Fish otoliths from the middle Miocene Pebas Formation of the Peruvian Amazon

A small assemblage of 22 otoliths was identified from the historical collection of Bluntschli and Peyer gathered in 1912 on the Itaya riverbank at Iquitos, Peru (Amazonia), from the Pebas Formation. The Pebas Mega-Wetland System in western Amazonia during the Miocene represented a unique, albeit short-lived, biotope characterized by a pronounced endemic evolution with gigantism in some vertebrate groups (e.g., turtles, crocodylians). Thus far, fishes have mainly been recorded based on isolated skeletal remains and teeth. Here, we describe the first well-preserved otolith assemblage from the Pebas Formation. This otolith assemblage adds a new facet to the fauna by complementing the skeletal bony fish data, primarily with species of the Sciaenidae and, to a lesser extent, Ariidae and Cichlidae. The sciaenids and ariids indicate that migration must have occurred between the marginal marine environments to the north and the Pebas Wetland System. The otoliths also indicate the likelihood of endemic developments of adapted marine immigrants to the Pebas Wetland System, some of which have become extinct (Pogonias, Umbrina), while others now represent typical South American freshwater fish groups (Plagioscion). Six new species are described based on otoliths, one in the Cichlidae—Cichlasoma bluntschlii n. sp., one in the Ariidae—Cantarius ohei n. sp., and four in the Sciaenidae—Pebasciaena amazoniensis n. gen. et n. sp., Plagioscion peyeri n. sp., Pogonias tetragonus n. sp. and Umbrina pachaula n. sp

Crocodylian diversity peak and extinction in the late Cenozoic of the northern Neotropics

Northern South America and South East Asia are today’s hotspots of crocodylian diversity with up to six (mainly alligatorid) and four (mainly crocodylid) living species respectively, of which usually no more than two or three occur sympatrically. In contrast, during the late Miocene, 14 species existed in South America. Here we show a diversity peak in sympatric occurrence of at least seven species, based on detailed stratigraphic sequence sampling and correlation, involving four geological formations from the middle Miocene to the Pliocene, and on the discovery of two new species and a new occurrence. This degree of crocodylian sympatry is unique in the world and shows that at least several members of Alligatoroidea and Gavialoidea coexisted. By the Pliocene, all these species became extinct, and their extinction was probably related to hydrographic changes linked to the Andean uplift. The extant fauna is first recorded with the oldest Crocodylus species from South America.Facultad de Ciencias Naturales y Muse

A historical vertebrate collection from the Middle Miocene of the Peruvian Amazon

The Miocene aquatic and terrestrial fossil record from western Amazonia constitute a clear evidence of the palaeoenvironmental diversity that prevailed in the area, prior to the establishment of the Amazon River drainage. During the Miocene, the region was characterized by a freshwater megawetland basin, influenced by episodic shallow-marine incursions. A fossil vertebrate collection from the middle Miocene strata of the Pebas Formation is here studied and described. This historical collection was recovered in 1912 along the banks of the Itaya River (Iquitos, Peru), during a scientific expedition led by two scientists of the University of Zurich, Hans Bluntschli and Bernhard Peyer. Our findings include a total of 34 taxa, including stingrays, bony fishes, turtles, snakes, crocodylians, and lizards. Fishes are the most abundant group in the assemblage (~ 23 taxa), including the first fossil record of the freshwater serrasalmids Serrasalmus, and Mylossoma, and the hemiodontid Hemiodus for the Pebas system, with the latter representing the first fossil be discovered for the entire Hemiodontidae. The presence of a representative of Colubroidea in the middle Miocene of Iquitos supports the hypothesis of arrival and dispersal of these snakes into South America earlier than previously expected. This fossil assemblage sheds light on the palaeoenvironments, and the geographical/temporal range of several aquatic/terrestrial lineages inhabiting the Amazonian region

New insights into the fossil record of the turtle genus Chelus Duméril, 1806 including new specimens with information on cervicals and limb bones

Matamata turtles (Chelus Duméril, 1806) are composed of two extant species, Chelus fimbriata ­Schneider, 1783 and Chelus orinocensis Vargas-Ramírez, Caballero, Morales-Betancourt, Lasso, Amaya, Martínez, Silva-Viana, Vogt, Farias, Hrbek, Campbell & Fritz, 2020, inhabitants of the main freshwater drainages of northern South America. The systematics and palaeobiogeography of Chelus is still unresolved. Here, we describe several new fossil specimens from the Late Miocene of Urumaco (Venezuela) and Tatacoa (Colombia). The fossils are mostly complete, articulated shells that allow reestablishing validity of two extinct taxa, Chelus colombiana Wood, 1976 and Chelus lewisi Wood, 1976. One of the specimens of C. lewisi from Urumaco represents the first record within the genus for which autopodial bones (a left manus) and additional limb bones are preserved together with ashell, demonstrating evolutionary conservatism in limb anatomy for the genus. The specimen comes from the Socorro Formation, representing the earliest so far known record of Chelus for the Urumaco sequence. Additionally, one specimen from Tatacoa is the first fossil for which cervical and pectoral girdle elements are preserved. Phylogenetic analysis supports the existence of two separate clades inside of Chelus, one formed by the extinct species and the other by the extant ones

Structure and relaxations in liquid and amorphous Selenium

We report a molecular dynamics simulation of selenium, described by a three-body interaction. The temperatures T_g and T_c and the structural properties are in agreement with experiment. The mean nearest neighbor coordination number is 2.1. A small pre-peak at about 1 AA^-1 can be explained in terms of void correlations. In the intermediate self-scattering function, i.e. the density fluctuation correlation, classical behavior, alpha- and beta-regimes, is found. We also observe the plateau in the beta-regime below T_g. In a second step, we investigated the heterogeneous and/or homogeneous behavior of the relaxations. At both short and long times the relaxations are homogeneous (or weakly heterogeneous). In the intermediate time scale, lowering the temperature increases the heterogeneity. We connect these different domains to the vibrational (ballistic), beta- and alpha-regimes. We have also shown that the increase in heterogeneity can be understood in terms of relaxations

Giant extinct caiman breaks constraint on the axial skeleton of extant crocodylians

The number of precaudal vertebrae in all extant crocodylians is remarkably conservative, with nine cervicals, 15 dorsals and two sacrals, a pattern present also in their closest extinct relatives. The consistent vertebral count indicates a tight control of axial patterning by Hox genes during development. Here we report on a deviation from this pattern based on an associated skeleton of the giant caimanine Purussaurus, a member of crown Crocodylia, and several other specimens from the Neogene of the northern neotropics. P. mirandai is the first crown-crocodylian to have three sacrals, two true sacral vertebrae and one non-pathological and functional dorsosacral, to articulate with the ilium (pelvis). The giant body size of this caiman relates to locomotory and postural changes. The iliosacral configuration, a more vertically oriented pectoral girdle, and low torsion of the femoral head relative to the condyles are hypothesized specializations for more upright limb orientation or weight support

A Pliocene-Pleistocene continental biota from Venezuela

The Pliocene-Pleistocene transition in the Neotropics is poorly understood despite the major climatic changes that occurred at the onset of the Quaternary. The San Gregorio Formation, the younger unit of the Urumaco Sequence, preserves a fauna that documents this critical transition. We report stingrays, freshwater bony fishes, amphibians, crocodiles, lizards, snakes, aquatic and terrestrial turtles, and mammals. A total of 49 taxa are reported from the Vergel Member (late Pliocene) and nine taxa from the Cocuiza Member (Early Pleistocene), with 28 and 18 taxa reported for the first time in the Urumaco sequence and Venezuela, respectively. Our findings include the first fossil record of the freshwater fishes Megaleporinus, Schizodon, Amblydoras, Scorpiodoras, and the pipesnake Anilius scytale, all from Pliocene strata. The late Pliocene and Early Pleistocene ages proposed here for the Vergel and Cocuiza members, respectively, are supported by their stratigraphic position, palynology, nannoplankton, and 86 Sr/ 88 Sr dating. Mammals from the Vergel Member are associated with the first major pulse of the Great American Biotic Interchange. In contrast to the dry conditions prevailing today, the San Gregorio Formation documents mixed open grassland/forest areas surrounding permanent freshwater systems, following the isolation of the northern South American basin from western Amazonia. These findings support the hypothesis that range contraction of many taxa to their current distribution in northern South America occurred rapidly during at least the last 1.5 million years

Blood flow changes using a 3D xenogeneic collagen matrix or a subepithelial connective tissue graft for root coverage procedures: a pilot study.

BACKGROUND: The study investigated the early healing process following the treatment of single Miller class I and II recessions with a 3D xenogeneic collagen matrix (CMX) or connective tissue graft (CTG). METHODS: This pilot investigation was designed as a single-center randomized controlled parallel trial. A total of eight subjects (four per group) were treated with either CMX or CTG in the anterior maxilla. Vascular flow changes were assessed by laser Doppler flowmetry (LDF) before and after surgery and at days 1, 2, 3, 7, 14, and 30 while clinical evaluations took place at baseline and at days 60 and 180. Pain intensity perception was evaluated by the short-form McGill pain questionnaire (SF-MPQ), at days 1 and 14. RESULTS: The vascular flow fluctuated similarly in both groups pre- and post-operatively, but the CTG exhibited a more homogeneous pattern as opposed to CMX that showed a second phase of increased blood flow at 14 days. Clinically, the CTG led to greater change in mean root coverage and keratinized tissue gain but CMX was associated with lower early pain intensity scores. CONCLUSIONS: Within the limits of the study, the vascular flow alterations during the early healing of both graft types followed a similar pattern. The CMX was associated with a second peak of increased blood flow. CLINICAL RELEVANCE: The vascular flow changes after the application of CMX for single tooth recession root coverage did not show major differences from those observed after the use of a CTG. A trend for better clinical performance in terms of root coverage and keratinized tissue gain was noted for the CTG, but the initial patient morbidity was less for CMX

Internal sphincterotomy reduces postoperative pain after Milligan Morgan haemorrhoidectomy

<p>Abstract</p> <p>Background</p> <p>Over the last few years, there has been increasing attention on surgical procedures to treat haemorrhoids. The Milligan-Morgan haemorrhoidectomy is still one of the most popular surgical treatments of haemorrhoids. The aim of the present work is to assess postoperative pain, together with other early and late complications, after Milligan-Morgan haemorrhoidectomy as we could observe in our experience before and after performing an internal sphincterotomy.</p> <p>Methods</p> <p>from January 1980 to May 2007, we operated 850 patients, but only 699 patients (median age 53) were included in the present study because they satisfied our inclusion criteria. The patients were divided into two groups: all the patients operated on before 1995 (group A); all the patients operated on after 1995 (group B). Since 1995 an internal sphincterotomy of about 1 cm has been performed at the end of the procedure. The data concerning the complications of these two groups were compared. All the patients received a check-up at one and six months after operation and a telephone questionnaire three years after operation to evalue medium and long term results.</p> <p>Results</p> <p>after one month 507 patients (72.5%) did not have any postoperative complication. Only 192 patients (27.46%) out of 699 presented postoperative complication and the most frequent one (23.03%) was pain. The number of patients who suffered from postoperative pain decreased significantly when performing internal sphincterotomy, going from 28.8% down to 10.45% (χ²: 10,880; p = 0,0001); 95% Confidence Interval (CI) 24.7 to 28.9 (group A) and 10.17 to 10.72 (group B). In 51 cases (7.29%) urinary retention was registered. Six cases of bleeding (0.85%) were registered. Medium and long term follow up did not show any difference among the two groups.</p> <p>Conclusion</p> <p>internal sphincterotomy: reduces significantly pain only in the first postoperative period, but not in the medium-long term follow up; does not increase the incidence of continence impairment when performed; does not influence the incidence of the other postoperative complications especially as regard medium and long term results.</p