Anguimorph lizards (Squamata, Anguimorpha) from the Middle and Late Eocene of the Hampshire Basin of southern England

Abstract

The Hampshire Basin in southern England is the only sequence virtually spanning the Eocene-Oligocene boundary in western Europe. It has provided an opportunity to observe changes in populations across the Grande Coupure event, as an overturn in the squamate assemblage of continental Europe has also been noted. Five Tertiary formations have yielded lizard material: Creechbarrow Limestone, Barton Clay, Headon Hill, Bembridge Limestone and Bouldnor Formation. These formations span the period from the late Middle Eocene to the earliest Oligocene. Localities in the Hampshire Basin represent a depositional environment with an increasing tendency towards lacustrine and riparian influences in later horizons. The anguimorph fauna includes one new anguine, Headonhillia parva gen. et sp. nov., diagnosed by: (1) small size, (2) large parietal area levis, and (3) short parietal crista postfovealis. Another anguine, Ophisaurus sp., is identified on the basis of the morphology of the parietal. Three further morphotypes of anguines have been distinguished based on dentary, vertebrae and osteoderm specimens. Two types of indeterminate Anguidae are distinguished on the basis of maxillae and dentaries and three morphotypes of indeterminate Anguidae on the basis of vertebrae. Glyptosaurines have been identified in three members on the basis of osteoderms. 'Necrosaurs' have also been identified from the Hampshire Basin: two types, distinguished on the basis of dentary material and osteoderms, are identified as indeterminate 'necrosaurs'. One type of indeterminate Varanoidea is distinguished on the basis of dentaries. The presence of anguids in the Hampshire Basin is well documented, and they appear to form a consistently diverse assemblage throughout the sequence. Anguine osteoderms are present in both pre-and post-Grande Coupure material. Pre-Grande Coupure vertebrae and osteoderms are similar in size to those of adult Recent anguine Pseudopus apodus, although many of the Hampshire Basin anguines, including Headonhillia parva, represent the smallest anguines known to date.

Lizards and amphisbaenians (Reptilia, Squamata) from the late Eocene of Sossís (Catalonia, Spain)

“…Anguis and Ophisaurus are also recorded from the Neogene, as are representatives of the living Pseudopus, but the latter currently has no Paleogene record . considered Dopasia to be a synoym of Ophisaurus, as suggested by Sullivan et al (1999), but later (Klembara and Green, 2010) maintained Dopasia for some Oligocene species. Conrad et al (2010) also separated Dopasia harti and Pseudopus apodus from Ophisaurus.…”

“…With the exception of the partial parietal, which shows similarities to that of Headonhillia Klembara and Green, 2010 in the long area levis, the rest of material (including tooth-bearing bones) cannot be identified beyond Anguinae indet. At least two types of anguine osteoderms are present, but as they vary in shape along the different regions of the body, they do not necessarily indicate the presence of two taxa.…”

“…Indeterminate specimens of Glyptosaurini (Belgium, England, France, Portugal, and Switzerland; MP8+9 to MP20) and 'Melanosaurini' (France and Portugal, MP7-13) are also recorded from numerous localities across Europe (Augé, 2005). For Anguinae, complete skeletons of Ophisauriscus are known from the middle Eocene of Germany (Kuhn, 1940;Klembara, 1981;Sullivan et al, 1999), whereas Helvetisaurus and Headonhillia are based on disarticulated remains from the late Eocene of Switzerland and France (Augé, 2005), and from England (Headon Hill, Klembara and Green, 2010), respectively. Disarticulated and fragmentary remains from the Eocene and Oligocene have been referred to the extant genera Anguis (France, MP8+9 to MP30; Augé, 2005) and Ophisaurus (Belgium, England, France, and Switzerland ?MP1-5, MP7-30) (Hecht and Hoffstetter, 1962;Augé, 1992;Augé and Smith, 2009;Klembara and Green, 2010).…”

“…Eocene European lizard faunas are relatively well known from France, Germany, Switzerland, and England (Figure 1; e.g., Augé, 2005;Rage and Augé, 2010;Klembara and Green, 2010). However, the Iberian record has been limited to the early Eocene (MP7) Portuguese assemblage of Silveirinha (Rage and Augé, 2003), which is also the only described Paleogene herpetofauna from southern Europe.…”

First early Eocene lizards from Spain and a study of the compositional changes between late Mesozoic and early Cenozoic Iberian lizard assemblages

“…The parietal represents the earliest record of this element for a European anguine. This element is of high diagnostic power (see Klembara and Green, 2010) and might be of importance to establish the exact affinities of the taxon from Masia de l'Hereuet with other anguines from the Cenozoic of Europe. It is only slightly larger than that of the miniaturised Headonhillia from the late Eocene of the United Kingdom (see Klembara and Green, 2010), but it clearly differs from it in the presence of a long occipital shield (it is wider than long in Headonhillia).…”