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1.
Proc Biol Sci ; 284(1847)2017 01 25.
Artigo em Inglês | MEDLINE | ID: mdl-28123087

RESUMO

Iguanomorpha (stem + crown Iguania) is a diverse squamate clade with members that predominate many modern American lizard ecosystems. However, the temporal and palaeobiogeographic origins of its constituent crown clades (e.g. Pleurodonta (basilisks, iguanas, and their relatives)) are poorly constrained, mainly due to a meagre Mesozoic-age fossil record. Here, we report on two nearly complete skeletons from the Late Cretaceous (Campanian) of North America that represent a new and relatively large-bodied and possibly herbivorous iguanomorph that inhabited a semi-arid environment. The new taxon exhibits a mosaic of anatomical features traditionally used in diagnosing Iguania and non-iguanian squamates (i.e. Scleroglossa; e.g. parietal foramen at the frontoparietal suture, astragalocalcaneal notch in the tibia, respectively). Our cladistic analysis of Squamata revealed a phylogenetic link between Campanian-age North American and East Asian stem iguanomorphs (i.e. the new taxon + Temujiniidae). These results and our evaluation of the squamate fossil record suggest that crown pleurodontans were restricted to the low-latitude Neotropics prior to their early Palaeogene first appearances in the mid-latitudes of North America.


Assuntos
Fósseis , Lagartos/classificação , Filogenia , Animais , América do Norte
2.
PLoS One ; 10(7): e0127900, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26131767

RESUMO

A new fossil showing affinities with extant Laemanctus offers the first clear evidence for a casquehead lizard (Corytophanidae) from the Eocene of North America. Along with Geiseltaliellus from roughly coeval rocks in central Europe, the new find further documents the tropical fauna present during greenhouse conditions in the northern mid-latitudes approximately 50 million years ago (Ma). Modern Corytophanidae is a neotropical clade of iguanian lizards ranging from southern Mexico to northern South America.


Assuntos
Fósseis , Lagartos , Animais , Lagartos/anatomia & histologia , Lagartos/classificação , Lagartos/genética , América do Norte
3.
Anat Rec (Hoboken) ; 297(3): 545-59, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24482393

RESUMO

We describe an unusual squamate fossil from the Green River Formation (Uintan, Eocene) from the Piceance Creek Basin, Colorado, USA. The new specimen, USNM PAL 540708, is a small fossil squamate skin lacking skeletal elements. It is preserved as a part and counterpart in fine-grained limestone. Recovery of a fossil organism's skin (not a shed, but a true skin) is unusual and is most often accompanied by bone preservation. Phylogenetic analysis of a combined morphology (phenotype) and genetic data set reveals that USNM PAL 540708 is a shinisaur and reaffirms that shinisaurs are more closely related to varanids than to Xenosaurus. Shinisaur fossils are very rare, with only three species having been described (Dalinghosaurus longidigitus, Bahndwivici ammoskius, and Merkurosaurus ornatus). Despite differences in the relative size of scales, the new fossil demonstrates that shinisaurs have remained unchanged in the distribution of scales and patterns of scale size during the Cenozoic. This, paired with the osteological similarity between another Green River fossil (Bahndwivici ammoskius) demonstrates considerable overall conservatism within shinisaurs over the past 50 million years.


Assuntos
Fósseis , Lagartos/anatomia & histologia , Pele/anatomia & histologia , Animais , Evolução Biológica , Colorado , Extinção Biológica , Filogenia , Especificidade da Espécie
4.
PLoS One ; 7(8): e41767, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22900001

RESUMO

BACKGROUND: Varanidae is a clade of tiny (<20 mm pre-caudal length [PCL]) to giant (>600 mm PCL) lizards first appearing in the Cretaceous. True monitor lizards (Varanus) are known from diagnostic remains beginning in the early Miocene (Varanus rusingensis), although extremely fragmentary remains have been suggested as indicating earlier Varanus. The paleobiogeographic history of Varanus and timing for origin of its gigantism remain uncertain. METHODOLOGY/PRINCIPAL FINDINGS: A new Varanus from the Mytilini Formation (Turolian, Miocene) of Samos, Greece is described. The holotype consists of a partial skull roof, right side of a braincase, partial posterior mandible, fragment of clavicle, and parts of six vertebrae. A cladistic analysis including 83 taxa coded for 5733 molecular and 489 morphological characters (71 previously unincluded) demonstrates that the new fossil is a nested member of an otherwise exclusively East Asian Varanus clade. The new species is the earliest-known giant (>600 mm PCL) terrestrial lizard. Importantly, this species co-existed with a diverse continental mammalian fauna. CONCLUSIONS/SIGNIFICANCE: The new monitor is larger (longer) than 99% of known fossil and living lizards. Varanus includes, by far, the largest limbed squamates today. The only extant non-snake squamates that approach monitors in maximum size are the glass-snake Pseudopus and the worm-lizard Amphisbaena. Mosasauroids were larger, but exclusively marine, and occurred only during the Late Cretaceous. Large, extant, non-Varanus, lizards are limbless and/or largely isolated from mammalian competitors. By contrast, our new Varanus achieved gigantism in a continental environment populated by diverse eutherian mammal competitors.


Assuntos
Lagartos/anatomia & histologia , Animais , Tamanho Corporal , Feminino , Fósseis , Grécia , Lagartos/classificação , Lagartos/genética , Masculino , Filogenia , Crânio/anatomia & histologia , Vertebrados/anatomia & histologia
5.
Cladistics ; 27(3): 230-277, 2011 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-34875778

RESUMO

Anguimorpha is a clade of limbed and limbless squamates with ca. 196 extant species and a known fossil record spanning the past 130 million years. Morphology-based and molecule-based phylogenetic analyses disagree on several key points. The analyses differ consistently in the placements of monstersaurs (e.g. Gila Monsters), shinisaurs (Crocodile Lizards), the anguid Anniella (American Legless Lizards), carusioids (Knobby Lizards), and the major clades within Varanus (Monitor Lizards). Given different data sources with such different phylogenetic hypotheses, Anguimorpha is an excellent candidate for a combined phylogenetic analysis. We constructed a data matrix consisting of 175 fossil and extant anguimorphs, and 2281 parsimony-informative characters (315 morphological characters and 1969 molecular characters). We analysed these data using the computer program TNT using the "new technology search" with the ratchet. Our result is novel and shows similarities with both morphological and molecular trees, but is identical to neither. We find that a global combined evidence analysis (GCA) does not recover a holophyletic Varanoidea, but omission of fossil taxa reveals cryptic molecular support for that group. We describe these results and others from global morphological analysis, extant-only morphological analysis, molecular data-only analyses, combined evidence analysis of extant taxa, and GCA. © The Willi Hennig Society 2010.

6.
J Morphol ; 270(7): 856-79, 2009 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-19206153

RESUMO

The furcula is a structure formed by the midline fusion of the clavicles. This is the element which is unique to theropods and is important for understanding the link between birds and other theropods. New specimens from basal theropods suggest that the furcula appeared very early in theropod history. We review furcula development, function, and morphology, as well as the anatomical terminology applied to it. Furcular morphology is highly variable in crown-group avians but is rather conserved among nonavian theropods. Here we review, or describe for the first time, the furculae in many nonavian theropods. Furculae occur in nearly all major clades of theropods, as shown by new theropod specimens from the Early Cretaceous of China and a close inspection of previously collected specimens. Informative phylogenetic characters pertaining to the furcula occur throughout Theropoda, though care should betake to consider taphonomic effects when describing furcular morphology.


Assuntos
Aves/anatomia & histologia , Clavícula/anatomia & histologia , Dinossauros/anatomia & histologia , Animais , Evolução Biológica , Aves/crescimento & desenvolvimento , Clavícula/crescimento & desenvolvimento , Dinossauros/crescimento & desenvolvimento , Fósseis , Paleontologia , Filogenia
7.
J Morphol ; 267(7): 759-75, 2006 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-15570597

RESUMO

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.


Assuntos
Lagartos/anatomia & histologia , Sistema Musculoesquelético/anatomia & histologia , Animais , Ossos da Extremidade Inferior/anatomia & histologia , Ossos da Extremidade Superior/anatomia & histologia , Vértebras Cervicais/anatomia & histologia , Clavícula/anatomia & histologia , Fêmur/anatomia & histologia , Fíbula/anatomia & histologia , Úmero/anatomia & histologia , Lagartos/classificação , Modelos Anatômicos , Ossos Pélvicos/anatomia & histologia , Rádio (Anatomia)/anatomia & histologia , Sacro/anatomia & histologia , Ossos Sesamoides/anatomia & histologia , Coluna Vertebral/anatomia & histologia , Tíbia/anatomia & histologia , Ulna/anatomia & histologia
8.
Proc Biol Sci ; 271(1546): 1325-30, 2004 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-15306329

RESUMO

Abelisauroid predators have been recorded almost exclusively from South America, India and Madagascar, a distribution thought to document persistent land connections exclusive of Africa. Here, we report fossils from three stratigraphic levels in the Cretaceous of Niger that provide definitive evidence that abelisauroid dinosaurs and their immediate antecedents were also present on Africa. The fossils include an immediate abelisauroid antecedent of Early Cretaceous age (ca. 130-110 Myr ago), early members of the two abelisauroid subgroups (Noasauridae, Abelisauridae) of Mid-Cretaceous age (ca. 110 Myr ago) and a hornless abelisaurid skull of early Late Cretaceous age (ca. 95 Myr ago). Together, these fossils fill in the early history of the abelisauroid radiation and provide key evidence for continued faunal exchange among Gondwanan landmasses until the end of the Early Cretaceous (ca. 100 Myr ago).


Assuntos
Dinossauros/anatomia & histologia , Dinossauros/classificação , Fósseis , Filogenia , Animais , Demografia , Geografia , Fenômenos Geológicos , Geologia , Níger , Crânio/anatomia & histologia , Especificidade da Espécie , Coluna Vertebral/anatomia & histologia
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