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Reeder TW, Townsend TM, Mulcahy DG, Noonan BP, Wood PL, Sites JW, Wiens JJ. Integrated analyses resolve conflicts over squamate reptile phylogeny and reveal unexpected placements for fossil taxa. PLoS One 2015; 10:e0118199. [PMID: 25803280 PMCID: PMC4372529 DOI: 10.1371/journal.pone.0118199] [Citation(s) in RCA: 164] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Accepted: 01/08/2015] [Indexed: 11/18/2022] Open
Abstract
Squamate reptiles (lizards and snakes) are a pivotal group whose relationships have become increasingly controversial. Squamates include >9000 species, making them the second largest group of terrestrial vertebrates. They are important medicinally and as model systems for ecological and evolutionary research. However, studies of squamate biology are hindered by uncertainty over their relationships, and some consider squamate phylogeny unresolved, given recent conflicts between molecular and morphological results. To resolve these conflicts, we expand existing morphological and molecular datasets for squamates (691 morphological characters and 46 genes, for 161 living and 49 fossil taxa, including a new set of 81 morphological characters and adding two genes from published studies) and perform integrated analyses. Our results resolve higher-level relationships as indicated by molecular analyses, and reveal hidden morphological support for the molecular hypothesis (but not vice-versa). Furthermore, we find that integrating molecular, morphological, and paleontological data leads to surprising placements for two major fossil clades (Mosasauria and Polyglyphanodontia). These results further demonstrate the importance of combining fossil and molecular information, and the potential problems of estimating the placement of fossil taxa from morphological data alone. Thus, our results caution against estimating fossil relationships without considering relevant molecular data, and against placing fossils into molecular trees (e.g. for dating analyses) without considering the possible impact of molecular data on their placement.
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Affiliation(s)
- Tod W. Reeder
- Department of Biology, San Diego State University, San Diego, California, 92182, United States of America
| | - Ted M. Townsend
- Department of Biology, San Diego State University, San Diego, California, 92182, United States of America
| | - Daniel G. Mulcahy
- Laboratories of Analytical Biology, Smithsonian Institution, 10th & Constitution Aves. NW, Washington, D.C., 20560, United States of America
| | - Brice P. Noonan
- Department of Biology, University of Mississippi, Box 1848, Mississippi, 38677, United States of America
| | - Perry L. Wood
- Department of Biology and Bean Life Science Museum, Brigham Young University, Provo, Utah, 84602, United States of America
| | - Jack W. Sites
- Department of Biology and Bean Life Science Museum, Brigham Young University, Provo, Utah, 84602, United States of America
| | - John J. Wiens
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona, 85721, United States of America
- * E-mail:
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Makádi L, Caldwell MW, Ősi A. The first freshwater mosasauroid (Upper Cretaceous, Hungary) and a new clade of basal mosasauroids. PLoS One 2012; 7:e51781. [PMID: 23284766 PMCID: PMC3526648 DOI: 10.1371/journal.pone.0051781] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Accepted: 11/12/2012] [Indexed: 11/18/2022] Open
Abstract
Mosasauroids are conventionally conceived of as gigantic, obligatorily aquatic marine lizards (1000s of specimens from marine deposited rocks) with a cosmopolitan distribution in the Late Cretaceous (90-65 million years ago [mya]) oceans and seas of the world. Here we report on the fossilized remains of numerous individuals (small juveniles to large adults) of a new taxon, Pannoniasaurus inexpectatus gen. et sp. nov. from the Csehbánya Formation, Hungary (Santonian, Upper Cretaceous, 85.3-83.5 mya) that represent the first known mosasauroid that lived in freshwater environments. Previous to this find, only one specimen of a marine mosasauroid, cf. Plioplatecarpus sp., is known from non-marine rocks in Western Canada. Pannoniasaurus inexpectatus gen. et sp. nov. uniquely possesses a plesiomorphic pelvic anatomy, a non-mosasauroid but pontosaur-like tail osteology, possibly limbs like a terrestrial lizard, and a flattened, crocodile-like skull. Cladistic analysis reconstructs P. inexpectatus in a new clade of mosasauroids: (Pannoniasaurus (Tethysaurus (Yaguarasaurus, Russellosaurus))). P. inexpectatus is part of a mixed terrestrial and freshwater faunal assemblage that includes fishes, amphibians turtles, terrestrial lizards, crocodiles, pterosaurs, dinosaurs and birds.
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Affiliation(s)
- László Makádi
- Department of Paleontology and Geology, Hungarian Natural History Museum, Budapest, Hungary.
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Gauthier JA, Kearney M, Maisano JA, Rieppel O, Behlke AD. Assembling the Squamate Tree of Life: Perspectives from the Phenotype and the Fossil Record. BULLETIN OF THE PEABODY MUSEUM OF NATURAL HISTORY 2012. [DOI: 10.3374/014.053.0101] [Citation(s) in RCA: 352] [Impact Index Per Article: 29.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Polcyn MJ, Lindgren J, Bardet N, Cornelissen D, Verding L, Schulp AS. Description of new specimens of Halisaurus arambourgi Bardet & Pereda Suberbiola, 2005 and the relationships of Halisaurinae. ACTA ACUST UNITED AC 2012. [DOI: 10.2113/gssgfbull.183.2.123] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Abstract
Halisaurine mosasaurs are poorly known, represented by a small number of specimens from the Santonian-Maastrichtian (~86 Ma – ~66 Ma), but enjoyed broad palaeobiogeographic distribution during that time. They are important for understanding mosasaur evolution because certain aspects of their morphology retain the relatively plesiomorphic or minimally modified squamate conditions; however, existing material is limited and certain anatomical details are lacking. We report here two new specimens of Halisaurus arambourgi including a well-preserved, nearly complete skull and postcranial skeleton, and a partial skull that preserves details of the braincase and quadrate. We focus our description on morphology that augments the original description of this species and provides comparisons with other halisaurines. Braincase and temporal arcade characters confirm the plesiomorphic nature of Halisaurus, supporting a relatively basal position of Halisaurinae within Mosasauridae. Comparisons of cranial morphology support reconstruction of relationships within Halisaurinae, indicating that H. arambourgi is most closely related to H. platyspondylus, Phosphorosaurus (= H. ortliebi) is the sister taxon to those taxa, and Eonatator is the most basal described halisaurine. The proportions of the epipodials and the caudal vertebral centrum morphometrics indicate H. arambourgi is more derived than the Santonian to early Campanian Eonatator sternbergii but less derived than a Halisaurus sp. specimen from the mid-Maastrichtian of the Moreno Formation of California, USA. Moreover, vertebral morphometrics reveals that H. arambourgi possessed a downturned tail that likely supported a crescent-like fluke.
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Affiliation(s)
- Michael J. Polcyn
- Roy M. Huffington Department of Earth Sciences, Southern Methodist University, 3225 Daniel Avenue, Dallas, TX 75275, USA. E-mail:
| | - Johan Lindgren
- Department of Earth and Ecosystem Sciences, Lund University, Sölvegatan 12, SE-223 62 Lund, Sweden. E-mail:
| | - Nathalie Bardet
- CNRS UMR 7207, Département Histoire de la Terre, Muséum national d’Histoire naturelle, 8 rue Buffon, F-75005 Paris, France. E-mail:
| | - Dirk Cornelissen
- Natuurhistorisch Museum Maastricht, De Bosquetplein 6-7, NL-6211 KJ Maastricht, The Netherlands. e-mail: ; ;
| | - Louis Verding
- Natuurhistorisch Museum Maastricht, De Bosquetplein 6-7, NL-6211 KJ Maastricht, The Netherlands. e-mail: ; ;
| | - Anne S. Schulp
- Natuurhistorisch Museum Maastricht, De Bosquetplein 6-7, NL-6211 KJ Maastricht, The Netherlands. e-mail: ; ;
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Polcyn MJ, Lamb J. The snout of Halisaurus platyspondylusMarsh 1869: phylogenetic and functional implications. ACTA ACUST UNITED AC 2012. [DOI: 10.2113/gssgfbull.183.2.137] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Abstract
New material of Halisaurus platyspondylus allows description of the snout elements for the first time. The specimen was recovered from the Late Maastrichtian New Egypt Formation in Gloucester County, New Jersey. Portions of the frontal, both prefrontals, and the left quadrate are preserved and are nearly identical to the USNM H. platyspondylus specimen. It can be excluded from H. arambourgi by the extensive sutural contact of the prefrontal and ventral frontal. The new material demonstrates development of a relatively broad short skull in H. platyspondylus as in H. arambourgi, and articulations of constituent elements reveal a strong, akinetic snout. This stands in contrast to the elongate, narrow skulls of more basal halisaurines such as Eonatator. This pattern, also seen in derived members of other mosasaurid subfamilies, suggests a shift from high velocity jaw closure for prey acquisition in more basal forms to robust skulls optimized for increased bite force in some more derived forms.
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Affiliation(s)
- Michael J. Polcyn
- Roy M. Huffington Department of Earth Sciences, Southern Methodist University, 3225 Daniel Avenue, Dallas, TX 75275, USA., E-mail:
| | - James Lamb
- Black Belt Museum, University of West Alabama, Station 45 Livingston, AL 35470, USA, E-mail:
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Conrad JL, Ast JC, Montanari S, Norell MA. A combined evidence phylogenetic analysis of Anguimorpha (Reptilia: Squamata). Cladistics 2010; 27:230-277. [DOI: 10.1111/j.1096-0031.2010.00330.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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CALDWELL MICHAELW, COOPER JOHNA. Redescription, palaeobiogeography and palaeoecology of Coniasaurus crassidens Owen, 1850 (Squamata) from the Lower Chalk (Cretaceous; Cenomanian) of SE England. Zool J Linn Soc 2008. [DOI: 10.1111/j.1096-3642.1999.tb01380.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Conrad JL. Phylogeny And Systematics Of Squamata (Reptilia) Based On Morphology. BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY 2008. [DOI: 10.1206/310.1] [Citation(s) in RCA: 318] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Affiliation(s)
- M.S.Y. Lee
- a School of Biological Sciences , University of Sydney , Zoology Building A08, Sydney, NSW, 2006, Australia
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Abstract
The postcranial skeleton is poorly known for Shinisaurus crocodilurus, the Chinese crocodile lizard. Discrepancies exist between published accounts of Shinisaurus; moreover, comparisons with complete specimens show important differences from the published descriptions. Contrary to some publications, the axial skeleton variably consists of 26 or 27 presacral vertebrae, including eight cervical vertebrae. Humeral entepicondylar and ectepicondylar foramina are present, as are an epipubis and hypoischium, and the post-tubercular portion of the pubis is subequal in length to the proximal portion. Sesamoids are present in the knee, elbow, and between the penultimate phalanges and unguals. A cartilaginous strut joins the clavicles and interclavicle. Comparative investigation of extant anguimorphs add context to these observations and support the conclusion that Mosasauroidea possessed eight or more (rather than seven) cervical vertebrae. Overall, the postcranium of Shinisaurus is relatively unspecialized for Anguimorpha, although it may be diagnosed accurately by a combination of character states.
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Affiliation(s)
- Jack L Conrad
- Department of Organismal Biology and Anatomy, University of Chicago, Chicago, Illinois 60637, USA.
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BARDET NATHALIE, PEREDA SUBERBIOLA XABIER, IAROCHENE MOHAMED, BOUYA BAADI, AMAGHZAZ MBAREK. A new species of Halisaurus. from the Late Cretaceous phosphates of Morocco, and the phylogenetical relationships of the Halisaurinae (Squamata: Mosasauridae). Zool J Linn Soc 2005. [DOI: 10.1111/j.1096-3642.2005.00152.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Caldwell MW. From fins to limbs to fins: limb evolution in fossil marine reptiles. AMERICAN JOURNAL OF MEDICAL GENETICS 2002; 112:236-49. [PMID: 12357467 DOI: 10.1002/ajmg.10773] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Limb osteology and ontogenetic patterns of limb ossification are reviewed for extinct lineages of aquatically adapted diapsid reptiles. Phylogenies including these fossil taxa show that paddle-like limbs were independently derived, and that the varied limb morphologies were produced by evolutionary modifications to different aspects of the limb skeleton. Ancient marine reptiles modify the limb by reducing the relative size of the epipodials, modifying the perichondral and periosteal surface of elements distal to the propodials, and evolving extremes of hyperphalangy and hyperdactyly. Developmental genetic models illuminate gene systems that may have controlled limb evolution in these animals.
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Affiliation(s)
- Michael W Caldwell
- Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, Canada.
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Abstract
Although live-bearing (viviparity) has evolved around 100 times within reptiles, evidence of it is almost never preserved in the fossil record. Here, we report viviparity in mosasauroids, a group of Cretaceous marine lizards. This is the only known fossil record of live-bearing in squamates (lizards and snakes), and might represent the oldest occurrence of the trait in this diverse group; it is also the only known fossil record of viviparity in reptiles other than ichthyosaurs. An exceptionally preserved gravid female of the aigialosaur Carsosaurus (a primitive mosasauroid) contains at least four advanced embryos distributed along the posterior two-thirds of the long trunk region (dorsal vertebrae 9-21). Their orientation suggests that they were born tail-first (the nostrils emerging last) to reduce the possibility of drowning, an adaptation shared with other highly aquatic amniotes such as cetaceans, sirenians and ichthyosaurs; the orientation of the embryos also suggests that they were not gut contents because swallowed prey are usually consumed head-first. One embryo is located within the pelvis, raising the possibility that the adult died during parturition. Viviparity in early medium-sized amphibious aigialosaurs may have freed them from the need to return to land to deposit eggs, and permitted the subsequent evolution of gigantic totally marine mosasaurs.
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Affiliation(s)
- M W Caldwell
- Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E3.
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Lee MY, Caldwell M. Anatomy and relationships of Pachyrhachis problematicus, a primitive snake with hindlimbs. Philos Trans R Soc Lond B Biol Sci 1998. [DOI: 10.1098/rstb.1998.0308] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The anatomy of
Pachyrhachis problematicus
, an elongate, limb–reduced squamate from the Upper Cretaceous of Israel, is described and evaluated in detail. Previously considered a snake–like ‘lizard’ of uncertain affinities, it is here shown to be the most primitive snake, and the sister–group to all other snakes.
Pachyrhachis
exhibits numerous derived characters uniting it with modern snakes (scolecophidians and alethinophidians): e.g. mobile premaxilla–maxilla articulation, braincase enclosed by frontals and parietals, sagittal parietal crest, absence of tympanic recess, single postdentary bone, over 140 presacral vertebrae, and complete loss of shoulder girdle and forelimb. However, it is more primitive than all modern snakes in retaining some strikingly primitive (lizard–like) features: presence of a jugal, squamosal, normal sacral attachment, and well–developed hindlimb composed of femur, tibia, fibula, and tarsals.
Pachyrhachis
provides additional support for the hypothesis that snakes are most closely related to Cretaceous marine lizards (mosasauroids). Almost all of the derived characters proposed to unite snakes and mosasauroids are highly developed in
Pachyrhachis
: the mobile mandibular symphysis, intramandibular joint, long and recurved pterygoid teeth, quadrate suspended by the supratemporal, loosely united pelvic elements (ilium, ischium, and pubis), and separate astragalus and calcaneum.
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Affiliation(s)
- Michael.S. Y. Lee
- Zoology Building A08, School of Biological Sciences, University of Sydney, NSW 2006, Australia
| | - Michael.W. Caldwell
- Department of Geology, The Field Museum, Roosevelt Road at Lakeshore Drive, Chicago, IL 60605, USA
- Department of Biological Science, Biological Sciences Center, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada
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Abstract
Evidence that platynotan squamates (living varanoid lizards, snakes and their fossil relatives) are monophyletic is presented. Evolutionary relationships within this group are then ascertained through a cladistic analysis of 144 osteological characters. Mosasauroids (aigialosaurs and mosasaurs), a group of large marine lizards, are identified as the nearest relatives of snakes, thus resolving the long-standing problem of snake affinities. The mosasauroid–snake clade (Pythonomorpha) is corroborated by 40 derived characters, including recumbent replacement teeth, thecodonty, four or fewer premaxillary teeth, supratemporal–prootic contact, free mandibular tips, crista circumfenestralis, straight vertical splenio-angular joint, loss of posterior ramus of the coronoid, reduced basipterygoid processes, reduced interpterygoid vacuity, zygosphene–zygantral articulations, and absence of epiphyses on the axial skeleton and skull. After mosasauroids, the next closest relatives of snakes are varanids (Varanus , Saniwa and Saniwides ) and lanthanotids (Lanthanotus and Cherminotus ). Derived features uniting varanids and lanthanotids include nine cervical vertebrae and three or fewer pairs of sternal ribs. The varanid–lanthanotid–pythonomorph clade, here termed Thecoglossa, is supported by features such as the anteriorly positioned basal tubera, and the loss of the second epibranchial. Successive outgroups to thecoglossans are Telmasaurus , an unresolved polytomy (Estesia , Gobidermatidae and Helodermatidae), Paravaranus and Proplatynota . The 'necrosaurs' are demonstrated to be an artificial (polyphyletic) assemblage of primitive platynotans that are not particularly closely related to each other. Snakes are presumed to have evolved from small, limbless, burrowing lizards and the inability of previous analyses to resolve the affinities of snakes has been attributed to extensive convergence among the numerous lineages of such lizards. The present study contradicts this claim, demonstrating that the problem is due instead to omission of critical fossil taxa. No modern phylogenetic analysis of squamate relationships has simultaneously included both mosasauroids and snakes: previous studies have therefore failed to identify the mosasauroid–snake association and the suite of derived characters supporting it. Mosasauroids are large aquatic animals with well-developed appendages, and none of the derived characters uniting mosasauroids and snakes is obviously correlated with miniaturization, limb reduction or fossoriality. Recognition that mosasauroids, followed by varanids and lanthanotids, are the nearest relatives of snakes will also facilitate studies of relationships within snakes, which until now have been hampered by uncertainty over the most appropriate (closely-related) lizard outgroups.
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