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Nuevos Boidae Madtsoiinae en el Cretacico tardio de Patagonia (Formacion Los Alamitos, Rio Negro, Argentina)
... The prezygapophyses of Indeterminate genus and species 2 extend beyond the lateral margin of the synapophyses, a condition shared with selected snakes, particularly 'anilioids' (Rage 1984(Rage , 1998Fachini et al. 2020 The presence of paracotylar foramina is shared between Indeterminate genus and species 2, 'madtsoiids' (e.g. Madtsoia, Adinophis, Alamitophis), Dinilysia, some 'anilioids' including Colombophis, Coniophis, and Constrictores (Simpson 1933;Albino 1986Albino , 1994Albino , 2000Albino , 2011Scanlon 1997Scanlon , 2005Rage and Werner 1999;LaDuke et al. 2010;Mohabey et al. 2011;Longrich et al. 2012b;Vasile et al. 2013;Pritchard et al. 2014;Rio and Mannion 2017;Fachini et al. 2020;Georgalis and Smith 2020). Paracotylar foramina are absent in the basal squamates Najash, Diablophis, Parviraptor, Menarana and some 'anilioids', among others (Rage 1984(Rage , 1998Gómez et al. 2008;Zaher et al. 2009;LaDuke et al. 2010;Caldwell et al. 2015;Head et al. 2022;Smith and Georgalis 2022). ...
... As in Rionegrophis, the specimens described here show vertebral centrum with well-developed and narrow haemal keel, diapophysis wider than parapophysis, and subtriangular-shaped centrum in ventral view (Albino 1986). The same combination of characters is present in the recently described genus Eomadtsoia (Garberoglio et al. 2019), which differs from Rionegrophis by its proportionally lower neural spine and the less laterally extended paradiapophyses (Garberoglio et al. 2019), features largely variable along the vertebral column. ...
... Rionegrophis from Chorrillo Formation Moyano-Paz et al. 2022). However, all Chorrillo specimens differ by being much smaller, by having notably elongate vertebral centra, the haemal keel is much shallower, welldefined subcentral foramina are not present, and in that they show a single paracotylar foramen on each side of the centrum (see Albino 1986). These differences indicate that madtsoiids from Chorrillo Formation belong to a still undescribed Rionegrophis species or that they may pertain to a still unnamed genus. ...
... The Late Cretaceous South American record of madtsoiids is known mostly from isolated vertebrae, and includes a rich diversity of species of different size classes from Patagonia. Taxa considered to be small-sized, i.e., less than 2 meters in estimated length, include Alamitophis argentinus, Alamitophis elongatus, and Patagoniophis parvus (Albino, 1986(Albino, , 1994(Albino, , 2000(Albino, , 2007. Rionegrophis madtsoioides (Albino, 1986(Albino, , 2007, with an estimated length between 2 and 4 meters, represents a mid-sized form, and Eomadtsoia ragei, with an estimated length surpassing 4 meters is considered a large-sized form (Gómez et al., 2019). ...
... Taxa considered to be small-sized, i.e., less than 2 meters in estimated length, include Alamitophis argentinus, Alamitophis elongatus, and Patagoniophis parvus (Albino, 1986(Albino, , 1994(Albino, , 2000(Albino, , 2007. Rionegrophis madtsoioides (Albino, 1986(Albino, , 2007, with an estimated length between 2 and 4 meters, represents a mid-sized form, and Eomadtsoia ragei, with an estimated length surpassing 4 meters is considered a large-sized form (Gómez et al., 2019). In contrast, South American Cenozoic records are less diverse and only represented by the mid-to-large form Madtsoia (Simpson, 1933;Albino, 1993;Albino and Brizuela, 2014;Rage, 1998). ...
... Among Madtsoiidae, small Late Cretaceous and Paleogene taxa such as Adinophis, Alamitophis, Australophis, Patagoniophis, Herensugea, Nanowana, and Nidophis (Albino, 1986(Albino, , 1994(Albino, , 2000(Albino, , 2007Rage, 1996;Scanlon, 1997Scanlon, , 2005Vasile et al., 2013;Pritchard et al., 2014), are markedly smaller, with an estimated body length of less than 2 meters, and most of them have more elongate vertebrae. In contrast, the wide and short, large-sized vertebrae of Powellophis resembles medium-sized taxa such as Rionegrophis, Madtsoia camposi, Menarana nosymena, and Sanajeh (Albino, 1986(Albino, , 2007Rage, 1998;LaDuke et al., 2010;Wilson et al., 2010), which are estimated between 2 and 4 meters in length, and large-sized to gigantic taxa that exceed 4 meters in length such as Gigantophis, Wonambi naracoortensis, Menarana laurasiae, Yurlunggur, Eomadtsoia, Platyspondylophis, and remaining species of Madtsoia (Simpson, 1933;Smith, 1976;Scanlon, 1992;Rage, 1996;Scanlon and Lee, 2000;LaDuke et al., 2010;Mohabey et al., 2011;Rio and Mannion, 2017;Smith et al., 2016;Gómez et al., 2019). ...
The Madtsoiidae are an extinct lineage of snakes known from the Late Cretaceous to the Late Pleistocene, with a rich fossil record distributed mainly across Gondwanan landmasses. However, only a few taxa are represented by cranial or articulated remains, and most madtsoiids are known only by isolated vertebrae. The unambiguous record of Madtsoiidae from the Cenozoic in South America had been restricted to the genus Madtsoia from Eocene and Oligocene deposits of Patagonia and Brazil. Here, we describe a new madtsoiid taxon, Powellophis andina gen. et sp. nov., based on an articulated postcranial skeleton from the Mealla Formation (middle–late Paleocene) in northwestern Argentina. The new taxon is estimated to be around 3 meters long, with a vertebral morphology sharing similar features with other mid-to-large forms. Its inclusion in a recent analysis of madtsoiid relationships recovers Powellophis as an early member of a clade formed by mostly large bodied and gigantic taxa. Its presence in the Paleocene of northwestern Argentina fills the gap between the diverse Late Cretaceous and Eocene–Oligocene records of madtsoiids in South America, confirms their presence in northern Gondwana by the early Paleogene, and expands the diversity of the group.
... Estos sedimentos aflorantes se pueden observar en las siguientes provincias: Neuquén, sur de Mendoza, noroeste de Río Negro y suroeste de La Pampa, con un área total de 120.000 km2 (Digregorio y Uliana, 1979;Legarreta y Uliana, 1999;Howell et al., 2005). Esta cuenca ha sido establecida como de tipo retroarco multiepisódica (Mpodozis y Ramos, 1989), cuya secuencia se encuentra conformada por sedimentos marinos, continentales y de tipo transicional (Casamiquela, 1964;Digregorio y Uliana, 1980;Bonaparte et al., 1984;Albino, 1986;Bonaparte, 1987;Uliana y Biddle, 1988;Barrio, 1990;Powell, 1992;Salgado y Coria, 1996;Salgado y Azpilicueta, 2000;Coria, 2001;de la Fuente et al., 2001;Hugo y Leanza, 2001;Martinelli y Forasiepi, 2004;Coria y Salgado, 2005;Franzese et al. 2007 Arregui et al., 2011;Cingolani et al., 2011;Armas y Sanchez, 2013y Paz et al., 2014. Su basamento se encuentra conformado por rocas metamórficas, ígneas y sedimentarias, cuyas edades van desde el Silúrico-Devónico hasta el Triásico Tardío (Digregorio y Uliana 1980;Franzese et al. 2007;Cingolani et al. 2011y Paz et al., 2014. ...
... Esta formación se encuentra ubicada en la base del Grupo Malargüe, separada del subyacente Grupo Neuquén por una discordancia erosiva (Andreis et al., 1974;Hugo y Leanza, 2001). La misma es portadora de restos fósiles de suma importancia a nivel mundial (Casamiquela, 1964;Bonaparte et al., 1984;Albino, 1986;Bonaparte, 1987;Powell, 1992;Salgado y Coria, 1996;Salgado y Azpilicueta, 2000;Coria, 2001;de la Fuente et al., 2001;Martinelli y Forasiepi, 2004;Coria y Salgado, 2005;Salgado et al., 2007a, b). La edad de la Formación Allen, establecida sobre la base del análisis de ostrácodos (Ballent, 1980), ha sido restringida al Campaniano medio-Maastrichtiano temprano. ...
... Los estratos de esta unidad han brindado una gran diversidad de tetrápodos continentales, con un dominio de los dinosaurios terópodos (Casamiquela, 1964;Bonaparte et al., 1984;Albino, 1986;Bonaparte, 1987;Powell, 1992;Salgado y Coria, 1996;Salgado y Azpilicueta, 2000;Coria, 2001;Fuente et al., 2001;Martinelli y Forasiepi, 2004;Coria y Salgado, 2005;Coria, 2007;Salgado et al., 2007ab;Novas et al., 2009;Salgado et al., 2009;Agnolin et al., 2012). Estos últimos, se encuentran representados por al menos cuatro clados, es decir, Abelisauridae, Alvarezsauridae, Dromaeosauridae y un tetanuro indeterminado (Coria, 2001;Coria y Salgado, 2005;Juárez Valieri et al., 2007;Novas et al., 2009;Salgado et al., 2009;Agnolin et al., 2012;. ...
This Doctoral Thesis presents an exhaustive review of the Patagonian alvarezsaurids (Dinosauria, Theropoda). It includes a detailed osteological description of specimens of Patagonykus puertai (Holotype, MCF-PVPH-37), cf. Patagonykus puertai (MCF-PVPH-38), Patagonykinae indet. (MCF-PVPH-102), Alvarezsaurus calvoi (Holotype, MUCPv-54), Achillesaurus manazzonei (Holotype, MACN-PV-RN 1116), Bonapartenykus ultimus (Holotype, MPCA 1290), and cf. Bonapartenykus ultimus (MPCN-PV 738). A phylogenetic analysis and a discussion about the taxonomic validity of the recognized species and the taxonomic assignment of the materials MCF-PVPH-38, MCF-PVPH-102 and MPCN-PV 738 are presented. Different evolutionary and paleobiological studies were carried out in order to elucidate functional and behavioral aspects.
Alvarezsaurus calvoi (MUCPv-54), Achillesaurus manazzonei (MACN-PV-RN 1116), Patagonykus puertai (MCF-PVPH-37) and Bonapartenykus ultimus (MPCA 1290) are valid species due to the presence of many autapomorphies. In this sense, the hypothesis proposed by P. Makovicky and collaborators that Achillesaurus manazzonei is a junior synonym of Alvarezsaurus calvoi is rejected. Likewise, certain morphological evidence allows hypothesizing that Alvarezsaurus calvoi represents a growth stage earlier than skeletal maturity. Specimen MCF-PVPH-38 is referable as cf. Patagonykus puertai, while MCF-PVPH-102 is considered an indeterminate Patagonykinae. In turn, MPCN-PV 738 is assigned as cf. Bonapartenykus ultimus based on the little overlapping material with the Bonapartenykus ultimus holotype.
The results obtained from the mineralogical characterization through the X-ray diffraction method of specimens MPCN-PV 738 and the holotype of Bonapartenykus ultimus (MPCA 1290), allow to suggest that both specimens come from the same geographical area and stratigraphic level.
The phylogenetic analysis, which is based upon the matrix of Gianechini and collaborators of 2018 with the inclusion of proper characters, and the database of Xu and collaborators of 2018, recovered the South American members of Alvarezsauria, such as Alnashetri cerropoliciensis (Candeleros Formation; Cenomanian), Patagonykus puertai (Portezuelo Formation, Turonian-Coniacian), Alvarezsaurus calvoi and Achillesaurus manazzonei (Bajo de La Carpa Formation, Coniacian-Santonian), and Bonapartenykus ultimus (Allen Formation, Campanian-Maastrichtian), nesting within the family Alvarezsauridae. In this sense, the forms that come from the Bajo de La Carpa Formation (Coniacian-Santonian) are recovered at the base of the Alvarezsauridae clade, while Alnashetri cerropoliciensis nests as a non-Patagonykinae alvarezsaurid. Regarding the type specimens of Patagonykus puertai and Bonapartenykus ultimus, they are recovered as members of the Patagonykinae subclade, a group that is recovered as a sister taxon of Parvicursorinae, both nested within the Alvarezsauridae. In addition, the topology obtained allows discerning the pattern, rhythm and time of evolution of the highly strange and derived alvarezsaurian skeleton, concluding in a gradual evolution. The Bremer and Bootstrap supports of the nodes (Haplocheirus + Aorun), [Bannykus + (Tugulusaurus + Xiyunykus)], and Patagonykinae, show indices that represent very robust values for these nodes. Likewise, these values suggest that two endemic clades originated early in Asia, while one endemic clade is observed in Patagonia, i.e., Patagonykinae.
The analysis of the directional trends of the Alvarezsauria clade, tested by means of a own database on body masses based on the Christiansen and Fariña method, subsequently calibrated with the group's phylogeny using the R software, shows two independent miniaturization events in the alvarezsaurid evolution, namely the former originating from the base of the Alvarezsauridae (sustained by Alvarezsaurus), and the latter within the Parvicursorinae. Analysis of the Alvarezsauria dentition reveals possible dental synapomorphies for the Alvarezsauria clade that should be tested in an integrative phylogenetic analysis. The general characterization of the forelimb and a partial reconstruction of the myology of alvarezsaurs demonstrate different configurations for Patagonykinae and Parvicursorinae. The multivariate analyzes carried out from the databases of Elissamburu and Vizcaíno, plus that of Cau and collaborators, show that the Patagonykinae would have had ranges of movements greater than those observed in Parvicursorinae, although the latter would have had a greater capacity to carry out more strenuous jobs. The morphometric analysis of the hindlimb and the use of the Snively and collaborators equations, show that the configuration of this element in Alvarezsauria is indicative of a highly cursorial lifestyle, as well as possible particular strategies for more efficient locomotion. The topology obtained in the phylogenetic analysis that was carried out in this Doctoral Thesis, allowed clarifying the ontogenetic changes observed in the ontogenetic series of the manual ungueal element II-2 within the clade Alvarezsauridae. In addition, the multivariate analysis carried out from the manual phalanx II-2 allows us to infer that alvarezsaurs could have performed functions such as hook-and-pull and piercing, where the arm would function as a single unit. The anatomy and myology of the alvarezsaurian tail show that the caudal vertebrae of alvarezsaurians exhibit a combination of derived osteological features that suggests functions unique among theropods, such as considerable dorsal and lateral movements, as well as exceptional abilities to support distal loading of their long tail without compromising stability and/or mobility.
... This pseudo-keel is poorly-developed, but distinctive. Comments: Albino (Albino, 1986(Albino, , 1987(Albino, , 1994; see also Martinelli & Forasiepi, 2004) described several serpent taxa based on isolated vertebrae from the Latest Cretaceous (Maastrichtian) Los Alamitos Formation, Rio Negro province. These specimens belong to basal snakes of the "madtsoiid" grade. ...
... In spite of being incomplete, the specimen MPM 21522 shows a combination of characters unique among snakes. Presence of a paracotylar foramen is shared with madtsoiids, Dinilysia, several specimens of Colombophis (Simpson, 1933;Albino, 1986Albino, , 1994Albino, , 2000Rage & Wagner, 1999;Scanlon, 2006), boiids (Albino, 2010), and it is variably present among anilioids (Hsiou et al., 2019). Paracotylar foramina are absent in Najash, Menarana, and most anilioiids (Rage, 1984(Rage, , 1998Gómez et al., 2008;Zaher et al., 2009;La Duke et al., 2010). ...
... Resembling Dinilysia, and the madtsoiids Alamitophis (Albino, 1986;MACN-RN 27,38), Nidophis, Menarana and Madtsoia pisdurensis (La Duke et al., 2010;Mohabey et al., 2011;Vasile et al., 2013), the prezygapophysis of MPM 21522 extends slightly beyond the lateral margin of the synapophysis. In Colombophis and anilioiids (Rage, 1984(Rage, , 1998Hsiou et al., 2010) the prezygapophyses extend much further than the synapophisys, whereas the reverse condition applies for Najash, Adinophis, Gigantophis, Nanowana, Patagoniophis and several Madtsoia species (Scanlon, 1997;Rage, 1998;Zaher et al., 2009;La Duke et al., 2010;Pritchard et al., 2014). ...
The first fossil remains of vertebrates, invertebrates, plants and palynomorphs of the Chorrillo Formation (Austral Basin), about 30km to the SW of the town of El Calafate (Province of Santa Cruz), are described. Fossils include the elasmarian (basal Iguanodontia) Isasicursor santacrucensis gen. et sp. nov., the large titanosaur Nullotitan glaciaris gen. et sp. nov., both large and small Megaraptoridae indet., and fragments of sauropod and theropod eggshells. The list of vertebrates is also composed by the Neognathae Kookne yeutensis gen. et sp. nov., two isolated caudal vertebrae of Mammalia indet., and isolated teeth of a large mosasaur. Remains of fishes, anurans, turtles, and snakes are represented by fragmentary material of low taxonomical value, with the exception of remains belonging to Calyptocephalellidae. On the other hand, a remarkable diversity of terrestrial and freshwater gastropods has been documented, as well as fossil woods and palinological assemblages. The Chorrillo Formation continues south, in the Las Chinas River valley, southern Chile, where it is called Dorotea Formation. Both units share in their lower two thirds abundant materials of titanosaurs, whose remains cease to appear in the upper third, registering only elasmarians (Chorrillo Formation) and hadrosaurs (Dorotea Formation). Above both units there are levels with remains of invertebrates and marine reptiles. It is striking that the dinosaurs of the lower two thirds of the Chorrillo and Dorotea formations are represented by large basal titanosaurs and Megaraptoridae coelurosaurs, being the Saltasaurinae and Aeolosaurinae sauropods and Abelisauridae theropods totally absent. In contrast, these taxa are dominant components in sedimentary units of central and northern Patagonia (e.g., Allen, Los Alamitos, La Colonia formations). Such differences could reflect, in part, a greater antiquity (i.e., late Campanian-early Maastrichtian) for the Chorrillo fossils, or, more probably, different environmental conditions. Thus, knowledge of the biota of the southern tip of Patagonia is expanded, particularly those temporarily close to the K-Pg boundary.
... Madtsoiids are renowned for including some of the largest snakes that have ever crawled on earth; large forms are already present in the Latest Cretaceous of India, Madagascar, and Europe (LaDuke et al., 2010;Mohabey et al., 2011;Wilson et al., 2010), becoming truly gigantic worldwide in the Paleogene (Rage et al., 2014;Rio and Mannion, 2017;Simpson, 1933). Diverse small-tomedium-sized madtsoiids are also known over most of the stratigraphic range of the group (Pritchard et al., 2014;Rage, 1996;Scanlon, 1997Scanlon, , 2006Vasile et al., 2013), which are the only size-class of unambiguous madtsoiids represented to date in the Upper Cretaceous of Patagonia (Albino, 1986(Albino, , 1994(Albino, , 2000(Albino, , 2007Gómez, 2006Gómez, , 2011Báez, 2005, 2006;Martinelli and Forasiepi, 2014). Understanding how and when these disparate body sizes have evolved among madtsoiids has been hampered mainly by the lack of resolution and consensus on their phylogeny (Rio and Mannion, 2017;Vasile et al., 2013), but also by the paucity of madtsoiid taxa in general, and particularly, new taxa showing novel character combinations. ...
... Only a few fragmentary snake vertebrae from middle levels of the La Colonia Formation between El Buitre and Buitre Chico hills have been described so far and were ascribed to the small madtsoiid Alamitophis argentinus,?Madtsoiidae,?Boidae or Madtsoiidae, and a 'Serpentes incertae sedis' (Albino, 2000). Alamitophis argentinus as well as other small-to-mid sized madtsoiids have also been reported based on isolated vertebrae from the Campanian-Maastrichtian Los Alamitos and Allen formations of northern Patagonia (Albino, 1986(Albino, , 1994(Albino, , 2007Gómez, 2006;Báez, 2005, 2006;Martinelli and Forasiepi, 2014). ...
... Eomadtsoia further differs from most other madtsoiids from Patagonia by its markedly larger size. Additionally, it differs from the mid-sized Rionegrophis (Albino, 1986(Albino, , 2007; ROG pers. observ. ...
Madtsoiids constitute a successful group of extinct snakes widely distributed across Gondwana and the European archipelago during Late Cretaceous times, surviving in reduced numbers to the Pleistocene. They are renowned for including some of the largest snakes that have ever crawled on earth, yet diverse small madtsoiids are also known. Uncovering the evolutionary trends that led these snakes into disparate body sizes has been hampered mainly by the lack of phylogenetic consensus and the paucity of taxa with novel combinations of features. Here we describe a new large madtsoiid snake based on isolated vertebrae from the La Colonia Formation (Maastrichtian–Danian) of Patagonia, Argentina. A comprehensive phylogenetic analysis recovers Madtsoiidae as a basal ophidian lineage and the new snake as sister to a clade of mostly big-to-gigantic taxa, providing insights into early stages and evolutionary trends towards madtsoiid gigantism.
... The Late Cretaceous Los Alamitos Formation (Maastrichtian; Franchi and Sepúlveda, 1983;Bonaparte et al., 1984;Andreis, 1987;Franchi et al., 2001) is a well-known stratigraphical unit, mostly because of the abundant vertebrate record (Bonaparte et al., 1984;Bonaparte, 1987Bonaparte, , 2002. These include pipoid and calyptocephalellid anurans, diverse madtsoiid snakes and chelid turtles, meiolaniid tortoises, sphenodontians, sauropod, non-avian theropods and birds, abundant specimens of the hadrosaurid dinosaur Huallasaurus australis, and particularly diverse mammals, including a dozen of species belonging to dryolestoids, including meridiolestidans, gondwanatherians, and taxa of uncertain affinities (Bonaparte et al., 1984;Bonaparte, 1986Bonaparte, , 1987Bonaparte, , 1994Bonaparte, , 2002Báez, 1987;Broin, 1987;Powell, 1987Powell, , 2003Albino, 1987Albino, , 2000Apesteguía, 2005;Agnolin and Martinelli, 2009;Gómez, 2016;Rougier et al., 2021;Rozadilla et al., 2021). ...
... These contain almost all microvertebrates previously reported for this stratigraphical unit (Bonaparte et al., 1984;Bonaparte, 1987) (Fig. 1). The specimens described here were found together with land snails and abundant microvertebrates, including percomorph and lepisosteioid fishes, pipoid and calyptocephalellid anurans, madtsoiid snakes, meiolaniid and chelid chelonians, sauropod, theropod and hadrosaurid teeth, abundant sauropod eggshells, and mammals (see Bonaparte et al., 1984;Bonaparte, 1987;Báez, 1987;Broin, 1987;Powell, 1987;Albino, 1987Albino, , 1994Cione, 1987). ...
... The present report of a madtsoiid snake from the Ladakh Molasse Group is the first evidence that the group persisted across the Eocene-Oligocene boundary in India. The Ladakh snake fossil can be allocated to Madtsoiidae based on the following combination of features (see, e.g., Scanlon, 1992Scanlon, , 2005Albino, 1986;LaDuke et al., 2010): (1) presence of parazygantral foramina located in an elliptical shallow depression on each side of the zygantrum; (2) markedly inclined prezygapophysis (in contrast to Pythonidae); (3) presence of paracotylar foramina; (4) relatively wide diapophyses, slightly exceeding width across prezygapophyses; (5) well-developed hemal keel; and (6) short laterally paired projections on the posterior part of the hemal keel. ...
... This is absent in WIMF/A 4816. The centrum of our specimen has moderate antero-posterior length (10.2 mm), thus it differs from smaller-sized madtsoiids such as Alamitophis, Herensuga, Nanowana, Nidophis, and Patagoniophis from the Late Cretaceous of Patagonia and Europe, and the Paleogene of Australia (Albino, 1986(Albino, , 1994(Albino, , 2007Rage, 1996;Scanlon, 1997Scanlon, , 2005Scanlon and Lee, 2000). ...
We here report on the first madtsoiid snake from the late Oligocene of India (the molasse deposits of Ladakh Himalaya). Madtsoiidae is an extinct group of medium sized to gigantic snakes, members of which were mostly distributed across Gondwana.
... The Allen Formation (middle Campanian−lower Maastrich tian) of Northern Patagonia, Argentina, has yielded a large diversity of continental tetrapods dominated by theropod dinosaurs (Casamiquela 1964;Bonaparte et al. 1984;Albino Dromaeosauridae, and an indeterminate tetanuran (Coria 2001;Coria and Salgado 2005;Valieri et al. 2007;Novas et al. 2009;Salgado et al. 2009;Agnolin et al. 2012;Currie and Carabajal 2012). Abelisauridae from the Río Negro Province are currently known from two taxa namely, Abelisaurus comahuensis based on a partial skull from Cinco Saltos (Bonaparte and Novas 1985), and Quilmesaurus curriei, known from a partial hindlimb discovered in Salitral Ojo de Agua (Coria 2001;Valieri et al. 2007). ...
The discovery of theropod shed teeth associated with sauropod remains is relatively common in Cretaceous deposits of Patagonia. However, only a handful of studies have thoroughly explored the phylogenetic affinities of the theropod dental material. Here, we describe and identify twelve theropod shed teeth associated with a partially complete skeleton of a titanosaur sauropod from the Allen Formation (middle Campanian–lower Maastrichtian; Upper Cretaceous) of Paso Córdoba, Río Negro, Argentina. Using three methods, namely a cladistic analysis performed on a dentition-based data matrix, and a discriminant and cluster analyses conducted on a large dataset of theropod teeth measurements, we identify three dental morphotypes which are confidently referred to abelisaurid theropods. Whether the morphotypes represent different abelisaurid subclades or different positional entities within the jaw of the same abelisaurid species, is unknown. Such an identification, nevertheless, provides additional evidence of abelisaurids feeding on sauropod carcasses. This study highlights the importance of using combined qualitative and quantitative methodologies to identify isolated theropod teeth, especially those that can provide direct information on feeding ecology.
We present the first known fossilized snake embryo/neonate preserved in early Late Cretaceous (Early Cenomanian) amber from Myanmar, which at the time, was an island arc including terranes from Austral Gondwana. This unique and very tiny snake fossil is an articulated postcranial skeleton, which includes posterior precloacal, cloacal, and caudal vertebrae, and details of squamation and body shape; a second specimen preserves a fragment of shed skin interpreted as a snake. Important details of skeletal ontogeny, including the stage at which snake zygosphene-zygantral joints began to form along with the neural arch lamina, are preserved. The vertebrae show similarities to those of fossil Gondwanan snakes, suggesting a dispersal route of Gondwanan faunas to Laurasia. Finally, the new species is the first Mesozoic snake to be found in a forested environment, indicating greater ecological diversity among early snakes than previously thought.
Madtsoiids are among the most basal snakes, with a fossil record dating back to the Upper Cretaceous (Cenomanian). Most representatives went extinct by the end of the Eocene, but some survived in Australia until the Late Cenozoic. Yurlunggur and Wonambi are two of these late forms, and also the best-known madtsoiids to date. A better understanding of the anatomy and palaeoecology of these taxa may shed light on the evolution and extinction of this poorly known group of snakes and on early snake evolution in general. A digital endocast of the inner ear of Yurlunggur was compared to those of 81 species of snakes and lizards with known ecological preferences using three-dimensional geometric morphometrics. The inner ear of Yurlunggur most closely resembles both that of certain semiaquatic snakes and that of some semifossorial snakes. Other cranial and postcranial features of this snake support the semifossorial interpretation. While the digital endocast of the inner ear of Wonambi is too incomplete to be included in a geometric morphometrics study, its preserved morphology is very different from that of Yurlunggur and suggests a more generalist ecology. Osteology, palaeoclimatic data and the palaeobiogeographic distribution of these two snakes are all consistent with these inferred ecological differences.
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