Paula Bona

Caiman gasparinae sp. nov., a huge alligatorid (Caimaninae) from the late Miocene of Paraná, Argentina

Bona, P. & Paulina Carabajal, A., 2013. Caiman gasparinae sp. nov., a huge alligatorid (Caimaninae) from the late Miocene of Paraná, Argentina. Alcheringa 37, 1–12. ISSN 0311-5518 Morphological studies of South American alligatorids are scarce, and the phylogenetic relationships within Caimaninae are poorly understood. In this context, systematic revision and detailed morphological description of the enigmatic Argentinean Miocene caimanines are highly relevant. The current record is characterized by numerous species within the genus Caiman, although morphological disparity remains unclear. Here, we describe Caiman gasparinae sp. nov., which is one of the largest known Caiman species from the late Miocene of Argentina. Similar to other Caiman species and Melanosuchus, the new taxon has orbits larger than the infratemporal fenestrae and small supratemporal fenestrae that are not lost, as in Paleosuchus. Together with the absence of conspicuous rostral crests, the shape of the snout distinguishes C. gasparinae from Melanosuchus. Caiman gasparinae can be further distinguished using other cranial characters, such as a broad and low rostrum with a narial opening oriented dorsally, a relatively long interpremaxillary suture, and the occipital surface of the braincase with a poorly developed crista tuberalis exposing the carotid foramina in lateral view. Paula Bona [paulabona26@gmail.com] CONICET—División Paleontología Vertebrados, Museo de La Plata. Paseo del Bosque s/n, 1900, La Plata, Argentina; Ariana Paulina Carabajal [a.paulinacarabajal@conicet.gov.ar] CONICET—Museo Carmen Funes. Av. Córdoba 55 (8318), Plaza Huincul, Neuquén, Argentina. Received 21.8.2012; revised 29.1.2013; accepted 9.3.2013.

CAIMAN CF. LATIROSTRIS (ALLIGATORIDAE, CAIMANINAE) IN THE LATE MIOCENE PALO PINTADO FORMATION, SALTA PROVINCE, ARGENTINA: PALEOGEOGRAPHIC AND PALEOENVIRONMENTAL CONSIDERATIONS

Abstract. The three recognized species of Caiman —C. latirostris, C. yacare and C. crocodilus— currently live in northern and central South America. Except for the fragmentary dentary of a putative Caiman from Oligocene rocks in Brazil, the genus has been reliably recorded in rocks of ages spanning the Neogene, when species of Caiman were a constant component of the South American crocodyliofauna. The major taxonomical diversification of Caiman occurred during the late Miocene, which is well documented in the area of Paraná (northeastern Argentina). Fossil crocodylians in Paraná are represented by one gavialid and caimanines, with at least five species of Caiman (including C. latirostris). This assemblage represents the southernmost record of Crocodylia living in “Amazonia” during the Miocene. In this work we confirm the record of Miocene caimans outside the Paraná and we prove the presence of Caiman cf. latirostris in present-day northwestern Argentina during the late Miocene. The taxonomic identification is based on a fragment of a left mandible with the same ornamentation, outline and dentition as Caiman, and with a symphyseal morphology similar to that of Caiman latirostris. The material comes from the upper part of the Palo Pintado Formation in the southern region of Valle Calchaquí (Salta Province). This unit was deposited in a sand-gravel fluvial system with associated ponds between 10.29 ±0.11 Ma (K/Ar) and 5.27 ±0.28 Ma (206Pb/238U).

A New Peirosaurid (Crocodyliformes, Mesoeucrocodylia) from the Upper Cretaceous of Patagonia, Argentina

Abstract. Peirosaurids are a group of Cretaceous continental crocodyliforms from Gondwana. Two species are known from the Neuquén Group in Argentina: Lomasuchus palpebrosus (Portezuelo Formation, late Turonian—early Coniacian) and Gasparinisuchus peirosauroides (Bajo de la Carpa and Anacleto formations, Santonian and early Campanian, respectively). Here, we describe the first peirosaurid from the Cerro Lisandro Formation, Bayomesasuchus hernandezi gen. et sp. nov. The material corresponds to a fragmentary skull and mandible. Although fragmentary, this is the most complete crocodyliform specimen recorded for the Cerro Lisandro Formation. In a phylogenetic analysis Bayomesasuchus is depicted in a polytomy together with South American peirosaurids and the African form Hamadasuchus rebouli.

Palaeoenvironmental implications of the giant crocodylian Mourasuchus (Alligatoridae, Caimaninae) in the Yecua Formation (late Miocene) of Bolivia

Tineo, D.E., Bona, P., Pérez, L.M., Vergani, G.D., González, G., Poiré, D.G., Gasparini, Z.N. & Legarreta, P., 1.10.2014. Palaeoenvironmental implications of the giant crocodylian Mourasuchus (Alligatoridae, Caimaninae) in the Yecua Formation (late Miocene) of Bolivia. Alcheringa 39, xxx–xxx. ISSN 0311-5518 Outcrops of the Yecua Formation (late Miocene) are exposed for approximately 230 m along the La Angostura section of the Piraí River (50 km southwest of Santa Cruz de la Sierra). These reveal massive (argillic palaeosols) and laminated (quiet-water lacustrine and marsh settings) mudstones interbedded with thin sandstones containing microfossils, molluscs and vertebrate remains. Significantly, the succession hosts a giant crocodylian, Mourasuchus (Alligatoridae, Caimaninae), which is represented by both skull and postcranial fragments found in association with freshwater turtles and fishes. Mourasuchus was distributed widely from the middle Miocene of Colombia to upper Miocene of Venezuela, Brazil and Argentina, suggesting connections between major fluvial systems and an active mechanism for dispersal of South American freshwater vertebrates during the Miocene. David Eric Tineo [tineo.d.e@gmail.com] and Daniel Gustavo Poiré [dgpoire@yahoo.com.ar], CONICET—Centro de Investigaciones Geológicas, Universidad Nacional de La Plata. Calle 1 (644), B1900FWA, La Plata, Argentina; Paula Bona [paulabona26@gmail.com] and Zulma Gasparini [zgaspari@fcnym.unlp.edu.ar], CONICET—División Paleontología Vertebrados, Museo de La Plata. Paseo del Bosque s/n, B1900FWA, La Plata, Argentina; Leandro Martín Pérez [pilosaperez@gmail.com] CONICET—División Paleozoología Invertebrados, Museo de La Plata. Paseo del Bosque s/n, B1900FWA, La Plata, Argentina; Gustavo Dardo Vergani [gvergani@pluspetrol.net]—Pluspetrol S.A. Lima (339), C1073AAG, Ciudad Autónoma de Buenos Aires, Argentina; Gloria González Rigas [ggonzalez@pluspetrol.net]—Pluspetrol Bolivia Corporation SA, Av. Grigotá esq. Las Palmas, Santa Cruz de la Sierra, Bolivia; Pablo Legarreta [plegarreta@pluspetrol.net]—Pluspetrol S.A. Lima (339), C1073AAG, Ciudad Autónoma de Buenos Aires, Argentina.

Cranial shape variation in jacarean caimanines (Crocodylia, Alligatoroidea) and its implications in the taxonomic status of extinct species: The case of Melanosuchus fisheri

Melanosuchus niger (Crocodylia, Alligatoroidea) is one of the six living caimanine species widely distributed throughout the Amazon River basin today. Although there is only one extant species of Melanosuchus, fossil material assigned to this genus, represented by M. fisheri, has been reported from the late Miocene in South America. However, the validity of this taxon has been questioned and a recent investigation indicates that the referred specimen of M. fisheri (MCZ 4336) actually belongs to Globidentosuchus brachyrostris, while those diagnostic characters present in the holotype (MCNC 243) fall into the spectrum of intraspecific variation of M. niger. Here, we compare the skull shape of the holotype of M. fisheri with the ontogenetic series of the four jacarean species (M. niger, Caiman yacare, Caiman crocodilus, and Caiman latirostris) using 2D‐geometric morphometric analyses in two different views. The analyses indicate that MCNC 243 falls into the morphospace of M. niger and C. latirostris. Despite strong shape similarities between juveniles of C. latirostris and MCNC 243, further anatomical comparisons reveal notable differences between them. In contrast, no concrete anatomical differences can be found between MCNC 243 and M. niger, although shape analyses indicate that MCNC 243 is relatively robust for its size. Thus, this study is able to confirm that the genus Melanosuchus was present in the late Miocene, but it still remains unclear if MCNC 243 should be treated as a junior synonym or probably a sister species of M. niger. Its Miocene age favors the second option, but as the shape analyses were also not able to extract any diagnostic characters, it should be retained as Melanosuchus cf. niger.

Neuroanatomy of Gryposuchus neogaeus (Crocodylia, Gavialoidea): a first integral description of the braincase and endocranial morphological variation in extinct and extant gavialoids

Morphological studies of the braincase and cranial endocast of fossil crocodylians, especially gavialids, are scarce. Here, we present a detailed description of the neuroanatomy of Gryposuchus neogaeus from the Miocene of Argentina, based on CT scans. The cranial endocast is sub-horizontal and the angle formed between the mid-brain and the hind-brain is poorly marked. When compared with Gavialis gangeticus , the mid-brain of G. neogaeus is relatively shorter, although the distribution of cranial nerves is similar. In the floor of the endocranial cavity, posterior to the dorsum sellae, there is a median foramen that leads into a canal that runs anteroventrally through the basisphenoid to penetrate the posterior wall of the pituitary fossa (open foramen for the basilar artery?). The same structure is present in G. gangeticus , but is absent in other living crocodylians, suggesting a potential synapomorphy of Gavialoidea. The pneumaticity of the skull roof and the lateral branches of the pharyngotympanic system in G. neogaeus are markedly reduced when compared with the extant species. Comparisons with the living Gavialis indicate that the pattern of braincase morphology of Gavialidae was present in the Miocene; however, the internal morphology, including brain shape, pneumaticity of the skull roof and basicranium, is different in the two species. This work is the first step to understand the variation of the neuroanatomy in this group of archosaurs and its palaeobiological implication.

Shedding light on the taxonomic diversity of the south american miocene caimans: the status of Melanosuchus fisheri (Crocodylia, Alligatoroidea)

Abstract. Melanosuchus niger Spix is distributed throughout the Amazon River basin today. The extinct Melanosuchus fisheri Medina from the late Miocene of Venezuela was erected based on two almost complete, but heavily deformed skulls (the holotype MCNC 243 and the referred specimen MCZ 4336), which show morphological differences from each other. The comparison indicates that only the holotype can be referred to Melanosuchus Gray. We propose MCZ 4336 is a representative of the caimanine Globidentosuchus brachyrostris Scheyer, Aguilera, Delfino, Fortier, Carlini, Sánchez, Carrillo-Briceño, Quiroz and Sãnchez-Villagra. Although the taxonomy of M. fisheri is taken into question herein, the classification of the holotype still sustains the hypothesis that the genus is registered in South America since the late Miocene.

The Oldest Record Of Aramayoichnus rheae from the Neogene of Northwestern Argentina

Fil: Tineo, David. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - La Plata. Centro de Investigaciones Geologicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geologicas; Argentina