Papers by Leonardo M Carneiro
Historical Biology , 2024
Protolipterna ellipsodontoides is a small bunodont South American native ungulate, generally cons... more Protolipterna ellipsodontoides is a small bunodont South American native ungulate, generally considered an early litoptern, exclusively found in the Palaeogene Itaboraí Basin. Its dentition is well known; however, its mandibular morphology was only known by fragmentary materials. Here, we describe the first complete mandible of this species. A micro-CT scan reveals the first case of alveolus resorption in this putative early litoptern. Two accessory canals on the retromolar region are also described. Canals on the retromolar region are documented for other mammalian orders; however, this represents the first description of this feature for the Protolipternidae. Unlike more advanced litopterns, this species lacks specialisations related to strict herbivory, and its dental and mandibular morphology suggests an omnivore habit. A comparison with the mandible of another Itaboraian protolipternid, Miguelsoria parayirunhor, indicates the presence of different dietary specialisations. Body mass estimations for both species are also provided.
Journal of South American Earth Sciences, 2024
The Itaboraí Basin, municipality of Itaboraí, Rio de Janeiro, Brazil, preserved an early Eocene v... more The Itaboraí Basin, municipality of Itaboraí, Rio de Janeiro, Brazil, preserved an early Eocene vertebrate assemblage. Among its representatives, Metatheria comprises its most diverse clade, with at least 29 genera and 43 species. Among large- to very large-sized taxa, protodidelphids are represented by Protodidelphis vanzolinii, P. mastodontoides, and Carolocoutoia ferigoloi. Protodidelphis mastodontoides was initially considered a different genus, Robertbutleria; however, the synonymy of Robertbutleria with Protodidelphis has never been tested. A phylogenetic analysis recovered Robertbutleria as the sister taxon of Carolocoutoia and not Protodidelphis. Robertbutleria and Carolocoutoia share the presence of rounded upper molars, evident bunodonty, rounded postmetacrista, U-shaped protocone, asymmetric placement of m4, obliquely oriented p1-3, and absence of diastemata. The analysis recovered that the dental features considered for the synonymy of Robertbutleria with Protodidelphis represented plesiomorphies for Protodidelphidae (e.g., sinuous crest between StB and StD, marked increase in the size of the molars from M/m1 to M/m3). Based on the results, an emended diagnosis of Protodidelphinae (the clade that includes Protodidelphis, Robertbutleria, and Carolocoutoia) is presented. Two principal component analyses (PCAs) recognized protodidelphine taxa in different morphospaces, indicating differential allometric and morphofunctional patterns. Protodidelphis was a generalized frugivore, Robertbutleria was a fibrous frugivore, and Carolocoutoia was a turgent frugivore. Moreover, the similar morphological and morphofunctional indexes of protodidelphines suggest a “short time” evolutionary diversification for this clade, and that trophic specializations do not necessarily require great morphological changes, allowing the sympatric co-existence of morphologically similar ingroup genera.
Journal of South American Earth Sciences, 2024
The Itaboraí Basin, located in Itaboraí, Rio de Janeiro, Brazil, has preserved one of the most im... more The Itaboraí Basin, located in Itaboraí, Rio de Janeiro, Brazil, has preserved one of the most important early Eocene vertebrate assemblages of the Southern Hemisphere. Among its representatives, Metatheria comprises its most diverse group, with a minimum of 29 genera and 43 species. Considering this diversity, tiny and very small taxa are represented by Jaskhadelphyidae and closely related taxa, “Peradectoidea”, Sternbergiidae, Derorhynchidae, and an undescribed taxon with uncertain affinities, previously referred to as “cf. Armintodelphys”. Here, this last taxon is named Thylacopygmaeus oliveirai gen. et sp. nov.; it is distinguished by its extremely small size (inferred body mass less than 15 g) and in that its lower molars show the metaconid placed distally to the protoconid and a developed postentocristid. Two PCA analyses of T. oliveirai and other tiny-sized taxa from Itaboraí indicate that the new taxon exhibits distinctive morphometric and morphofunctional patterns compared to other sympatric tiny-sized taxa. The inclusion of T. oliveirai gen. et sp. nov. in a phylogenetic analysis recovered it as the sister taxon of Rumiodon, an early Oligocene herpetotheriid from Peru, based on the presence of a labiolingually compressed metaconid on m3 and a labiolingually compressed protoconid on m4. We group these two taxa within the Herpetotheriidae in a new clade, the Rumiodontinae nov. Contrary to a previous hypothesis, Thylacopygmaeus is not closely related to Armintodelphys. The results confirm the Paleogene occurrence of Herpetotheriidae in South America.
Journal of South American Earth Sciences , 2024
The Itaboraí Basin, municipality of Itaboraí, Rio de Janeiro state, Brazil, preserved an Early Eo... more The Itaboraí Basin, municipality of Itaboraí, Rio de Janeiro state, Brazil, preserved an Early Eocene vertebrate assemblage. Among its representatives, Metatheria comprises its most diverse clade, with a minimum of 29 genera and 43 species. Considering this diversity, large-sized taxa (based on didelphid standards, i.e., between 1 kg and 3.3 kg) are represented by Didelphopsis, Protodidelphis and Patene, each considered to have explored different trophic niches. However, the discovery of a new large-sized metatherian from this locality, here named Xenocynus crypticus gen. et sp. nov., indicates that the trophic complexity of Itaboraí’s metatherians could not be so well-defined. Xenocynus crypticus gen. et sp. nov. is identified by the presence of its reduced StD, long postmetacrista, short protocone, talonid's area much smaller than the one of trigonid, spaced paraconid and metaconid (bases are not in contact), molar series increasing in size from m1 to m4, deep maxillary pits between upper molars, and robust symphysis. We included Itaboraidelphys camposi, X. crypticus gen. et sp. nov. and other large-sized taxa in two PCA analyses, the first considering morphometric measurements and the second considering some morphofunctional indexes, to test their placement in morphospace. Our analyses indicated that these taxa exhibit distinctive morphometric and morphofunctional patterns, suggesting low trophic niches overlapping between them. The results indicate that X. crypticus gen. et sp. nov. was a generalized carnivore (insectivory-carnivory), more specialized than the insectivorous/omnivorous Itaboraidelphys camposi, but less specialized than the larger Patene simpsoni, a carnivorous taxon.
Journal of South American Earth Sciences, 2024
Carolocoutoia ferigoloi is one of the largest metatherians of the Itaboraí fauna (Early Eocene, S... more Carolocoutoia ferigoloi is one of the largest metatherians of the Itaboraí fauna (Early Eocene, Southeastern Brazil). It was originally identified from a single upper molar with a markedly bunodont crown, wrinkled enamel, and a robust protocone. Here, we describe a nearly complete right dentary of C. ferigoloi with the alveoli of the premolars and first lower molar, a very worn second lower molar, complete third and fourth lower molars, and a right second upper molar. Carolocoutoia differs from other protodidelphids in having inflated, conical trigonid cusps, a more flattened entoconid, a developed entocristid, and a supernumerary cusp labial to the entoconid. Carolocoutoia was recovered in our phylogenetic analysis as the sister taxon of Protodidelphis ), since both share the presence of an anteriorly recurved dentary, wrinkled enamel, and a sinuous crest between stylar cusps B and D. The inflated, conical trigonid cusps of Carolocoutoia represent an evolutionary convergence with other South American Paleogene mammals, such as some ungulates, and the polydolopimorphian Roberthoffstetteria. We also present the second record of a pathology (molar extrusion) in a metatherian from Itaboraí. Based on its molar crown morphology, Carolocoutoia ferigoloi was a specialized frugivorous metatherian. The occurrence of a specialized frugivorous protodidelphid in the Itaboraí fauna is in line with the well-established increase in global temperatures and the expansion of tropical forests after the Paleocene-Eocene Thermal Maximum (around 55.5–55.3 million years ago).
Journal of South American Earth Sciences, 2024
Proborhyaenidae are the largest known sparassodonts, with a fossil record spanning from the early... more Proborhyaenidae are the largest known sparassodonts, with a fossil record spanning from the early Eocene to the Pliocene. The Eocene record of this group is scarce, occurring only in four geological units: Las Violetas Formation, lower Lumbrera Formation, Sarmiento Formation and Geste Formation, all in Argentina. Herein, a new occurrence of this clade is described from the Guabirotuba Formation (late middle Eocene) of the Curitiba Basin in Brazil. This unit, along with the Itaboraí and Taubaté basins are the only units in Brazil with Paleogene continental mammal records. The specimen MCN.P.1340 is an isolated lower left canine, that displays the main features associated with the lower canines of proborhyaenids, such as, an open root, median sulci, a thin enamel layer and posterior curvature. This new occurrence not only represents the biggest mammalian predator of the Guabirotuba Fauna, an expansion of the known geographical range of the family, but also provides further support for the relative dating of the Guabirotuba Formation and its fauna.
Journal of South American Earth Sciences, 2023
The Itaboraí fauna has preserved two of the oldest known sparassodonts in South America, Patene s... more The Itaboraí fauna has preserved two of the oldest known sparassodonts in South America, Patene simpsoni and Nemolestes brasiliensis. Of these, Nemolestes brasiliensis has been identified by just two isolated lower molars. This article presents the first known m1 and dentary elements of this species. We have observed that this taxon differs from Nemolestes spalacotherinus due to the presence of several symplesiomorphies for Sparassodonta, such as a well-developed metaconid and closely spaced paraconid and metaconid on m2. A phylogenetic analysis recovered N. brasiliensis as the sister taxon of Nemolestes sp. indet. from Guabirotuba based on an abrupt increase in the dentary height at p3-m1 level. These two taxa were recovered as basal to a clade that comprehends Nemolestes spalacotherinus and all other sparassodonts (except for Mayulestes, Allqokirus and Patene). Therefore, we have assigned the Itaboraí specimens to a new genus, Silvenator. This result provides further support that the Itaboraí fauna has only preserved early lineages of Sparassodonta. A principal component analysis based on five morphofunctional indices in extant and extinct small carnivorous metatherians recovered a likely mesocarnivorous (faunivory) diet for Silvenator, thereby placing this taxon close to the thylacinid Badjcinus and, to a lesser extent, Allqokirus.
Journal of Mammalian Evolution, 2023
Nemolestes and Procladosictis are Eocene sparassodonts of controversial affinities. Nevertheless,... more Nemolestes and Procladosictis are Eocene sparassodonts of controversial affinities. Nevertheless, despite the poor preservation of their holotypes, several other specimens have been tentatively assigned to these genera, as exemplified by some isolated teeth from the Itaboraí and Laguna Fría faunas. Here, we revise specimens referred to Nemolestes and Procladosictis from Itaboraí, Laguna Fría and Ameghino’s collection. Nemolestes differs from Patene in its more reduced metaconid, and “carnassialized” m4 (with reduced talonid and talonid cuspids, except the hypoconulid), features that make it possible to identify specimens from Itaboraí and Laguna Fría as Nemolestes. This taxon occurred from the early Eocene (Itaboraian SALMA) to the middle Eocene (Casamayoran SALMA). Nemolestes represents the oldest known hypercarnivorous sparassodont. The inclusion of Nemolestes and Procladosictis in a comprehensive phylogenetic analysis recovered them in a polytomy as the sister taxa of Borhyaenoidea and a new unnamed clade that includes Lycopsis, Dukecynus, Hathliacynidae, Hondadelphys and Stylocynus. Nemolestes shares with these taxa, but not Patene, the presence of a “carnassialized” m4. Nemolestes differs from known borhyaenoids in the absence of a medially positioned protoconid and short anterolabial cingulid. Therefore, Nemolestes is an early lineage of Sparassodonta. “Procladosictis erecta” is a lower premolar of the unnamed clade, as it shows symmetric walls and a small precingulid. "Procladosictis erecta" should be, in fact, referred to Procladosictis. Our phylogenetic analysis indicates that during the early middle Eocene (Laguna Fría and La Barda faunas), the unnamed clade and Borhyaenoidea had already diverged. Therefore, the evolutionary history of these groups is older than previously thought.
Anais da Academia Brasileira de Ciências, 2021
A new early Eocene, small-sized metatherian from the Itaboraí fauna is described. The new taxon i... more A new early Eocene, small-sized metatherian from the Itaboraí fauna is described. The new taxon is recognized on the basis of an incomplete dentary recovered from fi ssure fi llings in the travertine limestones from the Itaboraí Basin, State of Rio de Janeiro, Brazil. The phylogenetic analysis placed the new genus and species as the sister taxon of Derorhynchus, undescribed Derorhynchidae, and Coona plus Pauladelphys. When compared to Derorhynchus, the new taxon exhibits a shorter dentary, in which the fi rst lower premolar is not separated from the second by a diastema, and shows second and third lower molars with subequal trigonid and talonid width (in Derorhynchus the talonids are wider than the trigonids). This new taxon shows some plesiomorphic traits when compared with the remaining derorhynchids, such as the shallower dentary (less than 1.5 mm), and conical entoconids rather than fl attened in shape. The combination of very small size (~13-20g), sharp crests, tall and slender cuspids, broad talonid basins, as well as trigonid taller than the talonid is suggestive of an insectivorous diet for the new taxon.
Ameghiniana, 2019
The sparassodonts were the main mammalian predators during most of Cenozoic in South America. The... more The sparassodonts were the main mammalian predators during most of Cenozoic in South America. The lower Eocene Itaboraí Basin/Formation includes the second oldest fossil records of this group in South America: Patene and Nemolestes. Patene is by far the most abundant sparassodont from this formation, with more than 30 specimens referable to a single taxon, Patene simpsoni. Some specimens recovered from the Quebrada de Los Colorados Formation (former Lumbrera Formation – middle Eocene) in Northwestern Argentina have been also referred to P. simpsoni. In order to test the affinities of Patene and the taxonomy of the Argentinean specimens, we performed a review of the genus. We concluded that the specimens from Northwestern Argentina show significant differences from the Brazilian specimens: smaller size, paraconid more developed; metaconid, entoconid and hypoconid more reduced. As a result, the specimens from the Quebrada de Los Colorados Formation were assigned to a new species, Patene coloradensis. Our phylogenetic analysis supported previous hypotheses that exclude Patene from the “Hathliacynidae”, as the former was recovered as an earlier divergent lineage. The results also supported the hypothesis that Allqokirus australis and Mayulestes ferox from the Tiupampa Basin (El Molino Formation, lower Paleocene – Tiupampian), Bolivia, are the oldest known representatives of the Sparassodonta. The results also supported the monophyly of the Pucadelphyida with the inclusion of the Jaskhadelphyidae and closely related taxa in addition to the Pucadelphyidae + Sparassodonta. The Late Cretaceous, North American Varalphadon was not recovered in our phylogenetic analysis as a representative of the Sparassodonta.Based on our results, the Sparassodonta should be considered, based on the current fossil record, as a South American endemic lineage.
Anais da Academia Brasileira de Ciências, 2019
The Protodidelphidae was a group of marsupials that lived in Gondwana from the early to middle Eo... more The Protodidelphidae was a group of marsupials that lived in Gondwana from the early to middle Eocene. Among South American faunas, the Itaboraí Basin calls attention by the presence of four genera and six species. Herein is described Bergqvistherium primigenia gen. et sp. nov., a new protodidelphid from the Itaboraí Basin-lower Eocene. This taxon differs from other protodidelphids in the smaller size, developed entocristid, less brachyo-bunoid adaptations, and entoconid more mesial than the hypoconid. These characters are recovered as plesiomorphies of the Protodidelphidae, supporting Bergqvistherium as an early-divergent lineage of this group. The Protodidelphidae fauna of the Itaboraí Basin is represented by less specialized " basal " taxa, such as Bergqvistherium and Periprotodidelphis; and more specialized apical taxa, such as Guggenheimia, Protodidelphis, and Carolocoutoia. This result indicates that the diversification of apical protodidelphids probably was a result of a relatively short-time event, occurring during the early Eocene. This evolutionary event can be directly correlated to the increase in the temperatures and the extension of tropical forests resulted by the Paleocene-Eocene Thermal Maximum during the Itaboraiense time span. The study supported a Late Cretaceous origin for the Protodidelphidae, which agrees with molecular studies for the Didelphimorphia.
Revista Brasileira de Paleontologia, 2018
The Pediomyiodea has been largely regarded as a Late Cretaceous North American metatherian lineag... more The Pediomyiodea has been largely regarded as a Late Cretaceous North American metatherian lineage; however, some studies have suggested that a few South American taxa could be related to this family. Herein, Austropediomys marshalli gen. et sp. nov. from the Itaboraí Basin, Brazil (lower Eocene – Itaboraian SALMA), is described. Austropediomys gen. nov. represents the first report of a pediomyoid metatherian in the Paleogene of South America backed by a phylogenetic analysis. Several derived features in the upper molars support its belonging to the Pediomyoidea: presence of accessory ‘conular-like’ structures (here named conuloids) lingual to the conules; supernumerary stylar cusps; asymmetric stylar shelf, with parastylar shelf reduced to a narrow rim in M1; straight centrocrista; short and obliquely oriented prepacrista, which contacts StA in M2–3. The presence of ‘conular-like’ structures lingual to the paraconule and metaconule is identified in Austropediomys gen. nov. and in Late Cretaceous pediomyoids as well, and results in the phylogenetic analysis as a synapomorphy of the Pediomyoidea. Austropediomys gen. nov. is autapomorphyc in the presence of enlarged conuloids on protocristae. The record of a pediomyoid in the Paleogene of South America increases the temporal and biogeographical range of this lineage. Also, our results support the hypothesis that several non-related metatherian lineages dispersed from North to South America via the Caribbean Plate, most probably during the latest Cretaceous, in an island-hopping or sweepstakes model.
Cretaceous Research, 2018
The origin of the South American Sparassodonta has always been debated. Current data indicate a N... more The origin of the South American Sparassodonta has always been debated. Current data indicate a North American origin for this group, but no definitive fossil evidence was recovered so far to prove this hypothesis. Herein, Varalphadon janetae sp. nov. is described from the upper Cenomanian and lower Coniacian of southern Utah, which represents the oldest known Sparassodonta. This taxon can be considered to represent Varalphadon as it presents a markedly mesiodistally compressed protocone and M3; small StA, flattened StD, slightly labial contact of the cristid obliqua, labially salient protoconid and lacks StC. It differs from other species of the genus in the smaller size, proportionally narrower protoconal area, paracone slightly more labial than metacone in M3, more labiolingually compressed StD, keeled metaconid and narrower hypoconid and talonid basin. Varalphadon shares with other sparassodonts the presence of vestigial cuspules between StB and StD, flattened and poorly developed StD, absent StC, straight centrocrista, crested conules and an m1 markedly smaller and strongly labiolingually compressed. The phylogenetic analysis recovered Varalphadon as a basal Sparassodonta, corroborating previous studies that considered this taxon as more basal than remaining “Alphadontidae”, which is represented by Protalphadon, Eoalphadon, Alphadon, Albertatherium and Nortedelphys. “Varalphadon” crebreforme is recovered as a Hatcheriformes. The results demonstrate that Metatheria originates in North America during the late Early Cretaceous, with Gondwanan lineages evolving in the Northern Hemisphere during the Late Cretaceous prior to their dispersal to South American millions of years later (late Maastrichtian?). The analysis recovered Metatheria as a Gondwanan invasive lineage.
Revista Brasileira de Paleontologia, 2017
Eobrasilia coutoi Simpson is currently considered one of the most enigmatic metatherian mammals o... more Eobrasilia coutoi Simpson is currently considered one of the most enigmatic metatherian mammals of Itaboraí Basin, Brazil. A single badly broken and incomplete skull, with a single strongly worn M3, and an associated fragmentary dentary are the elements currently attributed to this taxon. This fragmentary condition contributes for its uncertain position within Metatheria. Herein, the preserved dental morphology of this species is re-analyzed. The morphology of these structures, such as a tiny, obliquely oriented, one-rooted P1; absence of retro-premolar spaces between the premolars and mesiodistally developed p3, supports the assignment of Eobrasilia as a South American stagodontid. This new result leads a systematic review of the affinities of " Eobrasiliinae " , currently represented by Eobrasilia, Gaylordia and Didelphopsis. The hypothesis that " Eobrasiliinae " represents a valid taxon is refuted in the phylogenetic analysis, which recovered Eobrasilia as more closely related to Didelphodon within Stagodontidae, Gaylordia as the sister taxon of Tiulordia and more closely related to Minusculodelphis and Marmosopsis, and Didelphopsis as the sister taxon of Itaboraidelphys and more closely related to Herpetotherium, Carolopaulacoutoia and Derorhynchus. The shared characters between Eobrasilia, Gaylordia and Didelphopsis were likely a result of convergent evolution, as these three lineages independently adapted to more durophagous diets. The phylogenetic analysis did not support the sister relation between Fumodelphodon and Didelphodon and Eodelphis and Hoodootherium. The grouping of Eobrasilia and Didelphodon corroborates the previous hypothesis that Metatheria dispersed from North to South America during the Late Cretaceous.
Acta Palaeontologica Polonica, 2017
Zeusdelphys complicatus is one of the most enigmatic metatherians from the Itaboraí Basin. The ty... more Zeusdelphys complicatus is one of the most enigmatic metatherians from the Itaboraí Basin. The type and only known specimen was previously regarded as the upper dentition of Eobrasilia; an M4 of a new taxon; an M3 of a Kollpaniidae (now regarded as a group of " condylarths "); a probable M1 of an incertae sedis taxon; and as an M1 of a Protodidelphidae. Herein, we present a morphological review of the dental structures of Zeusdelphys complicatus, presenting new interpretations and comparing it with other North and South American taxa. We also perform a phylogenetic analysis in order to test the affinities of Zeusdelphys and the validity of most studied characters. The results recovered Zeusdelphys complicatus as more closely related to Hatcheritherium alpha than to any other metatherian. Glasbiidae were recovered as the sister lineage of Protodidelphidae within Didelphimorphia, as true marsupials. Ectocentrocristus was recovered as the sister taxon of Zeusdelphys + Hatcheritherium, as a Hatcheriformes. The analysis recovered this suborder as an independent lineage from Polydolopimorphia, being more closely related to " Alphadontidae ". The affinities with Protodidelphidae are a result of convergent evolution, as Zeusdelphys is more closely related to Hatcheritherium alpha from the Late Cretaceous of North America. The results support a North American origin for Hatcheriformes. The presence of strong sea-level lowstands and islands in the Caribbean Plate during the Late Cretaceous provide valid data to support a faunal interchange between Americas during the latest Late Cretaceous. Based on the results, Zeusdelphys represents a South American early Eocene surviving Hatcheriformes.
Books by Leonardo M Carneiro
Springer, 2023
Metatherians represented the most diverse group of Paleogene mammals of South America. The early ... more Metatherians represented the most diverse group of Paleogene mammals of South America. The early Eocene metatherian fauna of Itaboraí, Brazil, was one of the most prominent. This fauna preserved a great diversity of tiny and very small insectivore assemblages, specialized durophagous, and brachydont-bunodont metatherians and is represented by 29 genera and 39 species, which are tooth-based taxa. The fauna preserved the oldest confirmed representatives of Didelphimorphia, as well as possible stem-Paucituberculata, but with no confirmed Australidelphia. Furthermore, the probable presence of the North American Late Cretaceous groups in the fauna, such as Pediomyoidea, Hatcheriformes, and Stagodontidae is also discussed. Sparassodonts, such as Patene, represented the top mammalian predators of the fauna. The large variety of Itaboraian “ameridelphians” includes, among others, “peradectoids,” caroloameghinioids, jaskhadelphyids, and sternbergiids, which represented earlier metatherian clades than the marsupials. Polydolopimorphians were represented by Epidolops, the most abundant metatherian of this fauna, and Gashternia. Caroloameghinioids should not be assigned to Didelphimorphia, and is here regarded as “peradectoids.” Derorhynchidae was the sister taxon of Herpetotheriidae. The reassessment of the eight petrosal morphotypes recovered in Itaboraí supports the common origin for the majority of South American clades and has enabled their reassessment to representatives of this fauna.
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Papers by Leonardo M Carneiro
Books by Leonardo M Carneiro