The earliest known occurrence of Elgaria (Squamata: Anguidae) and a minimum age for crown Gerrhonotinae: Fossils from the Split Rock Formation, Wyoming, USA

Scarpetta, Simon G.

doi:10.26879/837

Cited by 9 publications

(13 citation statements)

References 18 publications

(43 reference statements)

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“…A single anterior midline foramen is present on the anterior surface of the premaxilla in most species of Elgaria, but is absent in E. cedrosensis and E. panamintina. The foramen is also present in A. moreletti TNHC 29675, A. campbelli, and Ophisaurus [24]. Like Scarpetta [24], we interpret the foramen as separately derived in Ophisaurus and gerrhonotines.…”

Section: Remarksmentioning

confidence: 61%

“…1). One extralimital occurrence of Elgaria is known from Wyoming during the middle Miocene [24]. Previously, a paucity of fossils identified to Elgaria using apomorphies made interpretation of the biogeographic history of the genus largely reliant on molecular or other non-paleontological information [4,5].…”

Section: Diversification and Biogeographic History Of Elgariamentioning

confidence: 99%

“…The known fossil record of total clade Gerrhonotinae extends to the early Eocene [23]. Crown gerrhonotines are documented from the Miocene [24], and divergencetime analyses indicate a middle Oligocene [25], latemiddle Eocene [5], or late Eocene to early Oligocene [26] origin for the crown clade. Although many Late Cretaceous and Cenozoic lizard fossils, mostly disarticulated and fragmented cranial elements, were referred to Gerrhonotinae [1,23,24,[27][28][29][30][31][32][33][34][35][36][37], most fossils described during the twentieth century lacked known apomorphies of Gerrhonotinae [38].…”

Section: Introductionmentioning

confidence: 99%

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A new extinct species of alligator lizard (Squamata: Elgaria) and an expanded perspective on the osteology and phylogeny of Gerrhonotinae

2021

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Background Alligator lizards (Gerrhonotinae) are a well-known group of extant North American lizard. Although many fossils were previously referred to Gerrhonotinae, most of those fossils are isolated and fragmentary cranial elements that could not be placed in a precise phylogenetic context, and only a handful of known fossils are articulated skulls. The fossil record has provided limited information on the biogeography and phylogeny of Gerrhonotinae. Results We redescribe a nearly complete articulated fossil skull from the Pliocene sediments of the Anza-Borrego Desert in southern California, and refer the specimen to the alligator lizard genus Elgaria. The fossil is a representative of a newly described species, Elgaria peludoverde. We created a morphological matrix to assess the phylogeny of alligator lizards and facilitate identifications of fossil gerrhonotines. The matrix contains a considerably expanded taxonomic sample relative to previous morphological studies of gerrhonotines, and we sampled two specimens for many species to partially account for intraspecific variation. Specimen-based phylogenetic analyses of our dataset using Bayesian inference and parsimony inferred that Elgaria peludoverde is part of crown Elgaria. The new species is potentially related to the extant species Elgaria kingii and Elgaria paucicarinata, but that relationship was not strongly supported, probably because of extensive variation among Elgaria. We explored several alternative biogeographic scenarios implied by the geographic and temporal occurrence of the new species and its potential phylogenetic placements. Conclusions Elgaria peludoverde is the first described extinct species of Elgaria and provides new information on the biogeographic history and diversification of Elgaria. Our research expands the understanding of phylogenetic relationships and biogeography of alligator lizards and strengthens the foundation of future investigations. The osteological data and phylogenetic matrix that we provided will be critical for future efforts to place fossil gerrhonotines. Despite limited intraspecific sampled sizes, we encountered substantial variation among gerrhonotines, demonstrating the value of exploring patterns of variation for morphological phylogenetics and for the phylogenetic placement of fossils. Future osteological investigations on the species we examined and on species we did not examine will continue to augment our knowledge of patterns of variation in alligator lizards and aid in phylogenetics and fossil placement.

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Section: Remarksmentioning

confidence: 61%

Section: Diversification and Biogeographic History Of Elgariamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A new extinct species of alligator lizard (Squamata: Elgaria) and an expanded perspective on the osteology and phylogeny of Gerrhonotinae

2021

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“…2D ; 2=ossified bridge encloses the medial ethmoidal foramen (foramen for ophthalmic branch of CN5 of Evans (2008) ), Fig. 2E (modified from Good (1987) , characters 1 and 2; Campbell & Frost, 1993 ; Scarpetta, 2018 ).…”

Section: Resultsmentioning

confidence: 99%

“…Gerrhonotine fossils are known from early Eocene deposits ( Smith, 2009 ) and possibly from late Cretaceous sediments ( Estes, 1964 ; Good, 1988a ; Longrich, Bhullar & Gauthier, 2012 ). Crown gerrhonotines are known from at least the middle Miocene ( Scarpetta, 2018 ). The osteology of the group was previously studied by several researchers ( Cope, 1892 ; Tihen, 1949 ; McDowell & Bogert, 1954 ; Romer, 1956 ; Criley, 1968 ; Meszoely, 1970 ; Rieppel, 1980 ; Gauthier, 1982 ; Good, 1987 ; Good, 1988a ); however, only a few species from each group within Gerrhonotinae were sampled.…”

Section: Introductionmentioning

confidence: 99%

Variation in the skulls of Elgaria and Gerrhonotus (Anguidae, Gerrhonotinae) and implications for phylogenetics and fossil identification

Ledesma

Scarpetta

Bell

2021

PeerJ

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Background There are limited data on intra- and interspecific osteological variation for many squamate clades. Those data are relevant for phylogenetic analyses that use osteological characters and for apomorphic identifications of fossils. We investigate whether morphological features in the skulls of extant gerrhonotine lizards can be used to distinguish taxa at the species- and genus-level and assess whether newly discovered intra- and interspecific osteological variation alters the utility of previously reported apomorphic features. We examined skulls of species belonging to the gerrhonotine genera Elgaria and Gerrhonotus. These genera contain 17 extant species, but the cranial osteology of only a few species was previously examined. As a result, intra- and interspecific osteological variation of these gerrhonotines is poorly understood. Methods We employed high-resolution x-ray computed tomography (CT) to scan 25 alcohol-preserved specimens. We provide data on the skulls of all eight species of Elgaria, four for the first time, and five species of Gerrhonotus, three for the first time. We examined 3-D reconstructed skulls of the scanned specimens as well as dry, traditionally prepared skeletons (when they were available). Results We found that the purported diagnostic utility of many previously described morphological features is impacted because of substantial morphological variation between and within species. We present an assessment of osteological differences that may be useful to differentiate species of Elgaria and Gerrhonotus, many of which are present on isolated cranial elements commonly recovered as fossils, including the premaxilla, maxilla, parietal, pterygoid, prootic, dentary, and surangular. We demonstrate the importance of documenting patterns of osteological variation using large sample sizes, and the utility of examining disarticulated cranial elements of the squamate skull to identify diagnostic morphology. This study adds to a growing body of literature suggesting that extensive documentation of morphological variation is needed to further our understanding of the phylogenetic and diagnostic utility of morphological features across vertebrate clades. Efforts in that direction likely will benefit from examination of disarticulated skeletal elements.

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Evolution of North American Lizards

Scarpetta

Ledesma

Llauger

et al. 2020

Encyclopedia of Life Sciences

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Lizards are a diverse reptile group with an ancient and global evolutionary history. Fossil lizards first appeared in North America during the Mesozoic. Many lizard lineages have inhabited North America throughout geologic time, including several lineages that are extinct, others that no longer occur on the continent, and many groups that are still there today. Lizards are currently found in a diverse range of habitats and in regions across the continent, including islands and human‐modified habitats. The modern lizard biota of North America contains diverse biogeographic and phylogenetic components along with the evolution of many distinctive behaviours, morphologies, and ecologies, including the evolution of venom, repeated limb loss, and ecological specialisations. Some lizards have been introduced to North America from elsewhere in the world or the continent, posing a potential problem for native biodiversity. Key Concepts North America contains an astounding diversity of lizards both in the modern biota and through geologic time. Although many fossil lizards are documented, there is still a lot to learn from the fossil record. Historic extirpations and extinctions of lizards are known and conservation efforts are needed to preserve lizard biodiversity. Biogeographic scenarios of lizards in North America are often disputed but are informed by fossil and molecular evidence. North American lizards have a diverse set of behavioural, morphological and ecological characteristics.

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The earliest known occurrence of Elgaria (Squamata: Anguidae) and a minimum age for crown Gerrhonotinae: Fossils from the Split Rock Formation, Wyoming, USA

Cited by 9 publications

References 18 publications

A new extinct species of alligator lizard (Squamata: Elgaria) and an expanded perspective on the osteology and phylogeny of Gerrhonotinae

A new extinct species of alligator lizard (Squamata: Elgaria) and an expanded perspective on the osteology and phylogeny of Gerrhonotinae

Variation in the skulls of Elgaria and Gerrhonotus (Anguidae, Gerrhonotinae) and implications for phylogenetics and fossil identification

Evolution of North American Lizards

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