Geometric morphometrics of the scapula of South American caviomorph rodents (Rodentia: Hystricognathi): Form, function and phylogeny

The scapula of the ecomorphologically diverse South American caviomorph rodents was studied through geometric morphometric techniques, using landmarks and semilandmarks to capture the shape of this complex morphological structure. Representatives of 33 species from all caviomorph superfamilies, as well as Hystrix cristata for comparisons, were analyzed. Marked differences in scapular shape were found among the major caviomorph lineages analyzed, particularly in the shape and length of the scapular spine and development of the great scapular notch. Shape differences were not influenced by body size, and only partially influenced by locomotor mode. Thus, at this scale of analysis, phylogenetic history seems to be the strongest factor influencing scapular shape. The scapular shape of erethizontids, chinchillids and Cuniculus paca could represent the less specialized state with respect to the highly differentiated scapula of octodontoids and most cavioids. In this sense, the characteristic scapular morphologies of octodontoids and cavioids could reflect particular functional capabilities and constraints associated with the evolution of prevalent locomotor modes within each lineage.     

Molecular systematics,taxonomy and biogeography of the genus Cavia (Rodentia: Caviidae)

Phylogenetic analyses were conducted on cytochrome b sequence data of the most geographically and taxonomically broad sampling of Cavia taxa to date. Primary objectives included providing the first extensive molecular phylogenetic framework for the genus, testing the taxonomic and systematic hypotheses of previous authors and providing insight into the evolutionary and biogeographic history of the genus. Support was found for the morphologically defined species C. aperea, C. tschudii, C. magna and C. fulgida and the taxonomic placement of taxa previously subject to conflicting taxonomic opinions (e.g. C. nana, C. anolaimae and C. guianae) was further resolved. Additionally, we elevate the Ecuadorian C. a. patzelti to species status, restrict the distributional limits and suggest taxonomic affiliations of some C. tschudii subspecies, and provide strong evidence for the geographic origin of guinea pig domestication. Finally, we provide an estimated evolutionary timeline for the genus Cavia, which appears to extend well into the late Miocene.     

Phylogenetic relationships among the phyllotini (rodentia: Sigmodontinae) using morphological characters

Thirty-three species representing all 14 genera of the South American rodent tribe Phyllotini and 5 problematic genera are surveyed for 96 multistate and binary dental, cranial, skeletal, external, and male reproductive tract characters. Wagner parsimony analysis confirmsCalomys as the most basal phyllotine genus, and as currently constituted it is likely paraphyletic. The results are consistent with the exclusion ofPseudoryzomys from the phyllotines and the separation ofReithrodon andNeotomys fromHolochilus at the tribal level. Several highly differentiated generic groups that include a radiation of altiplano endemics centered onAuliscomys and the largely southern Andean/PatagonianReithrodon group appear to form a clade. AGraomys generic group that includesAndalgalomys andEligmodontia is also apparent, but its relationships to other phyllotines are obscured by poorly resolved internal nodes in the more species-rich and probably paraphyletic genusPhyllotis. The significance and consequences of more intensive taxonomic sampling are discussed. The taxonomic consequences of the phylogeny are presented.     

A new genus and species of long-clawed mouse (Rodentia: Muridae) from temperate rainforests of Chile

Morphological comparisons of long-clawed mice in southern South America reveal the existence of four genera, only three of which are named. The fourth genus is described and compared with Geoxus, Chelemys and Notiomys. External, cranial and dental characters indicate that the new mouse is most closely related to Geoxus , the raton topo or mole mouse. Geoxus and the new form may be distinguished using both qualitative and quantitative characters. The incipient specializations of the new mouse for fossorial life suggest that it represents an early offshoot along the line leading to the more highly specialized Geoxus. Discovery of a new mammalian genus in Chile, where naturalists have been active for more than two centuries, indicates the importance of continued biological surveys, even in ostensibly well-studied regions. The new mouse reinforces the strong differentiation of faunas inhabiting southern beech ( Nothofagus ) forests in South America, where generic endemism of rodents and marsupials reaches 67%.     

Biology meets engineering: The structural mechanics of fossil and extant shark teeth

The majority of studies on the evolution and function of feeding in sharks have focused primarily on the movement of cranial components and muscle function, with little integration of tooth properties or function. As teeth are subjected to sometimes extreme loads during feeding, they undergo stress, strain, and potential failure. As attributes related to structural strength such as material properties and overall shape may be subjected to natural selection, both prey processing ability and structural parameters must be considered to understand the evolution of shark teeth. In this study, finite element analysis was used to visualize stress distributions of fossil and extant shark teeth during puncture, unidirectional draw (cutting), and holding. Under the loading and boundary conditions here, which are consistent with bite forces of large sharks, shark teeth are structurally strong. Teeth loaded in puncture have localized stress concentrations at the cusp apex that diminish rapidly away from the apex. When loaded in draw and holding, the majority of the teeth show stress concentrations consistent with well designed cantilever beams. Notches result in stress concentration during draw and may serve as a weak point; however they are functionally important for cutting prey during lateral head shaking behavior. As shark teeth are replaced regularly, it is proposed that the frequency of tooth replacement in sharks is driven by tooth wear, not tooth failure. As the tooth tip and cutting edges are worn, the surface areas of these features increase, decreasing the amount of stress produced by the tooth. While this wear will not affect the general structural strength of the tooth, tooth replacement may also serve to keep ahead of damage caused by fatigue that may lead to eventual tooth failure. J. Morphol., 2011. © 2010 Wiley‐Liss, Inc.     

Scaling and adaptations of incisors and cheek teeth in caviomorph rodents (Rodentia,Hystricognathi)

The South American hystricognath rodents are one of the most diverse mammalian clades considering their occupied habitats, locomotor modes and body sizes. This might have been partly evolved by diversification of their masticatory apparatus' structure and its ecological commitment, for example, chisel‐tooth digging. In this phylogeny‐based comparative study, we test the relationship between ecological behavior and mechanical features of their incisors and molariforms. In 33 species of nine families of caviomorph rodents, we analyze incisor attributes related to structural stress resistance and molar features related with grinding capacity, for example, second moment of inertia and enamel index (EI) (enamel band length/occlusal surface area), respectively. Most of these variables scaled isometrically to body mass, with a strong phylogenetic effect. A principal component analysis discrimination on the EI clustered the species according to their geographic distribution. We presume that selective pressures in Andean–Patagonian regions, on particular feeding habits and chisel‐tooth digging behaviors, have modeled the morphological characteristics of the teeth. Subterranean/burrower ctenomyids, coruros, and plains viscachas showed the highest bending/torsion strength and anchorage values for incisors; a simplified enamel pattern in molariforms would be associated with a better grinding of the more abrasive vegetation present in more open and drier biomes. J. Morphol. 2012. © 2012 Wiley Periodicals, Inc.     

Phylogeny and evolutionary history of the Aplodontoidea (Mammalia: Rodentia)

Athough over a hundred species of fossil aplodontoids have been described since the extant species, Aplodontia rufa (the mountain beaver), was first described by Rafinesque in 1817, a thorough survey of the relationships among all the species in this clade has not been undertaken since McGrew's study in 1941. Here, a complete phylogenetic analysis of all published species of aplodontoids is used to reconstruct the evolutionary relationships within the clade, and to present an updated classification of the Aplodontoidea. Several of the traditionally recognized subfamilies are found to be paraphyletic, namely the Prosciurinae, the Allomyinae, and the Meniscomyinae. Others, however, including the Aplodontinae and the Mylagaulidae, appear to be monophyletic. These latter two taxa, which include all of the hypsodont members of the aplodontoid clade, seem to be sister taxa. The history of the aplodontoid clade shows several episodes of rapid diversification in the Early Oligocene, the Late Oligocene, and the Early to Middle Miocene. The Ansomyinae and Aplodontinae show comparatively low speciation rates. The patterns of change in morphology and evolutionary rates suggest a need for a more detailed study of the causes of diversification, extinction, and ecological change in this lineage.  © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 153 , 769–838.     

Ecophenotypic variation and phylogenetic inheritance in first lower molar shape of extant Italian populations of Microtus (Terricola) savii (Rodentia)

Seventeen extant populations of Microtus (Terricola) savii have been investigated for correlations of first lower molar shape to climatic variables by means of geometric morphometrics, and controlling for phylogenetic inheritance. Comparative methods revealed that climatic variables and phylogeography provide a very similar contribution to variation in first lower molars morphology, whereas tooth size does not appear to be affected by climatic conditions. Climate‐related changes have been recognized in the anteroconid portion of the tooth. This indicates that molar tooth variation is strongly influenced by climatic conditions, although in a complex way. Calabrian populations, often ascribed to Microtus (Terricola) brachycercus, form a distinct cluster, in agreement with the most recent genetic analyses. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 632–647.     

New rodents (Mammalia) from the late Oligocene of Cabeza Blanca (Chubut) and the first rodent radiation in Patagonia

Caviomorph rodents, the New World Hystricognathi, are one of the most characteristic groups of South American mammals. Although they have been in the continent at least since the middle Eocene, those of the Deseadan Land mammal Age (early–late Oligocene) are the best source to understanding their early history due of their good record, large geographic distribution and good temporal calibration of many of the local faunas. Here, we describe the following new taxa from the classical locality of Cabeza Blanca: Octodontoidea Acaremyidae Galileomys baiosn. sp., Octodontoidea incertae sedis Ethelomys loomisin. gen.,n. comb., Acarechimys leucotheaen. sp., Protacaremys? adilosn. sp., Chinchilloidea incertae sedis Loncolicu tretosn. gen., n. sp., Incamys menniorumn. sp., Caviomorpha incertae sedis Llitun notucan. gen., n. sp., Leucokephalos zeffiaen. gen., n. sp. and Cephalomyidae Cephalomys ceciaen. sp. The DP4 of an ‘eocardiid’, Asteromys punctus? is described for the first time. These new taxa allow us to reinterpret the relationships of some of the previously known Deseadan species and genera. They show a great early diversification at least for extra Andean Patagonia, involving at least three of the main caviomorph lineages: octodontoids, chinchilloids and cavioids.     

Killer sperm whale: a new basal physeteroid (Mammalia, Cetacea) from the Late Miocene of Italy

Zygophyseter varolai , a new genus and species of Physeteroidea (Cetacea, Odontoceti), is based on an almost complete skeleton from the Late Miocene (Tortonian) in southern Italy. The extreme elongation of the zygomatic process of the squamosal and the circular supracranial basin (probably for housing the spermaceti organ) delimited by a peculiar anterior projection of the supraorbital process of the right maxilla are the most distinctive features of this bizarre sperm whale. Large body size, large teeth present in both lower and upper jaw, and anteroposteriorly elongated temporal fossa and zygomatic process of the squamosal indicate that this cetacean (for which we suggest the English common name killer sperm whale) was an active predator adapted to feeding on large prey, similarly to the extant killer whale ( Orcinus orca ). A phylogenetic analysis reveals that Zygophyseter belongs to a Middle–Late Miocene clade of basal physeteroids, together with Naganocetus (new genus for the type of ' Scaldicetus ' shigensis ). Moreover, the phylogenetic analysis shows evidence of a wide physeteroid radiation during the Miocene and that the extant Physeter and Kogia belong to two distinct families that form a clade representing the crown-group Physeteroidea.  © 2006 The Linnean Society of London, Zoological Journal of the Linnean Society , 2006, 148 , 103–131.     

Late Quaternary caviomorph rodents (Rodentia: Hystricognathi) from the Serra da Capivara,northeastern Brazil,with description of a new taxon

In this paper, fossil rodents (Hystricognathi: Caviomorpha) from the late Quaternary of the southwestern State of Piauí, northeastern Brazil, are described. The material comes from archaeological/palaeontological sites located in the region of the Serra da Capivara. The late Quaternary taxa of this region include Galea Meyen, 1832, Kerodon rupestris Wied-Neuwied, 1820, Hydrochoeridae indet., Dasyprocta Illiger, 1811, cf. Myocastor Kerr, 1792, Thrichomys Trouessart, 1880, Phyllomys Lund, 1839, Coendou magnus Lund, 1839 and a new taxon with chinchilloid affinities. The Coendou magnus and cf. Myocastor material represents the northernmost records of these taxa. The unexpected presence of a new extinct taxon contributes to the understanding of the ancient rodent faunas from South America. Today, the studied area is located within the Caatinga Biome but some of the fossil taxa, such as Hydrochoeridae and cf. Myocastor, indicate wetter environments and permanent water bodies during the late Pleistocene–early Holocene.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:92711BC3-8997-4474-A8AF-83DF4F91BB48     

A new phylogenetic classification for the gymnophthalmid genera Cercosaura , Pantodactylus and Prionodactylus (Reptilia: Squamata)

Because of the poor state of knowledge of many of the gymnophthalmid genera, systematic revision is necessary to render the classification consistent with evolutionary history. To that end, I conducted a review of the species of three genera of the Cercosaurinae which appear to form a monophyletic group: Cercosaura , Pantodactylus , and Prionodactylus . Phylogenetic analysis of 61 morphological characters was conducted after specimens of all species were examined to evaluate the composition of each taxon. The phylogenetic reconstruction suggested that the genus Prionodactylus was paraphyletic. A new phylogenetic classification is proposed that synonymizes Pantodactylus and Prionodactylus with Cercosaura. Cercosaura is redefined to include 11 species and seven subspecies. A key is provided to distinguish among species.  © 2003 The Linnean Society of London, Zoological Journal of the Linnean Society, 2003, 137 , 101−115.     

Sauropod dinosaur phylogeny: critique and cladistic analysis

Sauropoda is among the most diverse and widespread dinosaurlineages, having attained a near‐global distribution by the MiddleJurassic that was built on throughout the Cretaceous. These giganticherbivores are characterized by numerous skeletal specializationsthat accrued over a 140 million‐year history. This fascinating evolutionaryhistory has fuelled interest for more than a century, yet aspectsof sauropod interrelationships remain unresolved. This paper presentsa lower‐level phylogenetic analysis of Sauropoda in two parts. First,the two most comprehensive analyses of Sauropoda are critiqued toidentify points of agreement and difference and to create a coreof character data for subsequent analyses. Second, a generic‐levelphylogenetic analysis of 234 characters in 27 sauropod taxa is presentedthat identifies well supported nodes as well as areas of poorerresolution. The analysis resolves six sauropod outgroups to Neosauropoda,which comprises the large‐nostrilled clade Macronaria and the peg‐toothedclade Diplodocoidea. Diplodocoidea includes Rebbachisauridae, Dicraeosauridae,and Diplodocidae, whose monophyly and interrelationships are supportedlargely by cranial and vertebral synapomorphies. In contrast, thearrangement of macronarians, particularly those of titanosaurs,are based on a preponderance of appendicular synapomorphies. The purportedChinese clade ‘Euhelopodidae’ is shown to comprisea polyphyletic array of basal sauropods and neosauropods. The synapomorphiessupporting this topology allow more specific determination for themore than 50 fragmentary sauropod taxa not included in this analysis.Their distribution and phylogenetic affinities underscore the diversityof Titanosauria and the paucity of Late Triassic and Early Jurassicgenera. The diversification of Titanosauria during the Cretaceousand origin of the sauropod body plan duringthe Late Triassic remain frontiers for future studies. © 2002The Linnean Society of London, Zoological Journal of the LinneanSociety, 2002, 136 , 217?276.     

Ecomorphological diversification among South American spiny rats (Rodentia; Echimyidae): a phylogenetic and chronological approach

The phylogeny of South American spiny rats (Rodentia; Echimyidae) was studied using the exon 28 of the von Willebrand Factor nuclear gene (vWF). Sequences were analysed separately and in combination with a mitochondrial dataset (cyt b, 12S and 16S rRNAs) used in previous publications. The basal polytomy of echimyids was partially resolved and unexpected intergeneric clades were recovered. Thus, the intimate nested position of Myocastor within echimyids is evidenced. A well-supported clade is identified, including all the arboreal genera, and a group formed by Myocastor, Thrichomys, and Proechimys+Hoplomys. The clustering of Euryzygomatomys+Clyomys with Trinomys is also suggested. On the opposite, the phylogenetic position of Capromys as well as the relationships among arboreal genera remain unclear. Molecular divergence times were estimated using a Bayesian relaxed molecular clock and suggest a Middle Miocene origin for most of modern genera. The ecomorphological diversification of echimyids is discussed in the light of these new results and past environmental modifications in South America.     

A new african fossil caprin and a combined molecular and morphological bayesian phylogenetic analysis of caprini (Mammalia: Bovidae)

Given that most species that have ever existed on Earth are extinct, no evolutionary history can ever be complete without the inclusion of fossil taxa. Bovids (antelopes and relatives) are one of the most diverse clades of large mammals alive today, with over a hundred living species and hundreds of documented fossil species. With the advent of molecular phylogenetics, major advances have been made in the phylogeny of this clade; however, there has been little attempt to integrate the fossil record into the developing phylogenetic picture. We here describe a new large fossil caprin species from ca. 1.9-Ma deposits from the Middle Awash, Ethiopia. To place the new species phylogenetically, we perform a Bayesian analysis of a combined molecular (cytochrome b) and morphological (osteological) character supermatrix. We include all living species of Caprini, the new fossil species, a fossil takin from the Pliocene of Ethiopia (Budorcas churcheri), and the insular subfossil Myotragus balearicus. The combined analysis demonstrates successful incorporation of both living and fossil species within a single phylogeny based on both molecular and morphological evidence. Analysis of the combined supermatrix produces superior resolution than with either the molecular or morphological data sets considered alone. Parsimony and Bayesian analyses of the data set are also compared and shown to produce similar results. The combined phylogenetic analysis indicates that the new fossil species is nested within Capra, making it one of the earliest representatives of this clade, with implications for molecular clock calibration. Geographical optimization indicates no less than four independent dispersals into Africa by caprins since the Pliocene.     

Studies of fossil hyaenids: the genus Adcrocuta Kretzoi and the interrelationships of some hyaenid taxa

Material of the Miocene hyaenid Adcrocuta eximia from China is analysed statistically. No heterogeneities were found within this material. Comparisons with material from Samos and Pikermi, Greece, show that no taxonomic differentiation between these three samples is warranted. Adcrocuta eximia latro from the Sivalik deposits is provisionally considered a valid subspecies. The species A. australis from Langebaanweg, South Africa is removed from Adcrocuta to the genus Chasmaporthetes . The phylogenetic position of Adcrocuta has been subject to dispute, and for this reason we present a study of the interrelationships of selected hyaenid taxa using numerical cladistic methods. Two equally parsimonious trees of length 47 and consistency index 0.766 were found. Adcrocuta is placed as a sister-group to the Recent Crocuta crocuta , and not as a separate clade as suggested by other workers. Recent hyaenids form a crown-group which does not extend deep into the cladogram. Hyaena hyaena and H. brunnea are not sister-groups, and we resurrect the genus Parahyaena for the latter species.     

Studies of fossil hyaenids: the genus Adcrocuta Kretzoi and the interrelationships of some hyaenid taxa

Material of the Miocene hyaenid Adcrocuta eximia from China is analysed statistically. No heterogeneities were found within this material. Comparisons with material from Samos and Pikermi, Greece, show that no taxonomic differentiation between these three samples is warranted. Adcrocuta eximia latro from the Sivalik deposits is provisionally considered a valid subspecies. The species A. australis from Langebaanweg, South Africa is removed from Adcrocuta to the genus Chasmaporthetes. The phylogenetic position of Adcrocuta has been subject to dispute, and for this reason we present a study of the interrelationships of selected hyaenid taxa using numerical cladistic methods. Two equally parsimonious trees of length 47 and consistency index 0.766 were found. Adcrocuta is placed as a sister-group to the Recent Crocuta crocuta, and not as a separate clade as suggested by other workers. Recent hyaenids form a crown-group which does not extend deep into the cladogram. Hyaena hyaena and H. brunnea are not sister-groups, and we resurrect the genus Parahyaena for the latter species.     

Generic interrelationships within the Spionidae (Annelida: Polychaeta)

The phylogenetic relationships of spionid genera are estimated from parsimony analyses of morphological characters, with Trochochaetidae, Poecilochaetidae and Uncispionidae as outgroups. A first analysis of currendy recognised genera proved inconclusive and even exclusion of six of the most polymorphic genera resulted in 13 305 equally parsimonious trees and a fully collapsed consensus tree. A second analysis using only the type species of each genus, yielded four equally parsimonious trees; reduced to two after successive weighting. The topologies of these two trees indicated division of the family into four main groups: (1) Aonidella and Xandaros; (2) Prionospio (sensu fato)-complex, Laonice, Spiophanes and Aonides; (3) a large assemblage of genera, including Polydora-{senm late), Scolelepis, Malacoceros and Spio; (4) Atherospio, Pseudatherospio and Pygospiopsis. Earlier literature classifications of the group are evaluated and compared with die new results.     

Fossil horses from "Eohippus" (Hyracotherium) to Equus, 2: rates of dental evolution revisited

Rates of dental evolution are calculated for four upper first molar (M¹) characters of 26 ancestral-descendant species pairs of Cenozoic horses from North America. On average, crown height evolved significantly more rapidly (= 0.104 darwins, d) than did occlusal dimensions (length and width; = 0.045 d and 0.047 d, respectively). As might be expected, low-crowned Eocene and Oligocene horses ( Hyracotherium through Mesohippus ) exhibit relatively slow rates of dental evolution. During the major early Miocene adaptive shift from browsers to grazers ( Parahippus to Merychippus ), only crown height evolved rapidly. Advanced Miocene-Pliocene three-toed hipparions and one-toed equines are generally normal, or horotelic, in their rates of dental evolution. The most rapid rates are exhibited in Miocene browsing anchitheres and the dwarf genus Pseudhipparion. Horses do not show the very high rates of dental evolution reported elsewhere for Paleogene mammals. The traditional notion of horses being a prime example of rapid morphological evolution as seen from the fossil record is not corroborated by the data presented here.     

Skull anatomy of the Oligocene toothed mysticete Aetioceus weltoni (Mammalia; Cetacea): implications for mysticete evolution and functional anatomy

Toothed mysticetes of the family Aetiocetidae from Oligocene rocks of the North Pacific play a key role in interpretations of cetacean evolution because they are transitional in grade between dorudontine archaeocetes and edentulous mysticetes. The holotype skull of Aetiocetus weltoni from the late Oligocene (28–24 Ma) of Oregon, USA, has been further prepared, revealing additional morphological features of the basicranium, rostrum and dentary that have important implications for mysticete evolution and functional anatomy. The palate of Aetiocetus weltoni preserves diminutive lateral palatal foramina and associated delicate sulci which appear to be homologous with the prominent palatal foramina and sulci that occur along the lateral portion of the palate in extant mysticetes. In modern baleen whales these foramina allow passage of branches of the superior alveolar artery, which supplies blood to the epithelia of the developing baleen racks. As homologous structures, the lateral palatal foramina of A. weltoni suggest that baleen was present in this Oligocene toothed mysticete. Cladistic analysis of 46 cranial and dental characters supports monophyly of the Aetiocetidae, with toothed mysticetes Janjucetus and Mammalodon positioned as successive sister taxa. Morawanacetus is the earliest diverging aetiocetid with Chonecetus as sister taxon to Aetiocetus species. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 154 , 308–352.