Multiple exostoses and an osteochondroma in a Pliocene canid from Langebaanweg 'E' Quarry (South Africa).

Langebaanweg is a Mio-Pliocene locality located on the West Coast of South Africa. It is renowned for its rich diversity of both terrestrial and marine vertebrate fossils. Several carnivorans have been identified from this site, amongst which is the recently described jackal-like canid, Eucyon khoikhoi. One of the skeletons assigned to E. khoikhoi exhibits anatomical deformities on several bones of the skeleton. Here, we use multiple methodologies (anatomical descriptions, CT scanning and histology) to investigate the bony overgrowths or exostoses evident in the radius, and we compare these findings with those of a radius from a healthy individual of the same species from Langebaanweg. Our results show that anatomical observations are important for first level observation of the pathology, but that micro-CT scanning permits a more precise assessment of how the pathology affected the internal organization of the bone, both periosteally and endosteally. This methodology permitted us to diagnose the tumors as benign rather than cancerous. Our observations of calcified cartilage in the histological thin sections in the region of the exostosis allowed us to further diagnose the exostosis as an osteochondroma. This study has demonstrated the usefulness of applying multiple techniques to characterize and diagnose pathological bony growths in a fossil canivoran. We have also demonstrated the usefulness of histological studies in permitting a more refined diagnosis of the exostosis as an osteochondroma.

The latest shallow-sea isocrinids from the Miocene of Paratethys and implications to the Mesozoic marine revolution.

The predation-driven Mesozoic marine revolution (MMR) is believed to have induced a dramatic change in the bathymetric distribution of many shallow marine invertebrates since the late Mesozoic. For instance, stalked crinoids - isocrinids (Isocrinida) have undergone a striking decline in shallow-sea environments and today they are restricted to deep-sea settings (below 100 m depth). However, the timing and synchronicity of this shift are a matter of debate. A delayed onset of MMR and/or shifts to a retrograde, low-predation community structure during the Paleogene in the Southern Ocean were invoked. In particular, recent data from the Southern Hemisphere suggest that the environmental restriction of isocrinids to the deep-sea settings may have occurred at the end of the Eocene around Antarctica and Australia, and later in the early Miocene in New Zealand. Here, we report the anomalous occurrence of the isocrinids in shallow nearshore marine facies from the middle Miocene of Poland (Northern Hemisphere, Central Paratethys). Thus, globally, this is the youngest record of shallow-sea stalked crinoids. This finding suggests that some relict stalked crinoids may have been able to live in the shallow-water environments by the middle Miocene, and further confirms that the depth restriction of isocrinids to offshore environments was not synchronous on a global scale.

Phylogenomic approaches reveal a robust time-scale phylogeny of the Terminal Fusarium Clade.

The Terminal Fusarium Clade (TFC) is a group in the Nectriaceae family with agricultural and clinical relevance. In recent years, various phylogenies have been presented in the literature, showing disagreement in the topologies, but only a few studies have conducted analyses on the divergence time scale of the group. Therefore, the evolutionary history of this group is still being determined. This study aimed to understand the evolutionary history of the TFC from a phylogenomic perspective. To achieve this objective, we performed a phylogenomic analysis using the available genomes in GenBank and ran eight different pipelines. We presented a new robust topology of the TFC that differs at some nodes from previous studies. These new relationships allowed us to formulate new hypotheses about the evolutionary history of the TFC. We also inferred new divergence time estimates, which differ from those of previous studies due to topology discordances and taxon sampling. The results suggested an important diversification process in the Neogene period, likely associated with the diversification and predominance of terrestrial ecosystems by angiosperms. In conclusion, we presented a robust time-scale phylogeny that allowed us to formulate new hypotheses regarding the evolutionary history of the TFC.

A pan-cheloniid turtle from the Middle Miocene of Portugal.

Currently, there is no information on the fossil record of Pan-Cheloniidae from the Neogene of the Iberian Peninsula. A well-preserved partial skeleton attributable to this lineage of turtles, from the Middle Miocene of Portugal, is presented here. It preserves much of the anterior half of its carapace, in which the plates remain articulated, as well as several articulated dorsal vertebrae, and an isolated cervical and a caudal vertebrae. The analysis of this Serravallian find shows that it cannot be attributed to a hitherto described taxon. Thus, a new member of Pan-Cheloniidae is defined, Lusochelys emilianoi gen. et sp. nov., improving the relatively limited knowledge about this lineage for the Middle Miocene global record. It represents the first generic and specific systematic attribution for a member of Pan-Chelonioidea in the Neogene record of the Iberian Peninsula.

Facies analysis, biostratigraphy, and provenance of the late Neogene Seulimeum Formation, Northwest Aceh basin, Sumatra (Indonesia).

A sedimentological, biostratigraphic, and petrographical investigation was conducted on exposed sedimentary rocks in the Seulimeum Formation in the Northwest Aceh Basin, Sumatra. Sedimentary facies analysis suggests a deep-marine depositional environment consists of an inner fan, middle fan, and outer fan to basin plain deposits. New foraminiferal data designated a late Miocene to early Pleistocene age for the studied rock unit, equivalent to N17 to N21 zone, with paleobathymetry in the bathyal environment. Petrographically, the sandstone of the Seulimeum Formation is included as subarkose, sublithic arenite, and lithic arenite, or classified as litho-quartzose, feldspatho-litho-quartzose, and litho-feldspatho-quartzose. Provenance analysis suggests that the origin of the sandstones is from the arc orogen sources. Furthermore, it is concluded that the development of the GSF zone in the late Neogene controls the formation of the deep-marine depositional setting. The west-south-west part of the fault is the footwall part (the Barisan Mountains), as the main high area of sedimentary source material consisting dominantly of the Woyla Group, with some contributions from Bentaro volcanic and Paleogene to early Neogene sediments. Our findings also suggest that the beginning of the Great Sumatran Fault, which corresponds with the uplift of the Barisan Mountains in the northern part of Sumatra, took place in the late Miocene, between 8.6 and 5.9 Ma.

New evidence for the antiquity of Desmostylus (Desmostylia) from the Skooner Gulch Formation of California.

Desmostylus is an extinct marine mammal genus that belongs to Desmostylia, a clade of extinct herbivorous mammals. While desmostylian remains are widely reported from Paleogene and Neogene marine strata of the North Pacific Rim, occurrences of the genus Desmostylus are almost entirely limited to middle Miocene strata, with only a few early Miocene records from Japan. Here we report a Desmostylus tooth from the earliest Miocene (Aquitanian) Skooner Gulch Formation in northern California, USA. This specimen exhibits cuspules around the crown, a primitive trait of the subfamily Desmostylidae, as seen in more basal branching desmostylid taxa such as Cornwallius and Ounalashkastylus, but with a high tooth crown and thickened enamel. The specimen is also diagnostically different from all other desmostylid genera, such as Cornwallius, and Ounalashklastylus. The Aquitanian age of the Skooner Gulch Formation implies that the distinctive tooth morphology of Desmostylus has persisted, largely unchanged, for more than 15 million years and that desmostylids possibly originated in western North America.

Pliocene seeds of Passiflora subgenus Decaloba (Gray Fossil Site, Tennessee) and the impact of the fossil record on understanding the diversification and biogeography of Passiflora.

PREMISE: Passiflora is a diverse genus of ~570 extant species primarily distributed in the Americas, from the eastern United States to Argentina and Chile. Nevertheless, the known fossil record of Passiflora is small. To date, only two fossil seed species have been unequivocally assigned to the genus. In this contribution, rare sulcate seeds from Gray Fossil Site are described as a third fossil seed species of Passiflora. METHODS: Three partial seeds with sulcate sculpture from Gray Fossil Site, early Pliocene, Tennessee, USA, were examined, photographed, and measured. They were compared to samples of sulcate seeds from six extant Passiflora species in supersection Decaloba. A broader survey of sulcate seeds produced by modern species in the subgenera Decaloba, Deidamioides, and Tryphostemmatoides was done using published illustrations and descriptions. RESULTS: The Gray Fossil Site seeds are described as Passiflora sulcatasperma, sp. nov., and assigned to subgenus Decaloba, supersection Decaloba. They are characterized by their small size, elliptical shape, ridged-and-sulcate sculpture, rugulose ridges, and thin palisade seed coat. CONCLUSIONS: The two largest subgenera of Passiflora can be identified from Neogene fossils. Subgenus Decaloba is represented by two fossil seed species, P. bulgarica (Miocene, Bulgaria) and P. sulcatasperma (Pliocene, USA). Subgenus Passiflora is represented by fossil pollen (Miocene, Argentina and Brazil) and P. appalachiana seeds (Pliocene, USA). The distributions of fossil and modern species suggest that Passiflora may have used both North Atlantic and Antarctic routes to expand into Europe and the Asian-Oceanian Paleotropics, respectively.

Osteohistology and palaeobiology of giraffids from the Mio-Pliocene Langebaanweg (South Africa).

The reconstruction of life history traits, such as growth rate, age at maturity and age at death can be estimated from the histological analysis of long bones. Here, we studied 20 long bones (metapodials, tibia and femora) of Sivatherium hendeyi and Giraffa cf. Giraffa jumae recovered from the Miocene-Pliocene locality of Langebaanweg on the West Coast of South Africa. We analysed the long bone histology and growth marks of juvenile and adult specimens of these taxa. Our results show that bone tissue types and vascular canal orientation varies during ontogeny, as well as between the different skeletal elements, and also across single cross sections of bones. Majority of our specimens appear to be still growing, with only an adult metacarpal of S. hendeyi being skeletally mature as indicated by the presence of an outer circumferential layer. We propose that the growth marks preserved in the cortices of the bones studied are most likely related to multiple catastrophic events as opposed to being annual/seasonal.

A redescription of Palaeogekko risgoviensis (Squamata, Gekkota) from the Middle Miocene of Germany, with new data on its morphology.

After its original description, the Middle Miocene gekkotan Palaeogekko risgoviensis remained an enigma for palaeontologists due to a rather poor knowledge of its osteology and relationships. Coming from a single locality in southern Germany, this gecko lived in central Europe during a period when a single gekkotan lineage (i.e., euleptine sphaerodactylids) is confidently reported to have inhabited the continent. However, it is unclear whether P. risgoviensis may represent a member of this same lineage or a second clade of Gekkota. In order to shed light on this issue, the type material of P. risgoviensis is here redescribed, refigured and extensively compared with extinct and extant geckos from Europe. A phylogenetic analysis is also conducted in order to investigate its relationships. The new observations confirm the validity of the German species as a distinct taxon, and exclude the previously-suggested chimeric status of the type material of this gecko (with the exception of a single dentary included in the type series, which clearly belong to a different lizard). Phylogenetic relationships of Palaeogekko are still unclear, though, with different positions within the gekkotan tree recovered for the taxon. Nevertheless, it is confidently supported as a non-eublepharid gekkonoid, in agreement with hypothesys presented by other scholars.

A new large-sized species of Chelonoidis (Testudinidae) without gibbosities from the middle Miocene of Aguada Escondida (NW Chubut, Patagonia, Argentina).

Previously, only one small-sized species of Testudinidae (Chelonoidis gringorum) was named from Lower-Middle Miocene of Central Patagonia. In this short article, we describe a new large Testudinidae, here named Chelonoidis meridiana sp. nov. This large new species (carapace up to 80 cm) differs from other large species of the southern South American fossil record by the absence of gibbosities on neural and costal carapacial bones, a short and wide entoplastron with a humeropectoral sulcus that was placed well behind its posterior end, and pectoral scutes that are medially longer, approximately one-third of the medial length of the hyoplastra. The discovery of this new species in the Middle Miocene increases the raw turtle diversity in Chubut, permitting to reduce the gap between the raw and phylogenetic diversity previously proposed. This occurrence is also important from both a temporal and geographic point of view. It permits fixing the presence of large-sized tortoises in the continent since ~15 million years ago (Middle Miocene). This occurrence predates all other large and giant tortoises from Argentina and South America and it is older than the giant Chelonoidis from the Langhian-Tortonian of Colombia. This is also the southernmost occurrence of a large-sized testudinid in the world.

A lower Pliocene Erymnochelyini turtle (Pleurodira, Podocnemididae) from the Democratic Republic of Congo.

The presence of a pleurodiran turtle putatively attributable to Erymnochelys madagascariensis (i.e., the only representative of Erymnochelyini that is part of the current biodiversity) or to a closely related form was recognized, in the early 1990s, for the Lower Pliocene record of the Sinda-Mohari region (Democratic Republic of Congo). The material attributable to it was restricted to postcranial remains. Although some elements of the anterior region of the skull were subsequently found, this taxon had not been analyzed in detail until now. Knowledge about Erymnochelyini has increased remarkably since the 1990s and, especially, during the 21st century. The taxon from the Democratic Republic of Congo is here analyzed in detail, not only considering current knowledge about the lineage but also incorporating new material into this study, highlighting several partial skulls. Thus, it corresponds to one of the members of this lineage represented by a greater number of skulls. It is attributed to a new taxon, Mokelemys mbembe gen. et sp. nov., being the only representative of Erymnochelyini currently known for the Pliocene record.

Tortoises and turtles from Huayquerías del Este (late Miocene-early Pliocene), Mendoza, Argentina.

We report new occurrences of Testudinidae and Chelidae from 11 different fossil sites in the Huayquerías and Tunuyán formations (late Miocene-Pliocene) in the Huayquerías del Este, Mendoza, Argentina. A total of 36 specimens were collected, representing at least three taxa from two different clades: 80.6% Testudinidae and 19.4% Chelidae. Testudinids are present throughout the stratigraphic succession, in alluvial, fluvial, and interdune sedimentary environments, represented by dorsal and plastron carapace plates, with some remains of the appendicular skeleton. A complete articulated plastron with some peripheral plates of the carapace was also recognized and is assigned to the extant species Chelonoidis chilensis, representing the oldest record for this taxon (late Miocene, Messinian). Another possible morphotype was recognized in the form of a large scapular girdle and femur that likely corresponded to an individual with a dorsal carapace of about 80 cm. This assemblage of small and large tortoise species is recognized for first time in the Messinian Age/Stage of Mendoza. Chelids are mostly restricted to fluvial deposits in the upper part of the Huayquerías Formation, except for two specimens which appear in the lower part. One specimen is represented by a right half plastron of an indeterminate Chelidae species which could correspond to a carapace of up to 24 cm in length with plastral lobes narrower than those observed in Phrynops species. Another specimen is characterized by a large costovertebral tunnel in the carapace, peripheral plates of the posterior margin of the carapace with ornamentation of fine grooves forming irregular polygons.

The northernmost Eurasian Miocene beavers: Euroxenomys (Castoridae, Mammalia) from Olkhon Island, Lake Baikal (Eastern Siberia).

The castorid dental material described in this paper derives from Miocene, fossiliferous deposits of the Baikal rift valley, exposed at Tagay Bay on Olkhon Island in the Lake Baikal, in eastern Siberia. It consists of maxillary fragments and isolated upper and lower teeth of the small trogontheriine beaver Euroxenomys minutus (von Meyer, 1838). It is the first record of the species in Asia and at the same time the northernmost occurrence of Eurasian Miocene beavers. The magnetostratigraphic correlation of the Tagay -1 section, indicates a late Burdigalian, Early/early Middle Miocene age of ~16.5 to ~16.3 Ma that corresponds to the Mammalian Neogene zone MN4/5. The presence of E. minutus in Tagay is an indicator for an Orleanian European-Siberian bioprovince during the Mid-Miocene Climate Optimum, and for a continuous belt of humid, warm-temperate to subtropical forests, stretching from Europe to Siberia, and probably further to East and South-Eastern Asia. In Eurasia, beaver remains are an indicator of permanent water bodies, which is in agreement with the palaeoenvironment of the Tagay locality.

Fossil Sirenia from the Pleistocene of Qatar: new questions about the antiquity of sea cows in the Gulf Region.

One of the largest and least documented populations of dugongs (Dugong dugon) resides in the coastal waters of the United Arab Emirates, and waters surrounding Saudi Arabia, Bahrain, and Qatar. The archaeological record of dugongs in the Gulf Region is abundant, but little is known about their fossil record in the region. Here we report an isolated sirenian rib fragment from the Futaisi Member of the Fuwayrit Formation near the town of Al Ruwais, in northern Qatar. The Fuwayrit Formation is a marine Pleistocene deposit exposed onshore in Qatar and the United Arab Emirates. Based on the correlative dating of the basal Futaisi Member with other onshore platforms, the rib fragment is approximately 125 ka. We propose that this isolated rib (likely the first rib from the right side) belongs to Dugongidae, with strong similarities to extant Dugong. We cannot, however, eliminate the possibility that it belongs to an extinct taxon, especially given its similarities with other fossil dugongid material from both Qatar and elsewhere in the world. Aside from reflecting the presence of Gulf seagrass communities in the Pleistocene, this occurrence also suggests that different (and potentially multiple) lineages of sirenians inhabited the Gulf Region in the geologic past.

The significance of recent diversification in the Northern Hemisphere in shaping the modern global flora revealed from the herbaceous tribe of Rubieae (Rubiaceae).

The global herbaceous flora is probably shaped by both ancient and/or recent diversification, companied with the impacts from geographic differences between the Northern and Southern Hemispheres. Therefore, its biogeographic pattern with respect to temporal and spatial divergence is far from full understanding. Tribe Rubieae, the largest herbaceous tribe in the woody-dominant Rubiaceae, provides an excellent opportunity for studying the macroevolution of worldwide colonization. Here, we aim to reconstruct the evolutionary history of Rubieae with regard to climate fluctuation and geological history in the Cenozoic. A total of 204 samples of Rubieae representing all the distribution areas of the tribe were used to infer its phylogenetic and biogeographic histories based on two nrDNA and six cpDNA regions. The ancestral area of Rubieae was reconstructed using a time-calibrated phylogeny in RASP and diversification rates were inferred using Bayesian analysis of macroevolutionary mixtures (BAMM). Our results show Rubieae probably originated in European region during the middle Oligocene, with the two subtribes separating at 26.8 million years ago (Ma). All the genera in Rubieae formed separate clades between 24.79 and 6.23 Ma. The ancestral area of the subtribe Rubiinae was the Madrean-Tethyan plant belt and the North Atlantic land bridge (NALB) provided passage between North America and Europe for Rubiinae. The subtribe Galiinae clade originated in Europe/central Asia during the late Oligocene. Two diversification shifts were detected within Rubieae in the late Neogene. Most extant Rubieae species diverged recently during the Neogene within clades that generally were established during the late Paleogene. The tribe shows complex migration/dispersal patterns within the North Hemisphere combined with multiple recent dispersals into Southern Hemisphere. Our results highlighted the important role of recent biogeographic diversification in the Northern Hemisphere in shaping the modern global herbaceous flora during the latest and rapid worldwide expansion in the Neogene.

SETMAR, a case of primate co-opted genes: towards new perspectives.

BACKGROUND: We carry out a review of the history and biological activities of one domesticated gene in higher primates, SETMAR, by discussing current controversies. Our purpose is to open a new outlook that will serve as a framework for future work about SETMAR, possibly in the field of cognition development. MAIN BODY: What is newly important about SETMAR can be summarized as follows: (1) the whole protein sequence is under strong purifying pressure; (2) its role is to strengthen existing biological functions rather than to provide new ones; (3) it displays a tissue-specific pattern of expression, at least for the alternative-splicing it undergoes. Studies reported here demonstrate that SETMAR protein(s) may be involved in essential networks regulating replication, transcription and translation. Moreover, during embryogenesis, SETMAR appears to contribute to brain development. SHORT CONCLUSION: Our review underlines for the first time that SETMAR directly interacts with genes involved in brain functions related to vocalization and vocal learning. These findings pave the way for future works regarding SETMAR and the development of cognitive abilities in higher primates.

Diversity, biogeography, and reproductive evolution in the genus Pipa (Amphibia: Anura: Pipidae).

The genus Pipa is a species-poor clade of Neotropical frogs and one of the most bizarre-looking due to many highly derived anatomical traits related to their fully aquatic lifestyle. With their African relatives, they form the Pipidae family, which has attracted much attention, especially regarding its anatomy, reproductive biology, paleontology and biogeography. However, the actual diversity and phylogenetic relationships within Pipa remain poorly understood, and thus so do their historical biogeography and the evolution of striking features, such as the absence of teeth and endotrophy in some species. Using short mtDNA sequences across the distribution of the genus, we identified 15 main lineages (Operational Taxonomic Units - OTUs). This more than doubles the number of the currently seven valid nominal species. Several closely related OTUs do not share nuDNA alleles, confirming species divergence. Time-calibrated phylogenies obtained from mitogenomes and from 10 nuclear loci provide highly similar topologies but strikingly distinct node ages for Pipa. High dN/dS ratios and the variation of substitution rates across the trees suggest a strong effect of saturation on fast evolving positions of mtDNA, producing a substantially shorter stem branch of Pipa. Focusing on the nuDNA topology, we inferred an early Neogene Amazonian origin of the diversification of Pipa, with an initial split between the Guiana-Brazilian Shields and Western Amazonia, a pattern observed in many other co-distributed groups. All the western species are edentate, suggesting a single loss in the genus. Each of these groups diversified further out of Amazonia, toward the Atlantic Forest and toward trans-Andean forests, respectively. These events are concomitant with paleogeographic changes and match patterns observed in other co-distributed taxonomic groups. The two Amazonian lineages have probably independently acquired endotrophic larval development.

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 86Sr/88Sr 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.

Radiostrontium sorption on natural glauconite sands of the Neogene-Paleogene formations in Belgium.

The Neogene-Paleogene glauconite sands are investigated for radionuclide sorption in the framework of the Belgian radioactive waste disposal program. This study was set up to measure the adsorption of radiostrontium (85Sr) on the sands and on glauconite fractions to identify factors explaining variable sorption among different formations. Batch 85Sr sorption experiments were set up with 45 different glauconite sands and glauconite fractions (125-250 µm) in a background solution of 1 mM CaCl2.H2O and 0.5 mM KCl. The distribution coefficients (KD) for 85Sr2+ ranged 23-65 L kg-1 for the intact sands and ranged 50-144 L kg-1 for the glauconite fractions. The KD values strongly correlated with the CEC (R2 = 0.62 for sands and 0.82 for glauconite fractions) and corresponded well with CEC based predictions based on two existing models calibrated to soils. The KD on the complete sand is proportional to the glauconite content and the KD of the glauconite fraction if no other clay minerals are present in significant amounts. Sorption equilibrium was reached within 48 h in the complete sands, in milled complete sands, in glauconite fractions and in milled glauconite fractions, suggesting no diffusive boundaries in the glauconite pellets. It is concluded that glauconite sands have a suitably high retention of radiostrontium and the sorption strength is in line with that of other geological barriers when judged from the CEC.

Diversity and biostratigraphy of the late Oligocene-late Miocene sand dollars (Echinoidea: Scutelliformes) of Argentina and Uruguay / Diversidad y bioestratigrafía de las galletas de mar (Echinoidea: Scutelloida: Scutellifomes) del Oligoceno tardío-Mioceno tardío de Argentina y Uruguay

Introduction: Scutelliforms were diverse and widespread in shallow marine environments during Neogene times in South America. Nevertheless, they have almost never been used as biostratigraphic tools. Objective: To provide a refined stratigraphic frame useful for calibrating temporal dimensions of scutelliform diversity from Argentina and Uruguay and its correlation with the molluscan assemblages previously proposed. Methods: A detailed survey of their geographic and stratigraphic provenance was carried out. We revised both the bibliography and collections (institutional and from our own field work). Results: The group is represented by 14 species belonging to six genera, and four assemblages were identified. Numerical dates of the Neogene marine rocks obtained recently allowed their placement in a chronological scheme: "Iheringiella" sp. A is restricted to the late Oligocene, the genera Camachoaster and "Eoscutella" and the species Monophoraster telfordi to the early Miocene, Abertella gualichensis and Abertella miskellyi to the middle Miocene, and Monophoraster duboisi, Amplaster coloniensis and Amplaster ellipticus to the late Miocene. Non-lunulate scutelliforms are not restricted to the late Oligocene as previously supposed. The oldest occurrence of the genus Monophoraster corresponds to the early Miocene, and along with Iheringiella are long-living taxa that embrace the 25.3 Ma-18.1 Ma (Iheringiella patagonensis) and approximately 15 Ma-6.48 Ma (Monophoraster darwini) intervals. The presence of Iheringiella in the early Miocene of northeastern Patagonia is corroborated, reaching there its northernmost distribution. Monophoraster darwini has a temporal range from the late Miocene (where it was previously thought to be restricted) back to the middle Miocene, since this is the species yielded in the well-known and discussed "Monophoraster and Venericor Beds". Conclusions: The Paleogene-Neogene scutelliforms of Argentina and Uruguay range from the late Oligocene to the late Miocene. There is a good correspondence among the numerical ages, molluscan biozones and scutelliform assemblages.

Introducción: Realizamos una síntesis actualizada de la composición taxonómica de las asociaciones de escutélidos del Oligoceno tardío-Mioceno tardío de Argentina y Uruguay. Objetivo: Ubicar los escutélidos en un marco estratigráfico refinado, a los efectos de observar su diversidad a lo largo del tiempo y la correlación de sus ensambles con los ya conocidos de moluscos. Métodos: Revisamos en detalle la procedencia geográfica y estratigráfica de los ejemplares y su asignación taxonómica, basándonos tanto en la bibliografía como en colecciones institucionales y producto de nuestras campañas de colecta. Resultados: El grupo está representado por 14 especies agrupadas en seis géneros, siendo identificadas en cuatro ensambles. Las edades numéricas recientemente obtenidas permitieron su ubicación en un esquema cronológico: "Iheringiella" sp. A se restringe al Oligoceno tardío, Camachoaster y "Eoscutella", y Monophoraster telfordi al Mioceno temprano, Abertella gualichensis y Abertella miskellyi al Mioceno medio, y Monophoraster duboisi, Amplaster coloniensis y Amplaster ellipticus al Mioceno tardío. Los escutélidos sin lúnula no están restringidos al Oligoceno tardío como se suponía. Monophoraster aparece en el Mioceno temprano y junto con Iheringiella abarcan largos períodos de tiempo, encontrándoselos entre los 25.3 Ma-18.1 Ma (Iheringiella patagonensis) y aproximadamente los 15 Ma-6.48 Ma (Monophoraster darwini). Se corrobora la presencia de Iheringiella en el Mioceno temprano del noreste de Patagonia, donde alcanza su punto más septentrional. Monophoraster darwini se encuentra desde el Mioceno medio hasta el Mioceno tardío (lapso para el cual previamente se consideraba restringido), ya que se trata de la especie presente en los bien conocidos "estratos con Monophoraster y Venericor". Conclusiones: Los escutélidos del Paleógeno-Neógeno de Argentina y Uruguay se encuentran desde el Oligoceno tardío hasta el Mioceno tardío. Hay una buena correspondencia entre las edades numéricas, las biozonas de moluscos y los ensambles de escutélidos.