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Molecular phylogenetics unveils the ancient evolutionary origins of the enigmatic fairy armadillos

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Abstract

Fairy armadillos or pichiciegos (Xenarthra, Dasypodidae) are among the most elusive mammals. Due to their subterranean and nocturnal lifestyle, their basic biology and evolutionary history remain virtually unknown. Two distinct species with allopatric distributions are recognized: Chlamyphorus truncatus is restricted to central Argentina, while Calyptophractus retusus occurs in the Gran Chaco of Argentina, Paraguay, and Bolivia. To test their monophyly and resolve their phylogenetic affinities within armadillos, we obtained sequence data from modern and museum specimens for two mitochondrial genes (12S RNA [MT-RNR1] and NADH dehydrogenase 1 [MT-ND1]) and two nuclear exons (breast cancer 1 early onset exon 11 [BRCA1] and von Willebrand factor exon 28 [VWF]). Phylogenetic analyses provided a reference phylogeny and timescale for living xenarthran genera. Our results reveal monophyletic pichiciegos as members of a major armadillo subfamily (Chlamyphorinae). Their strictly fossorial lifestyle probably evolved as a response to the Oligocene aridification that occurred in South America after their divergence from Tolypeutinae around 32 million years ago (Mya). The ancient divergence date (∼17Mya) for separation between the two species supports their taxonomic classification into distinct genera. The synchronicity with Middle Miocene marine incursions along the Paraná river basin suggests a vicariant origin for pichiciegos by the disruption of their ancestral range. Their phylogenetic distinctiveness and rarity in the wild argue in favor of high conservation priority.

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... Armadillos comprise approximately 21 extant species, and recent molecular analysis (Delsuc et al. 2012;) divide them into two families: Dasypodidae with a single extant subfamily (Dasypodinae); and Chlamyphoridae with three extant subfamilies (Chlamyphorinae, Euphractinae and Tolypeutinae; but see below). According to Gaudin and Lyon (2017) this reordering at the family level diversity among cingulates does not adequately reflect the age, morphological disparity, and taxonomic diversity encompassed by cingulates in general, and the Chlamyphoridae in particular (see below). ...
... The inner ear anatomy of extant xenarthrans has recently been examined, showing that it is possible to find correlations with aspects of their locomotion, as well as with their phylogenetic history (Billet et al. 2012(Billet et al. , 2015Coutier et al. 2017). In the case of extant cingulates, Billet et al. (2015) observe that the morphological study of the bony labyrinth shows its morphology is largely congruent with phylogenetic relationships based on molecular analyses (Delsuc et al. 2012;. Studies of the inner ear of extinct xenarthrans are limited and had mostly been carried out in folivorans (Billet et al. 2013;Boscaini et al. 2018) until recently, when Tambusso et al. (2021) described the inner ear anatomy of extinct cingulates (glyptodonts and pampatheres). ...
... The cerebrum presents differences in its shape that largely corresponds to the division into two families of extant armadillos (Delsuc et al. 2012;. In Dasypodidae, the cerebrum has an ovoid shape ( Fig. 18.2a), while in Chlamyphoridae the shape is rather triangular both in dorsal and lateral views . ...
Chapter
Xenarthrans, a largely endemic group originating in South America, constitute one of the four major clades of placental mammals. The order Cingulata is composed of extant and extinct xenarthrans that possess a carapace formed by dermal ossicles, i.e. armadillos, pampatheres and glyptodonts. Towards the end of the nineteenth century the study of natural endocasts showed that the brain of glyptodonts was small relative to their body size, with an unusual external neuroanatomy, particularly due to the large size of the olfactory bulbs and cerebellum, and the lissencephalic neocortex. Recently, CT scans allowed us to increase our knowledge of cingulate paleoneurology, including glyptodonts and pampatheres. These new analyses largely corroborate early observations of the glyptodont brain, and show that the pampathere brain presents differences with both glyptodonts and armadillos. Furthermore, it has allowed to reconstruct their inner ear anatomy. Some functional aspects of cingulate paleobiology has also been inferred from the anatomy of the semicircular canals. These analyses have allowed us to obtain a more complete picture of the paleoneurological evolution in this group of mammals. However, more specimens and new species are still needed to better understand their intraspecific variation, as well as their evolutionary patterns and functional implications.
... In this sense, most hypotheses claim that greatest cladistic events within the group took place at tropical latitudes, including the tribe origin Ciancio et al. 2013). Molecular data suggest an ancient divergence for the Dasypodinae at ca. 40 Ma, being the first group of armadillos in diverge, followed by the Euphractinae at ca. 37 Ma to ca. 34 Ma (Delsuc et al. 2012;Gibb et al. 2016). ...
... In turn, representatives of the tribes Stegotheriini and Dasypodini have been included in several phylogenetic analyses based on morphological evidence, which place them in a separate clade from the rest of the armadillos, suggesting an early divergence between Dasypodidae and Chlamyphoridae (see Engelmann 1985;Gaudin and Wible 2006;Billet et al. 2011;Barasoain et al. 2020). This hypothesis is also in concordance with phylogenetic analysis incorporating molecular data (see Möller-krull et al. 2007;Delsuc et al. 2012;Gibb et al. 2016;Mitchell et al. 2016), which allow to estimate this divergence at ~40 Ma (Delsuc et al. 2012;Gibb et al. 2016). ...
... In turn, representatives of the tribes Stegotheriini and Dasypodini have been included in several phylogenetic analyses based on morphological evidence, which place them in a separate clade from the rest of the armadillos, suggesting an early divergence between Dasypodidae and Chlamyphoridae (see Engelmann 1985;Gaudin and Wible 2006;Billet et al. 2011;Barasoain et al. 2020). This hypothesis is also in concordance with phylogenetic analysis incorporating molecular data (see Möller-krull et al. 2007;Delsuc et al. 2012;Gibb et al. 2016;Mitchell et al. 2016), which allow to estimate this divergence at ~40 Ma (Delsuc et al. 2012;Gibb et al. 2016). ...
Article
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The subfamily Dasypodinae (including Astegotheriini, Stegotheriini and Dasypodini) constitutes the sister group of the remaining diversity of 'armadillos', with an ancient divergence estimated in ca. 40 Ma. (Eocene). Dasypodini represent the only living Dasypodinae, with their oldest records, previous to this contribution, ranging from the middle Miocene (ca. 12 Ma). Here, we describe a new genus and species of armadillo from the middle Miocene deposits of La Victoria Formation (ca. 13 Ma, La Venta, Colombia), which represents the oldest known Dasypodini. Remains include an articulated fragment of the dorsal carapace, and the first described cranium of a Miocene Dasypodini. Despite that most of the characters support its inclusion within Dasypodini, its dorsal carapace shows an unique combination of characters from the clades Dasypodini and Euphractinae, allowing to carry out inferences about the transitional morphological processes that took place between both groups. The cladistics analysis corroborates the basal position of this new taxon within Dasypodini, in concordance with its stratigraphic provenance, and reinforces the idea of a tropical origin of the Dasypodini. Finally, the evolutionary history and palaeobiogeography of Dasypodini and Glyptodontinae (large cingulates) show noticeable parallelism, despite the fact that both represent different lineages with evident different ecological characteristics.
... The phylogeny of extant Dasypodidae shows an early split of the Dasypodinae from the other clades of extant armadillos (Euphractinae, Tolypeutinae and Chlamyphorinae; the three subfamilies are included in Chlamyphoridae sensu Gibb et al., 2016 andMitchell et al., 2016). This early dichotomy is supported by most current phylogenies based on either morphological (Engelmann, 1978(Engelmann, , 1985Abrantes & Bergqvist, 2006;Gaudin & Wible, 2006;Billet et al., 2011;Ciancio et al., 2012) or molecular evidence (Delsuc et al., 2002(Delsuc et al., , 2003(Delsuc et al., , 2004(Delsuc et al., , 2012Möller-Krull et al., 2007;Gibb et al., 2016;Mitchell et al., 2016). Chronologically, the divergence of the Dasypodinae would have occurred in the early Cenozoic (~40 Mya) according to molecular clock estimates (Delsuc et al., 2004(Delsuc et al., , 2012Gibb et al., 2016). ...
... This early dichotomy is supported by most current phylogenies based on either morphological (Engelmann, 1978(Engelmann, , 1985Abrantes & Bergqvist, 2006;Gaudin & Wible, 2006;Billet et al., 2011;Ciancio et al., 2012) or molecular evidence (Delsuc et al., 2002(Delsuc et al., , 2003(Delsuc et al., , 2004(Delsuc et al., , 2012Möller-Krull et al., 2007;Gibb et al., 2016;Mitchell et al., 2016). Chronologically, the divergence of the Dasypodinae would have occurred in the early Cenozoic (~40 Mya) according to molecular clock estimates (Delsuc et al., 2004(Delsuc et al., , 2012Gibb et al., 2016). This inference agrees with the oldest fossil records, which are from the early Eocene . ...
... We applied the 'Trace Character History' command in MESQUITE v.2.5 (Maddison & Maddison, 2011), using a maximum parsimony criterion. The distribution of characters was analysed on a composite phylogenetic hypothesis, based on molecular and morphological data (Gaudin & Wible, 2006;Asher et al., 2009;Billet et al., 2011;Delsuc et al., 2012;Meredith et al., 2013;Castro, 2015;Gibb et al., 2016). The suggested positions of Astegotherium Ameghino, 1902 andUtaetus Ameghino, 1902 were inferred by their taxonomical relationships, based on the proposals of Vizcaíno (1994), Carlini et al. (1997Carlini et al. ( , 2010, Ciancio et al. (2014Ciancio et al. ( , 2019, because they were never included in phylogenetic analyses. ...
Article
Most xenarthrans have a reduced and simplified dentition that lacks enamel. However, the presence of prismatic enamel has been recorded in the Eocene armadillos Utaetus buccatus (Euphractinae) and Astegotherium dichotomus (Astegotheriini). Among extant xenarthrans, the occurrence of enamel has been recognized only in the long-nosed armadillo, Dasypus novemcinctus (Dasypodinae), but its microstructure has never been described. In this contribution, we analyse the enamel microstructure in deciduous and permanent teeth of four Dasypus species. In deciduous molariform teeth of some species, we identify an apical cap of vestigial enamel (without crystalline structure), interpreted as an amorphous ameloblastic secretion. In permanent teeth, a thin layer of true enamel is found in the apical portion of unworn molariforms. The enamel is prismatic in D. novemcinctus, but in Dasypus hybridus, Dasypus sabanicola and Dasypus punctatus it is prismless. Taking into account the Eocene species of armadillos, the ancestral condition of enamel in cingulates could have been more complex (as in other placentals) and undergone progressive reduction, as shown in the Dasypus lineage. In light of previous genetic and developmental studies, we review and briefly discuss the processes that can account for the reduction/loss of enamel in extant and extinct armadillos. The retention of enamel and the fact that this genus is the only living xenarthran with two functional generations of teeth support the early divergence of the Dasypus lineage among living cingulates. This is in agreement with morphological and molecular analyses.
... Both morphological and molecular evidence strongly supports the hypothesis that cingulates experienced a complex evolutionary history (e.g. Gaudin and Wible, 2006;Möller-Krullet al. 2007;Delsuc et al., 2012Delsuc et al., , 2016Gibb et al., 2016;Mitchell et al., 2016;Fernicola et al., 2017), in which the isolation of South America during most part of the Cenozoic had important influence (Cione et al., 2015). As occurred with other mammal lineages, cingulates participated in the Great American Biotic Interchange, reaching Central and North America during the Pliocene and Pleistocene (Carlini and Zurita, 2010). ...
... Recent molecular analysis places Chlamyphorinae as close relatives of Tolypeutinae (see Möller-Krull et al., 2007;Delsuc et al., 2012;Gibb et al., 2016). However, its inclusion within a matrix exclusively based on morphological characters reflects a clear separation between both clades in the obtained trees topology, which is linked to the peculiar anatomy of chlamyphorines, adapted to a "fully" subterranean lifestyle. ...
... with respect to P. proximus and P. exilis: 1) the infraorbital foramen is located in an anterior position, a character shared with the Dasypodidae group (e.g. Propraopus, Dasypus), which is considered the first diverging group of armadillos according to both morphological and molecular information (see Möller-Krull et al., 2007;Delsuc et al., 2012;Gibb et al., 2016); 2) the occipital condyles show a different morphology (located in a more ventral position and with an absence of any lateral condyle indentation), resembling that of basal armadillos such as Peltephilus; and 3) the median palatine suture is flat, without developing a crest, again resembling that of basal armadillos such as Peltephilus. This result has a notable significance, since the new species comes from more modern levels than P. proximus and P. exilis. ...
... Recent reevaluations of the systematic schemes of Cingulata, mainly based on molecular information, have pointed out that the evolutionary history of this clade could be more complex than previously believed (Möller-Krull et al., 2007;Delsuc et al., 2012Delsuc et al., , 2016Gibb et al., 2016;Fernicola et al., 2018). This change of the systematic paradigm clearly affected the relationships between armadillos, showing new phylogenetic hypotheses that contrast with the classic proposals. ...
... Some authors Gibb et al., 2016) suggested an ancient divergence for the armadillos, ∼45 Ma, which separates Dasypodinae from the other three subfamilies. The branching of Euphractinae was estimated at ∼37 Ma and ∼34 Ma (Delsuc et al., 2012), whereas the separation between Chlamyphorinae and Tolypeutinae was estimated at ∼33-32 Ma (Möller-Krull et al., 2007;Delsuc et al., 2012;Gibb et al., 2016). ...
... Some authors Gibb et al., 2016) suggested an ancient divergence for the armadillos, ∼45 Ma, which separates Dasypodinae from the other three subfamilies. The branching of Euphractinae was estimated at ∼37 Ma and ∼34 Ma (Delsuc et al., 2012), whereas the separation between Chlamyphorinae and Tolypeutinae was estimated at ∼33-32 Ma (Möller-Krull et al., 2007;Delsuc et al., 2012;Gibb et al., 2016). ...
Article
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Recent molecular analyses suggest that the evolutionary history of Cingulata (Xenarthra) could be more complex than believed previously. An ancient divergence was proposed for armadillos, recognizing two large monophyletic groups: Dasypodidae (including Dasypodinae) and Chlamyphoridae (including Euphractinae, Tolypeutinae, and Chlamyphorinae). Extant Chlamyphorinae (fairy armadillos) are among the most bizarre, elusive, and unknown mammals of the world. Here, we report the first accurate fossil record of this enigmatic xenarthran from the upper Miocene of the Argentine Pampas in southern South America, which represents a new genus and species (Chlamyphractus dimartinoi, gen. et sp. nov.). The phylogenetic analysis reflects the monophyly of the chlamyphorines. It is well supported by several unambiguous synapomorphies and includes the new fossil taxon as a sister group of the two extant species. This new taxon represents the most basal lineage among Chlamyphorinae and increases its diversity. The morphology of the forelimb suggests that it would have been a good digger, although, unlike extant species, it would not have had ‘fully’ subterranean habits.
... We used the "Trace Character History" command in Mesquite 2.5 (Maddison & Maddison, 2011). The distribution of characters was analyzed considering four different phylogenetic hypotheses, using two topologies obtained from molecular analyses by Delsuc, Superina, Tilak, Douzery, and Hassanin (2012) and Gibb et al. (2016), based on maximum likelihood analysis of data from nuclear and mitochondrial genomes, and two other topologies based on morphological analyses of cranio-dental characters by Gaudin and Wible (2006) and Billet, Hautier, de Muizon, and Valentin (2011), both obtained from parsimony analyses. The topologies of the different cladograms were modified according to the taxa involved in this study; in particular, the Chlamyphorinae were excluded given that the dorsal carapace of these particular armadillos was not studied. ...
... However, they are not enough to solve the phylogenetic relationships between the taxa involved, because of the strong structural homogeneity of the internal osteoderm morphology. This could be reflecting the fact that the diversification of the living Euphractini is recent; according to molecular data, the speciation events involved would have taken place between 6 and 11 Ma (Delsuc et al., 2003;Delsuc et al., 2012;Gibb et al., 2016). On the other hand, the split of the clade Euphractini is estimated to have occurred at around 30 Ma, according to molecular clocks (Delsuc, Vizcaíno, & Douzery, 2004). ...
... According to Wetzel's (1985) and Gardner's (2007) hypotheses, the Tolypeutinae are not a natural group and Tolypeutes is the sister group of the Euphractinae, more derived than Priodontes and Cabassous. Carlini, Vizcaíno, and Scillato-Yané (1997) (Delsuc et al., 2004(Delsuc et al., , 2012Gibb et al., 2016;Moller-Krull et al., 2007). Regarding osteoderm morphology, Priodontes shares more features with Cabassous than with Tolypeutes. ...
Article
Osteoderms are present in a variety of extinct and extant vertebrates, but among mammals, the presence of osteoderms is essentially restricted to armadillos (Cingulata, Dasypodidae). Osteoderms have been proposed to exhibit a variety of functionalities in Dasypodidae, mainly protection and thermoregulation, and they have been considered as one of the synapomorphies of this group. In this study, we use high‐resolution microcomputed tomography to describe the osteoderm micromorphology of several extant species of Dasypodidae in a comparative context. This study allowed the identification, 3D‐reconstruction and volume quantification of different internal structures of osteoderms as well as their interrelations. This detailed characterization of the internal osteoderm morphology was compared in a phylogenetic context to assess the evolutionary trends of the species involved. This enables the identification of distinctive patterns for the most widely recognized clades, the Dasypodinae and Euphractinae with a morphological homogeneity in the microstructure of their osteoderms, in comparison with Tolypeutinae where it has not been possible to establish a common morphological pattern. The most important features for linage differentiation is the degree of compaction of the osteoderms, the number of cavities and the development of hairs. It is likely that the differential development of the various structures occurred as adaptive response to climate changes. Osteoderms are present in a variety of animals, and have been proposed to exhibit a variety of functionalities in Dasypodidae (Mammalia, Xenarthra), mainly protection and thermoregulation. Also, has been considered as one of their most conspicuous synapomorphies of this group. This detailed characterization of the internal morphology of osteoderms enabled the identification of distinctive patterns for the most widely recognized clades.
... The authors listed both "Dasy-poda" and "Cingulata" at the stem leading to the branching of Dasypodidae and Chlamyphoridae on their first cladogram fig. 1) and, likewise, they titled the heading of the armadillo section of the paper, "Armadillos (Cingulata/Dasypoda)" (Gibb et al. 2016:628). Not considered in their study are extinct clades of armored xenarthrans that are believed to fall outside the domain of crown armadillos, such as the Peltephilidae (Gaudin and Wible 2006;Billet et al 2011;Mitchell et al. 2016) and likely other taxa, such as Palaeopeltis Ameghino 1895; Pseudorophodon Hoffstetter, 1958;and species of Machlydotherium Ameghino, 1902, as well as other fossil taxa that are older than the hypothetical origin of crown clade of armadillos (e.g., Itaboraian taxa; Oliveira and Bergqvist 1998); an origin that molecular clock dating suggests as having occurred from about 40 to 45 Ma (Delsuc et al. 2004(Delsuc et al. , 2012Gibb et al. 2016). ...
... The recent advances in studies of the Xenarthra in general include three major points: (1) the New Early Diverging Cingulate (Xenarthra: Peltephilidae) from Bolivia • Shockey "xenarthra" (= Xenarthra sensu lato, crown + stem) represent one of the three major clades of placental mammals; the other two being the Afrotheria and Boreotheria, where Boreotheria ϭ Laurasiatheria + Euarchontaglires; (Murphy et al. 2001;Madsen et al. 2001); (2) the "xenarthra" diverged from Afrotheria and Boreotheria roughly 100 million years ago (Springer et al. 2003;Delsuc et al. 2004;Foley et al. 2016) or, perhaps, even earlier (Nishihara et al. 2009); and (3) Cingulata and Pilosa diverged about 65 million years ago (Figure 2; Delsuc et al. 2004Delsuc et al. , 2012. Thus, it seems that there was a significant (more than 35 million years) "ghost" lineage (sensu Norrell 1992) prior to the evolution of crown clade Xenarthra (Delsuc et al. 2004(Delsuc et al. , 2012. ...
... The recent advances in studies of the Xenarthra in general include three major points: (1) the New Early Diverging Cingulate (Xenarthra: Peltephilidae) from Bolivia • Shockey "xenarthra" (= Xenarthra sensu lato, crown + stem) represent one of the three major clades of placental mammals; the other two being the Afrotheria and Boreotheria, where Boreotheria ϭ Laurasiatheria + Euarchontaglires; (Murphy et al. 2001;Madsen et al. 2001); (2) the "xenarthra" diverged from Afrotheria and Boreotheria roughly 100 million years ago (Springer et al. 2003;Delsuc et al. 2004;Foley et al. 2016) or, perhaps, even earlier (Nishihara et al. 2009); and (3) Cingulata and Pilosa diverged about 65 million years ago (Figure 2; Delsuc et al. 2004Delsuc et al. , 2012. Thus, it seems that there was a significant (more than 35 million years) "ghost" lineage (sensu Norrell 1992) prior to the evolution of crown clade Xenarthra (Delsuc et al. 2004(Delsuc et al. , 2012. ...
Article
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Remains of peltephilid cingulates from the late Oligocene (Deseadan, South American Land Mammal Age) of Salla, Bolivia, are described and organized as two morphs, the larger referred to a new taxon, Ronwolffia pacifica, and the smaller as indeterminate. A fairly well-preserved cranium serves as the holotype for Ronwolffia pacifica, with referred material consisting of jaws, osteoderms, and a partial pelvis. Ronwolffia is recognized by a combination of characters, some of which are regarded as general placental traits compared to some distinctive features of the wellknown Santacrucian species of Peltephilus. Such generalized traits in Ronwolffia include tendencies for eight (rather than seven) mandibular teeth, unfused mandibular symphysis, incompletely ossified auditory bulla, and a low occiput and cranial vault. Like those of other peltephilids, the temporomandibular joint (TMJ) is low, but, unlike typical armadillos and the genotypic Peltephilus strepens, the glenoid fossa forms part of the wall of the external acoustic porus. Similar crowding of the TMJ and porus is noted in Peltephilus pumilus and Peltephilus ferox. Terminology related to the classification of xenarthrans is considered. Dasypodoidea Gray, 1821 is herein used for the crown clade that includes armadillos and glyptodonts, with Cingulata designating the total clade (crown + stem); that is, taxa more closely related to Dasypus than to any pilosan taxon (sloth or anteater). It is also desirable to clearly discriminate between the crown and total clade Xenarthra; thus Xenarthra is herein used exclusively for the crown, with the biogeographically inspired name, Americatheria, being proposed for the total clade; that is, taxa more closely related to Dasypus than to any members of Afrotheria or Boreotheria.
... Xenarthra represents one of the four early diverging natural groups of placental mammals (Meredith et al. 2011); recent molecular studies estimated its time of divergence by the end of the Cretaceous (Meredith et al. 2011;Delsuc et al. 2012Delsuc et al. , 2016Gibb et al. 2016). This group includes the Folivora (terrestrial and arboreal sloths), Vermilingua (anteaters), and Cingulata (extinct and extant armadillos, glyptodonts, pampatheres, and horned peltephilines), and it represents one of the most bizarre clades of all known mammals, with its most distinctive character being the presence of a supplementary intervertebral joint in the vertebrae after the diaphragm (Gaudin 1999), called xenarthrous articulations, from which the group gets its name. ...
... This early diversification also supported by the wide geographical distribution of this fauna (the outcrops of Brazil and Argentina are located more 2000 km from each other, and both are very close to the Tropic of Capricorn), the morphological diversity in the carapace models, and the lateral mobility of the osteoderms. This scheme is in line with the oldest values of the diversification ranges provided by different molecular studies that are positioned between 49.1 and 52.1 (Delsuc et al. 2004(Delsuc et al. , 2012Gibbs et al. 2016). Thus, this new early Eocene cingulate scenario supports a Paleocene (and perhaps even Late Cretaceous) diversification for the Cingulata. ...
Article
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Recently, the basal beds of the lower section of the Lumbrera Formation have been referred to the early Eocene (Ypresian) based on the identification of a succession of hyperthermal events globally dated between 52 and 55 Ma. Nevertheless, this section have also been referred to the middle Eocene (Lutetian) based on the ‘evolutionary stage’ of its fossil mammals. In this contribution, we present a new 238U-206Pb isochron age (46.2 Ma) obtained from samples taken on various independent points across paleosol and matrix positioned at the top of the lower section of the Lumbrera Formation. The new age is consistent with the hyperthermal scheme and constrains the deposition of the lower section of the Lumbrera Fm. between 55–46.2 Ma. In this new geochronological framework, we present one of the most ancient cingulate assemblages from America, recorded during the early Eocene hyperthermal. The specimens involved were recovered from the lowest levels of the lower section of the Lumbrera Formation at Los Cardones National Park, Calchaquí Valleys, Salta Province, Argentina. This cingulate assemblage is formed by the armadillos Pucatherium parvum, a species widely distributed in the Eocene of northwestern Argentina and a new taxon, Noatherium emilioi, gen. et sp. nov. In this new geochronological framework, the taxonomic composition and morphological variations observed in the two species described here and their probably contemporaneous Riostegotherium yanei from the Itaboraí basin (Brazil) support an early diversification of the Cingulata during the Paleocene, and reinforce an intertropical origin for the group.
... Previous studies explored the phylogenetic relationships among Vermilingua using morphological (Engelmann, 1985;Gaudin & Branham, 1998;Hirschfeld, 1976;Patterson et al., 1992) or molecular data in a broader context (Delsuc, Ctzeflis, Stanhope, & Douzery, 2001;Delsuc et al., 2002;Gibb et al., 2016;M€ oller-Krull et al., 2007), and estimated divergence times with molecular data for living anteaters, also in broader contexts (Coimbra, Miranda, Clozato, Schetino, & Santos, 2017;Delsuc, Superina, Tilak, Douzery, & Hassanin, 2012;Delsuc, Vizca ıno, & Douzery, 2004;Delsuc et al., 2018Delsuc et al., , 2019Gibb et al., 2016;Miranda et al., 2018). None of the previous studies combined both kinds of data in a total-evidence analysis of the phylogeny and divergence times of Vermilingua, despite its potential advantages (Ronquist et al., 2012;Wortley & Scotland, 2006). ...
... Those older estimates are probably artefacts resulting from large morphological datasets, in which many unlikely events like convergences would take more time to occur , but this is not the case for the moderate size morphological matrix used in this study. Applying a single node calibration at the root of the tree along with tip-dates returned highly congruent estimates with those observed in previous node-dating analyses for living taxa (Coimbra et al., 2017;Delsuc et al., 2018Delsuc et al., , 2019Delsuc et al., , 2012Delsuc et al., , 2004Gibb et al., 2016;Miranda et al., 2018). This is the first study to estimate divergence times for fossil Vermilingua. ...
Article
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Vermilingua is a peculiar group of xenarthran placental mammals with well-established phylogenetic relationships based on morphological and molecular data, but until now, no combined analysis of those data types. Here we perform the first total-evidence phylogenetic analysis of Vermilingua and estimate divergence times for living and fossil anteaters with a tip-dating approach, using the Fossilized Birth-Death model in a Bayesian framework. Using combined analyses, we recovered as monophyletic the two families, Cyclopedidae and Myrmecophagidae, as in previous studies, although our revised morphological data alone do not support the monophyly of Cyclopedidae. We show how the combination of molecular and morphological data indirectly affects the position and support for fossil taxa even though molecular datasets do not contain direct information for them. The estimated divergence times of Palaeomyrmidon and Protamandua are much older than the ages of those fossils, reinforcing the scarcity of the vermilinguan fossil record. In addition, we obtained evidence that the extinct Neotamandua is an ancestor of the extant Myrmecophaga, not a sister taxon as in previous studies, that did not incorporate the possibility of anagenetic evolution between fossil and living taxa.
... The latter includes eight genera grouped into three subfamilies: Chlamyphorinae (fairy armadillos), Euphractinae (hairy armadillos) and Tolypeutinae (giant, threebanded and naked-tailed armadillos). Delsuc et al. (2012) proposed that the fossorial lifestyle of fairy armadillos probably evolved as a response to the Oligocene aridification that occurred in South America, after their divergence from the Tolypeutinae around 32 million years ago. ...
... The pink fairy armadillo C. truncatus, known also as pichiciego menor or pichiciego pampeano, is the smallest extant armadillo. It is usually considered a strictly subterranean species (Borghi et al. 2011;Delsuc et al. 2012;Torres et al. 2015), but it lacks the extreme anatomical adaptations to a subterranean environment found in, for example, some talpid moles, mole-rats and golden moles. Although it feeds mainly underground, it also consumes above-ground items (Meritt, 1985) and is said to leave its burrows occasionally (Minoprio, 1945;Rood, 1970). ...
Article
The pink fairy armadillo Chlamyphorus truncatus is the smallest extant armadillo and one of the least-known fossorial mammals. The aim of this study was to establish if its middle ear is specially adapted to the subterranean environment, through comparison with more epigeic relatives of the groups Euphractinae (Chaetophractus villosus, Chaetophractus vellerosus, Zaedyus pichiy) and Dasypodinae (Dasypus hybridus). We examined the middle ears using micro-computed tomography and subsequent three-dimensional reconstructions. D. hybridus has a relatively small middle ear cavity, an incomplete bulla and 'ancestral' ossicular morphology. The other species, including Chlamyphorus, have fully ossified bullae and middle ear ossicles, with a morphology between 'transitional' and 'freely mobile', but in all armadillos the malleus retains a long anterior process. Unusual features of armadillo ears include the lack of a pedicellate lenticular apophysis and the presence, in some species, of an element of Paaw within the stapedius muscle. In common with many subterranean mammals, Chlamyphorus has a relatively flattened malleo-incudal articulation and appears to lack a functional tensor tympani muscle. Its middle ear cavity is not unusually enlarged, and its middle ear ossicles seem less robust than those of the other armadillos studied. In comparison with the euphractines, there is no reason to believe that the middle ear of this species is specially adapted to the subterranean environment; some aspects may even be indicative of degeneration. The screaming hairy armadillo, Chaetophractus vellerosus, has the most voluminous middle ear in both relative and absolute terms. Its hypertrophied middle ear cavity likely represents an adaptation to low-frequency hearing in arid rather than subterranean conditions.
... Miocene marine introgressions have been suggested as probable drivers of diversification of some vertebrate groups in southern South America, like some mammals and reptiles (Candela et al., 2012;Delsuc et al., 2012;Morando et al., 2014). At least three extensive marine introgressions have been recorded for this region (Ottone et al., 2013). ...
... Based on fossil faunas, Candela et al. (2012) suggested that the Paranense Sea acted as an important geographic barrier promoting vicariance between Mesopotamic and northwestern Patagonic faunas. Delsuc et al. (2012) dated the divergence between the two species of fairy armadillos (pichiciegos) at about 17 Ma and suggested that the diversification was promoted by the disruption of the ancestral range, isolating populations to the south and north of the current Chaco. Finally, Morando et al. (2014) suggested that the three species groups of the gecko genus Homonota split by isolation of populations on emergent lands that surrounded the Paranense Sea. ...
Article
The Chaco is one the most neglected and least studied regions of the world. This highly-seasonal semiarid biome is an extensive continuous plain without any geographic barrier, and in spite of its high species diversity, the events and processes responsible have never been assessed. Miocene marine introgressions and Pleistocene glaciations have been mentioned as putative drivers of diversification for some groups of vertebrates in adjacent biomes of southern South America. Here we used multilocus data (one mitochondrial and six nuclear loci) from the three species of the endemic frog genus Lepidobatrachus (Lepidobatrachus asper, Lepidobatrachus laevis, and Lepidobatrachus llanensis) to determine if any of the historical events suggested as drivers of vertebrate diversification in southern South America are related to the diversification of the genus and if the Chaco is indeed a biome without barriers. Using fossil calibration in a coalescent framework we estimated that the genus diversified in the second half of the Miocene, coinciding with marine introgressions. Genetic patterns and historical demography suggest an important role of old archs and cratons as refuges during floods. In one species of the genus, L. llanensis, genetic structure reveals some breaks along the landscape, the main one of which corresponds to an area of the central Chaco that may act as a climatic barrier. Additionally, we found differential effects of the main Chacoan rivers on species of Lepidobatrachus that could be related to the time of persistence of populations in the areas influenced by these rivers.
... Polyembryony is unique to the genus Dasypus. Current classifications [29] supported by molecular phylogenies [30], classify armadillos in three subfamilies with the most recent analysis suggesting a fourth [31]. Obligate polyembryony is confined to Dasypodinae with evidence from 5 species [4]. ...
... In Tolypeutinae, reports on Cabassous chacoensis (Chacoan Naked-tailed Armadillo) [4,28], C. unicinctus (Southern Naked-tailed Armadillo) [33] and Tolypeutes matacus (Southern Three-banded Armadillo) [28] all suggest singletons are the norm. Recently, Chlamyphorinae was erected for the two species of fairy armadillo [31]. Very little is known of their reproduction, but Calyptophractus retusus (Greater Fairy Armadillo) is thought to bear a single young [34]. ...
Article
Background Miguel Fernández was an Argentinian zoologist who published the first account of obligate polyembryony in armadillos. His contribution is here discussed in relation to his contemporaries, Newman and Patterson, and more recent work. Findings Fernandez worked on the mulita (Dasypus hybridus). He was able to get early stages before twinning occurred and show it was preceded by inversion of the germ layers. By the primitive streak stage there were separate embryonic shields and partition of the amnion. There was, however, a single exocoelom and all embryos were enclosed in a common set of membranes comprising chorion towards the attachment site in the uterine fundus and inverted yolk sac on the opposite face. He showed that monozygotic twinning did not occur in another armadillo, the peludo (Chaetophractus villosus). Conclusions Fernández's work represented a major breakthrough in understanding how twinning occurred in armadillos. His work and that of others is of intrinsic interest to zoologists and has a direct bearing on the origin of monozygotic twins and birth defects in humans.
... Systematics partially follow the proposals of McKenna and Bell (1997), Gardner (2005), Delsuc et al. (2004Delsuc et al. ( , 2012, and Barasoain et al. (2021). Morphological descriptions of the distinct osteoderms ( Fig. 2) follow the terminology adopted by Scillato-Yané (1982), Carlini et al. (2014), and Barasoain et al. (2021). ...
Article
The deposits of the Neogene Salicas Formation crop out along the north area and western flanks of the Velasco range, in the northern area of La Rioja Province, Argentina. Previous known remains from the formation include Notoungulata, Litopterna, and Rodentia, in addition to several Xenarthra, including Pilosa (sloths) and Cingulata Glyptodontidae and Dasypodidae. In this contribution, new remains recovered from the Salicas Formation at the area of El Degolladito are described and referred to distinct species of Dasypodidae: Vetelia ghandii Esteban and Nasif 1996, Chasicotatus peiranoi Esteban and Nasif 1996, Chorobates villosissimus (Reig, 1958), Macrochorobates scalabrinii (Moreno and Mercerat, 1891), Paleuphractus argentinus (Moreno and Mercerat, 1891), and Prozaedyus sp. This association of dasypodids increases their diversity for this formation and suggests a Late Miocene age for the bearing levels. Additionally, this association shows great affinities with those reported for other Late Miocene localities along northwestern Argentina, including several species that represent endemic taxa not shared with the Pampean Region. In this context, the differences of Dasypodidae taxa between these regions may be related to both orogenic and paleoambiental features.
... The macrotaxonomy follows McKenna and Bell (1997), Möller-Krull et al. (2007) Delsuc et al. (2012Delsuc et al. ( , 2016, Mitchell et al. (2016), Gibb et al. (2016), and Barasoain et al. (2021a, b), and the anatomical nomenclature of cingulates osteoderms and carapace follows Carlini et al. (2010), Porpino et al. (2014), Krmpotic et al. (2015), González Ruiz et al. (2017) and Barasoain et al. (2021a, b). The open taxonomy follows Bengtson (1988). ...
Article
Cingulates (“armadillos and glyptodonts”), is a group of xenarthran mammals characterized mainly by the presence of an armor of articulated osteoderms which are usually used for systematic recognition, and which are found in most fossiliferous localities of South, Central and southern North America since the Eocene. The aim of this contribution is to describe the cingulates (“armadillos and glyptodonts”) from Roth's collection that have been previously mentioned, which have been remain unpublished for more than 100 years, and are part of the collection that was used for the recognition of the formerly “Etage Friaséen” of the Miocene of South America. The cingulate osteoderms described herein are assigned to 1) Vetelia puncta (MLP 16–171, MLP 16–172, MLP 16–174) given the osteoderms's foramina in the sulcus that delimits the longitudinal central figure, and at the lateral margins of the osteoderm; 2) Proeutatus cf. deleo (MLP 16–171, MLP 16–172, MLP 16–174) given that the osteoderms have no evident keel, and no foramina on the exposed surface; and 3) Eucinepeltus cf. petesatus (MLP 16–171, MLP 16–172, MLP 16–173) given that the osteoderms of the cephalic shield have no figures on the exposed surface. After the revision of the Roth collection and the literature, the association of cingulates from all fossil localities and fossil levels of Río Cisnes Formation at Alto Río Cisnes (Chile) includes the armadillos Peltephilidae (a potential new taxon), Stegotherium caroloameghinoi, Prozaedyus sp., Vetelia puncta, Proeutatus cf. deleo, Proeutatus sp., and the glyptodonts Propalaehoplophorinae gen. et sp. indet., and Eucinepeltus cf. petesatus.
... maximus) e os tatus-de-rabo-mole (gênero Cabassous) pertencem ao mesmo grupo, Priodontini (Engelman, 1985;Wetzel, 1985). O grupo Chlamyphorini contém duas espécies atribuídas a dois gêneros de distribuição alopátrica, Chlamyphorus e Calyptophractus (Delsuc et al., 2012). ...
Article
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Xenarthra contém duas ordens, seis famílias, 14 gêneros e 38 espécies viventes. A ordem Cingulata (tatus) representa 22 das espécies de xenartros e seis destas são encontradas no Pantanal (Dasypus novemcinctus, Cabassous tatouay, C. squamicaudis, Tolypeutes matacus, Euphractus sexcinctus e Priodontes maximus). Os tatus se diferem de outros mamíferos por terem uma carapaça formada por placas ósseas articuladas que, como um escudo, cobrem a cabeça e o dorso. Neste artigo, baseamo-nos em extensa revisão bibliográfica e décadas de trabalho realizado pelos autores para descrever o estado do conhecimento sobre ecologia, biologia, características morfológicas, saúde, estado de conservação e distribuição dos tatus no Pantanal. Visando dar subsídios a futuros trabalhos com as espécies, também descrevemos melhores práticas para a captura e o manejo (e.g., anestesia e coleta de material biológico) das espécies em campo. Apesar do recente aumento do número de estudos, ainda restam diversas lacunas de informação sobre a ecologia e a biologia da maioria das espécies de tatus do Pantanal. Sendo assim, esperamos que as informações e os métodos descritos aqui sirvam de estímulo e base para o desenvolvimento de novos estudos, que aumentem nosso conhecimento sobre estas espécies na região do Pantanal e permitam o planejamento de estratégias de conservação eficientes.
... The evolutionary history of xenarthrans was notably influenced by the "splendid isolation" of South America during most of the Cenozoic (Simpson 1980;Cione et al. 2015). Xenarthra includes two large orders, which are very different both morphologically and ecologically: Pilosa, including Folivora (sloths) and Vermilingua (anteaters), and Cingulata, the so-called "armored" xenarthrans (Delsuc et al. 2004(Delsuc et al. , 2012Gaudin and Croft 2015). ...
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Glyptodonts (Xenarthra, Cingulata) are one of the most amazing Cenozoic South American mammals, with some terminal forms reaching ca. two tons. The Paleogene record of glyptodonts is still poorly known, although some of their diversification is observable in Patagonian Argentina. Since the early and middle Miocene (ca. 19-13 Ma), two large clades can be recognized in South America. One probably has a northern origin (Glyptodontinae), while the other one, called the "austral clade", is interpreted to have had an austral origin, with the oldest records represented by the "Propalaehoplophorinae" from the late early Miocene of Patagonian Argentina. In this scenario, the extra-Patagonian radiations are still poorly known, despite their importance for understanding the late Miocene and Pliocene diversity. Here, we carry out a comprehensive revision of late Miocene (Chasicoan Stage/Age) glyptodonts of central Argentina (Buenos Aires and San Juan provinces). Our results show that, contrary to what is traditionally assumed, it was a period of very low diversity, with only one species recognized in this region, Kelenkura castroi gen et sp. nov. Our phylogenetic analysis shows that this species represents the sister taxon of the remaining species of the "austral clade", representing the first branch of the extra-Patagonian radiation. Additionally, K. castroi is the first taxon showing a "fully modern" morphology of the caudal tube.
... The evolutionary history of xenarthrans was notably influenced by the "splendid isolation" of South America during most of the Cenozoic (Simpson 1980;Cione et al. 2015). Xenarthra includes two large orders, which are very different both morphologically and ecologically: Pilosa, including Folivora (sloths) and Vermilingua (anteaters), and Cingulata, the so-called "armored" xenarthrans (Delsuc et al. 2004(Delsuc et al. , 2012Gaudin and Croft 2015). ...
Article
Full-text available
Glyptodonts (Xenarthra, Cingulata) are one of the most amazing Cenozoic South American mammals, with some terminal forms reaching ca. two tons. The Paleogene record of glyptodonts is still poorly known, although some of their diversification is observable in Patagonian Argentina. Since the early and middle Miocene (ca. 19–13 Ma), two large clades can be recognized in South America. One probably has a northern origin (Glyptodontinae), while the other one, called the “austral clade”, is interpreted to have had an austral origin, with the oldest records represented by the “Propalaehoplophorinae” from the late early Miocene of Patagonian Argentina. In this scenario, the extra-Patagonian radiations are still poorly known, despite their importance for understanding the late Miocene and Pliocene diversity. Here, we carry out a comprehensive revision of late Miocene (Chasicoan Stage/Age) glyptodonts of central Argentina (Buenos Aires and San Juan provinces). Our results show that, contrary to what is traditionally assumed, it was a period of very low diversity, with only one species recognized in this region, Kelenkura castroi gen et sp. nov. Our phylogenetic analysis shows that this species represents the sister taxon of the remaining species of the “austral clade”, representing the first branch of the extra-Patagonian radiation. Additionally, K. castroi is the first taxon showing a “fully modern” morphology of the caudal tube.
... The latter are gathered in a large clade that is, in turn, divided in two welldifferentiated clades, one formed by Dasypodidae (Dasypus + Stegotherium) and another by Chlamyphoridae (all the remaining taxa). This main division agrees with the latest phylogenetic analyses based on molecular data of extant armadillos (e.g., Delsuc et al. 2002Delsuc et al. , 2012MöllerKrull et al. 2007). ...
Article
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Vetelia is a Miocene genus of armadillos from Argentina and Chile, traditionally included within the subfamily Euphractinae (Chlamyphoridae, Cingulata, Xenarthra). It includes the species Vetelia puncta (early–middle Miocene), Vetelia perforata (middle–late Miocene), and Vetelia gandhii (late Miocene), mostly known by isolated osteoderms. In this contribution, we provide the first description of the skull for this genus, based on new materials (PVSJ 289 and PVSJ-154) here assigned to V. gandhii. A detailed characterization allows us to amend the diagnosis of the three known species, and to include, for the first time, the genus Vetelia into a morphological phylogenetic analysis. Phylogenetic results reveal a closer affinity to the Tolypeutinae, including the extant genera Priodontes (giant armadillos), Cabassous (naked-tailed armadillos), and Tolypeutes (three banded armadillos), and the fossil genera Pedrolypeutes and Kuntinaru, than to the Euphractinae. More specifically, Vetelia is included within the Priodontini, as sister group of the clade composed by Cabassous + Priodontes. Taking into account the scarce record of fossil Tolypeutinae, this new proposal fills an important temporal gap in the evolutionary history of this linage. Finally, we also provide new information on the diagnostic morphological characters of the Priodontini and Tolypeutini.
... The sea occupied most areas of northern Argentina and Uruguay [59], and could have isolated the genetically divergent Paraguayan population of T. trivitattus. The same mechanism has been postulated for frogs in the genus Lepidobatrachus, armadillos in the genus Calyptophractus, and geckos in the genus Homonota [60][61][62]. Given the divergence date estimates, genetically differentiated Tityus populations could have originated by vicariance as Miocene marine incursions along the Paraná river basin fragmented their ancestral range. ...
Article
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Envenoming by scorpions in genus Tityus is a public health problem in Tropical America. One of the most medically significant species is Tityus trivittatus, which is known to occur from southwest Brazil to central-northern and eastern Argentina. In this work, we studied the lethality, composition, antigenicity, and enzymatic activity of venom from a T. trivittatus population found further north in urban areas of eastern Paraguay, where it has caused serious envenomation of children. Our results indicate that the population is of medical importance as it produces a potently toxic venom with an LD 50 around 1.19 mg/kg. Venom neutralization in preliminary mouse bioassays was complete when using Brazilian anti-T. serrulatus antivenom but only partial when using Argentinean anti-T. trivittatus antivenom. Venom competitive solid-phase enzyme immunoassays and immunoblotting from Argentin-ean and Paraguayan T. trivittatus populations indicated that antigenic differences exist across the species range. SDS-PAGE showed variations in type and relative amounts of venom proteins between T. trivitattus samples from Argentina and Paraguay. MALDI-TOF mass spectrometry indicated that while some sodium channel toxins are shared, including β-toxin Tt1g, others are population-specific. Proteolytic activity by zymography and peptide identification through nESI-MS/MS also point out that population-specific proteases may exist in T. trivitattus, which are postulated to be involved in the envenoming process. A time-calibrated molecular phylogeny of mitochondrial COI sequences revealed a significant (8.14%) genetic differentiation between the Argentinean and Paraguayan populations, which appeared to have diverged between the mid Miocene and early Pliocene. Altogether, toxinological and genetic evidence indicate that T. trivitattus populations from Paraguay and PLOS NEGLECTED TROPICAL DISEASES PLOS Neglected Tropical Diseases | https://doi.org/10.1371/journal.pntd.) to AB (https:// www.conacyt.gov.py/), and the Fondo para la Convergencia Estructural del MERCOSUR (FOCEM/ MERCOSUR COF N˚03/11, travel funding to AB) Argentina correspond to distinct, unique cryptic species, and suggest that further venom and taxonomic diversity exists in synanthropic southern South American Tityus than previously thought. Author summary Scorpionism (the medical consequence of scorpion stings in humans) is a neglected health problem in tropical and subtropical areas associated with poverty. This study is the first to compare venoms among core (Argentinean) and peripheral (Paraguayan) populations of the noxious Tityus trivittatus, the most medically important scorpion in the southernmost section of South America. The work demonstrated the lethality of the venom of urban populations of T. trivittatus in Paraguay, where it has caused severe cases in children. We obtained data indicating that there are significant differences in venom composition and function, and also recognition by therapeutic antivenoms available in the region, among these Argentinean and Paraguayan scorpion populations which historically have been assigned to the same species. Our genetic study revealed that in fact these two populations diverged between~15-5 Million years ago, indicating they are distinct species. These results indicate that southern South American scorpions in the genus Tityus which co-distribute with humans are more diverse in terms of their venoms and species composition than previously thought, and that further studies are warranted to design more effective therapeutic tools against scorpionism in the region to tackle such diversity.
... Armadillos comprise approximately 21 extant species, with recent molecular analysis (Delsuc et al., 2012;Gibb et al., 2016) dividing the clade into two families: Dasypodidae, with a single extant subfamily (Dasypodinae), and Chlamyphoridae, with three subfamilies (Chlamyphorinae, Euphractinae, and Tolypeutinae). Morphological phylogenetic analyses have considered armadillos a paraphyletic group and suggested a close relationship between glyptodonts and the armadillo subfamily Euphractinae (Billet et al., 2011;Gaudin and Wible, 2006). ...
Article
In recent years, the increase in studies on the inner ear anatomy of xenarthrans provided new insights regarding some locomotor and phylogenetic aspects. These works have begun to include fossil specimens, although so far, only two extinct representatives of the suborder Folivora (ground sloths) have been analyzed. In the present study, we present the first reconstruction and description of the bony labyrinth of five extinct specimens of the suborder Cingulata, the glyptodonts Glyptodon, Doedicurus, Panochthus, and Pseudoplohophorus, as well as the pampathere Holmesina, in order to analyze their morphology and evaluate functional and phylogenetic aspects. The anatomical and morphometric comparison shows that the inner ear of glyptodonts is largely similar to that of modern armadillos, particularly sharing many characteristics with Chlamyphorus. While the inner ear of Holmesina is similar to that of glyptodonts, it presents some characteristics that make it more similar to extant armadillos. Regarding some functional aspects inferred from the anatomy of the semicircular canals, glyptodonts would have had low levels of agility, although similar to most extant armadillos, and low head angular velocity. On the other hand, Holmesina would have had an agility level similar to that of the giant armadillo Priodontes, although it would also present low head angular velocity as seen in most extant armadillos. Finally, preliminary parsimony and Bayesian phylogenetic inference analyses based on a reduced set of inner ear characters showed interesting results, with glyptodonts and Holmesina recovered as closely related to Chlamyphorus. These results closely resemble the recent topologies obtained using ancient DNA and markedly contrast with the topologies obtained using more traditional morphological characters, highlighting the importance of inner ear data for the inference of phylogenetic relationships in cases where DNA preservation in fossil taxa is unaccessible.
... Roig et al. (2009) reviewed the biogeography of Argentina and concluded that the Monte and population structures of many central and northern Argentinian animal species (e.g. Delsuc et al., 2012;Morando et al., 2014;Brusquetti et al., 2019). From the middle Miocene to the present in Argentina, rainshadow aridity has increased owing to the rise of the Andes over the last 15 Myr, with accelerated uplift in the central Andes ~5 Mya (Farías et al., 2008;Folguera et al., 2011). ...
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Phylogenetic asymmetry is common throughout the tree of life and results from contrasting patterns of speciation and extinction in the paired descendant lineages of ancestral nodes. On the depauperate side of a node, we find extant ‘relict’ taxa that sit atop long, unbranched lineages. Here, we show that a tiny, pale green, inconspicuous and poorly known cicada in the genus Derotettix, endemic to degraded salt-plain habitats in arid regions of central Argentina, is a relict lineage that is sister to all other modern cicadas. Nuclear and mitochondrial phylogenies of cicadas inferred from probe-based genomic hybrid capture data of both target and non-target loci and a morphological cladogram support this hypothesis. We strengthen this conclusion with genomic data from one of the cicada nutritional bacterial endosymbionts, Sulcia, an ancient and obligate endosymbiont of the larger plant-sucking bugs (Auchenorrhyncha) and an important source of maternally inherited phylogenetic data. We establish Derotettiginae subfam. nov. as a new, monogeneric, fifth cicada subfamily, and compile existing and new data on the distribution, ecology and diet of Derotettix. Our consideration of the palaeoenvironmental literature and host-plant phylogenetics allows us to predict what might have led to the relict status of Derotettix over 100 Myr of habitat change in South America.
... Despite the fact that Xenarthra is currently the least diverse large clade within Eutheria (Abba et al. 2012;Gibb et al. 2015), it had remarkable taxonomic and ecological diversity for most of the Cenozoic Era (Delsuc et al. 2004;Vizca ıno 2009;Vizca ıno et al. 2012a). This diversity includes two main clades, Cingulata and Pilosa (the latter with two sub-clades, Tardigrada and Vermilingua), whose evolution was linked to the heterogeneous topography, wide latitudinal distribution and many paleoenvironmental changes recorded in South America during this interval (Delsuc et al. 2004(Delsuc et al. , 2012Gaudin & Croft 2015). ...
Article
Xenarthrans constitute a relict clade of endemic South American placental mammals with a long evolutionary history starting, at least, in the early Eocene. Within Xenarthra, Glyptodontidae (late Eocene–earliest Holocene) was a conspicuous group of large-sized armoured herbivores. During the Pleistocene (ca. 2.6–0.001 Ma) several genera (e.g. Panochthus and Glyptodon) achieved a remarkable latitudinal distribution in South America, as members of one of the xenarthran groups that participated in the Great American Biotic Interchange. Knowledge of the evolutionary history of this clade in some areas remains poorly known, especially in the high elevation Andean and sub-Andean regions of South America. Here we describe a new species, Glyptodon jatunkhirkhi sp. nov., from several localities of the Eastern Cordillera in Bolivia (ca. 2500–4100 m above sea level). From a phylogenetic viewpoint this new taxon appears as the sister group of the two lowland species recorded in southern South America (Glyptodon munizi + G. reticulatus), and this is congruent with the morphological differences observed between both clades, mainly with respect to the general morphology of the dorsal carapace and the skull. This new species expands the complex biogeographical scenario for Pleistocene glyptodonts and highlights the importance of Andean areas as key in understanding the evolutionary history of this clade. According to this revision, the diversity of Glyptodon is limited to G. munizi and G. reticulatus (two chronologically successive lowland species) plus this new species. The genera Panochthus (P. hipsilis) and Glyptodon seem to be the only Pleistocene glyptodonts to have been adapted to high elevation environments. http://zoobank.org/urn:lsid:zoobank.org:pub:7B5EFC11-626A-4BB5-8A00-DF657741698C
... In this regard, previous studies have proposed that Miocene marine incursions would have promoted lineage divergence in some plant genera, such as Jaborosa (Moré et al., 2015) and Nierembergia (Acosta et al., 2016), and in animal species, such as geckos (Homonota, Morando et al., 2014) and frogs (Lepidobatrachus, Brusquetti et al., 2018). Moreover, a similar disjunct distribution as observed in P. chilensis was registered in fairy armadillos, proposing a vicariant origin due to the disruption of their ancestral range by the Paranean Ssea (Delsuc et al., 2012). Finally, the highly divergent lineage retrieved with the nuclear marker in P. chilensis, exclusively distributed in the limit between the Bolivian Chaco and the Chiquitania, supports the idea that the Bolivian Chaco would have been a fragmented ancestral area. ...
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The intraspecific evolutionary history of South American xerophytic plant species has been poorly explored. The tree species Prosopis chilensis has a disjunct distribution in four South American regions: southern Peru, southern Bolivia, central-western Argentina and central Chile. Here, we combined phylogeographical (based on chloroplast and nuclear markers), morphological and climatic data to evaluate the relative contribution of historical demo-stochastic and adaptive processes in differentiating the disjunct areas of distribution. The results obtained with the two molecular markers revealed two closely related phylogroups (Northern and Southern, predominating in Bolivian Chaco and in Argentine Chaco/Monte, respectively), which would have diverged at ~5 Mya, probably associated with transgression of the Paranaense Sea. Bolivia and Argentina have a larger number of exclusive haplotypes/ alleles and higher molecular diversity than Chile, suggesting a long-lasting in situ persistence in the former and a relatively recent colonization in the latter, from the Bolivian and Argentinian lineages. The two main lineages differ in morphology and climatic niche, revealing two significant, independent evolutionary units within P. chilensis promoted by local adaptation and geographical isolation. ADDITIONAL KEYWORDS: Chaco-Chilean Matorral-climatic centroid-dry forests-ecological niche modelling-Monte-leaf morphology-Miocene marine transgression-phylogeography-Pleistocene refugia.
... In this regard, previous studies have proposed that Miocene marine incursions would have promoted lineage divergence in some plant genera, such as Jaborosa (Moré et al., 2015) and Nierembergia (Acosta et al., 2016), and in animal species, such as geckos (Homonota, Morando et al., 2014) and frogs (Lepidobatrachus, Brusquetti et al., 2018). Moreover, a similar disjunct distribution as observed in P. chilensis was registered in fairy armadillos, proposing a vicariant origin due to the disruption of their ancestral range by the Paranean Ssea (Delsuc et al., 2012). Finally, the highly divergent lineage retrieved with the nuclear marker in P. chilensis, exclusively distributed in the limit between the Bolivian Chaco and the Chiquitania, supports the idea that the Bolivian Chaco would have been a fragmented ancestral area. ...
Article
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The intraspecific evolutionary history of South American xerophytic plant species has been poorly explored. The tree species Prosopis chilensis has a disjunct distribution in four South American regions: southern Peru, southern Bolivia, central-western Argentina and central Chile. Here, we combined phylogeographical (based on chloroplast and nuclear markers), morphological and climatic data to evaluate the relative contribution of historical demo-stochastic and adaptive processes in differentiating the disjunct areas of distribution. The results obtained with the two molecular markers revealed two closely related phylogroups (Northern and Southern, predominating in Bolivian Chaco and in Argentine Chaco/Monte, respectively), which would have diverged at ~5 Mya, probably associated with transgression of the Paranaense Sea. Bolivia and Argentina have a larger number of exclusive haplotypes/ alleles and higher molecular diversity than Chile, suggesting a long-lasting in situ persistence in the former and a relatively recent colonization in the latter, from the Bolivian and Argentinian lineages. The two main lineages differ in morphology and climatic niche, revealing two significant, independent evolutionary units within P. chilensis promoted by local adaptation and geographical isolation. ADDITIONAL KEYWORDS: Chaco-Chilean Matorral-climatic centroid-dry forests-ecological niche modelling-Monte-leaf morphology-Miocene marine transgression-phylogeography-Pleistocene refugia.
... Calyptophractus -Recientes análisis filogenéticos por Delsuc et al. (2012) sugieren que las dos especies de pichiciegos, Chlamyphorus truncatus y Ch. retusus, pertenecen a géneros distintos, posición que aceptamos en esta revisión. Por tanto, la especie Chlamyphorus retusus listada en Salazar-Bravo et al. (2019) manteienen a los perezosos de dos dedos dentro de la familia Megalonichidae y esta es la clasificación que mantenemos en esta lista. ...
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Resumen Presentamos la actualización más completa, a la fecha, de la lista de mamíferos de Bolivia. Incorporamos y describimos cambios taxonómicos recientes y nuevos registros para el país efectuados desde la última lista publicada en 2003. Para la elaboración de la lista se revisaron publicaciones científicas recientes y se consideró que las nuevas adiciones y los cambios taxonómicos incluidos cuenten con algún tipo de evidencia verificable. A la fecha la lista de mamíferos para Bolivia incluye 406 especies nativas, pertenecientes a 11 órdenes, 46 familias y 196 géneros, lo que representa un incremento de 51 especies con respecto a la lista de 2003. Entre aquellas adicionadas, 14 fueron nuevas para la ciencia y tienen localidad tipo en Bolivia. Los órdenes más diversos fueron Rodentia (148 especies), Chiroptera (138), Didelphimorphia (35) y Carnivora (27); un total de 25 especies son endémicas para Bolivia. Se listan además 14 especies de mamíferos introducidos. Se prevé que se adicionen nuevos registros y cambios taxonómicos a esta lista como resultado de inventarios biológicos actualmente en ejecución, reidentificación de especímenes depositados en colecciones de mamíferos nacionales y extranjeras, y revisiones taxonómicas futuras. Abstract We present an update to the list of mammals known to occur in Bolivia. We incorporate and describe recent taxonomic changes and new records for the country made since the last list published in 2003. New records and taxonomic changes were considered only if they had verifiable evidence. To date, the list of mammals for the country includes 406 native species, belonging to 11 orders, 46 families and 196 genera, representing an increase of 51 species over the 2003 list. Among those added, 14 were new to science and have type localities in Bolivia. The most diverse orders were Rodentia (148 species), Chiroptera (138), Didelphimorphia (35) and Carnivora (27); a total of 25 species are endemic to Bolivia. In addition, 14 species of introduced mammals are listed. Additional records and taxonomic changes are expected as a result of biological inventories currently in execution, re-identification of specimens deposited in national and foreign mammal collections, and future taxonomic revisions. Este trabajo está dedicado a la memoria de Boris Ríos-Uzeda, Mario Baudoin Weeks y Wendy Townsend. Excelencia, compromiso e infatigable esfuerzo por el conocimiento y la conservación de la biodiversidad de Bolivia, es el legado que nos dejan y la luz que ilumina el camino de los que los seguimos. Queridos amigos, los llevamos en el corazón.
... Its presence in the basin suggests that Xenarthra differentiated somewhere in the South American continent (Pascual and Ortiz-Jaureguizar 2007). this view, based on fossil records, received support from recent molecular studies, which estimated the divergence time of Xenarthra by the Cretaceous-Paleogene boundary (Meredith et al. 2011, Delsuc et al. 2012, Gibb et al. 2015. ...
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Riostegotherium yanei from the Itaboraí Basin, Brazil, is the oldest known Xenarthra. This paper aims to describe the internal morphology of the osteoderms of Riostegotherium yanei from the perspective of histology and micro-CT approaches, expanding the available data on cingulate osteoderm microstructure. Seven osteoderms of R. yanei were used for the internal microstructure description and eight of Dasypus novemcinctus for comparison. The osteoderms of Riostegotherium yanei lacks the diploë-like structure typical of glyptodonts but has a three-layered structure composed of two layers of non-Haversian compact bone enclosing a central layer of primary and secondary osteons. This internal organization is distinct from other Astegotheriini of comparable age, but similar to Dasypus. The 3D reconstruction of Riostegotherium yanei revealed two patterns of internal organization. Pattern 1 of movable osteoderm is composed of large remodeled areas at the base and a more compact bone at the tongue; in Pattern 2 (both movable and buckler), the internal cavities are much smaller, more numerous, and more interconnected to each other. In one buckler osteoderm, the cavities are organized somewhat radially with a compact central region (Pattern 1). Pattern 1 of both movable and buckler osteoderms resemble that of Dasypus.
... It is possible that D. kappleri has the same diploid chromosome number. Previous studies by Castro et al. (2014) described that the divergence of Dasypus was in the late Pliocene, about 3.5 million years ago and Delsuc et al. (2012) estimated divergence date between D. novemcinctus and D. kappleri about 11 ± 2 million years ago. However, in the most recent study, the phylogenetic tree obtained from mitochondrial genomes (mitogenomes) identified D. kappleri as basal to all other Dasypus species; it is the first to diverge within Dasypodinae, estimated at more than 12 million years ago ( Gibb et al. 2015). ...
Article
Dasypus kappleri Krauss, 1862, commonly known as greater long-nosed armadillo, is the second largest extant armadillo and readily distinguishable by the prominent spurs on the hind legs. It is diurnal-nocturnal, solitary, and insectivorous. It is a semi-fossorial species ranging east of the Andes across the central lowlands of South America. It occupies a wide range of habitats including rainforest, riparian forest, and grassland. D. kappleri is listed as “Least Concern” by the International Union for Conservation of Nature and Natural Resources in light of its wide distribution, which presumedly contains robust populations.
... Although Miocene marine introgressions, due to their magnitude (see Hernandez et al., 2005), may have played an important role in evolutionary processes in southern South America (Candela et al., 2012;Delsuc et al., 2012;Morando et al., 2014;Brusquetti et al., 2017), the South American Gran Chaco, due to its geographical location, has been influenced by other events as well, such as Pleistocene glaciations (Ortiz-Jauguerizar & Cladera, 2006). Pleistocene glaciations have been proposed as putative promoters of frog diversification in adjacent biomes in southern South America (Nuñez et al., 2011;Blotto et al., 2013;Langone et al., 2016). ...
Article
The Chaco is a semi-arid biome that has been influenced by Miocene marine introgressions and relatively recent glaciations. Marine introgressions have been suggested as an important driver of biodiversity for some Chacoan frog species, but the effects of Pleistocene glaciations have not previously been assessed. We used mitochondrial and nuclear markers to estimate the genetic structure and demographic history of Leptodactylus bufonius, a frog species widely distributed in the Chaco, to test if Pleistocene glaciations have had any influence on its evolutionary history. We found evidence to support recent range and demographic expansions and current gene flow among populations. Expansions may have occurred after the most extensive glaciations (Greatest Patagonian Glaciation and the coldest Pleistocene glaciation, 1-0.7 Mya) of the Late Pleistocene. Current gene flow is maintained by short-distance dispersal that follows a stepping-stone model allowing high connectivity, even among distant populations. Nevertheless, we cannot exclude some influence of large population sizes and retention of ancestral polymorphism in explaining the lack of population structure that we found. The genetic pattern of L. bufonius is concordant with the diversification of frogs in other semi-arid regions of the world.
... Although Miocene marine introgressions, due to their magnitude (see Hernandez et al., 2005), may have played an important role in evolutionary processes in southern South America (Candela et al., 2012;Delsuc et al., 2012;Morando et al., 2014;Brusquetti et al., 2017), the South American Gran Chaco, due to its geographical location, has been influenced by other events as well, such as Pleistocene glaciations (Ortiz-Jauguerizar & Cladera, 2006). Pleistocene glaciations have been proposed as putative promoters of frog diversification in adjacent biomes in southern South America (Nuñez et al., 2011;Blotto et al., 2013;Langone et al., 2016). ...
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The Chaco is a semi-arid biome that has been influenced by Miocene marine introgressions and relatively recent glaciations. Marine introgressions have been suggested as an important driver of biodiversity for some Chacoan frog species, but the effects of Pleistocene glaciations have not previously been assessed. We used mitochondrial and nuclear markers to estimate the genetic structure and demographic history of Leptodactylus bufonius, a frog species widely distributed in the Chaco, to test if Pleistocene glaciations have had any influence on its evolutionary history. We found evidence to support recent range and demographic expansions and current gene flow among populations. Expansions may have occurred after the most extensive glaciations (Greatest Patagonian Glaciation and the coldest Pleistocene glaciation, 1-0.7 Mya) of the Late Pleistocene. Current gene flow is maintained by short-distance dispersal that follows a stepping-stone model allowing high connectivity, even among distant populations. Nevertheless, we cannot exclude some influence of large population sizes and retention of ancestral polymorphism in explaining the lack of population structure that we found. The genetic pattern of L. bufonius is concordant with the diversification of frogs in other semi-arid regions of the world. ADDITIONAL KEYWORDS: Anura-Leptodactylidae-Leptodactylus bufonius-natural history-phylogeography-semi-arid biome.
... It has the widest distribution of the order, occurring from Argentina to the United States, encompassing the latitudes from 39˚S to 40˚N [4]. The monophyly of the genus is well supported both by morphological [5,6] and molecular data [7,8,9,10]. Dasypus is the only living representative of the subfamily Dasypodinae (or Dasypodidae a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 ...
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Dasypus is the most speciose genus of the order Cingulata, including approximately 40% of known living armadillos. Nine species are currently recognized, although comprehensive analyses of the entire genus have never been done. Our aim is to revise the taxonomy of the long-nosed armadillos and properly define the taxa. We examined 2126 specimens of Dasypus preserved in 39 different museum collections, including 17 type specimens. Three complementary methods were applied to explore morphological datasets both qualitatively and quantitatively. Qualitative morphological variation in discrete characters was assessed by direct observations of specimens. Linear morphometric variation was based on external data and cranial measurements of 887 adult skulls. The shape and size of the skull was abstracted through two-dimensional geometric morphometric analyses of dorsal, lateral and ventral views of respectively 421, 211, and 220 adult specimens. Our results converge on the recognition of eight living species (D. beniensis, D. kappleri, D. mazzai, D. novemcinctus, D. pastasae, D. pilosus, D. sabanicola, and D. septemcinctus), and three subspecies of D. septemcinctus (D. s. septemcinctus, D. s. hybridus, and a new subspecies from Cordoba described here). Information on type material, diagnosis, distribution, and taxonomic comments for each taxon are provided. We designate a lectotype for D. novemcinctus; and a neotype for Loricatus hybridus (= D. septemcinctus hybridus).
... Armadillos (grouped in the families Dasypodidae and Chlamyphoridae) are the most diverse xenarthran lineage. Phylogeographic and phylogenetic studies as those of Delsuc et al. [3,4], Poljak et al. [5], Loughry & McDonoug [6], Abba et al. [7], Moraes Barros et al. [8] among others, provided information about South American biogeographic history and general patterns of species diversification in this group. ...
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Little is known about phylogeography of armadillo species native to southern South America. In this study we describe the phylogeography of the screaming hairy armadillo Chaetophractus vellerosus, discuss previous hypothesis about the origin of its disjunct distribution and propose an alternative one, based on novel information on genetic variability. Variation of partial sequences of mitochondrial DNA Control Region (CR) from 73 individuals from 23 localities were analyzed to carry out a phylogeographic analysis using neutrality tests, mismatch distribution, median-joining (MJ) network and paleontological records. We found 17 polymorphic sites resulting in 15 haplotypes. Two new geographic records that expand known distribution of the species are presented; one of them links the distributions of recently synonimized species C. nationi and C. vellerosus. Screaming hairy armadillo phylogeographic pattern can be addressed as category V of Avise: common widespread linages plus closely related lineages confined to one or a few nearby locales each. The older linages are distributed in the north-central area of the species distribution range in Argentina (i.e. ancestral area of distribution). C. vellerosus seems to be a low vagility species that expanded, and probably is expanding, its distribution range while presents signs of genetic structuring in central areas. To explain the disjunct distribution, a hypothesis of extinction of the species in intermediate areas due to quaternary climatic shift to more humid conditions was proposed. We offer an alternative explanation: long distance colonization, based on null genetic variability, paleontological record and evidence of alternance of cold/arid and temperate/humid climatic periods during the last million years in southern South America.
... The morphological differentiation of these structures in different carapace areas would Fig. 6 Approximate temporal placement of Cenozoic dasypodidcontaining faunas discussed in the text, in relation to Cenozoic the main climatic events. The taxa of Dasypodidae studied in this work are represented in a simplified phylogenetic relationship of fossil and extant xenarthrans based on morphological and molecular results (Asher et al. 2009;Billet et al. 2011;Delsuc et al. 2012;Meredith et al. 2013). Phylogenetical position of taxa not included in known phylogenetic analyses was inferred based on the literature and taxonomical position. ...
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The most complete and continuous fossil record of armadillos is composed mostly by isolated osteoderms, frequently found in paleontological and archaeological sites that bear continental South American mammals. Their external morphology has been used to define several species. In the last decade, many authors have focused on the internal structure of vertebrate osteoderms using histological and paleohistological studies. These studies allowed identification of useful features in systematic and phylogenetic contexts. In armadillos, osteoderms are constituted by compact bone tissue (primary and secondary osteons, and concentric layers or lamellae) that delimits cavities, which could contain different soft tissues (adipose tissue, hair follicles, bone marrow, and sweat and sebaceous glands). Traditional paleohistological techniques have allowed the recognition of homologous cavities to those found in osteoderms of current species and from comparison deduce which kind of tissue could had occupied them. We have recently utilized 3D reconstructions in osteoderms of extant species of armadillos to analyze the micromorphology, disposition, and the relationship of different cavities and understand them in depth. Here, we present the results of the application of paleohistology and microtomography in osteoderms of representatives of diferent taxa of extinct Dasypodidae (Astegotheriini, Stegotheriini, “Utaetini,” Euphractini, Eutatini), which allowed us to compare homologous structures based on their three-dimensional reconstruction. The results, added to the previous external morphology studies, have allowed us to define morphological patterns (consistent within each linage). The variation of the volume and extension of cavities associated with different tissues could be strongly associated with changes in the climate and environmental conditions of the species distribution areas.
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Fossil remains herein described are referred to different species of Dasypodidae Gray, 1821 (Mammalia, Xenarthra, Cingulata) and come from the upper levels of the lower member (Late Miocene-Early Pliocene) of the Toro Negro Formation at Quebrada de Las Torrecillas, La Rioja Province, Argentina, where previous vertebrate records only include those of Pyramiodontherium scillatoyanei De Iuliis, Ré & Vizcaíno, 2004 (Mammalia, Xenarthra) and Opisthodactylus cf. kirchneri Noriega, Jordan, Vezzosi & Areta, 2017 (Aves, Rheidae). The remains of Dasypodidae herein presented include Vetelia ghandii Esteban & Nasif, 1996, Chasicotatus peiranoi Esteban & Nasif, 1996, Macrochorobates scalabrinii (Moreno & Mercerat, 1891), Prozaedyus sp., and Paleuphractus argentinus (Moreno & Mercerat, 1891), and constitute the first records of these species for the Toro Negro Formation, increasing the mammal diversity for this unit. The association of dasypodids here described shows strong affinities with those described for Late Miocene localities of Northwestern Argentina. Under these evidences, the Dasypodidae here reported for Quebrada de Las Torrecillas site show a characteristic association of taxa from Northwestern Argentina, suggesting a Messinian age (Late Miocene) for the bearing levels of the Toro Negro Formation. In this way, these records support the accurate ages recently proposed for the lower Member of the Toro Negro Formation (i.e., Late Miocene-Early Pliocene).
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The recent influx of genomic data has provided greater insights into the molecular basis for regressive evolution, or vestigialization, through gene loss and pseudogenization. As such, the analysis of gene degradation patterns has the potential to provide insights into the evolutionary history of regressed anatomical traits. We specifically applied these principles to the xenarthran radiation (anteaters, sloths, armadillos), which is characterized by taxa with a gradation in regressed dental phenotypes. Whether the pattern among extant xenarthrans is due to an ancient and gradual decay of dental morphology or occurred repeatedly in parallel is unknown. We tested these competing hypotheses by examining 11 core dental genes in most living species of Xenarthra, characterizing shared inactivating mutations and patterns of relaxed selection during their radiation. Here we report evidence of independent and distinct events of dental gene loss in the major xenarthran subclades. First, we found strong evidence of complete enamel loss in the common ancestor of sloths and anteaters, suggested by the inactivation of four enamel-associated genes (AMELX, AMTN, MMP20, ENAM). Next, whereas sloths halted their dental regression, presumably a critical event that ultimately permitted adaptation to an herbivorous lifestyle, anteaters continued losing genes on the path towards complete tooth loss. Echoes of this event are recorded in the genomes of all living anteaters, being marked by a 2-bp deletion in a gene critical for dentinogenesis (DSPP) and a putative shared 1-bp insertion in a gene linked to tooth retention (ODAPH). By contrast, in the two major armadillo clades, genes pertaining to the gingival-tooth junction appear to have been independently inactivated prior to losing all or most enamel. These genomic data provide evidence for multiple pathways and rates of anatomical regression, and underscore the utility of using pseudogenes to reconstruct evolutionary history when fossils are sparse.
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Envenoming by scorpions in genus Tityus is a public health problem in Tropical America. One of the most medically significant species is Tityus trivittatus, which is known to occur from southwest Brazil to central-northern and eastern Argentina. In this work, we studied the lethality, composition, antigenicity, and enzymatic activity of venom from a T. trivittatus population found further north in urban areas of eastern Paraguay, where it has caused serious envenomation of children. Our results indicate that the population is of medical importance as it produces a potently toxic venom with an LD50 around 1.19 mg/kg. Venom neutralization in preliminary mouse bioassays was complete when using Brazilian anti-T. serrulatus antivenom but only partial when using Argentinean anti-T. trivittatus antivenom. Venom competitive solid-phase enzyme immunoassays and immunoblotting from Argentinean and Paraguayan T. trivittatus populations indicated that antigenic differences exist across the species range. SDS-PAGE showed variations in type and relative amounts of venom proteins between T. trivitattus samples from Argentina and Paraguay. MALDI-TOF mass spectrometry indicated that while some sodium channel toxins are shared, including β-toxin Tt1g, others are population-specific. Proteolytic activity by zymography and peptide identification through nESI-MS/MS also point out that population-specific proteases may exist in T. trivitattus, which are postulated to be involved in the envenoming process. A time-calibrated molecular phylogeny of mitochondrial COI sequences revealed a significant (8.14%) genetic differentiation between the Argentinean and Paraguayan populations, which appeared to have diverged between the mid Miocene and early Pliocene. Altogether, toxinological and genetic evidence indicate that T. trivitattus populations from Paraguay and Argentina correspond to distinct, unique cryptic species, and suggest that further venom and taxonomic diversity exists in synanthropic southern South American Tityus than previously thought.
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Descriptions of myology reflect adaptations of the post‐cranium and are essential for understanding the functional morphology of animal limbs. Armadillos (Cingulata) are the most species‐rich group of the basal superorder Xenarthra, which is evident by their various lifestyles (subterranean vs. terrestrial) and levels of fossoriality (fossorial vs. semi‐fossorial). While there have been several studies on limb bone proportions in numerous armadillos, limb myology has been reported for a limited number of species. Many of these descriptions need updating, and detailed quantitative muscle data are available only for nine‐banded armadillos. The main objective of this study is to assess the forelimb myology of the pichi (Zaedyus pichiy), screaming hairy (Chaetophractus vellerosus), large hairy (Chaetophractus villosus), and pink fairy (Chlamyphorus truncatus) armadillos with comparisons to previous observations to specify muscle traits that indicate scratch‐digging specializations in cingulates. Several myological features are variable among the species studied, including the origin of m. trapezius pars cervicalis, presence of a distinct m. rhomboideus profundus and m. omotransversarius, and number of heads present for m. triceps brachii and m. flexor digitorum profundus, all of which can be associated with variability in their respective habitats and functional habits. These traits are consistently observed in the members of the Euphractinae, whereas they are slightly divergent (i.e., reduced complexity) in the pink fairy armadillo despite a similar distribution of muscle mass in the limb retractors, elbow extensors, and carpal/digital flexors across species. The ecomorphology observed here among cingulates also confirms their recent reorganization into separate families and subfamilies.
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Large cylindrical structures with a dominantly laminated fill occurring in the loess-paleosol sequence of the late Miocene Cerro Azul Formation (central Argentina) are interpreted as mammal burrows. A total of 115 burrow fills from three localities were measured. The fills typically are shallowly dipping, subcylindrical, unbranched structures with a rounded end and lacking enlargements. The horizontal diameter of the burrows range between 0.15 and 1.50 m, with most of the burrows in the interval of 0.39 to 0.98 m. Geometric morphometric analysis of transverse cross-sections support the distinction of subcircular and elliptical (horizontally flattened) fills. Burrows fills are typically laminated in the lower part and massive in the upper part. The laminated intervals reflect pulses of aqueous currents entering the abandoned burrow during moderate rains, whereas massive intervals reflect en masse input of sediment-water mixtures during heavy rains that produced sheet floods. About 1% of the burrow fills contained fragmentary, disarticulated and weathered mammal bones that were introduced in the open burrow by currents along with other sedimentary particles. Analysis of the tetrapod burrow fossil record suggests that Miocene burrows, including those studied herein; reflect a remarkable increase in the average size of the fossorial fauna. We conclude that large late Miocene mammals dug burrows essentially as a shelter against environmental extremes and also to escape predation. Several mammal groups acquired fossorial habits in response to cold and seasonally dry climatic conditions that prevailed during the late Miocene in southern South America. The ample range of horizontal diameters of the studied burrow fills can be attributed to a variety of producers, including dasypodids, the notoungulate Paedotherium minor , Glyptodontidae and Proscelidodon sp. The simple architecture of the burrows suggests that the producers essentially foraged aboveground.
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Large cylindrical structures with a dominantly laminated fill occurring in the loess-paleosol sequence of the late Miocene Cerro Azul Formation (central Argentina) are interpreted as mammal burrows. A total of 115 burrow fills from three localities were measured. The fills typically are shallowly dipping, subcylindrical, unbranched structures with a rounded end and lacking enlargements. The horizontal diameter of the burrows range between 0.15 and 1.50 m, with most of the burrows in the interval of 0.39 to 0.98 m. Geometric morphometric analysis of transverse cross-sections support the distinction of subcircular and elliptical (horizontally flattened) fills. Burrows fills are typically laminated in the lower part and massive in the upper part. The laminated intervals reflect pulses of aqueous currents entering the abandoned burrow during moderate rains, whereas massive intervals reflect en masse input of sediment-water mixtures during heavy rains that produced sheet floods. About 1% of the burrow fills contained fragmentary, disarticulated and weathered mammal bones that were introduced in the open burrow by currents along with other sedimentary particles. Analysis of the tetrapod burrow fossil record suggests that Miocene burrows, including those studied herein; reflect a remarkable increase in the average size of the fossorial fauna. We conclude that large late Miocene mammals dug burrows essentially as a shelter against environmental extremes and also to escape predation. Several mammal groups acquired fossorial habits in response to cold and seasonally dry climatic conditions that prevailed during the late Miocene in southern South America. The ample range of horizontal diameters of the studied burrow fills can be attributed to a variety of producers, including dasypodids, the notoungulate Paedotherium minor , Glyptodontidae and Proscelidodon sp. The simple architecture of the burrows suggests that the producers essentially foraged aboveground.
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The armadillo genus Dasypus is the most species-rich and widely distributed genus of the order Cingulata and it has a dynamic taxonomic history. Recent morphology-based studies have proposed new taxonomic arrangements, but these were not yet assessed with molecular data. The two comprehensive phylogenetic hypotheses available for the genus are conflicting and were each based on a subset of taxa, hampering a proper evaluation of species boundaries. Using a multilocus molecular dataset, based on the broadest geographic sampling of Dasypus to date, we inferred the phylogenetic relationships of all species of the genus, including the recently reinstated D. beniensis and D. pastasae. We tested recent taxonomic hypotheses using several species-delimitation approaches. Our phylogeny recovered three main lineages of long-nosed armadillos that we treat as subgenera (Hyperoambon, Muletia and Dasypus) and identified the majority of its diversification as having occurred during the Pliocene. Molecular species delimitation supported morphological evidence in assigning D. hybridus as a subspecies of D. septemcinctus and confirming the split of the D. kappleri complex into three species. Our results strongly support the recognition of Guiana Shield populations formerly assigned to D. novemcinctus as a distinct species. The phylogenetic positions of D. mazzai and D. sabanicola remain uncertain. Further investigation using faster-evolving genes and additional samples may help to clarify the relationships of these young species.
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Background. The systematics of long-nosed armadillos (genus Dasypus ) has been mainly based on a handful of external morphological characters and classical measurements. Here, we studied the pattern of morphological variation in the skull of long-nosed armadillos species, with a focus on the systematics of the widely distributed nine-banded armadillo ( D. novemcinctu s). Methods. We present the first exhaustive 3D comparison of the skull morphology within the genus Dasypus , based on µCT-scans. We used geometric morphometric approaches to explore the patterns of the intra- and interspecific morphological variation of the skull with regard to several factors such as taxonomy, geography, allometry, and sexual dimorphism. Results. We show that the shape and size of the skull vary greatly between Dasypus species, with D. pilosus representing a clear outlier compared to other long-nosed armadillos. The study of the cranial intraspecific variation in D. novemcinctus evidences clear links to the geographic distribution and argue in favour of a revision of past taxonomic delimitations. Our detailed morphometric comparisons detected previously overlooked morphotypes of nine-banded armadillo, especially a very distinctive unit circumscribed to the Guiana Shield. Discussion. As our results are congruent with recent molecular data and analyses of the structure of paranasal sinuses, we propose that D. novemcinctus should be regarded either as a polytypic species (with three to four subspecies) or as a complex of several distinct species.
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The species within Xenarthra (sloths, anteaters, and armadillos) are quintessential South American mammals. Of the three groups, Vermilingua (anteaters) contains the fewest extant and paleontological species. Here, we sampled and sequenced the entire mitochondrial genomes (mitogenomes) of two Tamandua species (Tamandua tetradactyla and Tamandua mexicana) (n=74) from Central and South America, as well as Myrmecophaga tridactyla (n=41) from South America. Within Tamandua, we detected three different haplogroups. The oldest (THI) contained many specimens with the T. tetradactyla morphotype (but also several with the T. mexicana morphotype) and originated in southeastern South America (currently Uruguay) before moving towards northern South America, where the THII haplogroup originated. THII primarily contained specimens with the T. mexicana morphotype (but also several with the T. tetradactyla morphotype) and was distributed in Central America, Colombia, and Ecuador. THI and THII yielded a genetic distance of 4%. THII originated in either northern South America or "in situ" in Central America with haplogroup THIII, which consisted of ~50% T. mexicana and 50% T. tetradactyla phenotypes. THIII was mostly located in the same areas as THII, i.e., Central America, Ecuador, and Colombia, though mainly in the latter. The three haplogroups overlapped in Colombia and Ecuador. Thus, T. tetradactyla and T. mexicana were not reciprocally monophyletic. For this reason, we considered that a unique species of Tamandua likely exists, i.e., T. tetradactyla. In contrast to Tamandua, M. tridactyla did not show different morphotypes throughout its geographical range in the Neotropics. However, two very divergent genetic haplogroups (MHI and MHII), with a genetic distance of ~10%, were detected. The basal haplogroup, MHI, originated in northwestern South America, whereas the more geographically derived haplogroup, MHII, overlapped with MHI, but also expanded into central and southern South America. Thus, Tamandua migrated from south to north whereas Myrmecophaga migrated from north to south. Our results also showed that temporal mitochondrial diversification for Tamandua began during the Late Pliocene and Upper Pleistocene, but for Myrmecophaga began during the Late Miocene. Furthermore, both taxa showed elevated levels of mitochondrial genetic diversity. Tamandua showed more evidence of female population expansion than Myrmecophaga. Tamandua experienced population expansion ~0.6-0.17 million years ago (Mya), whereas Myrmecophaga showed possible population expansion ~0.3-0.2 Mya. However, both taxa experienced a conspicuous female decline in the last 10 000-20 000 years. Our results also showed little spatial genetic structure for both taxa. However, several analyses revealed higher spatial structure in Tamandua than in Myrmecophaga. Therefore, Tamandua and Myrmecophaga were not subjected to the same biogeographical, geological, or climatological events in shaping their genetic structures.
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The intrageneric relationships of the pampatheriid genus Scirrotherium and its affinities with supposedly related genera Kraglievichia and Holmesina are revised through new comparative morphological descriptions and parsimony phylogenetic analyses. Unpublished material of pampatheriids (numerous osteoderms, one partial skull and a few postcranial bones) from Neogene formations of Colombia was analyzed. Results show that Scirrotherium is paraphyletic when including all its referred species, i.e., Scirrotherium hondaensis, S. carinatum, and S. antelucanus. The species S. carinatum appears closer to Kraglievichia paranensis than to S. hondaensis or S. antelucanus, therefore the new combination Kraglievichia carinatum is proposed. The relationship between S. hondaensis and S. antelucanus could not be resolved, so these species should be designated in aphyly. In spite of failing to recover S. hondaensis and S. antelucanus as one single clade, it is preferred to maintain the generic name Scirrotherium for both species based on diagnostic evidence. New emended diagnoses for Scirrotherium, S. hondaensis and Kraglievichia are provided. The genus Holmesina was found to be monophyletic and positioned as the sister clade of Scirrotherium + Kraglievichia. The evolutionary and biogeographic implications of the taxonomic re-arrangements and the new phylogeny are discussed. A possible geographic origin of the family Pampatheriidae and Scirrotherium in low latitudes of South America as early as the early Miocene is claimed. The immediate South American sister taxon of Holmesina is predicted to be morphologically more similar to Scirrotherium than to Kraglievichia.
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The armadillo genus Dasypus is the most species-rich and widely distributed genus of the order Cingulata and it has a dynamic taxonomic history. Recent morphology-based studies have proposed new taxonomic arrangements, but these were not yet assessed with molecular data. The two comprehensive phylogenetic hypotheses available for the genus are conflicting and were each based on a subset of taxa, hampering a proper evaluation of species boundaries. Using a multilocus molecular dataset, based on the broadest geographic sampling of Dasypus to date, we inferred the phylogenetic relationships of all species of the genus, including the recently reinstated D. beniensis and D. pastasae. We tested recent taxonomic hypotheses using several species-delimitation approaches. Our phylogeny recovered three main lineages of long-nosed armadillos that we treat as subgenera (Hyperoambon, Muletia and Dasypus) and identified the majority of its diversification as having occurred during the Pliocene. Molecular species delimitation supported morphological evidence in assigning D. hybridus as a subspecies of D. septemcinctus and confirming the split of the D. kappleri complex into three species. Our results strongly support the recognition of Guiana Shield populations formerly assigned to D. novemcinctus as a distinct species. The phylogenetic positions of D. mazzai and D. sabanicola remain uncertain. Further investigation using faster-evolving genes and additional samples may help to clarify the relationships of these young species.
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Sloths, like other xenarthrans, are an extremely interesting group of mammals that, after a long history of evolution and diversification in South America, became established on islands in the Caribbean and later reached North America during the Great American Biotic Interchange. In all three regions, they were part of the impressive Pleistocene megafauna. Most taxa became extinct and only two small, distantly related tree-dwelling genera survived. Here we incorporate several recently described genera of sloths into an assembled morphological data supermatrix and apply Bayesian inference, using phylogenetic and morphological clock methods, to 64 sloth genera. Thus, we investigate the evolution of the group in terms of the timing of divergence of different lineages and their diversity, morphological disparity and biogeographical history. The phylogeny obtained supports the existence of the commonly recognized clades for the group. Our results provide divergence time estimates for the major clades within Folivora that could not be dated with molecular methods. Lineage diversity shows an early increase, reaching a peak in the Early Miocene followed by a major drop at the end of the Santacrucian (Early Miocene). A second peak in the Late Miocene was also followed by a major drop at the end of the Huayquerian (Late Miocene). Both events show differential impact at the family level. After that, a slight Plio-Pleistocene decline was observed before the marked drop with the extinction at the end of the Pleistocene. Phenotypic evolutionary rates were high during the early history of the clade, mainly associated with Mylodontidae, but rapidly decreased to lower values around 25 Ma, whereas Megalonychidae had lower rates at the beginning followed by a steady increase, peaking during the Late Miocene and the Pliocene. Morphological disparity showed a similar trend, with an early increase, followed by a slowly increasing phase through the Late Oligocene and Early Miocene, and ending with another increase beginning at the middle of the Miocene. Biogeographic analysis showed southern South America as the most probable area of origin of the clade and the main region in which the early diversification events took place. Both Megatheriinae and Nothrotheriinae basal nodes were strongly correlated with Andean uplift events, whereas the early history of Mylodontidae is closely associated with southern South America and also shows an early occupation of the northern regions. Within Megalonychidae, our results show Choloepus as a descendant of an island dispersing ancestor and a probable re-ingression to South America by a clade that originated in Central or North America.
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Mylodon darwinii is the extinct giant ground sloth named after Charles Darwin, who first collected its remains in South America. We have successfully obtained a high-quality mitochondrial genome at 99-fold coverage using an Illumina shotgun sequencing of a 12 880-year-old bone fragment from Mylodon Cave in Chile. Low level of DNA damage showed that this sample was exceptionally well preserved for an ancient subfossil, probably the result of the dry and cold conditions prevailing within the cave. Accordingly, taxonomic assessment of our shotgun metagenomic data showed a very high percentage of endogenous DNA with 22% of the assembled metagenomic contigs assigned to Xenarthra. Additionally, we enriched over 15 kb of sequence data from seven nuclear exons, using target sequence capture designed against a wide xenarthran dataset. Phylogenetic and dating analyses of the mitogenomic dataset including all extant species of xenarthrans and the assembled nuclear supermatrix unambiguously place Mylodon darwinii as the sister-group of modern two-fingered sloths, from which it diverged around 22 million years ago. These congruent results from both the mitochondrial and nuclear data support the diphyly of the two modern sloth lineages, implying the convergent evolution of their unique suspensory behaviour as an adaption to arboreality. Our results offer promising perspectives for whole-genome sequencing of this emblematic extinct taxon.
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Background The systematics of long-nosed armadillos (genus Dasypus ) has been mainly based on a handful of external morphological characters and classical measurements. Here, we studied the pattern of morphological variation in the skull of long-nosed armadillos species, with a focus on the systematics of the widely distributed nine-banded armadillo ( Dasypus novemcinctus ). Methods We present the first exhaustive 3D comparison of the skull morphology within the genus Dasypus , based on micro-computed tomography. We used geometric morphometric approaches to explore the patterns of the intra- and interspecific morphological variation of the skull with regard to several factors such as taxonomy, geography, allometry, and sexual dimorphism. Results We show that the shape and size of the skull vary greatly among Dasypus species, with Dasypus pilosus representing a clear outlier compared to other long-nosed armadillos. The study of the cranial intraspecific variation in Dasypus novemcinctus evidences clear links to the geographic distribution and argues in favor of a revision of past taxonomic delimitations. Our detailed morphometric comparisons detected previously overlooked morphotypes of nine-banded armadillos, especially a very distinctive unit restricted to the Guiana Shield. Discussion As our results are congruent with recent molecular data and analyses of the structure of paranasal sinuses, we propose that Dasypus novemcinctus should be regarded either as a polytypic species (with three to four subspecies) or as a complex of several distinct species.
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The ongoing generation of prodigious amounts of genomic sequence data from myriad vertebrates is providing unparalleled opportunities for establishing definitive phylogenetic relationships among species. The size and complexities of such comparative sequence data sets not only allow smaller and more difficult branches to be resolved but also present unique challenges, including large computational requirements and the negative consequences of systematic biases. To explore these issues and to clarify the phylogenetic relationships among mammals, we have analyzed a large data set of over 60 megabase pairs (Mb) of high-quality genomic sequence, which we generated from 41 mammals and 3 other vertebrates. All sequences are orthologous to a 1.9-Mb region of the human genome that encompasses the cystic fibrosis transmembrane conductance regulator gene (CFTR). To understand the characteristics and challenges associated with phylogenetic analyses of such a large data set, we partitioned the sequence data in several ways and utilized maximum likelihood, maximum parsimony, and Neighbor-Joining algorithms, implemented in parallel on Linux clusters. These studies yielded well-supported phylogenetic trees, largely confirming other recent molecular phylogenetic analyses. Our results provide support for rooting the placental mammal tree between Atlantogenata (Xenarthra and Afrotheria) and Boreoeutheria (Euarchontoglires and Laurasiatheria), illustrate the difficulty in resolving some branches even with large amounts of data (e.g., in the case of Laurasiatheria), and demonstrate the valuable role that very large comparative sequence data sets can play in refining our understanding of the evolutionary relationships of vertebrates.
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New data from Neogene strata in northern South America suggest that Miocene tectonism in the northeastern Andes was responsible for the genesis of the Amazon River and changes in the drainage patterns of other major rivers such as the Magdalena and the Orinoco. Here we present a new model for the paleogeographic evolution of northern South America during the Miocene. In the early Miocene, a large part of the drainage of northwest Amazonia was directed northward along the paleo Orinoco river system to a delta in Lake Maracaibo. Uplift of the Eastern Cordillera in the late middle Miocene caused the first development of the Amazon River; however, no connection with the Atlantic was established, and the Amazon fed the paleo Orinoco river system, which drained toward the Caribbean. Substantial Andean uplift in the late Miocene resulted in major changes in paleogeography: the Orinoco changed its course, the Amazon established a connection to the Atlantic, causing the drowning of carbonate platforms, and the Amazon Caribbean connection was closed. Thus the drainage and paleogeography of northern South America in the Miocene were strongly controlled by tectonic movements in the northeastern Andes.
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Advances in sequence stratigraphy and the development of depositional models have helped explain the origin of genetically related sedimentary packages during sea level cycles. These concepts have provided the basis for the recognition of sea level events in subsurface data and in outcrops of marine sediments around the world. Knowledge of these events has led to a new generation of Mesozoic and Cenozoic global cycle charts that chronicle the history ofnsea level fluctuations during the past 250 million years in greater detail than was possible from seismic-stratigraphic data alone. An effort has been made to develop a realistic and accurate time scale and widely applicable chronostratigraphy and to integrate depositional sequences documented in public domain outcrop sections from various basins with this chronostratigraphic framework. A description of this approach and an account of the results, illustrated by sea level cycle charts of the Cenozoic, Cretaceous, Jurassic, and Triassic intervals, are presented.
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The conservation status of the 21 extant armadillo species was re-assessed by specialists of the IUCN/SSC Anteater, Sloth and Armadillo Specialist Group between December 2009 and May 2010. Information on their geographic range, population size and status, habitat and ecology, threats, and existing conservation measures was collected from the literature and personal communications. Four armadillo species were classified as Vulnerable, four as Near Threatened, and four were categorized as Data Deficient. Less than half of all armadillo species were listed as Least Concern. Virtually all assessed species are affected by hunting as well as habitat fragmentation and degradation. The populations of only two species are thought to be increasing, while those of at least seven species are in decline. Much work is still needed to ensure the long-term survival of all species. Most armadillo species occur in at least one protected area, but other conservation actions are scarce.
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Molecular phylogenetic studies have resolved placental mammals into four major groups, but have not established the full hierarchy of interordinal relationships, including the position of the root. The latter is critical for understanding the early biogeographic history of placentals. We investigated placental phylogeny using Bayesian and maximum-likelihood methods and a 16.4-kilobase molecular data set. Interordinal relationships are almost entirely resolved. The basal split is between Afrotheria and other placentals, at about 103 million years, and may be accounted for by the separation of South America and Africa in the Cretaceous. Crown-group Eutheria may have their most recent common ancestry in the Southern Hemisphere (Gondwana).
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The cingulates of the mammalian order Xenarthra present a typical case of disagreement between molecular and morphological phylogenetic studies. We report here the discovery of two new skulls from the Late Oligocene Salla Beds of Bolivia (approx. 26 Ma), which are the oldest known well-preserved cranial remains of the group. A new taxon is described: Kuntinaru boliviensis gen. et sp. nov. A phylogenetic analysis clusters K. boliviensis together with the armadillo subfamily Tolypeutinae. These skulls document an early spotty occurrence for the Tolypeutinae at 26 Ma, in agreement with the temporal predictions of previous molecular studies. The fossil record of tolypeutines is now characterized by a unique occurrence in the Late Oligocene, and a subsequent 12 Myr lack in the fossil record. It is noteworthy that the tolypeutines remain decidedly marginal in the Late Palaeogene and Early Neogene deposits, whereas other cingulate groups diversify. Also, the anatomical phylogenetic analysis herein, which includes K. boliviensis, is congruent with recent molecular phylogenetic analyses. Kuntinaru boliviensis is the oldest confident calibration point available for the whole Cingulata.
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Motivation: A variety of probabilistic models describing the evolution of DNA or protein sequences have been proposed for phylogenetic reconstruction or for molecular dating. However, there still lacks a common implementation allowing one to freely combine these independent features, so as to test their ability to jointly improve phylogenetic and dating accuracy. Results: We propose a software package, PhyloBayes 3, which can be used for conducting Bayesian phylogenetic reconstruction and molecular dating analyses, using a large variety of amino acid replacement and nucleotide substitution models, including empirical mixtures or non-parametric models, as well as alternative clock relaxation processes.
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As a consequence of recent developments in molecular phylogenomics, all extant orders of placental mammals have been grouped into 3 lineages: Afrotheria, Xenarthra, and Boreotheria, which originated in Africa, South America, and Laurasia, respectively. Despite this advancement, the order of divergence of these 3 lineages remains unresolved. Here, we performed extensive retroposon analysis with mammalian genomic data. Surprisingly, we identified a similar number of informative retroposon loci that support each of 3 possible phylogenetic hypotheses: the basal position for Afrotheria (22 loci), Xenarthra (25 loci), and Boreotheria (21 loci). This result indicates that the divergence of the placental common ancestor into the 3 lineages occurred nearly simultaneously. Thus, we examined whether these molecular data could be integrated into the geological context by incorporating recent geological data. We obtained firm evidence that complete separation of Gondwana into Africa and South America occurred 120 +/- 10 Ma. Accordingly, the previous reported time frame (division of Pangea into Gondwana and Laurasia at 148-138 Ma and division of Gondwana at 105 Ma) cannot be used to validate mammalian divergence order. Instead, we use our retroposon results and the recent geological data to propose that near-simultaneous divisions of continents leading to isolated Africa, South America, and Laurasia caused nearly concomitant divergence of the ancient placental ancestor into 3 lineages, Afrotheria, Xenarthra, and Boreotheria, approximately 120 Ma.
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One and a half centuries after Charles Darwin and Alfred Russel Wallace outlined our current understanding of evolution, a new scientific era is dawning that enables direct observations of genetic variation. However, pure sequence-based molecular attempts to resolve the basal origin of placental mammals have so far resulted only in apparently conflicting hypotheses. By contrast, in the mammalian genomes where they were highly active, the insertion of retroelements and their comparative insertion patterns constitute a neutral, virtually homoplasy-free archive of evolutionary histories. The "presence" of a retroelement at an orthologous genomic position in two species indicates their common ancestry in contrast to its "absence" in more distant species. To resolve the placental origin controversy we extracted approximately 2 million potentially phylogenetically informative, retroposon-containing loci from representatives of the major placental mammalian lineages and found highly significant evidence challenging all current single hypotheses of their basal origin. The Exafroplacentalia hypothesis (Afrotheria as the sister group to all remaining placentals) is significantly supported by five retroposon insertions, the Epitheria hypothesis (Xenarthra as the sister group to all remaining placentals) by nine insertion patterns, and the Atlantogenata hypothesis (a monophyletic clade comprising Xenarthra and Afrotheria as the sister group to Boreotheria comprising all remaining placentals) by eight insertion patterns. These findings provide significant support for a "soft" polytomy of the major mammalian clades. Ancestral successive hybridization events and/or incomplete lineage sorting associated with short speciation intervals are viable explanations for the mosaic retroposon insertion patterns of recent placental mammals and for the futile search for a clear root dichotomy.
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The world's river dolphins (Inia, Pontoporia, Lipotes and Platanista) are among the least known and most endangered of all cetaceans. The four extant genera inhabit geographically disjunct river systems and exhibit highly modified morphologies, leading many cetologists to regard river dolphins as an unnatural group. Numerous arrangements have been proposed for their phylogenetic relationships to one another and to other odontocete cetaceans. These alternative views strongly affect the biogeographical and evolutionary implications raised by the important, although limited, fossil record of river dolphins. We present a hypothesis of river dolphin relationships based on phylogenetic analysis of three mitochondrial genes for 29 cetacean species, concluding that the four genera represent three separate, ancient branches in odontocete evolution. Our molecular phylogeny corresponds well with the first fossil appearances of the primary lineages of modern odontocetes. Integrating relevant events in Tertiary palaeoceanography, we develop a scenario for river dolphin evolution during the globally high sea levels of the Middle Miocene. We suggest that ancestors of the four extant river dolphin lineages colonized the shallow epicontintental seas that inundated the Amazon, Paraná, Yangtze and Indo-Gangetic river basins, subsequently remaining in these extensive waterways during their transition to freshwater with the Late Neogene trend of sea-level lowering.
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Since 65 million years ago (Ma), Earth's climate has undergone a significant and complex evolution, the finer details of which are now coming to light through investigations of deep-sea sediment cores. This evolution includes gradual trends of warming and cooling driven by tectonic processes on time scales of 105to 107 years, rhythmic or periodic cycles driven by orbital processes with 104- to 106-year cyclicity, and rare rapid aberrant shifts and extreme climate transients with durations of 103 to 105 years. Here, recent progress in defining the evolution of global climate over the Cenozoic Era is reviewed. We focus primarily on the periodic and anomalous components of variability over the early portion of this era, as constrained by the latest generation of deep-sea isotope records. We also consider how this improved perspective has led to the recognition of previously unforeseen mechanisms for altering climate.
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Extant xenarthrans (armadillos, anteaters and sloths) are among the most derived placental mammals ever evolved. South America was the cradle of their evolutionary history. During the Tertiary, xenarthrans experienced an extraordinary radiation, whereas South America remained isolated from other continents. The 13 living genera are relics of this earlier diversification and represent one of the four major clades of placental mammals. Sequences of the three independent protein-coding nuclear markers alpha2B adrenergic receptor (ADRA2B), breast cancer susceptibility (BRCA1), and von Willebrand Factor (VWF) were determined for 12 of the 13 living xenarthran genera. Comparative evolutionary dynamics of these nuclear exons using a likelihood framework revealed contrasting patterns of molecular evolution. All codon positions of BRCA1 were shown to evolve in a strikingly similar manner, and third codon positions appeared less saturated within placentals than those of ADRA2B and VWF. Maximum likelihood and Bayesian phylogenetic analyses of a 47 placental taxa data set rooted by three marsupial outgroups resolved the phylogeny of Xenarthra with some evidence for two radiation events in armadillos and provided a strongly supported picture of placental interordinal relationships. This topology was fully compatible with recent studies, dividing placentals into the Southern Hemisphere clades Afrotheria and Xenarthra and a monophyletic Northern Hemisphere clade (Boreoeutheria) composed of Laurasiatheria and Euarchontoglires. Partitioned likelihood statistical tests of the position of the root, under different character partition schemes, identified three almost equally likely hypotheses for early placental divergences: a basal Afrotheria, an Afrotheria + Xenarthra clade, or a basal Xenarthra (Epitheria hypothesis). We took advantage of the extensive sampling realized within Xenarthra to assess its impact on the location of the root on the placental tree. By resampling taxa within Xenarthra, the conservative Shimodaira-Hasegawa likelihood-based test of alternative topologies was shown to be sensitive to both character and taxon sampling.
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Bayesian methods for estimating evolutionary divergence times are extended to multigene data sets, and a technique is described for detecting correlated changes in evolutionary rates among genes. Simulations are employed to explore the effect of multigene data on divergence time estimation, and the methodology is illustrated with a previously published data set representing diverse plant taxa. The fact that evolutionary rates and times are confounded when sequence data are compared is emphasized and the importance of fossil information for disentangling rates and times is stressed.
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Organellar Genome Retrieval (OGRe) is a relational database of complete mitochondrial genome sequences for over 250 Metazoan species. OGRe provides a resource for the comparative analysis of mitochondrial genomes at several levels. At the sequence level, OGRe allows the retrieval of any selected set of mitochondrial genes from any selected set of species. Species are classified using a taxonomic system that allows easy selection of related groups of species. Sequence alignments are also available for some species. At the level of individual nucleotides, the system contains information on base frequencies and codon usage frequencies that can be compared between organisms. At the level of whole genomes, OGRe provides several ways of visualizing information on gene order. Diagrams illustrating the genome arrangement can be generated for any selected set of species automatically from the information in the database. Searches can be done based on gene arrangement to find sets of species that have the same order as one another. Diagrams for pairwise comparison of species can be produced that show the positions of break-points in the gene order and use colour to highlight the sections of the genome that have moved. OGRe is available from http://www.bioinf.man.ac.uk/ogre.
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Competing hypotheses for the timing of the placental mammal radiation focus on whether extant placental orders originated and diversified before or after the Cretaceous-Tertiary (KT) boundary. Molecular studies that have addressed this issue suffer from single calibration points, unwarranted assumptions about the molecular clock, andor taxon sampling that lacks representatives of all placental orders. We investigated this problem using the largest available molecular data set for placental mammals, which includes segments of 19 nuclear and three mitochondrial genes for representatives of all extant placental orders. We used the ThorneKishino method, which permits simultaneous constraints from the fossil record and allows rates of molecular evolution to vary on different branches of a phylogenetic tree. Analyses that used different sets of fossil constraints, different priors for the base of Placentalia, and different data partitions all support interordinal divergences in the Cretaceous followed by intraordinal diversification mostly after the KT boundary. Four placental orders show intraordinal diversification that predates the KT boundary, but only by an average of 10 million years. In contrast to some molecular studies that date the rat-mouse split as old as 46 million years, our results show improved agreement with the fossil record and place this split at 16-23 million years. To test the hypothesis that molecular estimates of Cretaceous divergence times are an artifact of increased body size subsequent to the KT boundary, we also performed analyses with a "KT body size" taxon set. In these analyses, interordinal splits remained in the Cretaceous.
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MrBayes 3 performs Bayesian phylogenetic analysis combining information from different data partitions or subsets evolving under different stochastic evolutionary models. This allows the user to analyze heterogeneous data sets consisting of different data types—e.g. morphological, nucleotide, and protein—and to explore a wide variety of structured models mixing partition-unique and shared parameters. The program employs MPI to parallelize Metropolis coupling on Macintosh or UNIX clusters. Availability: http://morphbank.ebc.uu.se/mrbayes Contact: fredrik.ronquist@ebc.uu.se * To whom correspondence should be addressed.
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Comparative genomic data among organisms allow the reconstruction of their phylogenies and evolutionary time scales. Molecular timings have been recently used to suggest that environmental global change have shaped the evolutionary history of diverse terrestrial organisms. Living xenarthrans (armadillos, anteaters and sloths) constitute an ideal model for studying the influence of past environmental changes on species diversification. Indeed, extant xenarthran species are relicts from an evolutionary radiation enhanced by their isolation in South America during the Tertiary era, a period for which major climate variations and tectonic events are relatively well documented. We applied a Bayesian approach to three nuclear genes in order to relax the molecular clock assumption while accounting for differences in evolutionary dynamics among genes and incorporating paleontological uncertainties. We obtained a molecular time scale for the evolution of extant xenarthrans and other placental mammals. Divergence time estimates provide substantial evidence for contemporaneous diversification events among independent xenarthran lineages. This correlated pattern of diversification might possibly relate to major environmental changes that occurred in South America during the Cenozoic. The observed synchronicity between planetary and biological events suggests that global change played a crucial role in shaping the evolutionary history of extant xenarthrans. Our findings open ways to test this hypothesis further in other South American mammalian endemics like hystricognath rodents, platyrrhine primates, and didelphid marsupials.