The anatomy of Dolichocebus gaimanensis, a stem platyrrhine monkey from Argentina

Dolichocebus is known from the type skull encased in a concretion, numerous isolated teeth, parts of two mandibles, and a talus. The specimens come from the Trelew Member (early Miocene, Colhuehuapian South American Land Mammal Age) of the Sarmiento Formation near the village of Gaiman, Chubut Province, Argentina, dated to about 20Ma. We describe all Dolichocebus fossil material using conventional surface anatomy and micro-CT data from the cranium. The new material and newly imaged internal anatomy of the skull demonstrate that anatomical characters hitherto supposed to support a phyletic link between Dolichocebus and either callitrichines (marmosets, tamarins, and Callimico) or Saimiri (squirrel monkeys) are either indeterminate or absent. To more fully explore the phyletic position of Dolichocebus, we undertook a comprehensive phylogenetic analysis. We examined 268 characters of the cranium and dentition of 16 living platyrrhine genera, some late Oligocene and early Miocene platyrrhines, Tarsius, some Eocene and Oligocene stem anthropoids, and several extant catarrhines. These analyses consistently indicate that Dolichocebus is a stem platyrrhine, as are late Oligocene Branisella and early Miocene Tremacebus, Soriacebus, and Carlocebus. Platyrrhine evolution often is conceived of as a single ancient adaptive radiation. Review of all available phyolgenetic data suggests a more layered evolutionary pattern, with several independent extinct clades filling modern platyrrhine niche space, and modern platyrrhine families and subfamilies appearing over a nine-million-year interval in the Miocene. The outcome of these analyses highlights the pervasiveness of homoplasy in dental and cranial characters. Homoplasy is a real evolutionary phenomenon that is present at all levels of biological analysis, from amino-acid sequences to aspects of adult bony morphology, behavior, and adaptation.     

New Miocene scarabeid and hymenopterous nests and early miocene (santacrucian) paleoenvironments,patagonian Argentina

Three new trace fossils are described from Miocene paleosols of southern Argentina. Celliforma pinturensis, n. ichnosp. and Celliforma rosellii, n. ichnosp. are interpreted as cells of digging bees, possibly Anthophoridae, and Coprinisphaerafrenguellii, n. ichnosp. are brood balls of dung‐beetles. Both burrowing bees and dung‐beetles are common nesters in relatively open areas, confirming previous reconstructions of the paleoenvironment of the Pinturas Formation. A brief review of scarabeid and bee fossil nests from South America is presented, and we propose that constructed nests have a higher preservation potential than excavated nests. This fact explains their more common occurrences as trace fossils in paleosols. A new ethological category, calichnia, is proposed for hymenopterous and coleopterous traces, in which adult individuals make nests exclusively for larvae.     

A new lorisid humerus from the early miocene of Uganda

An early Miocene (18–20 mya) distal humerus from Napak, Uganda, is the only element of the forelimb to be allocated to African Lorisinae. Its loris-like features distinguish it from other East African material that more closely resembles galagids. Tracing the evolution of the lorisoid body has been a difficult task due to the lack of good fossil material. Here, we add a single specimen to this poor record. This humerus helps to document the beginning of extant lorisid locomotor specialization and function.     

A brittle star bed from the Miocene of Patagonia, Argentina

Martínez, S., del Río, C.J. & Pérez, D.E. 2010: A brittle star bed from the Miocene of Patagonia, Argentina. Lethaia , Vol. 43, pp. 1–9.
As a consequence of the extremely poor fossil record of brittle stars, every new discovery is important. The Miocene example studied herein involves the recently described species Ophiocrossota kollenbergorum Caviglia, Martínez & del Río recovered from the Chenque Formation of southeastern Argentina. The information used here is derived from unpublished data and a new record from two discrete, thin, monospecific patches. The main taphonomic features of the patches, namely the presence of specimens concordant with bedding planes, (with either aboral or oral side upwards), and the good preservation of the delicate discs (ca. 6 mm wide on average), and the preservation of un-oriented arms complete with fragile tips (not wider than 0.2 mm), point to a suddenly buried census assemblage. Although broken or isolated arms were found, this is attributed to the erosive environmental conditions of the abrasion platform where the studied exposure is located today. Size frequency distributions suggest that both patches were buried at different seasons. Observed densities are 77 and 143 individuals/m², and distances between individuals are random. The arm length/disc diameter ratio indicates that Ophiocrossota kollenbergorum may have been an epifaunal surface dweller. No signs of predation (such as regenerated arms), were identified.     

Axial skeleton of Cebupithecia sarmientoi (Pitheciinae,Platyrrhini) from the middle miocene of La Venta,Colombia

The axial skeleton of Cebupithecia sarmientoi is described and analyzed for its functional and phylogenetic implications. The vertebrae of the holotype of C. sarmientoi (UCMP 38762) most closely resemble those of the extant pitheciine genus Pithecia and display features associated with adaptations for clinging and leaping as in that genus. Cebupithecia has a relatively long non-prehensile tail, which is most similar in absolute dimensions and proportions to Pithecia monachus. It also shares with P. monachus a distinctive morphology of the thoracic vertebrae, specifically the presence of a bony pillar spanning the vertebral lamina and body, caudal to the pedicle, herein designated the vinculum laminum. It is proposed that many of these features are shared primitive retentions from the last common ancestor of the Cebupithecia-pitheciine clade.     

Biostratigraphy and biochronology of the Late Miocene of central Argentina: Evidence from rodents and taphonomy

Biostratigraphy and biochronology of the Late Miocene of central Argentina is analyzed through evolutionary patterns of octodontoid rodents. The studied faunas were found in continental sediments assigned to the Cerro Azul and Saldungaray formations (La Pampa and Buenos Aires provinces, respectively). Taphonomic attributes of recovered mammals, linked mostly to the development of paleosols or to predators’ activities, constraint the deposition lapse to short intervals. A biostratigraphic scheme based mainly on the anagenetic pattern of change in the octodontoid rodent lineage Chasichimys-Xenodontomys is proposed. Since there is no stratigraphic superposition among the studied levels, relationships among deposits are established through the polarity evidenced by the stage of evolution of chronomorphs of this lineage. Five new biozones for the Late Miocene of central Argentina are recognized. Evidence of other anagenetic sequences, and general trends of increasing hypsodonty in octodontoids, support this proposal. The results enhance the value of the “stage of evolution” concept as a correlation tool in biostratigraphic and biochronologic studies, mainly when applied through phyletic sequences.     

Tropical freshwater teleosts from Miocene beds of eastern Patagonia, southern Argentina

Loricariid and pimelodid-like siluriforms—along with undetermined percomorph—are described for the first time from Patagonia. Vertebrate fossils, including fish, mammals and birds, were found in beds attributed to the top of the Puerto Madryn Formation. These levels supposedly corresponded to the “Rionegrense marino” of former authors. Mammals occurring in the site suggest a Huayquerian age for the fossiliferous beds. The base of the Huayquerian was dated at about 9 Ma and the top is younger than 6.5 Ma. Radioisotopic dating in the marine shell beds of the Puerto Madryn Formation ranges from 11 to 9 Ma. Consequently, the section described here appears to be younger than the typical Puerto Madryn Formation from which it is separated by an unconformity. The section is correlated with the type Río Negro Formation from northern Patagonia, which also includes Huayquerian fossils. Freshwater fishes were previously unknown in beds younger than the middle Miocene in southern South America. This is also the southernmost record of loricariid fishes. The association of aquatic continental and terrestrial vertebrates indicates for the first time in Península Valdés beds of freshwater origin. The evidence apported by fossils is also in agreement with global climate trends. The local extinction of loricariids in Patagonia possibly occurred much later than the time of deposition.     

Vertebrate taphonomy in loess-palaeosol deposits: A case study from the late Miocene of central Argentina

This paper deals with the taphonomic analysis of the late Miocene bone assemblage from the Cerro Azul Formation at Telén (La Pampa Province, Argentina). The faunal assemblage was assigned to the Huayquerian mammal age (late Miocene). The fossiliferous section shows a homogeneous lithology, and is interpreted as a loess deposit with two similar and slightly developed palaeosols, classified as calcic vertisols. The studied sample comprises 5598 remains anatomically and taxonomically determined. They were collected from an area of about 48,000 m², appearing randomly distributed through the section and with low density. Most remains are small- to very small-sized, disarticulated, and very fragmented. Different taphonomical histories are inferred for microvertebrates and macromammals. The microvertebrate assemblage is interpreted as the result of predator activities. After a brief period of pre-burial exposure, remains were dispersed from the original depositional area. On the other hand, a natural and gradual death process is envisaged for macromammals, followed by a long period of exposure to weathering and dispersal by physical agents. Remains of both groups, once buried, suffered the diagenetic processes of the host rock. Consequently, the fossil assemblage from Telén would represent a condensed assemblage corresponding to two distinct time spans, i.e., the accumulation of microvertebrates took place in a short time interval whereas that of macromammals occurred over a longer period, coincident with the development of both soils.     

Spirodesmos milanai n. isp.: A Shallow-Water Spiral Trace Fossil from the Cambrian of the Eastern Cordillera,Northwest Argentina

Abstract

A new ichnofossiliferous locality in Salta Province (northwest Argentina) contains an association with numerous irregular spiral traces assigned to Spirodesmos milanai n. isp., in mature sandstones and quartzites with rippled bedding surfaces, rare wavy lamination and cross-bedded stratification. This record of early spiral behavior is interpreted as a primitive grazing method formed on muddy laminae above sand layers, and is related to a feeding strategy of an annelid-type of organism. Associated traces are Cruziana cf. semiplicata, Diplocraterion isp., Monocraterion isp., Rusophycus isp., Skolithos linearis Haldeman and Skolithos magnus Howell. The ichnoassemblage is similar to a shallow-water ichnoassociation from the Permian Ecca Group of South Africa (Mason et al., 1983 Mason, T. R., Stanistreet, I. G. and Tavener-Smith, R. 1983. Spiral trace fossils from the Permian Ecca Group of Zululand. Lethaia, 16: 241–247. [Crossref], [Web of Science ®] , [Google Scholar]).     

Hypsosteiromys (Rodentia, Hystricognathi) from the Early Miocene of Patagonia (Argentina), the only Erethizontidae with a tendency to hypsodonty

Hypsosteiromys is the only New World porcupine that shows a tendency to hypsodonty. It is recorded exclusively from the Colhuehuapian Age (Early Miocene) of central Patagonia (Argentina). In addition to the type species, a second one, Hypsosteiromys nectus(AMEGHINO, 1902), is recognized, from the southern cliff of Colhuehuapi Lake (Chubut province). It differs from the type species in the lesser development of the anterolabial and posteroflexid notches of the m1-3, shorter p4 and dp4, and more slender incisors. Dental morphology suggests that the species of Hypsosteiromys lived in more open areas than most fossil and living Erethizontidae.     

An oreopithecid proximal humerus from the middle miocene of Maboko Island,Kenya

A proximal humerus, recently recovered from the middle Miocene of Maboko Island, Kenya, provides the earliest evidence of postcranial structure and adaptation of Oreopithecidae. Provisionally attributed toNyanzapithecus pickfordi (Harrison, 1986), the specimen manifests a globose head, subequally large tuberosities, and a board, shallow bicipital groove. Although readily distinguished from the fundamentally cercopithecoid proximal humeral morphology ofVictoriapithecus (Senut, 1986), the Maboko Island oreopithecid, shows none of the derived features that are characteristic of the proximal humeri of extant hominoids. It is inferred from proximal humeral anatomy that the Maboko Island oreopithecid was an active arboreal scansor with moderate mobility at the shoulder but lacking adaptations for circumduction of the arm. In combination with craniodental evidence, proximal humeral morphology indicates that Oreopithecidae was a clade of hominoids which originated before the last common ancestor of extant apes and went extinct, without issue, in the later Miocene.     

A cercopithecid primate from the late miocene of Molayan,Afghanistan, with remarks onMesopithecus

The first fossil primate discovered in Afghanistan comes from the Late Miocene of Molayan, Khurdkabul Basin. The materials consist of an almost-complete juvenile mandible and an isolated P₃. These two specimens do not significantly differ from thePikermi Mesopithecus pentelicus and are assigned to this species. The primate mandible from the Late Miocene of Maragheh, Iran, which has always been referred by all authors toM. pentelicus, differs from the Pikermi and Molayan materials. It must be assigned to another taxon, probably a new one. The geographic range ofM. pentelicus turns out to be considerably wider in view of the discovery of the species in Molayan, eastern Afghanistan.     

On the miocene centracanthidae (Teleostei, Perciformes) from the eastern Paratethys

A new genus, Naslavcea, is erected for the Middle Miocene species Spicara fundata Bannikov, 1990 (Centracanthidae) from the Lower Sarmatian of northern Moldova. This genus is characterized by the relatively small number of rays in the dorsal and anal fins. At the same time, Pelates islamdagicus Prokofiev, 2001 from the Lower Miocene of the Apsheron Peninsula (Azerbaijan) is transferred from the family Terapontidae to Centracanthidae and referred to the genus Spicara.     

A new species of Gaimanophis (Serpentes,Boidae) from the Miocene of northwestern Argentina with remarks on the Neogene boids of South America

Gaimanophis is an extinct boid genus represented so far by a single species (Gaimanophis tenuis) known by isolated vertebrae from the early Miocene of Patagonia. In this paper, a new species of Gaimanophis is described from the India Muerta Formation (late Miocene) of Tucumán province (Argentina). Gaimanophis powelli sp. nov. distinguishes itself from G. tenuis mainly in its larger size, prezygapophyses less slanting, neural spine shorter dorsally than ventrally, and zygosphene straight bearing an anteriorly protruding tongue. This record indicates a wider temporal and geographical distribution of the genus from the early Miocene of Patagonia to the late Miocene of northwestern Argentina. The recognition of a new species of boid in South America increases the known diversity of this group. Although boids have inhabited in this territory since the Paleocene, fossils belonging to the group only show a glimpse of the real past diversity in the continent.     

A new species of fossil lorisid from the miocene of east africa

Almost 50 years after its discovery, a cranium from the early Miocene of Rusinga Island, Kenya, is designated the type specimen for a new lorisid species in the genusMioeuoticus. This new species differs fromMioeuoticus bishopi in a number of dental attributes. Several cranial features place this species in Lorisidae, where it may represent the sister group to living lorises.     

A new sphenodontian (Lepidosauria: Rhynchocephalia) from the Late Triassic of Argentina and the early origin of the herbivore opisthodontians

Sphenodontians were a successful group of rhynchocephalian reptiles that dominated the fossil record of Lepidosauria during the Triassic and Jurassic. Although evidence of extinction is seen at the end of the Laurasian Early Cretaceous, they appeared to remain numerically abundant in South America until the end of the period. Most of the known Late Cretaceous record in South America is composed of opisthodontians, the herbivorous branch of Sphenodontia, whose oldest members were until recently reported to be from the Kimmeridgian–Tithonian (Late Jurassic). Here, we report a new sphenodontian, Sphenotitan leyesi gen. et sp. nov., collected from the Upper Triassic Quebrada del Barro Formation of northwestern Argentina. Phylogenetic analysis identifies Sphenotitan as a basal member of Opisthodontia, extending the known record of opisthodontians and the origin of herbivory in this group by 50 Myr.     

New tuber-bearing Solatium taxa from Bolivia and northern Argentina

Six new Solarium taxa, from Bolivia and northern Argentina, belonging to Solarium section Petota , are described.     

Arecaceae Fossil Fruits from the Paleocene of Patagonia,Argentina

We describe fossil fruits collected from outcrops of the Salamanca Fm. (Paleocene, Danian, 63.3–61.9 Ma) at the Estancia Las Violetas locality, Chubut, Argentina that show affinities with members of the Subtribe Attaleinae, Tribe Cocoseae, Subfamily Arecoideae within the Arecaceae. The fossils are preserved as permineralizations, and were examined by longitudinal, tangential and cross-sections, as well as by the application of Computed Tomography Scanning technology (CT Scan). The fruits are ovoid drupes with 3 longitudinal grooves delimiting three valves; displaying apical stigmatic remains and a single apical germination pore. The exocarp and mesocarp are fused and anatomically indistinguishable one from another; they contain longitudinal fibrous bands with brachysclereids. A centrally placed seed occupies the single locule entirely; the seeds are deltoid with a basal hilum and acuminate tip while the endosperm is ruminate. The taxonomic position of the fossils was explored using phylogenetic analyses of molecular sequences combined with morphological data. Along with the suite of morphological characters that points to an affinity with the Subtribe Attaleinae, Tribe Cocoseae, subfamily Arecoideae, the results of the combined phylogenetic analyses confirm the taxonomic placement. This report constitutes the first confirmed record for the Subtribe Attaleinae worldwide and the first record of fossil palm fruits from Argentina.     

Bivalves from Carboniferous glacial deposits of western Argentina

Late Palaeozoic glaciation of Gondwana affected ecosystems and caused provincialism in the earth’s biota. Periglacial seas favored the origin of endemic genera and species, and remarkable differences exist with faunas of the Palaeoequatorial realm. Carboniferous glacimarine deposits are almost everywhere associated with theLevipustula levis “cold” fauna. These bio- and lithofacies are ubiquitous along the peri-Gondwana belt that stretches from western Argentina to eastern Australia, including central Patagonia and Antarctica. Both glacial sediments and theLevipustula levis Zone are assumed to date from the beginning of the Namurian to an indeterminated part of the early Westphalian. The bivalve fauna associated with the Carboniferous glacial deposits of western Argentina is described, including four new species:Promytilus grandis n. sp.,Leptodesma (Leiopteria) aredesi n. sp.,Oriocrassatella andina n. sp., andMyofossa calingastensis n. sp. Six insufficiently preserved species are left in open nomenclature:Leptodesma (Leiopteria) n. sp.,Euchondria n. sp.,Schizodus n. sp.,Promytilus sp.,Cypricardinia? sp., andStreblopteria? sp.; it proved even impossible to decide whether a badly damaged incomplete specimen belongs toMyonia orVacunella. Five other species, which are known from single specimens, are assigned tentatively to the generaPhestia, Atomodesma, Pyramus, Vacunella, andPleurophorella.