eastern Morocco

“…They were found at sites in both formations, with several recovered at the pond locality Oum Tkout in the Douira Formation (Rage and Dutheil 2008). More recently, isolated vertebrae were also found in the Gara Sbaa Formation at Aferdou N'Chaft and nearby localities pertaining to Norisophis begaa, a new basal snake (Klein et al 2017). Centrum length is a little more than 5 mm.…”

“…The Kem Kem beds have revealed an important and remarkably diverse vertebrate assemblage including elasmobranchs, osteichthyes, and basal sarcopterygians (Choubert 1939, Tabaste 1963, Wenz 1981, Forey 1997, Forey and Grande 1998, Taverne and Maisey 1999, Cavin and Dutheil 1999, Dutheil 1999a, 1999b, Cavin and Brito 2001, Taverne 2000, 2004, Cavin and Forey 2001a, 2001b, Filleul and Dutheil 2001, 2004, Cavin and Forey 2004, Forey and Cavin 2007, Martill and Ibrahim 2012, amphibians (Rage and Dutheil 2008), lepidosauromorphs (Rage and Dutheil 2008, Apesteguía et al 2016a, Klein et al 2017, turtles (Gmira 1995, Tong and Buffetaut 1996, Gaffney et al 2002, 2006, crocodyliforms (Buffetaut 1976, Larsson and Sues 2007, Sereno and Larsson 2009 Lapparent de Broin 2016, Young et al 2017, pterosaurs (Wellnhofer and Buffetaut 1999, Mader and Kellner 1999, Ibrahim et al 2010, Rodrigues et al 2011, Martill and Ibrahim 2015, Jacobs et al 2019, non-avian dinosaurs…”

A new species of Coloborhynchus (Pterosauria, Ornithocheiridae) from the mid-Cretaceous of North Africa

“…Partial skeletons include a variety of fishes (Cavin et al, 2015), a sauropod dinosaur, Rebbachisaurus garasbae (Lavocat 1954), and the predatory dinosaurs Deltadromeus agilis and Spinosaurus aegyptiacus (Sereno et al, 1996, Ibrahim et al, 2014. A rich and highly diverse vertebrate assemblage is preserved, consisting of freshwater osteichthyans (Cavin and Brito, 2001;Yiabumoto and Uycno, 2005;Forey et al, 2011;Cavin et al, 2015), sharks (Dutheil and Brito, 2009;Martill and Ibrahim, 2012), amphibians (Rage and Dutheil, 2008), turtles (De Broin, 2002;Gaffney et al, 2002Gaffney et al, , 2006, snakes (Klein et al, 2017), crocodyliforms (Larsson and Sues, 2007;Sereno and Larsson, 2009), pterosaurs (Ibrahim et al, 2010;Martill et al, 2018;Rodrigues et al, 2011) and dinosaurs (Sereno et al, 1996;Cau et al, 2012;Ibrahim et al, 2014Ibrahim et al, , 2016Mannion and Barrett, 2013;Wilson and Allain, 2015). In addition, the Kem Kem assemblage also preserves a diverse ichnofauna (Ibrahim et al, 2014), notably rare dinosaur footprints.…”