Theropod Teeth Research Articles

Isolated theropod teeth from the Upper Cretaceous of Goias State (Brazil): Northernmost occurrence of Abelisauridae from the Bauru Basin

Dinosaur fossils are becoming increasingly well-known from the Bauru Basin of Brazil, and represent some of the last occurring dinosaurs in South America before the end-Cretaceous mass extinction. However, sampling across the basin is not uniform, and comparatively little is known about the fossils from the northern part of the basin. Our fieldwork team discovered two isolated and well-preserved ziphodont theropod teeth from northern basin strata of the Maastrichtian Marília Formation of the south of the state of Goiás. We here identify them using quantitative analysis of morphometric data and comparisons to teeth previously described in the literature. Our comparisons and analyses indicate that they can be assigned to Abelisauridae. These specimens have little evident crown enamel ornamentation, a characteristic widely present in the teeth of theropods from the Southern Hemisphere. The materials described here are the northernmost Bauru Basin abelisaurids reported so far, demonstrating that these carnivorous dinosaurs were important faunal components across the extent of the basin, as they were in other regions of South America.

Theropod teeth palaeodiversity from the uppermost Cretaceous of the South Pyrenean Basin (NE Iberia) and the intra-Maastrichtian faunal turnover

The South Pyrenean Basin has yielded abundant dinosaur and penecontemporaneous vertebrate fossils, becoming one of the most important areas in Europe for the study of these faunas. The studied isolated theropod teeth from the Western Tremp Syncline (NE Iberia) were recovered from the uppermost Maastrichtian (topmost Arén and Tremp formations). The studies conducted have led to the identification of eight tooth morphotypes, which are referred to cf. Paronychodon, cf. Richardoestesia, an abelisaurid, a dromaeosaurid, and a non-dromaeosaurid paravian. Together with the previously reported troodontid and ornithuromorph, this study increases the known theropod palaeobiodiversity in the area to seven taxa. The latest Maastrichtian theropod fauna of the Western Tremp Syncline is thus composed of a medium to large-sized abelisaurid as well as a high diversity of small-bodied early-branching coelurosaurians and avialans, as seen in other Ibero-Armorican localities. Revision of the literature concerning the theropods of the Ibero-Armorican domain indicates that, although similar theropod groups were present before, during, and after the intra-Maastrichtian faunal turnover (an event constrained to between the early Maastrichtian and the early late Maastrichtian; lower part of C31r to the C30r/C30n reversal), there were changes in the abelisaurid, dromaeosaurid, and large avialan assemblages, as well as in the proportions of indeterminate paravian and cf. Richardoestesia morphotypes, with the presence of troodontids only recorded in post-turnover faunas. These changes suggest that theropods might have been affected by the turnover event. Nevertheless, further studies and more complete specimens could shed more light on the effects of this faunal turnover, and on the affinities and palaeobiodiversity of the latest Cretaceous Ibero-Armorican theropods.

Large theropod teeth from the Upper Cretaceous of Guangdong Province, Southern China

Cretaceous dinosaur and other terrestrial tetrapod fossils are common throughout Guangdong Province (southern China), with the greatest documented concentrations in the Heyuan and Nanxiong basins and the Ganzhou area. Further south, the Sanshui Basin has a continuous Lower Cretaceous-Eocene sequence. Within the Sanshui Basin, abundant ostracod and mollusk fossils have been documented from the Upper Cretaceous sediments, but vertebrae fossils are rare. Here we report four isolated teeth collected from the Maastrichtian of the Sanshui Basin. Although fragmentary, the teeth can be confidently referred to the Tyrannosauroidea. These teeth constitute the first record of large theropods in southern Guangdong and are also the southernmost record of tyrannosauroids in China.

A theropod tooth from the Missão Velha Formation (Late Jurassic-Early Cretaceous) of the Araripe Basin: oldest Brazilian Abelisaurid record

ABSTRACT The Missão Velha Formation (Late Jurassic-Early Cretaceous), often referred to as Brejo Santo Formation, is one of the stratigraphic units of the Araripe Basin, included within the Vale do Cariri Group. This locality, characterised by its fluvio-estuarine paleoenvironment, yielded a diverse paleoichthyofauna while its terrestrial vertebrate record is still poorly known, with a single isolated theropod lateral tooth being briefly cited until now. This study aims to revisit this specimen (UERJ-PMB R008) in order to identify it through the current quantitative and qualitative methods. The quantitative analyses were unable to properly classify the Missão Velha specimen to a single theropod group, indicating paravian, piatnitzkysaurid and abelisaurid affinities, while most of cladistic analyses assigned the UERJ-PMB R008 as an abelisaurid tooth. The specimen was finally assigned as an abelisaurid lateral tooth due to its almost straight distal margin, hooked denticles, similarly sized mesial and distal denticles, a lanceolate cross section and an irregular enamel texture. This assignment represents not only the first definitive theropod record for Missão Velha Formation as it is also the oldest abelisaurid record in the South America, filling part of the 30-million-year gap between Eoabelisaurus and Spectrovenator.

New theropod remains from the late Barremian (Early Cretaceous) of Eastern Iberian Peninsula

ABSTRACT In the last decade, the Iberian Peninsula has become a hot spot in the understanding of the early evolutionary history of large-bodied theropods from the Early Cretaceous, especially for the Spinosauridae and Carcharodontosauridae families. To date, at least five species of spinosaurids and one species of carcharodontosaurid inhabited the Iberian region during the Barremian. However, the discovery of new fossil remains suggests that such a diversity of medium- to large-sized theropods could be even higher. Here, we describe an unpublished large theropod tooth and two caudal vertebrae collected in the late 70s in the upper Barremian strata of the Arcillas de Morella Formation (Morella, eastern Spain). The tooth element displays a series of features that allow its identification as cf. Protathlitis, while the vertebral elements are tentatively attributed to an indeterminate carcharodontosaurid. Interestingly, these last remains are different from those of Concavenator, allowing speculation about the occurrence of another species of carcharodontosaurid allosauroids in the Iberian Peninsula during the Early Cretaceous apart from the famed humpbacked dinosaurs and with some reminiscence to Acrocanthosaurus. Therefore, the new findings clearly illustrate the significance of any new theropod remains in depicting the theropod diversity before the final break-up of Pangea in the Iberian Peninsula.

A lost tooth in the jungle: revisiting the sole dinosaurian record from northern Brazil.

The record of Mesozoic reptiles in the Northern region of Brazil is extremely limited, with the only definite occurrence consisting of two ziphodont teeth recovered from an oil well core in the municipality of Nova Olinda do Norte, Amazonas state, from strata of the Alter do Chão Formation (Cenomanian) of the Amazonas Basin. In this study, we aim to reevaluate MCT.R.514 using the most recent methodologies available for the identification of isolated theropod teeth. The cladistic analyses recovered MCT.R.514 as a possible metriacanthosaurid or non carcharodontosaurid allosauroid while the LDAs showed affinities between the specimen and Abelisauridae, Piatniktzysauridae, and Tyrannosauridae. MCT.R.514 was assigned as an abelisaurid due to its overall morphology that lacked metriacanthosaurid synapomorphies (i.e. spiraling mesial carina, strongly labially displaced distal carina, and well-marked mesiolingual longitudinal groove), while maintaining homoplastic features between both groups (i.e. irregular enamel texture, a lingually biconcave cross section, and a straight distal margin). This, together with a mostly Laurasian distribution of Metriacanthosauridae favors the assignment of MCT.R.514 as an abelisaurid as the most parsimonious hypothesis in this occasion. The identification of the specimen as an abelisaurid further expands the still scarce "Mid'' Cretaceous record of this clade in Brazil.

A new geographical record of Abelisauridae (Theropoda, Dinosauria) for the Bauru Group (Upper Cretaceous)

Theropod teeth allow high-rank group assignments based on both phylogenetic positioning and morphometry. To the Bauru Group, abelisaurid distribution is known mostly from isolated teeth from relatively few localities. Based on teeth we extend their distribution to Ituiutaba, NNE of the basin. Teeth specimens from the neighboring Prata county, historically attributed to Carcharodontosauridae and Abelisauridae were also analyzed. For taxon assignment, we used methods such as phylogenetic, discriminant analysis, and direct comparisons. In our phylogenetic analysis, all teeth were recovered within abelisaurids whereas in the discriminant analyses, they nested close or within abelisaurids, neovenatorids, and dromaeosaurids. Therefore, our analyses support that teeth from Ituiutaba/Prata can be assigned to Abelisauridae, evidencing a continuous spatial distribution along the Bauru Group and those sites overlaying the Serra Geral formation in the southeastern state of Mato Grosso. Further studies at Ituiutaba, including information on the associated fauna, may subsidize the understanding of abelisaurid ecological requirements and the paleoenvironment of the Adamantina Formation.

Bite and tooth marks on sauropod dinosaurs from the Morrison Formation.

Tooth-marked bones provide important evidence for feeding choices made by extinct carnivorous animals. In the case of the dinosaurs, most bite traces are attributed to the large and robust osteophagous tyrannosaurs, but those of other large carnivores remain underreported. Here we report on an extensive survey of the literature and some fossil collections cataloging a large number of sauropod bones (68) from the Upper Jurassic Morrison Formation of the USA that bear bite traces that can be attributed to theropods. We find that such bites on large sauropods, although less common than in tyrannosaur-dominated faunas, are known in large numbers from the Morrison Formation, and that none of the observed traces showed evidence of healing. The presence of tooth wear in non-tyrannosaur theropods further shows that they were biting into bone, but it remains difficult to assign individual bite traces to theropod taxa in the presence of multiple credible candidate biters. The widespread occurrence of bite traces without evidence of perimortem bites or healed bite traces, and of theropod tooth wear in Morrison Formation taxa suggests preferential feeding by theropods on juvenile sauropods, and likely scavenging of large-sized sauropod carcasses.

The predominance of teeth in the non-avian dinosaur record from Cretaceous Brazil: a review

ABSTRACT Dinosaur fossils are commonly found in Brazilian Mesozoic strata, with teeth being frequently found in Cretaceous outcrops. Many studies have been made with the aim of reviewing the known diversity of Brazilian dinosaurs, mostly focusing solely on their palaeobiogeography. However, few tried to typify these body fossils in order to see which kinds were most prevalent in the fossil record. This study aims to count and identify all occurrences of non-avian dinosaur teeth (isolated or in situ) unearthed from Brazilian Cretaceous strata in order to objectively measure their representativity in the national fossil record. Our literature search showed that almost half of the dinosaur fossil record from the Cretaceous of Brazil is composed by teeth, those being particularly abundant in the Alcântara, Adamantina and Marília formations. Theropod teeth are more abundant in comparison to sauropod teeth, with spinosaurids, deinonychosaurs, and abelisaurids being amply found. Despite representing a large share of the Brazilian fossil record, dinosaur teeth have only recently been studied in depth, with many specimens being reassessed through the current identification methods. Other aspects besides primary taxonomic identification can also be further explored using the latest technologies on dinosaur teeth, allowing a deeper understanding of the palaeobiology of these reptiles.

Tectonic aspects of the Rio Parnaíba Lineament, Duque Bacelar Region, Maranhão State, based on the record of Dinosauria, Spinosaurinae

This article shows the tectonic influence of the Parnaíba River Lineament located in the Parnaíba Basin through a paleontological finding of a Cretaceous age close to a Permian sequence. The studied region is in the northeast of the State of Maranhão, near the town of Duque Bacelar, in the vicinity of the lineament. A normal fault in the NNE-SSW direction was responsible for the lowering of the Itapecuru Formation strata (Cretaceous) and the relative upward movement of the Pedra de Fogo Formation (Permian). The unprecedented finding of a Mesozoic (mid-Cretaceous) theropod tooth located topographically at the same level as a Paleozoic unit represents evidence of tectonic activity affecting the stratigraphic successions of the Parnaíba Basin. Keywords: Parnaíba River Lineament, Pedra de Fogo Formation, Itapecuru Formation, Spinosauridae.

A combined approach to identify isolated theropod teeth from the Cenomanian Kem Kem Group of Morocco: cladistic, discriminant, and machine learning analyses

ABSTRACT The Kem Kem Group of Southeastern Morocco, North Africa, is well known for theropod remains, especially isolated teeth. Here, a collection of isolated theropod teeth is assessed for diversity using a combination of linear discriminant, phylogenetic, and machine learning analyses for the first time. The results confirm earlier studies on Kem Kem theropod diversity, with teeth referred to Abelisauridae, Spinosaurinae, and Carcharodontosauridae. A single tooth is ascribed to a non-abelisauroid ceratosaur or a megaraptoran and may represent the enigmatic averostran Deltadromeus. Spinosaurine teeth are clearly differentiated by all three methodologies, whereas abelisaurid and carcharodontosaurid teeth could only be distinguished by the machine learning and phylogenetic analyses. This study shows that a combination of independent methods is most effective at providing strong evidence on theropod dental diversity in a particular assemblage, and that cladistic and machine learning analyses are the most reliable approaches to identify isolated dinosaur teeth. The methodology used here is likely to yield results in other dinosaur assemblages where isolated teeth are more abundant than body fossils.

Theropod dinosaur facial reconstruction and the importance of soft tissues in paleobiology

Large theropod dinosaurs are often reconstructed with their marginal dentition exposed because of the enormous size of their teeth and their phylogenetic association to crocodylians. We tested this hypothesis using a multiproxy approach. Regressions of skull length and tooth size for a range of theropods and extant varanid lizards confirm that complete coverage of theropod dinosaur teeth with extraoral tissues (gingiva and labial scales) is both plausible and consistent with patterns observed in living ziphodont amniotes. Analyses of dental histology from crocodylians and theropod dinosaurs, including Tyrannosaurus rex, further indicate that the most likely condition was complete coverage of the marginal dentition with extraoral tissue when the mouth was closed. This changes our perceptions about the appearance and oral configuration of these iconic predators and has broad implications for our interpretations of other terrestrial animals with large teeth.

Machine learning confirms new records of maniraptoran theropods in Middle JurassicUKmicrovertebrate faunas

AbstractCurrent research suggests that the initial radiation of maniraptoran theropods occurred in the Middle Jurassic, although their fossil record is known almost exclusively from the Cretaceous. However, fossils of Jurassic maniraptorans are scarce, usually consisting solely of isolated teeth, and their identifications are often disputed. Here, we apply different machine learning models, in conjunction with morphological comparisons, to a suite of isolated theropod teeth from Bathonian microvertebrate sites in the UK to determine whether any of these can be confidently assigned to Maniraptora. We generated three independent models developed on a training dataset with a wide range of theropod taxa and broad geographical and temporal coverage. Classification of the Middle Jurassic teeth in our sample against these models and comparison of the morphology indicates the presence of at least three distinct dromaeosaur morphotypes, plus a therizinosaur and troodontid in these assemblages. These new referrals significantly extend the ranges of Therizinosauroidea and Troodontidae by some 27 myr. These results indicate that not only were maniraptorans present in the Middle Jurassic, as predicted by previous phylogenetic analyses, but they had already radiated into a diverse fauna that pre‐dated the break‐up of Pangaea. This study also demonstrates the power of machine learning to provide quantitative assessments of isolated teeth in providing a robust, testable framework for taxonomic identifications, and highlights the importance of assessing and including evidence from microvertebrate sites in faunal and evolutionary analyses.

The vertebrate fossil record from the Feliz Deserto Formation (Lower Cretaceous), Sergipe, NE Brazil: paleoecological, taphonomic, and paleobiogeographic implications

The Feliz Deserto Formation (Berriasian–Valanginian, Sergipe–Alagoas Basin, NE Brazil) preserved some of the earliest South American fossil records of the rifting stages which resulted in the Gondwana supercontinent break-up during the Early Cretaceous. Recently, the first spinosaurid theropod record of this formation was described, based on a tooth recovered from Canafístula 01 locality in Sergipe State. We add herein twenty-seven isolated specimens to the fossil record of the Lower Cretaceous Feliz Deserto Formation. The new material includes seven isolated spinosaurid theropod teeth of the spinosaurine clade, as well as an indeterminate theropod preungual pedal phalanx. In addition, we describe an isolated crocodyliform osteoderm, as well as eighteen isolated teeth, some of which were taxonomically identified in three distinct morphotypes of neosuchian crocodyliforms. These findings expand the Gondwanan fossil record of both spinosaurine theropods and neosuchian crocodyliforms. Despite the fragmented nature of the specimens, these new fossils allowed the characterization of their general taphonomic features with low fluvial transport of bioclast prior to the burial. The depositional paleoenvironment of the Canafístula 01 locality is compatible with the deltaic system unit, that characterizes part of the Feliz Deserto Formation during the Early Cretaceous. These fossil findings exemplify the co-occurrence of spinosaurid dinosaurs and more than one taxon of crocodyliforms in the deltaic-lacustrine paleoenvironment represented by the Feliz Deserto Formation. These new occurrences reinforce the fossiliferous potential of the Canafístula 01 locality, especially related to the paleovertebrates from the Lower Cretaceous of Brazil.

A Jurassic Tibetan theropod tooth reveals dental convergency and its implication for identifying fragmentary fossils

<p><b>The Tibetan Plateau is among the least explored areas in terms of dinosaur paleontology in the world. Here, we report a dromaeosaurid-like tooth from the Middle Jurassic Dongdaqiao Formation at the eastern part of the plateau. The tooth exhibits dromaeosaurid dental features such as the absence of constriction at the cervix, a relatively small crown-to-base ratio, a strongly recurved apex, and it lacks large transverse and marginal undulations. Parsimonious phylogenetic analyses using both dentition-based and complete morphological matrices support a dromaeosaurid affinity for this tooth and place this Tibetan theropod as the sister taxon to</b> <i><b>Velociraptor</b></i><b>. However, Bayesian tip dating analyses based on the velociraptorine affinity of the Tibetan tooth place the majority of the diversifications of early-diverging Paravian within �C or earlier than �C the Middle Jurassic, which conflicts with the paravian fossil record. Furthermore, our discriminant analysis based on morphometric data places the Tibetan theropod within Metriacanthosauridae. These results may suggest that the broad resemblance between the Tibetan specimen and velociraptorine teeth is due to convergent evolution. Based on our results, other dromaeosaurid-like teeth reported from the Middle and Late Jurassic deposits throughout Eurasia could potentially be from non-dromaeosaurids. This study suggests the presence of an early diverged theropod lineage with a wide geographical distribution and potentially a dromaeosaurid-like dietary niche. This study also highlights the importance of using multiple lines of data to identify fragmentary fossils.</b></p>

Osteology and reassessment of Dineobellator notohesperus, a southern eudromaeosaur (Theropoda: Dromaeosauridae: Eudromaeosauria) from the latest Cretaceous of New Mexico.

Dromaeosaurids (Theropoda: Dromaeosauridae), a group of dynamic, swift predators, have a sparse fossil record, particularly at the end of the Cretaceous Period. The recently described Dineobellator notohesperus, consisting of a partial skeleton from the Upper Cretaceous (Maastrichtian) of New Mexico, is the only diagnostic dromaeosaurid to be recovered from the latest Cretaceous of the southwestern United States. Reinterpreted and newly described material include several caudal vertebrae, portions of the right radius and pubis, and an additional ungual, tentatively inferred to be from manual digit III. Unique features, particularly those of the humerus, unguals, and caudal vertebrae, distinguish D. notohesperus from other known dromaeosaurids. This material indicates different physical attributes among dromaeosaurids, such as use of the forearms, strength in the hands and feet, and mobility of the tail. Several bones in the holotype exhibit abnormal growth and are inferred to be pathologic features resulting from an injury or disease. Similar lengths of the humerus imply Dineobellator and Deinonychus were of similar size, at least regarding length and/or height, although the more gracile nature of the humerus implies Dineobellator was a more lightly built predator. A new phylogenetic analysis recovers D. notohesperus as a dromaeosaurid outside other previously known and named clades. Theropod composition of the Naashoibito Member theropod fauna is like those found in the more northern Late Cretaceous North American ecosystems. Differences in tooth morphologies among recovered theropod teeth from the Naashoibito Member also implies D. notohesperus was not the only dromaeosaurid present in its environment.

Theropod teeth from the upper Barremian (Lower Cretaceous) of Vadillos-1, Spain

The upper Barremian (Lower Cretaceous) palaeontological site of Vadillos-1 is located in the North of the Cuenca Province, Spain. It includes a sedimentary succession in “Weald” facies of brown and grey mudstones and red clays, corresponding to an alluvial-palustrine muddy floodplain. Among the collected fossils, there are several vertebrate remains belonging to theropod dinosaurs, including some teeth (VD1-197, VD1-178, VD1-179, and VD1-180) that are described and identified for the first time. The taxonomic assignment was approached following two methods beside the classical consideration of their overall morphology: a cladistic analysis performed on a tooth-based data matrix, and a discriminant analysis performed on a large dataset including measurements of non-avian theropod teeth. The DSDI > 1.2 and the braided enamel present seen in VD1-197 suggest that the specimen belongs to a Dromaeosauridae or a non-tyrannosaurid Tyrannosauroidea, but the cladistics analysis classifies this tooth in the latest. The analysis showed that VD1-178, VD1-179 and VD1-180 can be ascribed to Dromaeosauridae. The dental features characteristic of this clade and present in our specimens include a DSDI > 1.2, labial and lingual depressions, and a braided enamel surface texture, which allows to place these teeth more specifically within the Eudromaeosauria. The results show, for the first time, the presence of dromaeosaurids and possibly non-Tyrannosaurid Tyrannosauroidea at Vadillos-1, thus providing new data to the European Barremian record, and contributing to the updating the geographic distribution of these dinosaurs.

Morphometric and Cladistic Analyses of a Theropod Tooth from the Itsuki Formation of the Tetori Group in the Kuzuryu District, Ono City, Fukui Prefecture, Japan

An isolated theropod tooth was found in the Hauterivian–Barremian Itsuki Formation of the Tetori Group in the Kuzuryu district, Ono City, Fukui Prefecture, central Japan. The present specimen, OMFJ V-1, shows a thick lanceolate basal cross-section and small mesial and distal denticles. A cladistic analysis based on the dental characters suggested that OMFJ V-1 be classified as belonging to Allosauroidea or Tyrannosauroidea. Principal component and linear discriminant analyses also suggested that OMFJ V-1 belongs to either of these two theropod clades. The posterior probabilities obtained in the linear discriminant analyses indicated that the confidence of the classification as Allosauroidea is slightly higher than that for Tyrannosauridae. However, because these analyses also supported possibilities of OMFJ V-1 belonging to other theropod clades to lesser extents, its taxonomic referral remains ambiguous. If OMFJ V-1 belongs to Tyrannosauroidea, it would indicate that a medium-sized tyrannosauroid already appeared in central Japan during the Hauterivian–Barremian age. On the other hand, if OMFJ V-1 belongs to Allosauroidea, it would indicate that at least two medium-to-large-sized theropods, allosaurids and tyrannosaurids, lived almost coevally in this region. The third possibility is that OMFJ V-1 belongs to Megaraptora. If such affinities are established, it would represent the oldest record of this clade of theropods.

First discovery of theropod teeth from the Nenjiang Formation (early Campanian) in the Songliao Basin, northeast China

ABSTRACT Recently, a new fossil site containing microvertebrate remains has been discovered in the upper part of the Nenjiang Formation (early Campanian) in the Songliao Basin, northeast China. Five isolated theropod teeth were discovered. The teeth were analysed based on morphological traits and the results showed that they correspond to the clades of Troodontidae, Dromaeosauridae and ?Tyrannosauridae. One dromaeosaurid tooth can be furtherly assigned to Dromaeosaurinae. It is the first discovery of theropod teeth from the Nenjiang Formation, also the first record of the Dromaeosaurinae from China. This study extends the known geographic range of these clades of theropods. The new materials also expand knowledge of the terrestrial ecosystem during the Late Cretaceous of the Songliao Basin.

Theropods from the La Bonita site, Bajo de la Carpa Formation (Neuquén Group, Santonian), Río Negro, Argentina: analysis of dental evidence

The abundant record of theropods from Bajo de La Carpa Formation (Neuquén Group, Santonian), known from the end of the nineteenth century, come from numerous locations within the Neuquén Basin. During the excavation of the titanosaur Bonitasaura salgadoi at the La Bonita fossiliferous site, northwest of Río Negro province Argentina, were recovered three isolated teeth assignable to non-avian theropod dinosaurs. Previous studies of these dental materials suggested that MPCA-Pv-247 corresponds to an indeterminate tetanure possibly related to Orkoraptor, a taxon of uncertain phylogenetic position at that moment, and MPCA-Pv-249 and 251 as possible abelisauroids. Three methods were carried out, namely, a cladistic analysis performed on a dentition-based data matrix, and a discriminant and cluster analyses performed in a large dataset including measurements of non-avian theropod teeth. The results assign for the first time a confidently phylogenetic position to the described dental material. The analysis shows that MPCA-Pv 247 belongs to Megaraptoridae, whereas MPCA-Pv 249 and 251 were recovered as belonging to Abelisauridae, supporting in a reliable way the previous assignments. The results show the presence of Megaraptoridae at La Bonita and, additionally, they represent an evidence of the first direct association of megaraptorids and abelisaurids at the same locality of the Bajo de La Carpa Formation, according to similar associations from other units of the Neuquén Group.