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Saniwa is an extinct genus of varanid squamate from the Eocene of North America and Europe. Upto now, only one poorly known species, Saniwa orsmaelensis Dollo, 1923, has been reported from Europe. Diagnostic material was limited to vertebrae with only preliminary description and no figure provided, except of one dorsal vertebra that was designated as the lectotype. New specimens from the earliest Eocene of Dormaal, Belgium and Le Quesnoy, France, including recently recovered skull material, are described and illustrated here. These fossils representing the oldest varanid squamate allow further comparisons with the type species, Saniwa ensidens Leidy, 1870, from the early and middle Eocene of North America and to propose a new diagnosis for S. orsmaelensis. Its arrival in Europe is probably linked to rapid environmental changes around the Paleocene Eocene Thermal Maximum (PETM). The occurrence of S. orsmaelensis is restricted to the early Eocene of northwest Europe and paleogeographic considerations regarding the distribution of the genus Saniwa Leidy, 1870 suggest an Asian origin, but an African origin cannot be completely excluded.

The evolution and interrelationships of carnivorous squamates (mosasaurs, snakes, monitor lizards, Gila Monsters) are a contentious part of reptile systematics and go to the heart of conflict between morphological and molecular data in inferring evolutionary history. One of the best-preserved fossils in this motley grouping is “Saniwa” feisti Stritzke, 1983, represented by complete skeletons from the early-middle Eocene of Messel, Germany. We re-describe it on the basis of superficial examination, stereoradiography, and high-resolution X-ray computed tomography of new and published specimens. The scalation of the lizard is unique, consisting of small, keeled scales on the head (including a row of enlarged medial supraorbitals) and large, rhomboidal, keeled scales (invested by osteoderms) that covered the rest of the body. Two paired longitudinal rows of enlarged scales ran down the neck. The head was laterally compressed and box-shaped due to the presence of a strong canthal-temporal ridge; the limbs and tail were very long. Notable osteological features include: a toothed, strap-like vomer; septomaxilla with a long posterior process; palpebral with a long posterolateral process; a lacrimal boss and a single lacrimal foramen; a well-developed cultriform process of the parabasisphenoid; two hypoglossal (XII) foramina in addition to the vagus; a lack of resorption pits for replacement teeth; and possibly the presence of more than one wave of developing replacement teeth per locus. There are no osteological modifications suggestive of an intramandibular hinge, but postmortem displacement of the angular-prearticular-surangular complex in multiple specimens suggests that there might have been some degree of mobility in the lower jaw based on soft-tissue modifications. Using phylogenetic analyses on a data-set comprising 473 morphological characters and 46 DNA loci, we infer that a monophyletic Palaeovaranidae Georgalis, 2017, including Eosaniwa Haubold, 1977, lies on the stem of Varanidae Merrem, 1820, basal to various Cretaceous Mongolian taxa. We transfer feisti to the new genus Paranecrosaurus n. gen. Analysis of gut contents reveals only the second known specimen of the cryptozoic lizard Cryptolacerta hassiaca Müller, Hipsley, Head, Kardjilov, Hilger, Wuttke & Reisz, 2011, confirming a diet that was at least partly carnivorous; the preservation of the teeth of C. hassiaca suggests that the gastric physiology of Paranecrosaurus feisti (Stritzke, 1983) n. comb. had high acidity but low enzyme activity. Based on the foregoing and linear discriminant function analysis, we reconstruct P. feisti n. comb., as a powerful, widely roaming, faunivorous-carnivorous stem monitor lizard with a sensitive snout. If the molecular phylogeny of anguimorphs is correct, then many of the features shared by Helodermatidae Gray, 1837 and Varanidae must have arisen convergently, partly associated with diet. In that case, a reconciliation of morphological and molecular data would require the discovery of equally primitive fossils on the helodermatid stem.

A long-forgotten, old collection of lizards from the Phosphorites du Quercy in southern France, housed in the Naturhistorisches Museum in Vienna (NHMW), is described in detail in this paper. The material, consisting of several almost complete cranial and postcranial disarticulated elements, originates from different, imprecisely known localities. Nevertheless, the completeness and exceptional preservation of many of these specimens permitted the identification of new taxa, as well as the recognition and better understanding of novel anatomical features of previously described forms. Among the specimens, the material described herein and referred to Cadurcogekko cf. piveteaui ranks among the most complete cranial remains of Paleogene gekkotans. A clarification about the type material of the previously described species Cadurcogekko verusBolet, Daza, Auge & Bauer, 2015, is provided. A new species of lacertids is established, Pseudeumeces kyrillomethodicus n. sp. Additional, large lacertid material is referred to Mediolacerta Auge, 2005, representing also the largest one attributable to this genus. At least two glyptosaurine taxa are present in this collection, among which, the genus ParaplacosauriopsAuge & Sullivan, 2006, is represented by exceptional cranial material, referred to Paraplacosauriops quercyi (Filhol, 1882). The completeness of the cranial material of Paraplacosauriops permits a more comprehensive understanding of its maxillary and mandibular anatomy. A detailed documentation of cranial and postcranial material for the genus PalaeovaranusZittel, 1887-1890, is conducted. The new maxilla described herein allows a better understanding of the peculiar maxillary features of the genus Palaeovaranus. Emended diagnoses are provided for the genus Palaeovaranus and its type species Palaeovaranus cayluxiZittel, 1887-1890. The parietal morphology of Palaeovaranus is analyzed in detail and intraspecific variation in this element is assessed. A new species of Palaeovaranus is established, Palaeovaranus lismonimenos n. sp., on the basis of an almost complete parietal that can be differentiated from that of Palaeovaranus cayluxi on the basis of a number of distinctive features. Additional, previously published specimens from Quercy are here referred to Palaeovaranus lismonimenos n. sp., representing younger individuals of this species, and photographs of this material is provided for the first time. The diversity of platynotans in the Paleogene of Europe is discussed and their distinction on the basis of parietal morphology is provided. According to the new emended diagnosis for Palaeovaranus, the genus Melanosauroides Kuhn, 1940, is revalidated herein to accommodate Melanosauroides giganteus Kuhn, 1940, from the late early or middle Eocene of Geiseltal, Germany. So far, Melanosauroides giganteus is solely known from its type area in Geiseltal, and all previously supposed occurrences of this taxon in Quercy are discarded. Abundant anguimorph vertebral material is referred to Placosaurus sp., Melanosaurini indet., Anguinae indet., Palaeovaranus sp., Saniwa sp., and Anguimorpha indet., although it is highlighted that certain of these referrals should be taken into consideration with caution. Especially, the problem of certain large isolated lizard vertebrae from Quercy is addressed; a tentative, potential distinction between vertebrae of the genera Palaeovaranus and PlacosaurusGervais, 1848-1852, is suggested, although admittedly only articulated skeletons of these genera may confirm or refute such taxonomic referrals. The importance of fossil squamates from the area of the Phosphorites du Quercy is highlighted. Detailed figuring of the specimens is provided through the means of both photography and micro-CT scanning, with 3D models of the most significant material also presented. This is the first time that micro-CT scanning is conducted on fossil squamates from Quercy. The many figures provided in this paper may serve as a pictorial key guide for fossil lizards from the Paleogene of Europe.

Saniwa sp. (Figs 59-61) REFERRED SPECIMENS. — Three presacral vertebrae (NHMW 2019/0065/0001-NHMW 2019/0065/0003). DESCRIPTION Presacral vertebrae (Figs 59-61) The three vertebrae are large (Figs 59-61), with centrum lengths ranging from about 8.8 to 9.6 mm (seeAppendix 1). The centrum is almost triangular in ventral view and widens anteriorly (though not to that extent as in melanosaurine vertebrae described above). The subcentral ridges are straight in ventral view. The prezygapophyses are either much dorsally tilted (NHMW 2019/0065/0003) or only slightly so (in the other two specimens). The prezygapophyseal articular facets are massive and broad in dorsal view. The postzygapophyseal articular facets are also massive. The neural spine develops in height mostly in the posterior half of the neural arch. The neural arch is vaulted in posterior view. There are slight signs of “pseudozygosphene” and “pseudozygantrum” (sensu Hoffstetter 1969). The cotyle and the condyle are strongly depressed. The centrum appear more convex in lateral view is NHMW 2019/0065/0001 and NHMW 2019/0065/0002, while it is more straight in NHMW 2019/0065/0003. In all specimens though, the dorsal level of the cotyle can be clearly visible in ventral view of the specimen. Precondylar constriction can be observed (even slightly though) in NHMW 2019/0065/0001, as the respective portion of the centrum is eroded in the other two specimens. Anocotylar foramina are present and are most prominent in the largest vertebra NHMW 2019/0065/0001 (Fig. 59A). REMARKS These three vertebrae can be referred to Saniwa on the basis of their triangular centrum that widens anteriorly and the slight presence of “pseudozygosphene” and “pseudozygantrum” (Gilmore 1922; Rage & Augé 2003; Augé 2005). See Discussion below for further information on European material of Saniwa. Anguimorpha indet. (Figs 61; 62) REFERRED SPECIMENS. — Five presacral vertebrae (NHMW 2019/0046/0003- NHMW 2019/0046/0007); a partial pectoral girdle (NHMW 2019/0095/0001). DESCRIPTION AND REMARKS Presacral vertebrae (Fig. 61) These vertebrae are relatively large (Fig. 61), with centrum lengths ranging between 6.9 and 9.3 mm (see Appendix 1). The vertebrae demonstrate a mix of several features present in the above described specimens of Placosaurus, Anguinae indet., and Palaeovaranus. They have high neural spines, depressed cotyle and condyle, while the ventral surface of their centra is crossed by a wide surface or groove that is unlike the conditions seen above for the other taxa (Fig. 61). Considering the high intracolumnar variation observed in the vertebrae of extant lizards (e.g., Pseudopus), we are reluctant in assigning these specimens in a more precise taxonomic rank and we cannot even exclude that they (or part of them) pertain to some of the above described taxa. Pectoral girdle NHMW 2019/0095/0001 (Fig. 62) This specimen is incomplete, though preserving in relatively good state the right scapulocoracoid. The glenoid fossa is visible, well demarking the point of attachment with the humerus. Anteriorly to the glenoid fossa, lies the coracoid foramen. Dorsally to the foramen, the scapulocoracoid is of rectangular shape and is dorsoventrally elongated. The ventral portion of the element is anteroposteriorly elongated. It is readily obvious that this specimen apparently pertains to a rather large-sized lizard. Considering our currently inadequate state of knowledge of the appendicular skeleton of Paleogene European lizards, it is impossible to associate it with any of the above described glyptosaurines, palaeovaranids, and varanids, all of which could attain a considerably large size. Squamata indet. REFERRED SPECIMEN. — A?sacral vertebra (NHMW 2019/0095/0002). DESCRIPTION AND REMARKS. This vertebra is incomplete and not informative. Anguimorpha indet. (Figs 61; 62) REFERRED SPECIMENS. — Five presacral vertebrae (NHMW 2019/0046/0003- NHMW 2019/0046/0007); a partial pectoral girdle (NHMW 2019/0095/0001). DESCRIPTION AND REMARKS Presacral vertebrae (Fig. 61) These vertebrae are relatively large (Fig. 61), with centrum lengths ranging between 6.9 and 9.3 mm (see Appendix 1). The vertebrae demonstrate a mix of several features present in the above described specimens of Placosaurus, Anguinae indet., and Palaeovaranus. They have high neural spines, depressed cotyle and condyle, while the ventral surface of their centra is crossed by a wide surface or groove that is unlike the conditions seen above for the other taxa (Fig. 61). Considering the high intracolumnar variation observed in the vertebrae of extant lizards (e.g., Pseudopus), we are reluctant in assigning these specimens in a more precise taxonomic rank and we cannot even exclude that they (or part of them) pertain to some of the above described taxa. Pectoral girdle NHMW 2019/0095/0001 (Fig. 62) This specimen is incomplete, though preserving in relatively good state the right scapulocoracoid. The glenoid fossa is visible, well demarking the point of attachment with the humerus. Anteriorly to the glenoid fossa, lies the coracoid foramen. Dorsally to the foramen, the scapulocoracoid is of rectangular shape and is dorsoventrally elongated. The ventral portion of the element is anteroposteriorly elongated. It is readily obvious that this specimen apparently pertains to a rather large-sized lizard. Considering our currently inadequate state of knowledge of the appendicular skeleton of Paleogene European lizards, it is impossible to associate it with any of the above described glyptosaurines, palaeovaranids, and varanids, all of which could attain a considerably large size. Squamata indet. REFERRED SPECIMEN. — A?sacral vertebra (NHMW 2019/0095/0002). DESCRIPTION AND REMARKS. This vertebra is incomplete and not informative. Squamata indet. REFERRED SPECIMEN. — A?sacral vertebra (NHMW 2019/0095/0002). DESCRIPTION AND REMARKS. This vertebra is incomplete and not informative.

Genus Saniwa Leidy, 1870 TYPE SPECIES. — Saniwa ensidens Leidy, 1870 (type species by original designation; Leidy 1870)., Published as part of Georgalis, Georgios L., Čerňanský, Andrej & Klembara, Jozef, 2021, Osteological atlas of new lizards from the Phosphorites du Quercy (France), based on historical, forgotten, fossil material, pp. 219-293 in Geodiversitas 43 (9) on page 269, DOI: 10.5252/geodiversitas2021v43a9, http://zenodo.org/record/4720776, {"references":["LEIDY J. 1870. - Descriptions of Emys jeanesi, E. haydeni, Baena arenosa, and Saniwa ensidens. Proceedings of the Academy of Natural Sciences, Philadelphia 22: 123 - 124. https: // www. biodiversitylibrary. org / page / 26300494"]}

Early Eocene mammal faunas of North America were transformed by intercontinental dispersal at the Paleo- cene-Eocene boundary, but lizard faunas from the earliest Eocene of the same area were dominated by immigrants from within the continent. A new lizard assemblage from the middle early Eocene of Wyoming sheds light on the longer-term history of dispersal in relation to climate change. The assemblage consists of three iguanid species (including two new species possibly closely related to living Anolis), Scincoideus ,' Palaeoxantusia', four anguids, two spe- cies of an undescribed new anguimorph clade, Provaranosau- rus and a varanoid (cf. Saniwa). Most North American glyptosaurin glyptosaurines are now referred to Glyptosaurus, and Glyptosaurus hillsi is given a new diagnosis. Scincoideus is otherwise known only from the mid-Paleocene of Belgium, and the specimens described here are the first to document intercontinental dispersal to North America among lizards in the early Eocene. Like in mammals, some immigrant lizard lineages first appearing in the Bighorn Basin in the earliest Eocene persisted in the area long after the Paleocene-Eocene thermal maximum, but other immi- grants appear to have been restricted to the Paleocene- Eocene thermal maximum.

Three vertebrae of a large varanid lizard from the early Eocene Andarak 2 locality in Kirghizia are described. The sacral and proximal postsacral vertebrae are each characterized by a short dorso-ventrally deep centrum and a neural arch lacking the neural spine. The material is assigned to ?Saniwa sp., probably representing a new taxon of Varanidae.

The skeleton of a newly discovered, exceptionally preserved specimen of Saniwa ensidens is described in detail. The fossil consists of a complete articulated skeleton exposed in dorsal view. It adds important additional information to our knowledge of the anatomy of this fossil varanoid taxon, including a detailed description of the dermatocranium in dorsal view, complete vertebral counts, and a detailed account of the appendicular skeleton. Cartilage preservation allows the identification of treacheal rings, sternum, inscriptional ribs, epicoracoid and suprascapula. Patches of skin are preserved on dermal skull bones, and scattered scales surround the entire skeleton. Incomplete ossification of carpal and tarsal elements, as well as of epiphyses, indicate that the specimen is not fully mature.

During the field season of 1870, F. V. Hayden collected a number of sandstone blocks that contained the remains of a large fossil lizard (Middle Eocene Bridger Formation, Sweetwater County, Wyoming). Though mostly unprepared, the visible bones were described by Leidy (1870) as Saniwa ensidens (USNM 2185; holotype). Fifty years later all the blocks associated with USNM 2185 were prepared prior to Gilmore's (1922) more complete description of Saniwa ensidens and his assignment of the taxon to the Varanoidea. Gilmore (1922) notes that the skeletal remains in the blocks were partially disarticulated to dissociated despite the excellent articulation of some components (e.g., palatal elements and right and left maxillary fragments [Gilmore, 1922, p. 809; pl. 1). Gilmore (1928) altered the diagnosis of Saniwa ensidens (USNM 2185) by adding characterizations of a premaxilla, right and left anterior maxillary fragments, and anterior tips of the dentaries. Gilmore (1928, p. 57) stated that these missing elements were found after further preparation of the blocks when the type specimen was mounted for display. Re-examination of the reconstructed and mounted skull of the holotype of Saniwa ensidens (USNM 2185) has revealed characteristics of the premaxilla, premaxillary teeth, and anterior maxillary fragments and teeth, indicating that these elements belong to an entirely different family of lizards. Hence, Gilmore's (1928) association of this material with Saniwa ensidens is incorrect. I report here on the morphology and classification of these re-identified tooth-bearing elements as those of a xenosaur, and provisionally refer the elements to the Eocene xenosaur Restes (see Gauthier, 1982). The holotype specimen of Saniwa ensidens USNM 2185 was removed from display during the summer of 2000. Re-preparation of the specimen was not permitted. Specimen drawings were made using a microscope with camera lucida attachment. Photographs were taken using a Nikon camera. Measurements …

Aigialosaurs are known from three nearly complete skeletons from the Upper Cretaceous (Cenomanian-Turonian) of Yugoslavia. The Aigialosauridae is identified as the sister-group of mosasaurs on the basis of the following shared derived characters: fusion of frontal bones; circular configuration of quadrate; well-developed hinge joint between angular and splenial; surangular and articular contributing equally to articulating surface of lower jaw; reduction of transverse processes and zygapophyses of caudal vertebrae. No significant characters of the skull are known that distinguish aigialosaurs from primitive mosasaurs. In contrast, the trunk vertebrae and the limbs are indistinguishable from those of terrestrial varanoids. The tail and the ventral elements of the pelvic girdle resemble those of some other aquatic diapsids. Aigialosaurs share many derived characters with modern varanids (including Lanthanotus and Varanus and the Eocene genus Saniwa), to the exclusion of the Upper Cretaceous varanid...

Saniwa ensidens is a pivotal taxon for understanding varanid evolution. A complete specimen of Saniwa ensidens was recently described, offering important new insights into the morphology of this taxon. We apply these new data to a broader-scale study of squamate relationships in order to understand the phylogenetic position of Saniwa ensidens and of varanids more generally. Among the other fossils included in our analysis were the Eocene taxon ‘‘Saniwa’’ feisti, the Miocene Varanus rusingensis, and the giant Pleistocene varanid Megalania prisca. We compare the phylogenetic hypothesis from our analysis of morphology with a recent molecular-based hypothesis and find numerous differences in the phylogenetic relationships within Varanus .W e constrained our morphological data set to the phylogenetic pattern presented by the molecular data to further analyze the possible phylogenetic relationships of the fossil taxa. Our analyses show that Saniwa ensidens is the sister taxon to crown-group Varanus and that ‘‘Saniwa’’ feisti is a basal member of the varanid lineage, not closely related to Saniwa ensidens. Both Varanus rusingensis and Megalania prisca are members of the crown radiations of Varanus.