The first known fossil Uma: ecological evolution and the origins of North American fringe-toed lizards

Abstract

Background Fossil evidence suggests that extant North American lizard genera (north of Mexico) evolved during the Miocene. Although fossils of the clade Phrynosomatidae (spiny lizards and sand lizards) have been reported, there have been no previously described fossils of the fringe-toed sand lizards ( Uma ). In the extant biota, Uma inhabit arid deserts, and members of the western clade of Uma are restricted to sand dunes or other habitats containing fine-grained sand. Results I describe the first known fossil of Uma and refer the fossil to the total clade of Uma with an apomorphy-based diagnosis. The fossil is a partial premaxilla that was found in the Miocene strata of the Dove Spring Formation of southern California, dating to 8.77 Ma. The paleoenvironment of the Dove Spring Formation was semiarid and contained ephemeral streams that facilitated deposition, and there is no evidence of sand dune deposits in the strata containing the locality from which the Uma fossil was found. Divergence time analyses of a concatenated molecular dataset with four fossil calibrations support a Neogene origin of the total clade of Uma and of the crown clade of Uma . Those analyses also estimated a Neogene divergence between Uma scoparia and the Uma notata complex. Multispecies coalescent analyses with one fossil calibration inferred a Paleogene origin for the total clade of Uma and a Pliocene or Pleistocene divergence between Uma scoparia and the Uma notata complex. The fossil and the total and crown clades of Uma precede the evolution of modern desert ecosystems in the southwestern United States and northern Mexico by millions of years. Conclusions The total clade and the crown clade of Uma were not restricted to arid deserts throughout their evolutionary histories. I demonstrate that an apomorphy-based diagnosis can be used to identify fossils of isolated skeletal elements for at least one clade of phrynosomatid lizard, and suggest exercising caution when using environmental tolerances of extant taxa to hypothesize paleoecological reconstructions. Electronic supplementary material The online version of this article (10.1186/s12862-019-1501-5) contains supplementary material, which is available to authorized users.

Latitudinal and environmental patterns of species richness in lizards and snakes across continental North America

“…However, fossil evidence suggests that we cannot necessarily assume niche conservatism for all extant North American squamate genera (e.g. Bhullar & Smith, 2008; Scarpetta, 2019). Nevertheless, as demonstrated by our analyses and others (e.g.…”

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

“…Above (Materials and methods: Calibrations: Node 132 – Iguanidae) I argue for using the age of Kopidosaurus , about 53 million years, as the minimum age of Iguanidae. Kopidosaurus was named and described from a largely complete skull by Scarpetta (2020) in a publication where the words “oldest” and “older” do not occur at all, and “first” and “ancient” only occur in other contexts – even though Scarpetta (2019) had just published on calibration dates for molecular divergence date analyses. The reason may be that he did not think Kopidosaurus was the oldest iguanid; one of the two matrices he used for phylogenetic analyses contained the 56-Ma-old Suzanniwana , and his analyses found it as an iguanid (Scarpetta, 2020: supp.…”

“…Indeed, the one phylogenetic analysis that has ever included Bharatagama found it as a rhynchocephalian rather than a squamate, although close to the pleurosaurs (despite the more Diphydontosaurus -like plesiomorphic gradient of tooth implantation) and, not surprisingly given the limited material, with weak support (Conrad, 2017). In sum, the optimism of Scarpetta (2019) is unwarranted, and the status of Bharatagama as a pan-acrodontan is too doubtful for use in calibration.…”

“…The supposed chamaeleonid later turned out to be an albanerpetid amphibian with a ballistic tongue (Matsumoto and Evans, 2018: 52–53; Daza et al, 2020), and the supposed agamids are so incomplete that they probably provide more ecological than phylogenetic information; indeed, the only supposed pan-acrodontan Daza et al (2016) included in their phylogenetic analysis was the albanerpetid. Therefore, again unlike Scarpetta (2019), I do not think any of these four specimens can be used to calibrate divergence dates.…”

“…Xianglong from the Yixian Fm of Liaoning (China), which dates to around the Barremian-Aptian boundary (~ 125.0 Ma: ICSC), was described as a pan-acrodontan, possibly an acrodontan (Li et al, 2007). Unfortunately, this rests on very limited evidence: the one known individual is clearly juvenile, and much of the skeleton remains unknown because is covered by exquisitely preserved soft tissue and has not been μ CT-scanned (Li et al, 2007;Simões et al, 2017;Scarpetta, 2019, and reference therein). Daza et al (2016) briefly described three isolated hindlimbs from Burmese amber (99 Ma old: Daza et al, 2016Daza et al, , 2020 as agamids, and a largely complete articulated individual as a chamaeleonid.…”