Agustín G. Martinelli

New Jurassic Mammals from Patagonia, Argentina: A Reappraisal of Australosphenidan Morphology and Interrelationships

Abstract A new mammal, Henosferus molus, n.gen. and n.sp., from the Callovian–Oxfordian (latest Middle to earliest Late Jurassic) Cañadón Asfalto Formation from Chubut Province (Argentina) is described. This taxon corresponds to a new species clearly different from Asfaltomylos patagonicus from the same locality and stratigraphic level. This new species is based on three lower jaws with relatively well-preserved dentition. The lower jaw shows a primitive morphology having a Meckelian groove, a prominent medial flange associated with a lateral ridge of the dentary, and a deep dentary trough, which possibly indicates the presence, even though reduced, of postdentary bones still attached to the dentary. The lower dental formula is i4, c1, p5, m3. The premolars are simple, bearing a main cusp, while the molars appear to be tribosphenic, with an obtuse to right-angled trigonid and a basined talonid with three cusps. This association of plesiomorphic features in the jaw and derived features in the molars is documented in several taxa of the recently proposed Australosphenida. A phylogenetic analysis of mammaliaforms nests the new species with Asfaltomylos from the same locality and stratigraphic level; Henosferidae, new family, is recognized for Asfaltomylos and Henosferus, representing the basal radiation of Australosphenida. Henosferidae is the sister group to Ambondro from the Middle Jurassic of Madagascar, which, in agreement with previous phylogenies, is the sister taxon to the remaining australosphenidans. Additionally, our phylogenetic analysis does not support the inclusion of australosphenidans within eutherians. Henosferids likely retained some connection of the postdentary elements with the dentary; therefore, if the inclusion of Monotremata within Australosphenida is confirmed, final freeing of the postdentary elements and development of a tri-ossicular middle ear would be convergent events in Monotremata and Theria. Finally, the distinctiveness of the yet sparse South American record of Jurassic mammals when compared with the slightly better documented Cretaceous data is emphasized. The clear faunistic break between the Middle Jurassic and Early/Late Cretaceous underlies our rudimentary understanding of the evolution of Mesozoic mammals in Gondwana.

A new specimen of Guaibasaurus candelariensis (basal Saurischia) from the Late Triassic Caturrita Formation of southern Brazil

The comparison of the anatomy of a second incomplete skeleton of Guaibasaurus candelariensis to that of basal Saurischia suggests that the origin of the “Prosauropoda” was from unknown basal saurischians, after separating from theropods (except herrerasaurids). Guaibasaurus and Saturnalia are part of this early dichotomy, and they bear mixed characters-states of basal theropods and “prosauropods” type. The Late Triassic age of both Guaibasaurus and Saturnalia (the latter is older) predates the ‘dominance’ of basal sauropodomorphs as well as the appearance of the basal theropod Zupaysaurus, both recorded from the upper Los Colorados Formation of Argentina.

A new squamate lizard from the Upper Cretaceous Adamantina Formation (Bauru Group), São Paulo State, Brazil

The record of non-mosasaur squamates (Reptilia, Squamata) is sparse in the Cretaceus fossil record of Brazil and include six putative reports, three from the Aptian-Albian of the Araripe Basin (Tijubina pontei Bonfim-Júnior and Marques, Olindalacerta brasiliensis Evans and Yabumoto, and a lizard indet.) and three from the Upper Cretaceous of the Bauru Group (Pristiguana brasiliensis Estes and Price, Anilioidae gen. et sp. indet., and Squamata gen. et sp. indet.). In this contribution, a new genus and species of lizard, Brasiliguana prudentis gen. et sp. nov., is described based on an isolated left maxilla with teeth. The material was discovered in an outcrop of the Upper Cretaceous Adamantina Formation (Bauru Group) located in the proximity of Presidente Prudente Municipality, São Paulo State, Brazil. The new taxon is considered a basal non-Priscagamidae+Acrodonta iguanian based on the presence of a weakly inclined anterior margin of the maxillary nasal process and maxillary tooth shape and tooth implantation similar to that of iguanians rather than of other lizard groups (e.g. teiids). This finding significantly increases the squamate lizard diversity of South America, which is still poorly understood and sparsely represented in the fossil record.

Two New Cynodonts (Therapsida) from the Middle-Early Late Triassic of Brazil and Comments on South American Probainognathians

We describe two new cynodonts from the early Late Triassic of southern Brazil. One taxon, Bonacynodon schultzi gen. et sp. nov., comes from the lower Carnian Dinodontosaurus AZ, being correlated with the faunal association at the upper half of the lower member of the Chañares Formation (Ischigualasto-Villa Unión Basin, Argentina). Phylogenetically, Bonacynodon is a closer relative to Probainognathus jenseni than to any other probainognathian, bearing conspicuous canines with a denticulate distal margin. The other new taxon is Santacruzgnathus abdalai gen. et sp. nov. from the Carnian Santacruzodon AZ. Although based exclusively on a partial lower jaw, it represents a probainognathian close to Prozostrodon from the Hyperodapedon AZ and to Brasilodon, Brasilitherium and Botucaraitherium from the Riograndia AZ. The two new cynodonts and the phylogenetic hypothesis presented herein indicate the degree to which our knowledge on probainognathian cynodonts is incomplete and also the relevance of the South American fossil record for understanding their evolutionary significance. The taxonomic diversity and abundance of probainognathians from Brazil and Argentina will form the basis of deep and complex studies to address the evolutionary transformations of cynodonts leading to mammals.

First fossil record of amiid fishes (Halecomorphi, Amiiformes, Amiidae) from the Late Cretaceous of Uberaba, Minas Gerais State, Brazil

Martinelli, A.G., Bogan, S., Agnolin, F.L., Ribeiro, L.C.B., Cavellani, C.L., Ferraz, M.L.F. & Teixeira, V.P.A., iFirst article. First fossil record of amiid fishes (Halecomorphi, Amiiformes, Amiidae) from the Late Cretaceous of Uberaba, Minas Gerais State, Brazil. Alcheringa, 1–9. ISSN 0311-5518. The first fossil amiid fishes (Halecomorphi, Amiiformes) from the Late Cretaceous Marília Formation (Bauru Group) at Uberaba County, Triângulo Mineiro region (Minas Gerais State, Brazil), are described. The material includes some partial maxillae, a dermopterotic, a cleithrum, several vertebral centra and teeth. Features such as the absence of a supramaxillary notch on the dorsal edge of the maxilla, a wide and deep pit on the maxilla for the articulation of the premaxilla, anterior portion of the maxilla with a sub-circular cross-section, teeth with acrodine cup with strong mesial and distal keels, among others, permit confident referral of the material to the Subfamily Vidalamiine (Amiidae), previously recognized in Lower Cretaceous strata of northeasthern Brazil. These specimens constitute the first Late Cretaceous record of this group in Brazil and one of the few in South America. Agustín G. Martinelli [agustín_martinelli@yahoo.com.ar], Centro de Pesquisas Paleontológicas Llewellyn Ivor Price, Complexo Cultural e Científico Peirópolis (CCCP/UFTM), BR-262, Km 784, Bairro Peirópolis, Uberaba, Minas Gerais, Brazil; Sergio Bogan [sergiobogan@yahoo.com.ar], Fundación de Historia Natural ‘Félix de Azara’, Departamento de Ciencias Naturales y Antropología, CEBBAD—Universidad Maimónides, Hidalgo 775 piso 7 (1405BDB), Buenos Aires, Argentina. Federico Agnolín* [fedeagnolin@yahoo.com.ar], Sección Paleontología de Vertebrados, Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’, Av. Ángel Gallardo 470 (C1405BDB), Buenos Aires, Argentina. Luiz Carlos Borges Ribeiro [lcbrmg@terra.com.br], Camila Lourencini Cavellani [camila@patge.uftm.edu.br], Mara Lúcia da Fonseca Ferraz [mara@patge.uftm.edu.br] and Vicente de Paula Antunes Teixeira [vicente@patge.uftm.edu.br], Centro de Pesquisas Paleontológicas Llewellyn Ivor Price, Complexo Cultural e Científico Peirópolis (CCCP/UFTM), BR-262, Km 784, Bairro Peirópolis, Uberaba, Minas Gerais, Brazil. *Also affiliated with: Fundación de Historia Natural ‘Félix de Azara’, Departamento de Ciencias Naturales y Antropología, CEBBAD—Universidad Maimónides, Valentín Virasoro 732 (C1405BDB), Buenos Aires, Argentina. Received 15.4.2012; revised 11.6.2012; accepted 20.6.2012.

First bird remains from the Upper Cretaceous of the Peirópolis site, Minas Gerais state, Brazil

ABSTRACT We report on the first occurrence of Maastrichtian bird material from the Peirópolis locality (Uberaba district), Minas Gerais State (Brazil). The specimens consist of an indeterminate pedal ungual phalanx (CPP 481), a pedal phalanx 1 of left digit II (CPP 470) and an incomplete metatarsal III (CPP 482). The material can be assigned to Aves gen. et sp. indet. (CPP 470 and CPP 481) and to cf. Enantiornithes gen. et sp. indet. (CPP 482). Despite the isolated and incompleteness nature of these specimens, they add to the otherwise poor record of Cretaceous birds from Brazil.

The African cynodont Aleodon (Cynodontia, Probainognathia) in the Triassic of southern Brazil and its biostratigraphic significance

In this contribution we report the first occurrence of the enigmatic African probainognathian genus Aleodon in the Middle-early Late Triassic of several localities from the state of Rio Grande do Sul in southern Brazil. Aleodon is unusual among early probainognathians in having transversely-expanded postcanine teeth, similar to those of gomphodont cynognathians. This genus was previously known from the Manda Beds of Tanzania and the upper Omingonde Formation of Namibia. The Brazilian record of this genus is based upon multiple specimens representing different ontogenetic stages, including three that were previously referred to the sectorial-toothed probainognathian Chiniquodon theotonicus. We propose a new species of Aleodon (A. cromptoni sp. nov.) based on the specimens from Brazil. Additionally, we tentatively refer one specimen from the upper Omingonde Formation of Namibia to this new taxon, strengthening biostratigraphic correlations between these strata. Inclusion of A. cromptoni in a phylogenetic analysis of eucynodonts recovers it as the sister-taxon of A. brachyrhamphus within the family Chiniquodontidae. The discovery of numerous specimens of Aleodon among the supposedly monospecific Chiniquodon samples of Brazil raises concerns about chiniquodontid alpha taxonomy, particularly given the extremely broad geographic distribution of Chiniquodon. The discovery of Brazilian Aleodon and new records of the traversodontid Luangwa supports the hypothesis that at least two subzones can be recognized in the Dinodontosaurus Assemblage Zone.

A new prozostrodontian cynodont (Therapsida) from the Late Triassic Riograndia Assemblage Zone (Santa Maria Supersequence) of Southern Brazil

We report here on a new prozostrodontian cynodont, Botucaraitherium belarminoi gen. et sp. nov., from the Late Triassic Riograndia Assemblage Zone (AZ) of the Candelária Sequence (Santa Maria Supersequence), collected in the Botucaraí Hill Site, Candelária Municipality, state of Rio Grande do Sul, Brazil. The new taxon is based on a single specimen (holotype MMACR-PV-003-T) which includes the left lower jaw, without postdentary bones, bearing the root of the last incisor, canine and four postcanines plus one partial crown inside the dentary, not erupted, and two maxillary fragments, one with a broken canine and another with one postcanine. The features of the lower jaw and lower/upper postcanines resemble those of the prozostrodontians Prozostrodon brasiliensis from the older Hyperodapedon AZ and Brasilodon quadrangularis and Brasilitherium riograndensis from the same Riograndia AZ. The inclusion of Botucaraitherium within a broad phylogenetic analysis, positioned it as a more derived taxon than tritylodontids, being the sister-taxon of Brasilodon, Brasilitherium plus Mammaliaformes. Although the new taxon is based on few cranial elements, it represents a additional faunal component of the Triassic Riograndia AZ of southern Brazil, in which small-sized derived non-mammaliaform cynodonts, closely related to the origin of mammaliaforms, were ecologically well succeed and taxonomically diverse.

Deep faunistic turnovers preceded the rise of dinosaurs in southwestern Pangaea

The Triassic period documents the origin and diversification of modern amniote lineages and the Late Triassic fossil record of South America has been crucial to shed light on these early evolutionary histories. However, the faunistic changes that led to the establishment of Late Triassic ecosystems are largely ignored because of the global scarcity of fossils from assemblages a few million years older. Here we contribute to fill this gap with the description of a new tetrapod assemblage from the lowermost levels of the Chañares Formation (uppermost Middle–lower Late Triassic epochs) of Argentina, which is older than the other vertebrate assemblages of the same basin. The new assemblage is composed of therapsids, rhynchosaurids and archosaurs, and clearly differs from that of the immediately overlying and well-known historical Chañares vertebrate assemblage. The new tetrapod association is part of a phase of relatively rapidly changing vertebrate assemblage compositions, in a time span shorter than 6 million years, before the diversification of dinosaurs and other common Late Triassic tetrapods in southwestern Pangaea.A Middle–Late Triassic tetrapod assemblage from South America reveals a series of faunal turnovers prior to the rise of dinosaurs in the region.

The oldest archosauromorph from South America: postcranial remains from the Guadalupian (mid-Permian) Rio do Rasto Formation (Paraná Basin), southern Brazil

Abstract In this contribution, we report a distal portion of a left humerus that likely belongs to an indeterminate basal archosauromorph from the Guadalupian (mid-Permian) Rio do Rastro Formation (Paraná Basin) of southern Brazil. A precise taxonomy of the fragmented and isolated humerus UFRGS-PV-0546-P is not warranted at generic nor familiar level but, likely, this specimen belongs to an Archosauromorpha due to the lack of both the entepicondylar and the ectepicondylar foramina. The narrow distal end of the humerus, the rounded radial and ulnar condyles, and the moderately developed supinator process with a shallow ectepicondylar groove (not notched) are features reminiscent of tanystropheids rather than that of other archosauromorphs. This material likely represents the first and oldest Permian archosauromorph from South America and indicates the presence of this lineage before the P/T boundary.