Tritylodon longaevus Owen, 1884 is one of the most common members of the Lower Jurassic faunas of the Karoo Basin. The cranial and dental anatomy of this taxon is well known, but its postcranium has not been previously addressed in detail. Our analysis shows that T. longaevus shares many postcranial features with other tritylodontids that distinguish them from other non-mammaliaform cynodonts. The correlation between taxon size and postcranial anatomical traits is briefly explored among tritylodontids, showing that few morphological differences among species correlate with size. Analysis of the purported oldest remains of Tritylodon, from the Norian Los Colorados Formation of Argentina, suggests that they cannot be unambiguously assigned to this taxon, circumscribing the record of Tritylodon to African localities.

Sauropod dinosaurs achieved extreme body sizes via rapid and sustained growth, permitted in part by the delayed fusion of the neurocentral sutures. Unfused sutures are joined by cartilage, which is more susceptible to dislocation than the bone that replaces it. In sauropods, the competing interests of growth and strength were balanced by the presence of complex, interdigitated neurocentral sutures. Sutural complexity is correlated with the magnitude of stress the suture must resist. To better understand this relationship in sauropods, sutural complexity was measured from the articulated presacral vertebrae of Spinophorosaurus nigerensis, and patterns of gross morphology were observed. Complexity was calculated as a length ratio and as the fractal dimension of the suture. The complexity pattern indicates that stress increased proximally along the neck, was greatest in the anterior dorsal vertebrae, and then decreased towards the sacrum. This stress distribution is attributable to the weight of the neck and the ribcage. The sutural structures are oriented to resist anteroposterior translation of the neural arch in cervical vertebrae and lateral rotation in dorsal vertebrae. This pattern could result from the greater mechanical advantage of an elongate cervical centrum in resisting torsion relative to a short dorsal centrum and the greater mechanical advantage of wide dorsal transverse processes in generating torsion. The patterns and structures described are similar to those of Alligator. Complex neurocentral sutures may represent an archosauriform adaptation that facilitated rapid growth rates and large adult body sizes.

Lagostomine rodents (Caviomorpha, Chinchillidae) are very abundant in late Cenozoic vertebrate associations of the Pampean area but the study of their systematics has been mostly limited to a handful of works from the late 19^th Century and early 20^th Century. Although seven species of Lagostomus were described for the Chapadmalal Formation (late Pliocene; Buenos Aires Province, Argentina), the holotypes of these species do not present precise stratigraphic provenance and have not been studied since their original description. This study of lagostomines from the Chapadmalal Formation with precise stratigraphic provenance gives way to the recognition of at least three species: Lagostomus incisus, L. compressidens and L. euplasius. The comparative study of the holotypes of the previously recognized species in this unit indicates that ‘Viscaccia indefinita’ is a junior synonym of L. compressidens while ‘V. loberiaense’, ‘V. definita’ and ‘V. chapalmalense’ are junior synonyms of L. euplasius. The validity of ‘Viscaccia arcuata’ and its inclusion in the Chapadmalalan fauna has to be re-evaluated. This work clarifies part of the systematics of the genus Lagostomus, thus contributing to the comprehension of the taxonomic diversity of chinchillids during their most recent evolutionary history.

After a diversity peak during the Late Triassic, corals were severely affected by the end-Triassic extinction. The study of their recovery is fundamental for a better understanding of the ecological rearrangement undergone by Early Jurassic marine invertebrate faunas. In this contribution we analyze the morphologic recovery shown by scleractinians in southern Mendoza Province, which is the only place in the Neuquén Basin with marine outcrops spanning the Triassic/Jurassic boundary. A two-stage recovery pattern was recognized. During the first stage (Hettangian—Sinemurian) only solitary corals, most of them discoidal, could be found. After a hiatus encompassing the latest Early Sinemurian and the Late Sinemurian, the second stage (Pliensbachian) developed. A sharp increase in morphological diversity of solitary corals is then recorded, with discoidal, cupolate, patellate, turbinate, trochoid/turbinate, trochoid/ceratoid and maybe cylindrical morphologies. Additionally, colonial forms with low degree of corallite integration (phaceloid and cerioid colonies) appeared in the basin. The diversification trend hereby described provides useful insight regarding the scleractinian recovery after the end-Triassic mass extinction event within southern basins of South America. Furthermore, this recovery pattern is comparable with the one recognized for other regions (Chile, western North America, central Asia) yet it differs from that observed in some European basins. The trend outlined herein for Early Jurassic corals from the Neuquén Basin may reflect a large-scale phenomenon and/or the action of local adverse conditions (such as fluvial influence), which is open to further testing.

The earliest records of the genus Spiticeras Uhlig in Western Gondwana occur in the Upper Jurassic—Lower Cretaceous deposits of the Vaca Muerta Formation in the Neuquén Basin, Argentina. Those records involve two species, Spiticeras acutum Gerth and Spiticeras hauthali Gerth, which were firstly described from Arroyo Durazno, Mendoza. A systematic revision and reconsideration of the biostratigraphic distribution of both species was performed based on the study of type material and new bed-by-bed collections in the type locality and other southern Mendoza sections. S. acutum and S. hauthali display a succession of ornamentation stages that, together with other morphological characters, sustain their assignation to the genus Spiticeras. Addidionally, macroconchiate and microconchiate specimens were identified in both taxa. The record of S. acutum from the lowermost beds assigned to the Late Tithonian—Early Berrisian Substeueroceras koeneni Assemblage Biozone substantiates the downwards extension of the known range of the species in the Neuquén Basin. Given that the basal portion of the S. koeneni Biozone can be correlated with the Late Tithonian Standard “Durangites” Zone and that these early spiticeratins records have been found to be associated with a Late Tithonian secondary nannofossil bioevent (Raghodiscus asper (Stradner) first occurrence) in two of the studied sections, a Late Tithonian age is suggested for the earliest records of Spiticeras in Gondwana.

Information about barnacles as fossil components of hard substrate communities from middle latitudes in the Southern Hemisphere is scarce. Changes in these barnacle communities during episodes of extinction, such as that which occurred during the Cretaceous/Paleogene (K—Pg) boundary, are almost unknown. We describe encrusting and boring barnacles associated with Maastrichtian and Danian oysters, evaluate the involved taphonomic processes and report changes in their frequencies over time. A total of 1,174 valves belonging to nine oyster species, collected from the Jagüel and Roca formations of the Neuquén Basin, were analyzed. Presence/absence of barnacles or their bioerosional traces were recorded, frequencies of host incrustation and bioerosion were calculated and taphonomic and statistical analyses were performed. The encrusting barnacles identified on the oyster shells were assigned to Verruca rocana and, their traces, to the ichnospecies Centrichnus concentricus Bromley and Martinell. The boring barnacles are represented by traces assigned to the ichnogenus Rogerella. A preliminary taphonomic analysis indicated that late Maastrichtian and early Danian shells presented a fair-poor condition given by abrasion and fragmentation as taphonomic attributes while late Danian shells exhibited mostly good-fair or mixed condition for both attributes. Verruca rocana was not recorded during the late Maastrichtian but high frequencies of encrusted valves did become apparent after the K—Pg boundary. Boring barnacles represented by the trace Rogerella exhibited a decline in abundance during the early Danian but an increase during the late Danian. Both the encrusting and the boring barnacles associated with oysters presented an increase in their frequencies during the late Danian.

A new record of fossil moss in Miocene amber from Chiapas, southern Mexico, is hereby presented. The fossil moss is assigned to the genus Hypnodontopsis Iwatsuki et Noguchi (Family Rhachitheciaceae) and characterized primarily by narrowly lanceolate to linear leaves arranged in rosettes, with erect costae, and short apiculate leaf tips, with upper cells larger than the lower cells. This sample, for which current worldwide distribution consists of at least three disjunct and geographically restricted occurrences, represents the first fossil record of the genus Hypnodontopsis in the Americas. While Hypnodontopsis is represented by five fossil species known from Eocene Baltic and Saxon amber, extant species are known from Asia, Africa and Mexico. The new fossil specimen most closely resembles the extant species Hypnodontopsis mexicana (Thér.) H. Robins, synonymous with the fossil species Hypnodontopsis conferta (Goeppert and Berendt) J.-P. Frahm. from Eocene Baltic amber. Hypnodontopsis mexicana can only be found in central Mexico (America) and in Uganda (Africa). Accordingly, the distribution of current and extinct species of Hypnodontopsis suggests that the genus diversified in both Laurasia and Gondwana and then suffered extinction by the end of the Paleogene in Europe.